wind: Move more fallible operations before window creation

Classic "keeping a pointer to an element inside a vector after the vector is updated" bug, ah yes.

.gitignore

@@ -4,7 +4,14 @@ build/
 initrd/boot/moon
 env-local.sh
 initrd/bin/**
-base/usr/**
+base/usr/bin/**
+base/usr/include/**
+base/usr/lib/**
+base/usr/share/pkgdb/**
+!base/usr/share/fonts/*
+!base/usr/share/icons/*
+base/usr/share/**
+base/usr/x86_64-luna/**
 base/etc/skel/LICENSE
 .fakeroot
 kernel/config.cmake

CMakeLists.txt

@@ -45,8 +45,10 @@ endif()
 
 add_subdirectory(libluna)
 add_subdirectory(libos)
+add_subdirectory(libui)
 add_subdirectory(libc)
 add_subdirectory(kernel)
 add_subdirectory(apps)
 add_subdirectory(tests)
 add_subdirectory(shell)
+add_subdirectory(wind)

apps/CMakeLists.txt

@@ -41,3 +41,7 @@ luna_app(kill.cpp kill)
 luna_app(gol.cpp gol)
 luna_app(touch.cpp touch)
 luna_app(free.cpp free)
+luna_app(gclient.cpp gclient)
+target_link_libraries(gclient PUBLIC ui)
+luna_app(taskbar.cpp taskbar)
+target_link_libraries(taskbar PUBLIC ui)

apps/gclient.cpp

@@ -0,0 +1,65 @@
+#include <ui/App.h>
+#include <ui/Layout.h>
+
+struct ColorWidget : public ui::Widget
+{
+  public:
+    ColorWidget(ui::Color first, ui::Color second) : m_color(first), m_first_color(first), m_second_color(second)
+    {
+    }
+
+    Result<ui::EventResult> handle_mouse_move(ui::Point) override
+    {
+        m_color = m_second_color;
+        return ui::EventResult::DidHandle;
+    }
+
+    Result<ui::EventResult> handle_mouse_leave() override
+    {
+        m_color = m_first_color;
+        return ui::EventResult::DidHandle;
+    }
+
+    Result<void> draw(ui::Canvas& canvas) override
+    {
+        canvas.fill(m_color);
+        return {};
+    }
+
+  private:
+    ui::Color m_color;
+    ui::Color m_first_color;
+    ui::Color m_second_color;
+};
+
+Result<int> luna_main(int argc, char** argv)
+{
+    ui::App app;
+    TRY(app.init(argc, argv));
+
+    auto* window = TRY(ui::Window::create(ui::Rect { 200, 200, 400, 300 }));
+    app.set_main_window(window);
+
+    window->set_title("Main Window");
+    window->set_background(ui::CYAN);
+
+    ui::HorizontalLayout layout;
+    window->set_main_widget(layout);
+
+    ColorWidget green(ui::GREEN, ui::WHITE);
+    layout.add_widget(green);
+    ColorWidget blue(ui::BLUE, ui::GRAY);
+    layout.add_widget(blue);
+
+    ui::VerticalLayout sublayout;
+    layout.add_widget(sublayout);
+
+    ColorWidget red(ui::RED, ui::CYAN);
+    sublayout.add_widget(red);
+    ColorWidget white(ui::WHITE, ui::GREEN);
+    sublayout.add_widget(white);
+
+    window->draw();
+
+    return app.run();
+}

apps/init.cpp

@@ -261,7 +261,7 @@ static Result<void> load_service(const os::Path& path)
 
     if (service.command.is_empty())
     {
-        do_log("[init] service file is missing 'Command' or 'Script' entry, aborting!\n");
+        do_log("[init] service file is missing 'Command' entry, aborting!\n");
         return {};
     }
 

apps/login.cpp

@@ -45,7 +45,7 @@ Result<int> luna_main(int argc, char** argv)
         username = name.view();
     }
 
-    execl("/bin/su", "login", "-lp", "--", username.chars(), nullptr);
+    execl("/usr/bin/su", "login", "-lp", "--", username.chars(), nullptr);
 
     perror("su");
     return 1;

apps/ls.cpp

@@ -8,6 +8,7 @@
 #include <os/FileSystem.h>
 #include <os/Mode.h>
 #include <pwd.h>
+#include <unistd.h>
 
 void find_user_and_group(struct stat& st, StringView& owner, StringView& group)
 {
@@ -47,18 +48,46 @@ int sort_reverse(const os::Directory::Entry* a, const os::Directory::Entry* b)
     return 0;
 }
 
-static Result<String> entry_join(const Vector<os::Directory::Entry>& vec, StringView delim)
+#define RESET_COLORS "\x1b[m"
+#define SYMLINK_COLOR "\x1b[36m"
+#define FILE_COLOR "\x1b[1;32m"
+#define DIR_COLOR "\x1b[1;34m"
+#define SOCKET_COLOR "\x1b[33m"
+#define SPECIAL_COLOR "\x1b[35m"
+#define STICKY_COLOR "\x1b[30;1;42m"
+#define SETUID_COLOR "\x1b[30;1;41m"
+#define EXEC_COLOR "\x1b[1;31m"
+
+static const char* file_type_color(const os::Directory::Entry& entry)
+{
+    if (entry.mode & S_ISVTX) return STICKY_COLOR;
+    if (entry.mode & S_ISUID || entry.mode & S_ISGID) return SETUID_COLOR;
+
+    switch (entry.mode & S_IFMT)
+    {
+    case S_IFREG: return entry.mode & S_IXUSR ? EXEC_COLOR : FILE_COLOR;
+    case S_IFDIR: return DIR_COLOR;
+    case S_IFLNK: return SYMLINK_COLOR;
+    case S_IFSOCK: return SOCKET_COLOR;
+    default: return SPECIAL_COLOR;
+    }
+}
+
+static Result<String> entry_join(const Vector<os::Directory::Entry>& vec, StringView delim, bool colors)
 {
     if (vec.size() == 0) return String {};
-    if (vec.size() == 1) return vec[0].name.clone();
 
     StringBuilder sb;
+    if (colors) TRY(sb.add(StringView { file_type_color(vec[0]) }));
     TRY(sb.add(vec[0].name));
+    if (colors) TRY(sb.add(StringView { RESET_COLORS }));
 
     for (usize i = 1; i < vec.size(); i++)
     {
         TRY(sb.add(delim));
+        if (colors) TRY(sb.add(StringView { file_type_color(vec[i]) }));
         TRY(sb.add(vec[i].name));
+        if (colors) TRY(sb.add(StringView { RESET_COLORS }));
     }
 
     return sb.string();
@@ -75,6 +104,7 @@ Result<int> luna_main(int argc, char** argv)
     bool follow_symlink_args { false };
     bool one_per_line { false };
     bool list_directories { false };
+    bool no_colors { false };
 
     StringView sort_type { "name" };
 
@@ -98,6 +128,8 @@ Result<int> luna_main(int argc, char** argv)
     parser.add_switch_argument(list_directories, 'd', "directory"_sv, "list directories instead of their contents"_sv);
     parser.add_value_argument(sort_type, ' ', "sort"_sv, "sort by name, size or time"_sv);
     parser.add_switch_argument(reverse_sort, 'r', "reverse"_sv, "reverse order while sorting"_sv);
+    parser.add_switch_argument(no_colors, ' ', "no-colors"_sv,
+                               "disable coloring of output (defaults to true when not in a TTY)"_sv);
     parser.parse(argc, argv);
 
     Vector<os::Directory::Entry> files;
@@ -154,11 +186,13 @@ Result<int> luna_main(int argc, char** argv)
 
     if (!long_list)
     {
-        auto list = TRY(entry_join(files, one_per_line ? "\n"_sv : " "_sv));
+        auto list = TRY(entry_join(files, one_per_line ? "\n"_sv : " "_sv, !no_colors && isatty(STDIN_FILENO)));
         if (!list.is_empty()) os::println("%s", list.chars());
     }
     else
     {
+        bool colors = !no_colors && isatty(STDIN_FILENO);
+
         for (const auto& file : files)
         {
             struct stat st;
@@ -176,14 +210,32 @@ Result<int> luna_main(int argc, char** argv)
 
             if (!human_readable && !si)
             {
-                os::println("%s %u %4s %4s %10lu %s%s%s", formatted_mode, st.st_nlink, owner.chars(), group.chars(),
+                if (colors)
-                            st.st_size, file.name.chars(), link.is_empty() ? "" : " -> ", link.chars());
+                {
+                    os::println("%s %u %4s %4s %10lu %s%s" RESET_COLORS "%s" SYMLINK_COLOR "%s" RESET_COLORS,
+                                formatted_mode, st.st_nlink, owner.chars(), group.chars(), st.st_size,
+                                file_type_color(file), file.name.chars(), link.is_empty() ? "" : " -> ", link.chars());
+                }
+                else
+                {
+                    os::println("%s %u %4s %4s %10lu %s%s%s", formatted_mode, st.st_nlink, owner.chars(), group.chars(),
+                                st.st_size, file.name.chars(), link.is_empty() ? "" : " -> ", link.chars());
+                }
             }
             else
             {
                 auto size = TRY(to_dynamic_unit(st.st_size, 10, false, si ? Unit::SI : Unit::Binary, false));
-                os::println("%s %u %4s %4s %6s %s%s%s", formatted_mode, st.st_nlink, owner.chars(), group.chars(),
+                if (colors)
-                            size.chars(), file.name.chars(), link.is_empty() ? "" : " -> ", link.chars());
+                {
+                    os::println("%s %u %4s %4s %6s %s%s" RESET_COLORS "%s" SYMLINK_COLOR "%s" RESET_COLORS,
+                                formatted_mode, st.st_nlink, owner.chars(), group.chars(), size.chars(),
+                                file_type_color(file), file.name.chars(), link.is_empty() ? "" : " -> ", link.chars());
+                }
+                else
+                {
+                    os::println("%s %u %4s %4s %6s %s%s%s", formatted_mode, st.st_nlink, owner.chars(), group.chars(),
+                                size.chars(), file.name.chars(), link.is_empty() ? "" : " -> ", link.chars());
+                }
             }
         }
     }

apps/preinit.cpp

@@ -72,10 +72,9 @@ int main()
     // Now, mount the /dev file system on the new root.
     mount_devfs();
 
-    setenv("PATH", "/sbin:/usr/bin", 1);
+    char* argv[] = { "/usr/bin/init", nullptr };
-    char* argv[] = { "init", nullptr };
     char* envp[] = { nullptr };
-    execvpe(argv[0], argv, envp);
+    execve(argv[0], argv, envp);
 
     fail_errno("Failed to execute init");
 

apps/rm.cpp

@@ -1,10 +1,35 @@
 #include <os/ArgumentParser.h>
+#include <os/Directory.h>
+#include <os/File.h>
 #include <os/FileSystem.h>
 
+Result<void> remove_wrapper(const os::Path& path, bool verbose)
+{
+    TRY(os::FileSystem::remove(path));
+    if (verbose) os::println("removed '%s'", path.name().chars());
+    return {};
+}
+
+Result<void> remove_tree(const os::Path& path, bool verbose)
+{
+    auto rc = remove_wrapper(path, verbose);
+    if (!rc.has_error()) return {};
+    if (rc.error() != ENOTEMPTY) return rc.release_error();
+
+    auto dir = TRY(os::Directory::open(path));
+
+    Vector<String> entries = TRY(dir->list_names(os::Directory::Filter::ParentAndBase));
+
+    for (const auto& entry : entries) { TRY(remove_tree({ dir->fd(), entry.view() }, verbose)); }
+
+    return remove_wrapper(path, verbose);
+}
+
 Result<int> luna_main(int argc, char** argv)
 {
     StringView path;
     bool recursive;
+    bool verbose;
 
     os::ArgumentParser parser;
     parser.add_description("Remove a path from the file system."_sv);
@@ -12,11 +37,12 @@ Result<int> luna_main(int argc, char** argv)
     parser.add_positional_argument(path, "path"_sv, true);
     parser.add_switch_argument(recursive, 'r', "recursive"_sv,
                                "remove a directory recursively (by default, rm removes only empty directories)"_sv);
+    parser.add_switch_argument(verbose, 'v', "verbose"_sv, "log every removed file and directory"_sv);
     parser.parse(argc, argv);
 
-    if (!recursive) TRY(os::FileSystem::remove(path));
+    if (!recursive) TRY(remove_wrapper(path, verbose));
     else
-        TRY(os::FileSystem::remove_tree(path));
+        TRY(remove_tree(path, verbose));
 
     return 0;
 }

apps/su.cpp

@@ -127,7 +127,7 @@ Result<int> luna_main(int argc, char** argv)
     {
         chdir(entry->pw_dir);
         clearenv();
-        setenv("PATH", "/bin:/sbin", 1);
+        setenv("PATH", "/usr/bin:/usr/local/bin", 1);
         setpgid(0, 0);
     }
 

apps/taskbar.cpp

@@ -0,0 +1,49 @@
+#include <os/Process.h>
+#include <signal.h>
+#include <sys/wait.h>
+#include <ui/App.h>
+#include <ui/Button.h>
+#include <ui/Container.h>
+#include <ui/Image.h>
+#include <ui/Layout.h>
+
+void sigchld_handler(int)
+{
+    wait(nullptr);
+}
+
+Result<int> luna_main(int argc, char** argv)
+{
+    ui::App app;
+    TRY(app.init(argc, argv));
+
+    signal(SIGCHLD, sigchld_handler);
+
+    ui::Rect screen = app.screen_rect();
+
+    ui::Rect bar = ui::Rect { ui::Point { 0, screen.height - 50 }, screen.width, 50 };
+
+    auto window = TRY(ui::Window::create(bar, false));
+    app.set_main_window(window);
+    window->set_background(ui::GRAY);
+
+    ui::HorizontalLayout layout(ui::AdjustHeight::Yes, ui::AdjustWidth::No);
+    window->set_main_widget(layout);
+
+    ui::Button button({ 0, 0, 50, 50 });
+    layout.add_widget(button);
+
+    ui::Container container({ 0, 0, 50, 50 }, ui::VerticalAlignment::Center, ui::HorizontalAlignment::Center);
+    button.set_widget(container);
+    button.set_action([] {
+        StringView args[] = { "/usr/bin/gclient" };
+        os::Process::spawn("/usr/bin/gclient", Slice<StringView> { args, 1 }, false);
+    });
+
+    auto image = TRY(ui::ImageWidget::load("/usr/share/icons/32x32/start-icon.tga"));
+    container.set_widget(*image);
+
+    window->draw();
+
+    return app.run();
+}

base/etc/init/01-motd

@@ -1,4 +0,0 @@
-Name=motd
-Description=Show the message of the day to the user.
-Command=/usr/bin/cat /etc/motd
-Wait=true

base/etc/init/99-login

@@ -1,4 +1,6 @@
 Name=login
-Description=Start the command-line login program.
+Description=Start the display server.
-Command=/usr/bin/login
+Command=/usr/bin/wind --user=selene
+StandardOutput=/dev/uart0
+StandardError=/dev/uart0
 Restart=true

base/etc/passwd

@@ -1,2 +1,2 @@
-root:toor:0:0:Administrator:/:/bin/sh
+root:toor:0:0:Administrator:/:/usr/bin/sh
-selene:moon:1000:1000:User:/home/selene:/bin/sh
+selene:moon:1000:1000:User:/home/selene:/usr/bin/sh

base/etc/user/00-taskbar

@@ -0,0 +1,4 @@
+Name=taskbar
+Description=Start the taskbar.
+Command=/usr/bin/taskbar
+Restart=true

base/etc/user/01-gclient

@@ -0,0 +1,3 @@
+Name=gclient
+Description=Sample user application.
+Command=/usr/bin/gclient

kernel/src/arch/x86_64/CPU.cpp

@@ -161,7 +161,11 @@ void io_thread()
 static void timer_interrupt(Registers* regs, void*)
 {
     Timer::tick();
-    if (should_invoke_scheduler()) Scheduler::invoke(regs);
+    if (should_invoke_scheduler())
+    {
+        Scheduler::invoke(regs);
+        TextConsole::tick_cursor();
+    }
 }
 
 static void keyboard_interrupt(Registers*, void*)

kernel/src/arch/x86_64/PS2Mouse.cpp

@@ -43,8 +43,8 @@ static void process_mouse_event(u8 data)
     packet.buttons = 0;
 
     u8 flags = g_mouse_packet[0];
-    if (flags & PS2_MOUSE_X_SIGN) packet.xdelta = -packet.xdelta;
+    if (flags & PS2_MOUSE_X_SIGN) packet.xdelta = -(256 - packet.xdelta);
-    if (flags & PS2_MOUSE_Y_SIGN) packet.ydelta = -packet.ydelta;
+    if (flags & PS2_MOUSE_Y_SIGN) packet.ydelta = -(256 - packet.ydelta);
 
     if (flags & PS2_MOUSE_MIDDLE_BTN) packet.buttons |= moon::MouseButton::Middle;
     if (flags & PS2_MOUSE_RIGHT_BTN) packet.buttons |= moon::MouseButton::Right;

kernel/src/fs/devices/ConsoleDevice.cpp

@@ -246,6 +246,9 @@ Result<u64> ConsoleDevice::ioctl(int request, void* arg)
     }
     case TTYSETGFX: {
         s_is_in_graphical_mode = (bool)arg;
+        if (!s_is_in_graphical_mode) TextConsole::enable_cursor();
+        else
+            TextConsole::disable_cursor();
         return 0;
     }
     default: return err(EINVAL);

kernel/src/net/Socket.h

@@ -65,6 +65,12 @@ class Socket : public VFS::FileInode
         m_metadata.nlinks--;
     }
 
+    virtual bool can_accept_connections() const = 0;
+
+    virtual bool can_read_data() const = 0;
+
+    virtual bool peer_disconnected() const = 0;
+
     virtual ~Socket() = default;
 
   protected:

kernel/src/net/UnixSocket.h

@@ -17,6 +17,21 @@ class UnixSocket : public Socket
         return (m_state == Connected || m_state == Reset) && !m_data.size();
     }
 
+    bool can_read_data() const override
+    {
+        return (m_state == Connected || m_state == Reset) && m_data.size();
+    }
+
+    bool can_accept_connections() const override
+    {
+        return !m_listen_queue.is_empty();
+    }
+
+    bool peer_disconnected() const override
+    {
+        return m_state == Reset;
+    }
+
     Result<usize> send(const u8*, usize, int) override;
     Result<usize> recv(u8*, usize, int) const override;
 

kernel/src/sys/exec.cpp

@@ -59,6 +59,8 @@ Result<u64> sys_execve(Registers* regs, SyscallArgs args)
     Vector<String> envp;
     if (args[2]) envp = TRY(copy_string_vector_from_userspace(args[2]));
 
+    String cmdline = TRY(String::join(argv, " "));
+
     if ((calculate_userspace_stack_size(argv) + calculate_userspace_stack_size(envp)) > MAX_ARGV_STACK_SIZE)
         return err(E2BIG);
 
@@ -115,7 +117,7 @@ Result<u64> sys_execve(Registers* regs, SyscallArgs args)
     if (is_setuid) current->auth.euid = current->auth.suid = inode->metadata().uid;
     if (is_setgid) current->auth.egid = current->auth.sgid = inode->metadata().gid;
 
-    current->name = path.chars();
+    current->cmdline = cmdline.chars();
 
     image->apply(current);
 
@@ -159,7 +161,7 @@ Result<u64> sys_fork(Registers* regs, SyscallArgs)
     thread->state = ThreadState::Runnable;
     thread->is_kernel = false;
     thread->fp_data.save();
-    thread->name = current->name;
+    thread->cmdline = current->cmdline;
     thread->auth = current->auth;
     thread->current_directory = current->current_directory;
     thread->current_directory_path = move(current_directory_path);

kernel/src/sys/poll.cpp

@@ -2,6 +2,7 @@
 #include "Pledge.h"
 #include "fs/VFS.h"
 #include "memory/MemoryManager.h"
+#include "net/Socket.h"
 #include "sys/Syscall.h"
 #include "thread/Scheduler.h"
 #include <bits/poll.h>
@@ -47,10 +48,30 @@ Result<u64> sys_poll(Registers*, SyscallArgs args)
             auto& inode = inodes[i];
             if (!inode) continue;
 
-            if (kfds[i].events & POLLIN && !inode->will_block_if_read())
+            if (kfds[i].events & POLLIN)
             {
-                fds_with_events++;
+                if (inode->type() == VFS::InodeType::Socket)
-                kfds[i].revents |= POLLIN;
+                {
+                    auto socket = (Socket*)inode.ptr();
+                    if (socket->can_read_data() || socket->can_accept_connections())
+                    {
+                        fds_with_events++;
+                        kfds[i].revents |= POLLIN;
+                    }
+                    if (socket->peer_disconnected())
+                    {
+                        fds_with_events++;
+                        kfds[i].revents |= POLLHUP;
+                    }
+                }
+                else
+                {
+                    if (!inode->will_block_if_read())
+                    {
+                        fds_with_events++;
+                        kfds[i].revents |= POLLIN;
+                    }
+                }
             }
         }
 

kernel/src/sys/pstat.cpp

@@ -35,7 +35,7 @@ Result<u64> sys_pstat(Registers*, SyscallArgs args)
     set_timespec(proc.ps_time, thread->user_ticks_self + thread->kernel_ticks_self);
     set_timespec(proc.ps_ktime, thread->kernel_ticks_self);
     set_timespec(proc.ps_utime, thread->kernel_ticks_children);
-    strlcpy(proc.ps_name, thread->name.chars(), sizeof(proc.ps_name));
+    strlcpy(proc.ps_name, thread->cmdline.chars(), sizeof(proc.ps_name));
     strlcpy(proc.ps_cwd, thread->current_directory_path.is_empty() ? "/" : thread->current_directory_path.chars(),
             sizeof(proc.ps_cwd));
 

kernel/src/thread/Scheduler.cpp

@@ -27,7 +27,7 @@ namespace Scheduler
         g_idle.state = ThreadState::Idle;
         g_idle.is_kernel = true;
         g_idle.parent = nullptr;
-        g_idle.name = "[idle]";
+        g_idle.cmdline = "[idle]";
         g_idle.active_directory = nullptr;
 
         g_idle.ticks_left = 1;
@@ -96,7 +96,7 @@ namespace Scheduler
 
         thread->stack = thread_stack;
 
-        thread->name = name;
+        thread->cmdline = name;
 
         thread->is_kernel = true;
         thread->active_directory = MMU::kernel_page_directory();
@@ -148,7 +148,7 @@ namespace Scheduler
         thread->is_kernel = false;
         thread->id = 1;
         thread->pgid = 1;
-        thread->name = name;
+        thread->cmdline = name;
         thread->auth = Credentials { .uid = 0, .euid = 0, .suid = 0, .gid = 0, .egid = 0, .sgid = 0 };
 
         Vector<String> args;
@@ -374,7 +374,7 @@ namespace Scheduler
         {
             kdbgln("%p %c [%-20s] %4d, parent = (%-18p,%d), state = %d, ticks: (k:%04zu,u:%04zu), status = "
                    "%d, cwd = %s",
-                   thread, thread->is_kernel ? 'k' : 'u', thread->name.chars(), thread->id, thread->parent,
+                   thread, thread->is_kernel ? 'k' : 'u', thread->cmdline.chars(), thread->id, thread->parent,
                    thread->parent ? thread->parent->id : 0, (int)thread->state, thread->kernel_ticks_self,
                    thread->user_ticks_self, thread->status,
                    thread->current_directory_path.is_empty() ? "/" : thread->current_directory_path.chars());

kernel/src/thread/Thread.h

@@ -123,7 +123,7 @@ struct Thread : public LinkedListNode<Thread>
 
     mode_t umask { 0 };
 
-    StaticString<128> name;
+    StaticString<128> cmdline;
 
     String current_directory_path = {};
     SharedPtr<VFS::Inode> current_directory = {};

kernel/src/video/TextConsole.cpp

@@ -3,6 +3,7 @@
 #include "video/Framebuffer.h"
 #include <luna/CString.h>
 #include <luna/CType.h>
+#include <luna/EscapeSequence.h>
 #include <luna/Format.h>
 #include <luna/Result.h>
 #include <luna/ScopeGuard.h>
@@ -13,20 +14,48 @@ extern const BOOTBOOT bootboot;
 
 #include "video/BuiltinFont.h"
 
-static constexpr u32 BLACK = 0xff000000;
+// Default text color.
 static constexpr u32 WHITE = 0xffffffff;
 
+// xterm color palette.
+static constexpr u32 BLACK = 0xff000000;
+static constexpr u32 RED = 0xffcd0000;
+static constexpr u32 GREEN = 0xff00cd00;
+static constexpr u32 YELLOW = 0xffcdcd00;
+static constexpr u32 BLUE = 0xff0000ee;
+static constexpr u32 MAGENTA = 0xffcd00cd;
+static constexpr u32 CYAN = 0xff00cdcd;
+static constexpr u32 GRAY = 0xffe5e5e5;
+
+static constexpr u32 BRIGHT_BLACK = 0xff7f7f7f;
+static constexpr u32 BRIGHT_RED = 0xffff0000;
+static constexpr u32 BRIGHT_GREEN = 0xff00ff00;
+static constexpr u32 BRIGHT_YELLOW = 0xffffff00;
+static constexpr u32 BRIGHT_BLUE = 0xff5c5cff;
+static constexpr u32 BRIGHT_MAGENTA = 0xffff00ff;
+static constexpr u32 BRIGHT_CYAN = 0xff00ffff;
+static constexpr u32 BRIGHT_GRAY = 0xffffffff;
+
 static u32 g_background_color = BLACK;
 static u32 g_foreground_color = WHITE;
 
 static constexpr u32 FONT_HEIGHT = 16;
 static constexpr u32 FONT_WIDTH = 8;
 
+static bool bold = false;
+
 static u32 g_x_position = 0;
 static u32 g_y_position = 0;
 
+static constexpr int CURSOR_TIMEOUT = 500;
+static int current_cursor_timeout = CURSOR_TIMEOUT;
+static bool cursor_activated = true;
+static bool cursor_enabled = true;
+
 static Utf8StateDecoder utf8_decoder;
 
+static Option<EscapeSequenceParser> escape_sequence_parser;
+
 static void putwchar_at(wchar_t c, u32 x, u32 y)
 {
     const u8* glyph = &font[c * 16];
@@ -58,7 +87,7 @@ static void scroll()
 
 static bool should_scroll()
 {
-    return (g_y_position + FONT_HEIGHT) >= Framebuffer::height();
+    return g_y_position >= Framebuffer::height();
 }
 
 static void next_line()
@@ -82,11 +111,216 @@ static void erase_current_char()
     Framebuffer::rect(g_x_position, g_y_position, FONT_WIDTH, FONT_HEIGHT, BLACK);
 }
 
+static void draw_cursor()
+{
+    Framebuffer::rect(g_x_position, g_y_position, FONT_WIDTH, FONT_HEIGHT, WHITE);
+}
+
 static bool at_end_of_screen()
 {
     return (g_x_position + FONT_WIDTH) > Framebuffer::width();
 }
 
+static bool handle_escape_sequence(wchar_t c)
+{
+    auto rc = escape_sequence_parser->advance(static_cast<u8>(c));
+    if (rc.has_error())
+    {
+        escape_sequence_parser = Option<EscapeSequenceParser> {};
+        return false;
+    }
+    if (!rc.value()) return true;
+    if (!escape_sequence_parser->valid())
+    {
+        escape_sequence_parser = Option<EscapeSequenceParser> {};
+        return false;
+    }
+
+    const auto& params = escape_sequence_parser->parameters();
+    switch (escape_sequence_parser->code())
+    {
+    case EscapeCode::CursorUp: {
+        int lines = params.size() ? params[0] : 1;
+        int pixels = lines * FONT_HEIGHT;
+        if ((u32)pixels > g_y_position) g_y_position = 0;
+        else
+            g_y_position -= pixels;
+    };
+    break;
+    case EscapeCode::CursorDown: {
+        int lines = params.size() ? params[0] : 1;
+        int pixels = lines * FONT_HEIGHT;
+        if (pixels + g_y_position >= Framebuffer::height()) g_y_position = Framebuffer::height() - FONT_HEIGHT;
+        else
+            g_y_position += pixels;
+    };
+    break;
+    case EscapeCode::CursorBack: {
+        int chars = params.size() ? params[0] : 1;
+        int pixels = chars * FONT_WIDTH;
+        if ((u32)pixels > g_x_position) g_x_position = 0;
+        else
+            g_x_position -= pixels;
+    };
+    break;
+    case EscapeCode::CursorForward: {
+        int chars = params.size() ? params[0] : 1;
+        int pixels = chars * FONT_WIDTH;
+        if (pixels + g_x_position >= Framebuffer::width()) g_x_position = Framebuffer::width() - FONT_WIDTH;
+        else
+            g_x_position += pixels;
+    };
+    break;
+    case EscapeCode::CursorNextLine: {
+        int lines = params.size() ? params[0] : 1;
+        int pixels = lines * FONT_HEIGHT;
+        if ((u32)pixels > g_y_position) g_y_position = 0;
+        else
+            g_y_position -= pixels;
+        g_x_position = 0;
+    };
+    break;
+    case EscapeCode::CursorPreviousLine: {
+        int lines = params.size() ? params[0] : 1;
+        int pixels = lines * FONT_HEIGHT;
+        if (pixels + g_y_position >= Framebuffer::height()) g_y_position = Framebuffer::height() - FONT_HEIGHT;
+        else
+            g_y_position += pixels;
+        g_x_position = 0;
+    };
+    break;
+    case EscapeCode::CursorHorizontalAbsolute: {
+        int line = (params.size() ? params[0] : 1) - 1;
+        if (line < 0) break;
+        u32 position = line * FONT_HEIGHT;
+        if (position >= Framebuffer::height()) position = Framebuffer::height() - FONT_HEIGHT;
+        g_y_position = position;
+    };
+    break;
+    case EscapeCode::SetCursorPosition: {
+        int x = (params.size() ? params[0] : 1) - 1;
+        int y = (params.size() > 1 ? params[1] : 1) - 1;
+        if (x < 0 || y < 0) break;
+        u32 x_position = x * FONT_WIDTH;
+        if (x_position >= Framebuffer::width()) x_position = Framebuffer::width() - FONT_HEIGHT;
+        g_x_position = x_position;
+        u32 y_position = y * FONT_HEIGHT;
+        if (y_position >= Framebuffer::height()) y_position = Framebuffer::height() - FONT_HEIGHT;
+        g_y_position = y_position;
+    };
+    break;
+    case EscapeCode::SelectGraphicRendition: {
+        if (!params.size())
+        {
+            g_foreground_color = WHITE;
+            g_background_color = BLACK;
+            bold = false;
+            break;
+        }
+
+        for (usize i = 0; i < params.size(); i++)
+        {
+            int arg = params[i];
+            switch (arg)
+            {
+            case 0: {
+                g_foreground_color = BLACK;
+                g_background_color = WHITE;
+                bold = false;
+                break;
+            }
+            case 1: {
+                bold = true;
+                break;
+            }
+            case 22: {
+                bold = false;
+                break;
+            }
+            case 30: {
+                g_foreground_color = bold ? BRIGHT_BLACK : BLACK;
+                break;
+            }
+            case 31: {
+                g_foreground_color = bold ? BRIGHT_RED : RED;
+                break;
+            }
+            case 32: {
+                g_foreground_color = bold ? BRIGHT_GREEN : GREEN;
+                break;
+            }
+            case 33: {
+                g_foreground_color = bold ? BRIGHT_YELLOW : YELLOW;
+                break;
+            }
+            case 34: {
+                g_foreground_color = bold ? BRIGHT_BLUE : BLUE;
+                break;
+            }
+            case 35: {
+                g_foreground_color = bold ? BRIGHT_MAGENTA : MAGENTA;
+                break;
+            }
+            case 36: {
+                g_foreground_color = bold ? BRIGHT_CYAN : CYAN;
+                break;
+            }
+            case 37: {
+                g_foreground_color = bold ? BRIGHT_GRAY : GRAY;
+                break;
+            }
+            case 39: {
+                g_foreground_color = WHITE;
+                break;
+            }
+            case 40: {
+                g_background_color = bold ? BRIGHT_BLACK : BLACK;
+                break;
+            }
+            case 41: {
+                g_background_color = bold ? BRIGHT_RED : RED;
+                break;
+            }
+            case 42: {
+                g_background_color = bold ? BRIGHT_GREEN : GREEN;
+                break;
+            }
+            case 43: {
+                g_background_color = bold ? BRIGHT_YELLOW : YELLOW;
+                break;
+            }
+            case 44: {
+                g_background_color = bold ? BRIGHT_BLUE : BLUE;
+                break;
+            }
+            case 45: {
+                g_background_color = bold ? BRIGHT_MAGENTA : MAGENTA;
+                break;
+            }
+            case 46: {
+                g_background_color = bold ? BRIGHT_CYAN : CYAN;
+                break;
+            }
+            case 47: {
+                g_background_color = bold ? BRIGHT_GRAY : GRAY;
+                break;
+            }
+            case 49: {
+                g_background_color = BLACK;
+                break;
+            }
+            default: break;
+            }
+        }
+    }
+    break;
+    default: break;
+    }
+
+    escape_sequence_parser = Option<EscapeSequenceParser> {};
+    return true;
+}
+
 namespace TextConsole
 {
     void putwchar(wchar_t c)
@@ -94,6 +328,16 @@ namespace TextConsole
         // Unprintable (not in the built-in font) characters get represented as a box
         if (c > (wchar_t)255) c = (wchar_t)256;
 
+        if (escape_sequence_parser.has_value())
+        {
+            if (handle_escape_sequence(c)) return;
+        }
+
+        // Erase the current cursor.
+        if (cursor_enabled) erase_current_char();
+
+        bool should_draw_cursor = cursor_enabled;
+
         switch (c)
         {
         case L'\n': {
@@ -113,6 +357,13 @@ namespace TextConsole
                 erase_current_char();
             }
             break;
+        case L'\x1b':
+        case L'\x9b':
+        case L'\x90':
+        case L'\x9d':
+            escape_sequence_parser = EscapeSequenceParser { (u8)c };
+            should_draw_cursor = false;
+            break;
         default: {
             if (_iscntrl(c)) return;
             putwchar_at(c, g_x_position, g_y_position);
@@ -125,6 +376,42 @@ namespace TextConsole
             break;
         }
         }
+
+        if (should_draw_cursor)
+        {
+            current_cursor_timeout = CURSOR_TIMEOUT;
+            cursor_activated = true;
+            draw_cursor();
+        }
+    }
+
+    void tick_cursor()
+    {
+        if (!cursor_enabled) return;
+
+        current_cursor_timeout--;
+        if (current_cursor_timeout == 0)
+        {
+            current_cursor_timeout = CURSOR_TIMEOUT;
+            cursor_activated = !cursor_activated;
+
+            if (cursor_activated) draw_cursor();
+            else
+                erase_current_char();
+        }
+    }
+
+    void disable_cursor()
+    {
+        cursor_enabled = false;
+    }
+
+    void enable_cursor()
+    {
+        cursor_enabled = true;
+        cursor_activated = true;
+        current_cursor_timeout = CURSOR_TIMEOUT;
+        draw_cursor();
     }
 
     Result<void> putchar(char c)

kernel/src/video/TextConsole.h

@@ -19,6 +19,9 @@ namespace TextConsole
     Result<void> println(const char* str);
     void wprintln(const wchar_t* str);
     Result<usize> printf(const char* format, ...) _format(1, 2);
+    void tick_cursor();
+    void disable_cursor();
+    void enable_cursor();
 
     u16 rows();
     u16 cols();

libc/CMakeLists.txt

@@ -20,7 +20,6 @@ set(SOURCES
     src/pwd.cpp
     src/grp.cpp
     src/locale.cpp
-    src/scanf.cpp
     src/signal.cpp
     src/termios.cpp
     src/utime.cpp

libc/include/bits/poll.h

@@ -8,6 +8,7 @@
 #define POLLIN (1 << 0)
 #define POLLERR (1 << 1)
 #define POLLNVAL (1 << 2)
+#define POLLHUP (1 << 3)
 
 typedef __u64_t nfds_t;
 

libc/src/scanf.cpp

@@ -1,263 +0,0 @@
-#include <errno.h>
-#include <luna/CType.h>
-#include <luna/NumberParsing.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-
-#define FLAG_DISCARD (1 << 0)
-#define FLAG_ALLOC (1 << 1)
-#define FLAG_WIDTH (1 << 2)
-#define FLAG_LONG (1 << 3)
-#define FLAG_LONG_LONG (1 << 4)
-#define FLAG_SHORT (1 << 5)
-#define FLAG_CHAR (1 << 6)
-
-static int parse_flags(const char** format)
-{
-    int result = 0;
-
-    while (true)
-    {
-        switch (**format)
-        {
-        case '*':
-            result |= FLAG_DISCARD;
-            (*format)++;
-            break;
-        case 'm':
-            result |= FLAG_ALLOC;
-            (*format)++;
-            break;
-        default: return result;
-        }
-    }
-}
-
-static size_t parse_width(const char** format, int& flags)
-{
-    size_t result = 0;
-
-    if (_isdigit(**format))
-    {
-        result = scan_unsigned_integer(format);
-        flags |= FLAG_WIDTH;
-    }
-
-    return result;
-}
-
-static void parse_type(const char** format, int& flags)
-{
-    // FIXME: Support %j (intmax_t/uintmax_t)
-    switch (**format)
-    {
-    case 'h':
-        flags |= FLAG_SHORT;
-        (*format)++;
-        if (**format == 'h')
-        {
-            flags |= FLAG_CHAR;
-            (*format)++;
-        }
-        break;
-    case 'l':
-        flags |= FLAG_LONG;
-        (*format)++;
-        if (**format == 'l')
-        {
-            flags |= FLAG_LONG_LONG;
-            (*format)++;
-        }
-        break;
-    case 't':
-        flags |= (sizeof(ptrdiff_t) == sizeof(long)) ? FLAG_LONG : FLAG_LONG_LONG;
-        (*format)++;
-        break;
-    case 'z':
-        flags |= (sizeof(size_t) == sizeof(long)) ? FLAG_LONG : FLAG_LONG_LONG;
-        (*format)++;
-        break;
-    default: break;
-    }
-}
-
-static void write_parsed_signed_integer(ssize_t value, int flags, va_list ap)
-{
-    if (flags & FLAG_LONG_LONG) *va_arg(ap, signed long long*) = (signed long long)value;
-    else if (flags & FLAG_LONG)
-        *va_arg(ap, signed long*) = (signed long)value;
-    else if (flags & FLAG_SHORT)
-        *va_arg(ap, signed int*) = (signed short)value;
-    else if (flags & FLAG_CHAR)
-        *va_arg(ap, signed int*) = (signed char)value;
-    else
-        *va_arg(ap, signed int*) = (signed int)value;
-}
-
-static void write_parsed_unsigned_integer(size_t value, int flags, va_list ap)
-{
-    if (flags & FLAG_LONG_LONG) *va_arg(ap, unsigned long long*) = (unsigned long long)value;
-    else if (flags & FLAG_LONG)
-        *va_arg(ap, unsigned long*) = (unsigned long)value;
-    else if (flags & FLAG_SHORT)
-        *va_arg(ap, unsigned int*) = (unsigned short)value;
-    else if (flags & FLAG_CHAR)
-        *va_arg(ap, unsigned int*) = (unsigned char)value;
-    else
-        *va_arg(ap, unsigned int*) = (unsigned int)value;
-}
-
-#define WHITESPACE_CHARACTERS " \t\f\r\n\v"
-
-static void skip_whitespace(const char** str)
-{
-    *str += strspn(*str, WHITESPACE_CHARACTERS);
-}
-
-extern "C"
-{
-    int vsscanf(const char* str, const char* format, va_list ap)
-    {
-        int parsed = 0;
-        const char* s = str; // Keep a pointer to the beginning of the string for %n
-
-        if (*str == 0) return EOF;
-
-        while (*format)
-        {
-            if (*format != '%')
-            {
-            normal:
-                if (!_isspace(*format))
-                {
-                    if (*str != *format) return parsed;
-                    str++;
-                    format++;
-                    if (*str == 0) return parsed;
-                    continue;
-                }
-
-                skip_whitespace(&format);
-                skip_whitespace(&str);
-                if (*str == 0) return parsed;
-                continue;
-            }
-            else
-            {
-                format++;
-                if (*format == '%')
-                {
-                    skip_whitespace(&str);
-                    goto normal;
-                }
-
-                int flags = parse_flags(&format);
-                size_t width = parse_width(&format, flags);
-                parse_type(&format, flags);
-                char specifier = *format++;
-                if (!specifier) return parsed;
-
-                switch (specifier)
-                {
-                case 's': {
-                    skip_whitespace(&str);
-                    size_t chars = strcspn(str, WHITESPACE_CHARACTERS);
-                    if (!chars) return parsed;
-                    if ((flags & FLAG_WIDTH) && chars > width) chars = width;
-                    if (!(flags & FLAG_DISCARD))
-                    {
-                        char* ptr;
-                        if (flags & FLAG_ALLOC)
-                        {
-                            ptr = (char*)malloc(chars + 1);
-                            if (!ptr) return parsed;
-                            *va_arg(ap, char**) = ptr;
-                        }
-                        else
-                            ptr = va_arg(ap, char*);
-                        memcpy(ptr, str, chars);
-                        ptr[chars] = 0;
-                    }
-                    str += chars;
-                    parsed++;
-                    break;
-                }
-                case 'c': {
-                    if (strlen(str) < width) return parsed;
-                    if (!(flags & FLAG_WIDTH)) width = 1;
-                    if (!(flags & FLAG_DISCARD))
-                    {
-                        char* ptr;
-                        if (flags & FLAG_ALLOC)
-                        {
-                            ptr = (char*)malloc(width);
-                            if (!ptr) return parsed;
-                            *va_arg(ap, char**) = ptr;
-                        }
-                        else
-                            ptr = va_arg(ap, char*);
-                        memcpy(ptr, str, width);
-                    }
-                    str += width;
-                    parsed++;
-                    break;
-                }
-                case 'd': {
-                    skip_whitespace(&str);
-                    ssize_t value = scan_signed_integer(&str, 10);
-                    if (!(flags & FLAG_DISCARD)) write_parsed_signed_integer(value, flags, ap);
-                    parsed++;
-                    break;
-                }
-                case 'i': {
-                    skip_whitespace(&str);
-                    ssize_t value = scan_signed_integer(&str, 0);
-                    if (!(flags & FLAG_DISCARD)) write_parsed_signed_integer(value, flags, ap);
-                    parsed++;
-                    break;
-                }
-                case 'o': {
-                    skip_whitespace(&str);
-                    size_t value = scan_unsigned_integer(&str, 8);
-                    if (!(flags & FLAG_DISCARD)) write_parsed_unsigned_integer(value, flags, ap);
-                    parsed++;
-                    break;
-                }
-                case 'u': {
-                    skip_whitespace(&str);
-                    size_t value = scan_unsigned_integer(&str, 10);
-                    if (!(flags & FLAG_DISCARD)) write_parsed_unsigned_integer(value, flags, ap);
-                    parsed++;
-                    break;
-                }
-                case 'X':
-                case 'x': {
-                    skip_whitespace(&str);
-                    size_t value = scan_unsigned_integer(&str, 16);
-                    if (!(flags & FLAG_DISCARD)) write_parsed_unsigned_integer(value, flags, ap);
-                    parsed++;
-                    break;
-                }
-                case 'p': {
-                    skip_whitespace(&str);
-                    size_t value = scan_unsigned_integer(&str, 16);
-                    if (!(flags & FLAG_DISCARD)) *va_arg(ap, void**) = (void*)value;
-                    parsed++;
-                    break;
-                }
-                case 'n': {
-                    if (!(flags & FLAG_DISCARD)) *va_arg(ap, int*) = (int)(str - s);
-                    break;
-                }
-                default: {
-                    fprintf(stderr, "vsscanf: unknown conversion specifier: %%%c\n", specifier);
-                    return parsed;
-                }
-                }
-            }
-        }
-
-        return parsed;
-    }
-}

libc/src/stdio.cpp

@@ -2,6 +2,7 @@
 #include <fcntl.h>
 #include <luna/Common.h>
 #include <luna/Format.h>
+#include <luna/Scanf.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -618,12 +619,17 @@ extern "C"
         return rc;
     }
 
+    int vsscanf(const char* str, const char* format, va_list ap)
+    {
+        return scanf_impl(str, format, ap);
+    }
+
     int sscanf(const char* str, const char* format, ...)
     {
         va_list ap;
         va_start(ap, format);
 
-        int rc = vsscanf(str, format, ap);
+        int rc = scanf_impl(str, format, ap);
 
         va_end(ap);
 
@@ -634,7 +640,7 @@ extern "C"
     {
         char buf[BUFSIZ];
         if (!fgets(buf, sizeof(buf), stream)) return EOF;
-        return vsscanf(buf, format, ap);
+        return scanf_impl(buf, format, ap);
     }
 
     int fscanf(FILE* stream, const char* format, ...)

libc/src/unistd.cpp

@@ -23,7 +23,7 @@ static Result<int> try_execvpe(const char* name, char* const* argv, char* const*
     if (strchr(name, '/')) return execve(name, argv, envp);
 
     char* path = getenv("PATH");
-    if (!path) path = const_cast<char*>("/bin:/sbin");
+    if (!path) path = const_cast<char*>("/usr/bin:/usr/local/bin");
 
     Vector<String> paths = TRY(StringView { path }.split(":"));
 

libluna/CMakeLists.txt

@@ -5,6 +5,7 @@ file(GLOB HEADERS include/luna/*.h)
 set(FREESTANDING_SOURCES
     ${HEADERS}
     src/CRC32.cpp
+    src/EscapeSequence.cpp
     src/Format.cpp
     src/Sort.cpp
     src/NumberParsing.cpp
@@ -14,6 +15,7 @@ set(FREESTANDING_SOURCES
     src/SystemError.cpp
     src/Bitmap.cpp
     src/Buffer.cpp
+    src/Scanf.cpp
     src/Stack.cpp
     src/String.cpp
     src/StringBuilder.cpp

libluna/include/luna/Buffer.h

@@ -23,6 +23,9 @@ class Buffer
     Buffer(Buffer&& other);
     Buffer(const Buffer& other) = delete; // For now.
 
+    Buffer& operator=(Buffer&&);
+    Buffer& operator=(const Buffer&) = delete;
+
     /**
      * @brief Create a Buffer object, allocating a specific amount of memory for it.
      *

libluna/include/luna/CircularQueue.h

@@ -37,7 +37,7 @@ template <typename T, usize Size> class CircularQueue
      * @return true The queue is empty.
      * @return false The queue is not empty.
      */
-    bool is_empty()
+    bool is_empty() const
     {
         return m_tail.load() == m_head.load();
     }
@@ -124,7 +124,7 @@ template <typename T> class DynamicCircularQueue
      * @return true The queue is empty.
      * @return false The queue is not empty.
      */
-    bool is_empty()
+    bool is_empty() const
     {
         return m_tail.load() == m_head.load();
     }

libluna/include/luna/EscapeSequence.h

@@ -0,0 +1,67 @@
+/**
+ * @file EscapeSequence.h
+ * @author apio (cloudapio.eu)
+ * @brief ANSI escape sequence parsing.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <luna/Vector.h>
+
+enum class EscapeCode
+{
+    SaveCursor,
+    RestoreCursor,
+    CursorUp,
+    CursorDown,
+    CursorForward,
+    CursorBack,
+    CursorNextLine,
+    CursorPreviousLine,
+    CursorHorizontalAbsolute,
+    SetCursorPosition,
+    SelectGraphicRendition,
+};
+
+class EscapeSequenceParser
+{
+  public:
+    EscapeSequenceParser(u8 begin);
+
+    Result<bool> advance(u8 byte);
+
+    bool valid() const
+    {
+        return m_valid;
+    }
+
+    const Vector<int>& parameters() const
+    {
+        return m_parameters;
+    }
+
+    EscapeCode code() const
+    {
+        return m_escape_code;
+    }
+
+  private:
+    enum class SequenceType
+    {
+        ESC,
+        CSI,
+        DCS,
+        OSC,
+    };
+
+    Vector<u8> m_parameter;
+    Vector<int> m_parameters;
+
+    SequenceType m_sequence_type;
+    bool m_parsing_parameter { false };
+    bool m_valid { false };
+
+    EscapeCode m_escape_code;
+};

libluna/include/luna/Scanf.h

@@ -0,0 +1,21 @@
+/**
+ * @file Scanf.h
+ * @author apio (cloudapio.eu)
+ * @brief Scanf implementation.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <stdarg.h>
+
+/**
+ * @brief scanf() implementation.
+ *
+ * @param str The string to read input from.
+ * @param format The format string.
+ * @param ap The variadic argument list.
+ * @return int The number of arguments read, or -1 if the string was empty.
+ */
+int scanf_impl(const char* str, const char* format, va_list ap);

libluna/src/Buffer.cpp

@@ -24,6 +24,16 @@ Buffer::Buffer(Buffer&& other) : m_data(other.data()), m_size(other.size())
     other.m_data = nullptr;
 }
 
+Buffer& Buffer::operator=(Buffer&& other)
+{
+    if (&other == this) return *this;
+    if (m_data) free_impl(m_data);
+    m_data = other.m_data;
+    m_size = other.m_size;
+    other.m_data = nullptr;
+    return *this;
+}
+
 Buffer::~Buffer()
 {
     if (m_data) free_impl(m_data);

libluna/src/EscapeSequence.cpp

@@ -0,0 +1,146 @@
+/**
+ * @file EscapeSequence.cpp
+ * @author apio (cloudapio.eu)
+ * @brief ANSI escape sequence parsing.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <luna/CType.h>
+#include <luna/Check.h>
+#include <luna/EscapeSequence.h>
+#include <luna/NumberParsing.h>
+
+EscapeSequenceParser::EscapeSequenceParser(u8 begin)
+{
+    switch (begin)
+    {
+    case 0x1b: m_sequence_type = SequenceType::ESC; break;
+    case 0x9b: m_sequence_type = SequenceType::CSI; break;
+    case 0x90: m_sequence_type = SequenceType::DCS; break;
+    case 0x9d: m_sequence_type = SequenceType::OSC; break;
+    default: fail("Unrecognized escape sequence type");
+    }
+}
+
+Result<bool> EscapeSequenceParser::advance(u8 byte)
+{
+    switch (m_sequence_type)
+    {
+    case SequenceType::ESC: {
+        switch (byte)
+        {
+        case '[': {
+            m_sequence_type = SequenceType::CSI;
+            return false;
+        };
+        case 'P': {
+            m_sequence_type = SequenceType::DCS;
+            return false;
+        };
+        case ']': {
+            m_sequence_type = SequenceType::OSC;
+            return false;
+        };
+        case '7': {
+            m_escape_code = EscapeCode::SaveCursor;
+            m_valid = true;
+            return true;
+        };
+        case '8': {
+            m_escape_code = EscapeCode::RestoreCursor;
+            m_valid = true;
+            return true;
+        };
+        default: {
+            m_valid = false;
+            return true;
+        }
+        }
+    };
+    break;
+    case SequenceType::CSI: {
+        if (_isdigit(byte))
+        {
+            m_parsing_parameter = true;
+            TRY(m_parameter.try_append(byte));
+            return false;
+        }
+
+        if (!m_parsing_parameter && byte == ';')
+        {
+            TRY(m_parameters.try_append(0));
+            return false;
+        }
+
+        if (m_parsing_parameter)
+        {
+            TRY(m_parameter.try_append(0));
+            int value = static_cast<int>(parse_unsigned_integer((const char*)m_parameter.data(), nullptr, 10));
+            m_parameter.clear();
+            TRY(m_parameters.try_append(value));
+        }
+
+        switch (byte)
+        {
+        case 'A': {
+            m_escape_code = EscapeCode::CursorUp;
+            m_valid = true;
+            return true;
+        };
+        case 'B': {
+            m_escape_code = EscapeCode::CursorDown;
+            m_valid = true;
+            return true;
+        };
+        case 'C': {
+            m_escape_code = EscapeCode::CursorForward;
+            m_valid = true;
+            return true;
+        };
+        case 'D': {
+            m_escape_code = EscapeCode::CursorBack;
+            m_valid = true;
+            return true;
+        };
+        case 'E': {
+            m_escape_code = EscapeCode::CursorNextLine;
+            m_valid = true;
+            return true;
+        };
+        case 'F': {
+            m_escape_code = EscapeCode::CursorPreviousLine;
+            m_valid = true;
+            return true;
+        };
+        case 'G': {
+            m_escape_code = EscapeCode::CursorHorizontalAbsolute;
+            m_valid = true;
+            return true;
+        };
+        case 'H': {
+            m_escape_code = EscapeCode::SetCursorPosition;
+            m_valid = true;
+            return true;
+        };
+        case 'm': {
+            m_escape_code = EscapeCode::SelectGraphicRendition;
+            m_valid = true;
+            return true;
+        };
+        case ';': {
+            return false;
+        };
+        default: {
+            m_valid = false;
+            return true;
+        }
+        }
+    };
+    break;
+    case SequenceType::DCS: todo();
+    case SequenceType::OSC: todo();
+    default: todo();
+    }
+}

libluna/src/Scanf.cpp

@@ -0,0 +1,270 @@
+/**
+ * @file Scanf.cpp
+ * @author apio (cloudapio.eu)
+ * @brief Scanf implementation.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <luna/CString.h>
+#include <luna/CType.h>
+#include <luna/DebugLog.h>
+#include <luna/Heap.h>
+#include <luna/NumberParsing.h>
+#include <luna/SystemError.h>
+#include <sys/types.h>
+
+#define FLAG_DISCARD (1 << 0)
+#define FLAG_ALLOC (1 << 1)
+#define FLAG_WIDTH (1 << 2)
+#define FLAG_LONG (1 << 3)
+#define FLAG_LONG_LONG (1 << 4)
+#define FLAG_SHORT (1 << 5)
+#define FLAG_CHAR (1 << 6)
+
+static int parse_flags(const char** format)
+{
+    int result = 0;
+
+    while (true)
+    {
+        switch (**format)
+        {
+        case '*':
+            result |= FLAG_DISCARD;
+            (*format)++;
+            break;
+        case 'm':
+            result |= FLAG_ALLOC;
+            (*format)++;
+            break;
+        default: return result;
+        }
+    }
+}
+
+static size_t parse_width(const char** format, int& flags)
+{
+    size_t result = 0;
+
+    if (_isdigit(**format))
+    {
+        result = scan_unsigned_integer(format);
+        flags |= FLAG_WIDTH;
+    }
+
+    return result;
+}
+
+static void parse_type(const char** format, int& flags)
+{
+    // FIXME: Support %j (intmax_t/uintmax_t)
+    switch (**format)
+    {
+    case 'h':
+        flags |= FLAG_SHORT;
+        (*format)++;
+        if (**format == 'h')
+        {
+            flags |= FLAG_CHAR;
+            (*format)++;
+        }
+        break;
+    case 'l':
+        flags |= FLAG_LONG;
+        (*format)++;
+        if (**format == 'l')
+        {
+            flags |= FLAG_LONG_LONG;
+            (*format)++;
+        }
+        break;
+    case 't':
+        flags |= (sizeof(ptrdiff_t) == sizeof(long)) ? FLAG_LONG : FLAG_LONG_LONG;
+        (*format)++;
+        break;
+    case 'z':
+        flags |= (sizeof(size_t) == sizeof(long)) ? FLAG_LONG : FLAG_LONG_LONG;
+        (*format)++;
+        break;
+    default: break;
+    }
+}
+
+static void write_parsed_signed_integer(ssize_t value, int flags, va_list ap)
+{
+    if (flags & FLAG_LONG_LONG) *va_arg(ap, signed long long*) = (signed long long)value;
+    else if (flags & FLAG_LONG)
+        *va_arg(ap, signed long*) = (signed long)value;
+    else if (flags & FLAG_SHORT)
+        *va_arg(ap, signed int*) = (signed short)value;
+    else if (flags & FLAG_CHAR)
+        *va_arg(ap, signed int*) = (signed char)value;
+    else
+        *va_arg(ap, signed int*) = (signed int)value;
+}
+
+static void write_parsed_unsigned_integer(size_t value, int flags, va_list ap)
+{
+    if (flags & FLAG_LONG_LONG) *va_arg(ap, unsigned long long*) = (unsigned long long)value;
+    else if (flags & FLAG_LONG)
+        *va_arg(ap, unsigned long*) = (unsigned long)value;
+    else if (flags & FLAG_SHORT)
+        *va_arg(ap, unsigned int*) = (unsigned short)value;
+    else if (flags & FLAG_CHAR)
+        *va_arg(ap, unsigned int*) = (unsigned char)value;
+    else
+        *va_arg(ap, unsigned int*) = (unsigned int)value;
+}
+
+#define WHITESPACE_CHARACTERS " \t\f\r\n\v"
+
+static void skip_whitespace(const char** str)
+{
+    *str += strspn(*str, WHITESPACE_CHARACTERS);
+}
+
+int scanf_impl(const char* str, const char* format, va_list ap)
+{
+    int parsed = 0;
+    const char* s = str; // Keep a pointer to the beginning of the string for %n
+
+    if (*str == 0) return -1;
+
+    while (*format)
+    {
+        if (*format != '%')
+        {
+        normal:
+            if (!_isspace(*format))
+            {
+                if (*str != *format) return parsed;
+                str++;
+                format++;
+                if (*str == 0) return parsed;
+                continue;
+            }
+
+            skip_whitespace(&format);
+            skip_whitespace(&str);
+            if (*str == 0) return parsed;
+            continue;
+        }
+        else
+        {
+            format++;
+            if (*format == '%')
+            {
+                skip_whitespace(&str);
+                goto normal;
+            }
+
+            int flags = parse_flags(&format);
+            size_t width = parse_width(&format, flags);
+            parse_type(&format, flags);
+            char specifier = *format++;
+            if (!specifier) return parsed;
+
+            switch (specifier)
+            {
+            case 's': {
+                skip_whitespace(&str);
+                size_t chars = strcspn(str, WHITESPACE_CHARACTERS);
+                if (!chars) return parsed;
+                if ((flags & FLAG_WIDTH) && chars > width) chars = width;
+                if (!(flags & FLAG_DISCARD))
+                {
+                    char* ptr;
+                    if (flags & FLAG_ALLOC)
+                    {
+                        ptr = (char*)malloc_impl(chars + 1).value_or(nullptr);
+                        if (!ptr) return parsed;
+                        *va_arg(ap, char**) = ptr;
+                    }
+                    else
+                        ptr = va_arg(ap, char*);
+                    memcpy(ptr, str, chars);
+                    ptr[chars] = 0;
+                }
+                str += chars;
+                parsed++;
+                break;
+            }
+            case 'c': {
+                if (strlen(str) < width) return parsed;
+                if (!(flags & FLAG_WIDTH)) width = 1;
+                if (!(flags & FLAG_DISCARD))
+                {
+                    char* ptr;
+                    if (flags & FLAG_ALLOC)
+                    {
+                        ptr = (char*)malloc_impl(width).value_or(nullptr);
+                        if (!ptr) return parsed;
+                        *va_arg(ap, char**) = ptr;
+                    }
+                    else
+                        ptr = va_arg(ap, char*);
+                    memcpy(ptr, str, width);
+                }
+                str += width;
+                parsed++;
+                break;
+            }
+            case 'd': {
+                skip_whitespace(&str);
+                ssize_t value = scan_signed_integer(&str, 10);
+                if (!(flags & FLAG_DISCARD)) write_parsed_signed_integer(value, flags, ap);
+                parsed++;
+                break;
+            }
+            case 'i': {
+                skip_whitespace(&str);
+                ssize_t value = scan_signed_integer(&str, 0);
+                if (!(flags & FLAG_DISCARD)) write_parsed_signed_integer(value, flags, ap);
+                parsed++;
+                break;
+            }
+            case 'o': {
+                skip_whitespace(&str);
+                size_t value = scan_unsigned_integer(&str, 8);
+                if (!(flags & FLAG_DISCARD)) write_parsed_unsigned_integer(value, flags, ap);
+                parsed++;
+                break;
+            }
+            case 'u': {
+                skip_whitespace(&str);
+                size_t value = scan_unsigned_integer(&str, 10);
+                if (!(flags & FLAG_DISCARD)) write_parsed_unsigned_integer(value, flags, ap);
+                parsed++;
+                break;
+            }
+            case 'X':
+            case 'x': {
+                skip_whitespace(&str);
+                size_t value = scan_unsigned_integer(&str, 16);
+                if (!(flags & FLAG_DISCARD)) write_parsed_unsigned_integer(value, flags, ap);
+                parsed++;
+                break;
+            }
+            case 'p': {
+                skip_whitespace(&str);
+                size_t value = scan_unsigned_integer(&str, 16);
+                if (!(flags & FLAG_DISCARD)) *va_arg(ap, void**) = (void*)value;
+                parsed++;
+                break;
+            }
+            case 'n': {
+                if (!(flags & FLAG_DISCARD)) *va_arg(ap, int*) = (int)(str - s);
+                break;
+            }
+            default: {
+                dbgln("vsscanf: unknown conversion specifier: %%%c\n", specifier);
+                return parsed;
+            }
+            }
+        }
+    }
+
+    return parsed;
+}

libos/CMakeLists.txt

@@ -14,6 +14,10 @@ set(SOURCES
     src/Mode.cpp
     src/Prompt.cpp
     src/Security.cpp
+    src/LocalServer.cpp
+    src/LocalClient.cpp
+    src/IPC.cpp
+    src/SharedMemory.cpp
 )
 
 add_library(os ${SOURCES})

libos/include/os/FileSystem.h

@@ -68,15 +68,6 @@ namespace os
          */
         Result<void> remove(const Path& path);
 
-        /**
-         * @brief Remove a directory tree from the file system recursively, deleting subfiles and subdirectories as
-         * well.
-         *
-         * @param path The path to remove.
-         * @return Result<void> Whether the operation succeeded.
-         */
-        Result<void> remove_tree(const Path& path);
-
         /**
          * @brief Read the target of a symbolic link.
          *

libos/include/os/IPC.h

@@ -0,0 +1,157 @@
+/**
+ * @file IPC.h
+ * @author apio (cloudapio.eu)
+ * @brief Inter-process communication primitives.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <os/LocalClient.h>
+#include <os/LocalServer.h>
+
+#define IPC_ENUM_SERVER(name) __##name##_SERVER_ERROR = 0
+#define IPC_ENUM_CLIENT(name) __##name##_CLIENT_ERROR = 0
+
+/**
+ * @brief Called to handle IPC events (client-side).
+ *
+ * @param conn The connection object being used.
+ * @param id The ID of the message.
+ * @return Result<void> Whether the operation succeded.
+ */
+extern Result<void> handle_ipc_client_event(os::LocalClient& conn, u8 id);
+
+/**
+ * @brief Called to handle IPC events (server-side).
+ *
+ * @param conn The connection object being used.
+ * @param id The ID of the message.
+ * @return Result<void> Whether the operation succeded.
+ */
+extern Result<void> handle_ipc_server_event(os::LocalServer::Client& conn, u8 id);
+
+namespace os
+{
+    namespace IPC
+    {
+        static constexpr usize IPC_STRING_LENGTH = 256;
+
+#define IPC_STRING(name) char name[os::IPC::IPC_STRING_LENGTH];
+#define COPY_IPC_STRING(name)                                                                                          \
+    TRY(String::from_string_view(StringView::from_fixed_size_cstring(name, os::IPC::IPC_STRING_LENGTH)))
+#define SET_IPC_STRING(name, value) strlcpy(name, value, os::IPC::IPC_STRING_LENGTH)
+
+        /**
+         * @brief Sends an IPC message without waiting for a reply.
+         *
+         * @tparam Client The type of the client interface being used to communicate.
+         * @tparam T The type of the message.
+         * @param client The connection object being used to communicate.
+         * @param message The IPC message.
+         * @return Result<void> Whether the operation succeded.
+         */
+        template <typename Client, typename T> Result<void> send_async(Client& client, const T& message)
+        {
+            u8 id = T::ID;
+            TRY(client.send_typed(id));
+            TRY(client.send_typed(message));
+            return {};
+        }
+
+        /**
+         * @brief Sends an error result to the IPC connection, indicating that an operation could not be performed.
+         *
+         * @tparam Client The type of the client interface being used to communicate.
+         * @param client The connection object being used to communicate.
+         * @param error The error code.
+         * @return Result<void> Whether the operation succeded.
+         */
+        template <typename Client> Result<void> send_error(Client& client, int error)
+        {
+            u8 id = 0;
+            TRY(client.send_typed(id));
+            TRY(client.send_typed(error));
+            return {};
+        }
+
+        /**
+         * @brief Sends an IPC message and waits for a reply (client-only).
+         *
+         * @tparam ResponseType The type of the response.
+         * @tparam T The type of the message.
+         * @param client The connection object being used to communicate.
+         * @param message The IPC message.
+         * @param handler The function used to handle messages that do not match the reply.
+         * @return Result<ResponseType> An error, or the response.
+         */
+        template <typename ResponseType, typename T>
+        Result<ResponseType> send_sync(os::LocalClient& client, const T& message,
+                                       decltype(handle_ipc_client_event) handler = handle_ipc_client_event)
+        {
+            u8 id = T::ID;
+            TRY(client.send_typed(id));
+            TRY(client.send_typed(message));
+
+            // We allow receiving 5 messages of different types, but if those have passed and we still don't have a
+            // reply, fail with ENOMSG.
+            int max_other_messages = 5;
+
+            while (max_other_messages)
+            {
+                u8 response_id;
+                auto rc = client.recv_typed(response_id);
+                if (rc.has_error() && (rc.error() == EAGAIN || rc.error() == EINTR)) continue;
+
+                if (response_id == 0) // Error result
+                {
+                    while (1)
+                    {
+                        int code;
+                        rc = client.recv_typed(code);
+                        if (rc.has_error() && (rc.error() == EAGAIN || rc.error() == EINTR)) continue;
+                        return err(code);
+                    }
+                }
+
+                if (response_id != ResponseType::ID)
+                {
+                    TRY(handler(client, response_id));
+                    max_other_messages--;
+                    continue;
+                }
+
+                while (1)
+                {
+                    ResponseType response;
+                    rc = client.recv_typed(response);
+                    if (rc.has_error() && (rc.error() == EAGAIN || rc.error() == EINTR)) continue;
+                    return response;
+                }
+            }
+
+            return err(ENOMSG);
+        }
+
+        /**
+         * @brief Check for new IPC messages on a connection and handle them appropriately.
+         *
+         * @param client The client connection.
+         * @param handler The function used to handle messages.
+         * @return Result<void> Whether the operation succeded.
+         */
+        Result<void> check_for_messages(os::LocalClient& client,
+                                        decltype(handle_ipc_client_event) handler = handle_ipc_client_event);
+
+        /**
+         * @brief Check for new IPC messages on a connection and handle them appropriately.
+         *
+         * @param server The server connection.
+         * @param handler The function used to handle messages.
+         * @return Result<void> Whether the operation succeded.
+         */
+        Result<void> check_for_messages(os::LocalServer::Client& server,
+                                        decltype(handle_ipc_server_event) handler = handle_ipc_server_event);
+    }
+}

libos/include/os/LocalClient.h

@@ -0,0 +1,99 @@
+/**
+ * @file LocalClient.h
+ * @author apio (cloudapio.eu)
+ * @brief UNIX local domain client class.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <luna/OwnedPtr.h>
+#include <luna/StringView.h>
+
+namespace os
+{
+    /**
+     * @brief A client used to connect to a local server socket.
+     */
+    class LocalClient
+    {
+      public:
+        /**
+         * @brief Create a new client object and connect it to a local server.
+         *
+         * @param path The path of the server socket to connect to.
+         * @param blocking Whether the client should block if no data is available and recv() is called.
+         * @return Result<OwnedPtr<LocalClient>> An error, or a new client object.
+         */
+        static Result<OwnedPtr<LocalClient>> connect(StringView path, bool blocking);
+
+        /**
+         * @brief Return the underlying socket file descriptor used by this object.
+         *
+         * @return int The file descriptor.
+         */
+        int fd() const
+        {
+            return m_fd;
+        }
+
+        /**
+         * @brief Read arbitrary data from the server. The call will block if there is no data and this object has not
+         * been created as non-blocking.
+         *
+         * @param buf The buffer to read data into.
+         * @param length The maximum amount of bytes to read.
+         * @return Result<usize> An error, or the number of bytes read.
+         */
+        Result<usize> recv(u8* buf, usize length);
+
+        /**
+         * @brief Read an object from the server. The call will block if there is no data and this object has not been
+         * created as non-blocking.
+         *
+         * @tparam T The type of the object.
+         * @param out A reference to the object to read data into.
+         * @return Result<void> Whether the operation succeded.
+         */
+        template <typename T> Result<void> recv_typed(T& out)
+        {
+            TRY(recv((u8*)&out, sizeof(T)));
+            return {};
+        }
+
+        /**
+         * @brief Send arbitrary data to the server.
+         *
+         * @param buf The buffer to send data from.
+         * @param length The amount of bytes to send.
+         * @return Result<usize> An error, or the number of bytes actually sent.
+         */
+        Result<usize> send(const u8* buf, usize length);
+
+        /**
+         * @brief Send an object to the server.
+         *
+         * @tparam T The type of the object.
+         * @param out A reference to the object to send data from.
+         * @return Result<void> Whether the operation succeded.
+         */
+        template <typename T> Result<void> send_typed(const T& out)
+        {
+            TRY(send((const u8*)&out, sizeof(T)));
+            return {};
+        }
+
+        /**
+         * @brief Disconnect from the attached server.
+         *
+         * This will make any further reads on this connection return ECONNRESET, and will make this object invalid.
+         */
+        void disconnect();
+
+        ~LocalClient();
+
+      private:
+        int m_fd;
+    };
+}

libos/include/os/LocalServer.h

@@ -0,0 +1,142 @@
+/**
+ * @file LocalServer.h
+ * @author apio (cloudapio.eu)
+ * @brief UNIX local domain server class.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <luna/OwnedPtr.h>
+#include <luna/Result.h>
+#include <luna/StringView.h>
+
+namespace os
+{
+    /**
+     * @brief A local domain server, used to communicate between processes on the same machine.
+     */
+    class LocalServer
+    {
+      public:
+        /**
+         * @brief Create a new server object and bind it to a local address.
+         *
+         * @param path The path to use for the server socket.
+         * @param blocking Whether the server should block if no connections are available when calling accept().
+         * @return Result<OwnedPtr<LocalServer>> An error, or a new server object.
+         */
+        static Result<OwnedPtr<LocalServer>> create(StringView path, bool blocking);
+
+        /**
+         * @brief Activate the server and start listening for connections.
+         *
+         * @param backlog The number of unaccepted connections to keep.
+         * @return Result<void> Whether the operation succeded.
+         */
+        Result<void> listen(int backlog);
+
+        /**
+         * @brief Return the underlying socket file descriptor used by this object.
+         *
+         * @return int The file descriptor.
+         */
+        int fd() const
+        {
+            return m_fd;
+        }
+
+        /**
+         * @brief An interface to communicate with clients connected to a local server.
+         */
+        class Client
+        {
+          public:
+            /**
+             * @brief Read arbitrary data from the client. The call will block if there is no data and the parent server
+             * object has not been created as non-blocking.
+             *
+             * @param buf The buffer to read data into.
+             * @param length The maximum amount of bytes to read.
+             * @return Result<usize> An error, or the number of bytes read.
+             */
+            Result<usize> recv(u8* buf, usize length);
+
+            /**
+             * @brief Read an object from the client. The call will block if there is no data and the parent server
+             * object has not been created as non-blocking.
+             *
+             * @tparam T The type of the object.
+             * @param out A reference to the object to read data into.
+             * @return Result<void> Whether the operation succeded.
+             */
+            template <typename T> Result<void> recv_typed(T& out)
+            {
+                TRY(recv((u8*)&out, sizeof(T)));
+                return {};
+            }
+
+            /**
+             * @brief Send arbitrary data to the client.
+             *
+             * @param buf The buffer to send data from.
+             * @param length The amount of bytes to send.
+             * @return Result<usize> An error, or the number of bytes actually sent.
+             */
+            Result<usize> send(const u8* buf, usize length);
+
+            /**
+             * @brief Send an object to the client.
+             *
+             * @tparam T The type of the object.
+             * @param out A reference to the object to send data from.
+             * @return Result<void> Whether the operation succeded.
+             */
+            template <typename T> Result<void> send_typed(const T& out)
+            {
+                TRY(send((const u8*)&out, sizeof(T)));
+                return {};
+            }
+
+            /**
+             * @brief Disconnect from the attached client.
+             *
+             * This will make any further reads on the client return ECONNRESET, and will make this object invalid.
+             */
+            void disconnect();
+
+            /**
+             * @brief Return the underlying socket file descriptor used by this object.
+             *
+             * @return int The file descriptor.
+             */
+            int fd() const
+            {
+                return m_fd;
+            }
+
+            Client(Client&& other);
+            Client(int fd);
+            ~Client();
+
+          private:
+            int m_fd;
+        };
+
+        /**
+         * @brief Accept a new incoming connection and return a handle to it. If there are no incoming connections,
+         * accept() either blocks until there is one (if the object was created with blocking=true), or returns EAGAIN
+         * (if the object was created with blocking=false).
+         *
+         * @return Result<Client> An error, or a handle to the new connection.
+         */
+        Result<Client> accept();
+
+        ~LocalServer();
+
+      private:
+        int m_fd;
+        bool m_blocking;
+    };
+}

libos/include/os/SharedMemory.h

@@ -0,0 +1,36 @@
+/**
+ * @file SharedMemory.h
+ * @author apio (cloudapio.eu)
+ * @brief Create and map areas of memory shared between processes.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <luna/Result.h>
+#include <luna/StringView.h>
+
+namespace os
+{
+    namespace SharedMemory
+    {
+        /**
+         * @brief Create a new shared memory region and map it.
+         *
+         * @param path The shared memory path to use. It must be of the same format as shm_open().
+         * @param size The amount of bytes to use for the shared memory region.
+         * @return Result<u8*> An error, or a pointer to the shared memory region.
+         */
+        Result<u8*> create(StringView path, usize size);
+
+        /**
+         * @brief Map an existing shared memory region, possibly created by another process.
+         *
+         * @param path The shared memory path to use. It must be of the same format as shm_open().
+         * @param size The amount of bytes to map from the shared memory region.
+         * @param delete_fs Whether to delete the region from the file system so no other processes can open it.
+         * @return Result<u8*> An error, or a pointer to the shared memory region.
+         */
+        Result<u8*> adopt(StringView path, usize size, bool delete_fs = true);
+    };
+}

libos/src/Directory.cpp

@@ -12,7 +12,6 @@
 #include <luna/CString.h>
 #include <os/Directory.h>
 #include <os/FileSystem.h>
-#include <sys/syscall.h>
 #include <unistd.h>
 
 static bool should_skip_entry(const char* name, os::Directory::Filter filter)
@@ -33,8 +32,8 @@ namespace os
     {
         auto dir = TRY(adopt_shared_if_nonnull(new (std::nothrow) Directory({})));
 
-        long rc = syscall(SYS_openat, path.dirfd(), path.name().chars(), O_RDONLY | O_DIRECTORY, 0);
+        int fd = openat(path.dirfd(), path.name().chars(), O_RDONLY | O_DIRECTORY, 0);
-        int fd = TRY(Result<int>::from_syscall(rc));
+        if (fd < 0) return err(errno);
 
         DIR* dp = fdopendir(fd);
         if (!dp)

libos/src/File.cpp

@@ -10,7 +10,6 @@
 #include <errno.h>
 #include <luna/StringBuilder.h>
 #include <os/File.h>
-#include <sys/syscall.h>
 #include <unistd.h>
 
 static SharedPtr<os::File> g_stdin = {};
@@ -83,8 +82,8 @@ namespace os
     {
         auto file = TRY(adopt_shared_if_nonnull(new (std::nothrow) File({})));
 
-        long rc = syscall(SYS_openat, path.dirfd(), path.name().chars(), flags, mode);
+        int fd = openat(path.dirfd(), path.name().chars(), flags, mode);
-        int fd = TRY(Result<int>::from_syscall(rc));
+        if (fd < 0) return err(errno);
 
         file->m_file = fdopen(fd, stdio_mode_from_openmode(flags));
         if (!file->m_file) return err(errno);

libos/src/FileSystem.cpp

@@ -10,13 +10,13 @@
 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <luna/Buffer.h>
 #include <luna/PathParser.h>
 #include <luna/String.h>
 #include <os/Directory.h>
 #include <os/FileSystem.h>
 #include <pwd.h>
 #include <stdlib.h>
-#include <sys/syscall.h>
 #include <unistd.h>
 
 namespace os::FileSystem
@@ -41,39 +41,26 @@ namespace os::FileSystem
 
     Result<void> stat(const Path& path, struct stat& st, bool follow_symlinks)
     {
-        long rc = syscall(SYS_fstatat, path.dirfd(), path.name().chars(), &st,
+        int rc = fstatat(path.dirfd(), path.name().chars(), &st,
-                          (int)(path.is_empty_path() | (follow_symlinks ? 0 : AT_SYMLINK_NOFOLLOW)));
+                         (int)(path.is_empty_path() | (follow_symlinks ? 0 : AT_SYMLINK_NOFOLLOW)));
 
-        return Result<void>::from_syscall(rc);
+        if (rc < 0) return err(errno);
+        return {};
     }
 
     Result<void> create_directory(StringView path, mode_t mode)
     {
-        long rc = syscall(SYS_mkdir, path.chars(), mode);
+        int rc = mkdir(path.chars(), mode);
-
+        if (rc < 0) return err(errno);
-        return Result<void>::from_syscall(rc);
+        return {};
     }
 
     Result<void> remove(const Path& path)
     {
-        long rc = syscall(SYS_unlinkat, path.dirfd(), path.name().chars(), 0);
+        // FIXME: This will not work on many operating systems that require rmdir() for directories.
-
+        int rc = unlinkat(path.dirfd(), path.name().chars(), 0);
-        return Result<void>::from_syscall(rc);
+        if (rc < 0) return err(errno);
-    }
+        return {};
-
-    Result<void> remove_tree(const Path& path)
-    {
-        auto rc = remove(path);
-        if (!rc.has_error()) return {};
-        if (rc.error() != ENOTEMPTY) return rc.release_error();
-
-        auto dir = TRY(os::Directory::open(path));
-
-        Vector<String> entries = TRY(dir->list_names(os::Directory::Filter::ParentAndBase));
-
-        for (const auto& entry : entries) { TRY(remove_tree({ dir->fd(), entry.view() })); }
-
-        return remove(path);
     }
 
     Result<String> readlink(const Path& path)
@@ -82,14 +69,13 @@ namespace os::FileSystem
         TRY(stat(path, st, false));
         if (!S_ISLNK(st.st_mode)) return String {};
 
-        char* buf = (char*)TRY(calloc_impl(st.st_size + 1, 1));
+        Buffer buf = TRY(Buffer::create_sized(st.st_size + 1));
-        auto guard = make_scope_guard([buf] { free_impl(buf); });
+        memset(buf.data(), 0, buf.size());
-        usize nread = TRY(
-            Result<usize>::from_syscall(syscall(SYS_readlinkat, path.dirfd(), path.name().chars(), buf, st.st_size)));
 
-        guard.deactivate();
+        ssize_t nread = readlinkat(path.dirfd(), path.name().chars(), (char*)buf.data(), st.st_size);
+        if (nread < 0) return err(errno);
 
-        return String { buf, nread };
+        return String { (char*)buf.release_data(), (usize)nread };
     }
 
     Result<String> working_directory()
@@ -112,8 +98,8 @@ namespace os::FileSystem
 
     Result<void> change_directory(StringView path)
     {
-        long rc = syscall(SYS_chdir, path.chars());
+        int rc = chdir(path.chars());
-
+        if (rc < 0) return err(errno);
-        return Result<void>::from_syscall(rc);
+        return {};
     }
 }

libos/src/IPC.cpp

@@ -0,0 +1,43 @@
+/**
+ * @file IPC.cpp
+ * @author apio (cloudapio.eu)
+ * @brief Inter-process communication primitives.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <os/IPC.h>
+
+namespace os::IPC
+{
+    Result<void> check_for_messages(os::LocalClient& client, decltype(handle_ipc_client_event) handler)
+    {
+        u8 id;
+        auto rc = client.recv_typed(id);
+        if (rc.has_error())
+        {
+            if (rc.error() == EAGAIN) return {}; // No messages, and the caller does not want us to block.
+            if (rc.error() == EINTR)
+                return {}; // Let the caller check for anything having happened because a signal handler ran.
+            return rc.release_error();
+        }
+
+        return handler(client, id);
+    }
+
+    Result<void> check_for_messages(os::LocalServer::Client& client, decltype(handle_ipc_server_event) handler)
+    {
+        u8 id;
+        auto rc = client.recv_typed(id);
+        if (rc.has_error())
+        {
+            if (rc.error() == EAGAIN) return {}; // No messages, and the caller does not want us to block.
+            if (rc.error() == EINTR)
+                return {}; // Let the caller check for anything having happened because a signal handler ran.
+            return rc.release_error();
+        }
+
+        return handler(client, id);
+    }
+}

libos/src/LocalClient.cpp

@@ -0,0 +1,68 @@
+/**
+ * @file LocalClient.cpp
+ * @author apio (cloudapio.eu)
+ * @brief UNIX local domain client class.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <os/LocalClient.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+namespace os
+{
+    Result<OwnedPtr<LocalClient>> LocalClient::connect(StringView path, bool blocking)
+    {
+        auto client = TRY(make_owned<LocalClient>());
+
+        int sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
+        if (sockfd < 0) return err(errno);
+
+        struct sockaddr_un un;
+        un.sun_family = AF_UNIX;
+        strncpy(un.sun_path, path.chars(), sizeof(un.sun_path));
+
+        if (::connect(sockfd, (struct sockaddr*)&un, sizeof(un)) < 0)
+        {
+            close(sockfd);
+            return err(errno);
+        }
+
+        if (!blocking) { fcntl(sockfd, F_SETFL, O_NONBLOCK); }
+
+        fcntl(sockfd, F_SETFD, FD_CLOEXEC);
+
+        client->m_fd = sockfd;
+        return client;
+    }
+
+    LocalClient::~LocalClient()
+    {
+        close(m_fd);
+    }
+
+    Result<usize> LocalClient::recv(u8* buf, usize length)
+    {
+        ssize_t nread = read(m_fd, buf, length);
+        if (nread < 0) return err(errno);
+        return nread;
+    }
+
+    Result<usize> LocalClient::send(const u8* buf, usize length)
+    {
+        ssize_t nwrite = write(m_fd, buf, length);
+        if (nwrite < 0) return err(errno);
+        return nwrite;
+    }
+
+    void LocalClient::disconnect()
+    {
+        close(m_fd);
+        m_fd = -1;
+    }
+}

libos/src/LocalServer.cpp

@@ -0,0 +1,101 @@
+/**
+ * @file LocalServer.cpp
+ * @author apio (cloudapio.eu)
+ * @brief UNIX local domain server class.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <os/FileSystem.h>
+#include <os/LocalServer.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+namespace os
+{
+    Result<OwnedPtr<LocalServer>> LocalServer::create(StringView path, bool blocking)
+    {
+        auto server = TRY(make_owned<LocalServer>());
+
+        (void)os::FileSystem::remove(path); // We explicitly ignore any error here, either it doesn't exist (which is
+                                            // fine), or it cannot be removed, which will make bind() fail later.
+
+        int sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
+        if (sockfd < 0) return err(errno);
+
+        struct sockaddr_un un;
+        un.sun_family = AF_UNIX;
+        strncpy(un.sun_path, path.chars(), sizeof(un.sun_path));
+
+        if (bind(sockfd, (struct sockaddr*)&un, sizeof(un)) < 0)
+        {
+            close(sockfd);
+            return err(errno);
+        }
+
+        if (!blocking) { fcntl(sockfd, F_SETFL, O_NONBLOCK); }
+        server->m_blocking = blocking;
+
+        fcntl(sockfd, F_SETFD, FD_CLOEXEC);
+
+        server->m_fd = sockfd;
+        return server;
+    }
+
+    Result<void> LocalServer::listen(int backlog)
+    {
+        if (::listen(m_fd, backlog) < 0) return err(errno);
+        return {};
+    }
+
+    Result<LocalServer::Client> LocalServer::accept()
+    {
+        int fd = ::accept(m_fd, nullptr, nullptr);
+        if (fd < 0) return err(errno);
+        if (!m_blocking) fcntl(fd, F_SETFL, O_NONBLOCK);
+        return Client { fd };
+    }
+
+    LocalServer::~LocalServer()
+    {
+        close(m_fd);
+    }
+
+    LocalServer::Client::Client(Client&& other) : m_fd(other.m_fd)
+    {
+        other.m_fd = -1;
+    }
+
+    LocalServer::Client::Client(int fd) : m_fd(fd)
+    {
+    }
+
+    LocalServer::Client::~Client()
+    {
+        if (m_fd >= 0) close(m_fd);
+    }
+
+    Result<usize> LocalServer::Client::recv(u8* buf, usize length)
+    {
+        ssize_t nread = read(m_fd, buf, length);
+        if (nread < 0) return err(errno);
+        return nread;
+    }
+
+    Result<usize> LocalServer::Client::send(const u8* buf, usize length)
+    {
+        ssize_t nwrite = write(m_fd, buf, length);
+        if (nwrite < 0) return err(errno);
+        return nwrite;
+    }
+
+    void LocalServer::Client::disconnect()
+    {
+        close(m_fd);
+        m_fd = -1;
+    }
+}

libos/src/Process.cpp

@@ -9,8 +9,8 @@
 
 #include <errno.h>
 #include <os/Process.h>
+#include <signal.h>
 #include <stdlib.h>
-#include <sys/syscall.h>
 #include <unistd.h>
 
 extern char** environ;
@@ -19,8 +19,9 @@ namespace os
 {
     Result<pid_t> Process::fork()
     {
-        long rc = syscall(SYS_fork);
+        pid_t pid = ::fork();
-        return Result<pid_t>::from_syscall(rc);
+        if (pid < 0) return err(errno);
+        return pid;
     }
 
     Result<void> Process::exec(StringView path, Slice<String> args, bool search_in_path)
@@ -121,14 +122,16 @@ namespace os
 
     Result<pid_t> Process::wait(pid_t child, int* status, int options)
     {
-        long rc = syscall(SYS_waitpid, child, status, options);
+        pid_t pid = waitpid(child, status, options);
-        return Result<pid_t>::from_syscall(rc);
+        if (pid < 0) return err(errno);
+        return pid;
     }
 
     Result<void> Process::kill(pid_t pid, int signo)
     {
-        long rc = syscall(SYS_kill, pid, signo);
+        int rc = ::kill(pid, signo);
-        return Result<void>::from_syscall(rc);
+        if (rc < 0) return err(errno);
+        return {};
     }
 
     [[noreturn]] void Process::exit(int status)

libos/src/SharedMemory.cpp

@@ -0,0 +1,77 @@
+/**
+ * @file SharedMemory.cpp
+ * @author apio (cloudapio.eu)
+ * @brief Create and map areas of memory shared between processes.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <errno.h>
+#include <luna/Alignment.h>
+#include <os/File.h>
+#include <os/SharedMemory.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+namespace os::SharedMemory
+{
+    Result<u8*> create(StringView path, usize size)
+    {
+        int fd = shm_open(path.chars(), O_RDWR | O_CREAT | O_EXCL, 0600);
+        if (fd < 0)
+        {
+            int olderr = errno;
+            os::eprintln("os: could not create shared memory region: shm_open failed (%s) - %s", path,
+                         strerror(olderr));
+            return err(olderr);
+        }
+
+        size = align_up<PAGE_SIZE>(size);
+
+        if (ftruncate(fd, size) < 0)
+        {
+            int olderr = errno;
+            os::eprintln("os: could not create shared memory region: ftruncate failed (%d, %zu) - %s", fd, size,
+                         strerror(olderr));
+            shm_unlink(path.chars());
+            close(fd);
+            return err(olderr);
+        }
+
+        void* p = mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+        if (p == MAP_FAILED)
+        {
+            int olderr = errno;
+            os::eprintln("os: could not create shared memory region: mmap failed (%zu, %d) - %s", size, fd,
+                         strerror(olderr));
+            shm_unlink(path.chars());
+            close(fd);
+            return err(olderr);
+        }
+
+        close(fd);
+        return (u8*)p;
+    }
+
+    Result<u8*> adopt(StringView path, usize size, bool delete_fs)
+    {
+        int fd = shm_open(path.chars(), O_RDWR, 0600);
+        if (delete_fs) shm_unlink(path.chars());
+        if (fd < 0) return err(errno);
+
+        void* p = mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+        if (p == MAP_FAILED)
+        {
+            int olderr = errno;
+            os::eprintln("os: could not adopt shared memory region: mmap failed (%zu, %d) - %s", size, fd,
+                         strerror(olderr));
+            close(fd);
+            return 0;
+        }
+
+        close(fd);
+        return (u8*)p;
+    }
+}

libui/CMakeLists.txt

@@ -0,0 +1,30 @@
+# The UI and graphics library for Luna.
+
+file(GLOB HEADERS include/ui/*.h)
+
+set(SOURCES
+    ${HEADERS}
+    include/ui/ipc/Server.h
+    include/ui/ipc/Client.h
+    src/Canvas.cpp
+    src/Rect.cpp
+    src/Font.cpp
+    src/Image.cpp
+    src/App.cpp
+    src/Window.cpp
+    src/Layout.cpp
+    src/Alignment.cpp
+    src/Container.cpp
+    src/Button.cpp
+)
+
+add_library(ui ${SOURCES})
+target_compile_options(ui PRIVATE ${COMMON_FLAGS} -fno-threadsafe-statics)
+target_include_directories(ui PUBLIC ${CMAKE_CURRENT_LIST_DIR}/include/)
+target_include_directories(ui PUBLIC ${LUNA_BASE}/usr/include)
+target_link_libraries(ui PUBLIC os)
+
+add_custom_command(
+    TARGET ui
+    COMMAND "${CMAKE_COMMAND}" -E copy ${CMAKE_CURRENT_BINARY_DIR}/libui.a ${LUNA_BASE}/usr/lib/libui.a
+)

libui/include/ui/Alignment.h

@@ -0,0 +1,30 @@
+/**
+ * @file Alignment.h
+ * @author apio (cloudapio.eu)
+ * @brief UI component alignment.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <ui/Rect.h>
+
+namespace ui
+{
+    enum class VerticalAlignment
+    {
+        Top,
+        Center,
+        Bottom
+    };
+
+    enum class HorizontalAlignment
+    {
+        Left,
+        Center,
+        Right
+    };
+
+    Rect align(Rect container, Rect contained, VerticalAlignment valign, HorizontalAlignment halign);
+}

libui/include/ui/App.h

@@ -0,0 +1,65 @@
+/**
+ * @file App.h
+ * @author apio (cloudapio.eu)
+ * @brief UI application event loop.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <luna/HashMap.h>
+#include <os/LocalClient.h>
+#include <ui/Window.h>
+
+namespace ui
+{
+    class App
+    {
+      public:
+        App();
+        ~App();
+
+        Result<void> init(int, char**);
+        Result<int> run();
+
+        Rect screen_rect();
+
+        os::LocalClient& client()
+        {
+            return *m_client;
+        }
+
+        void set_should_close(bool b)
+        {
+            m_should_close = b;
+        }
+
+        void set_main_window(Window* window)
+        {
+            check(!m_main_window);
+            m_main_window = window;
+        }
+
+        Window* main_window()
+        {
+            return m_main_window;
+        }
+
+        Result<void> register_window(OwnedPtr<Window>&& window, Badge<Window>);
+        void unregister_window(Window* window, Badge<Window>);
+
+        Result<void> handle_ipc_event(u8 id);
+
+        static App& the();
+
+      private:
+        static App* s_app;
+        OwnedPtr<os::LocalClient> m_client;
+        Window* m_main_window { nullptr };
+        HashMap<int, OwnedPtr<Window>> m_windows;
+        bool m_should_close { false };
+
+        Window* find_window(int id);
+    };
+}

libui/include/ui/Button.h

@@ -0,0 +1,35 @@
+/**
+ * @file Button.h
+ * @author apio (cloudapio.eu)
+ * @brief A clickable component that triggers an action when pressed.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <ui/Widget.h>
+
+namespace ui
+{
+    class Button : public Widget
+    {
+      public:
+        Button(Rect rect);
+
+        void set_widget(Widget& widget);
+        void set_action(void (*action)(void));
+
+        Result<EventResult> handle_mouse_move(Point position) override;
+        Result<EventResult> handle_mouse_leave() override;
+        Result<EventResult> handle_mouse_down(Point position, int buttons) override;
+        Result<EventResult> handle_mouse_up(Point position, int buttons) override;
+        Result<void> draw(Canvas& canvas) override;
+
+      private:
+        bool m_hovered { false };
+        bool m_clicked { false };
+        Widget* m_child;
+        void (*m_action)(void);
+    };
+}

libui/include/ui/Canvas.h

@@ -0,0 +1,73 @@
+/**
+ * @file Canvas.h
+ * @author apio (cloudapio.eu)
+ * @brief Drawable surfaces.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <luna/Result.h>
+#include <luna/Types.h>
+#include <ui/Color.h>
+#include <ui/Point.h>
+#include <ui/Rect.h>
+
+namespace ui
+{
+    /**
+     * @brief A drawable surface.
+     */
+    struct Canvas
+    {
+        int width;
+        int height;
+        int stride;
+        u8* ptr;
+
+        /**
+         * @brief Create a new Canvas object.
+         *
+         * @param ptr The memory to use for the canvas. It must be of at least width * height * 4 bytes of length.
+         * @param width The width of the canvas.
+         * @param height The height of the canvas.
+         * @return Canvas The new Canvas object.
+         */
+        static Canvas create(u8* ptr, int width, int height);
+
+        /**
+         * @brief Return a new Canvas that represents a subsection of the current one.
+         *
+         * @param rect The dimensions of the new canvas. If these exceed the bounds of the current canvas, they will be
+         * clamped.
+         * @return Canvas The new Canvas object.
+         */
+        Canvas subcanvas(Rect rect);
+
+        /**
+         * @brief Return the dimensions of the current canvas.
+         *
+         * @return Rect This canvas's dimensions, as a Rect object.
+         */
+        Rect rect()
+        {
+            return Rect { .pos = { 0, 0 }, .width = width, .height = height };
+        }
+
+        /**
+         * @brief Fill the entire canvas with one color.
+         *
+         * @param color The color to use.
+         */
+        void fill(Color color);
+
+        /**
+         * @brief Fill the canvas with pixels.
+         *
+         * @param pixels The array of pixels (must be at least width*height).
+         * @param stride The number of pixels to skip to go to the next line.
+         */
+        void fill(u32* pixels, int stride);
+    };
+};

libui/include/ui/Color.h

@@ -0,0 +1,113 @@
+/**
+ * @file Color.h
+ * @author apio (cloudapio.eu)
+ * @brief RGBA colors.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <luna/Types.h>
+
+namespace ui
+{
+    /**
+     * @brief A 32-bit ARGB color.
+     */
+    struct Color
+    {
+        union {
+            u32 raw;
+            u8 colors[4];
+        };
+
+        /**
+         * @brief Return the blue value of this color.
+         *
+         * @return constexpr u8 The blue value.
+         */
+        constexpr u8 red() const
+        {
+            return colors[2];
+        }
+
+        /**
+         * @brief Return the green value of this color.
+         *
+         * @return constexpr u8 The green value.
+         */
+        constexpr u8 green() const
+        {
+            return colors[1];
+        }
+
+        /**
+         * @brief Return the blue value of this color.
+         *
+         * @return constexpr u8 The blue value.
+         */
+        constexpr u8 blue() const
+        {
+            return colors[0];
+        }
+
+        /**
+         * @brief Return the alpha value of this color.
+         *
+         * @return constexpr u8 The alpha value.
+         */
+        constexpr u8 alpha() const
+        {
+            return colors[3];
+        }
+
+        /**
+         * @brief Construct a new color from a 32-bit ARGB integer.
+         *
+         * @param raw The integer representing the color.
+         * @return constexpr Color The new color.
+         */
+        static constexpr Color from_u32(u32 raw)
+        {
+            return Color { .raw = raw };
+        }
+
+        /**
+         * @brief Construct a new color from its separate RGBA values (from 0 to 255).
+         *
+         * @param red The red value.
+         * @param green The green value.
+         * @param blue The blue value.
+         * @param alpha The alpha value.
+         * @return constexpr Color The new color.
+         */
+        static constexpr Color from_rgba(u8 red, u8 green, u8 blue, u8 alpha)
+        {
+            return Color { .colors = { blue, green, red, alpha } };
+        }
+
+        /**
+         * @brief Construct a new color from its separate RGB values (from 0 to 255).
+         *
+         * @param red The red value.
+         * @param green The green value.
+         * @param blue The blue value.
+         * @return constexpr Color The new color.
+         */
+        static constexpr Color from_rgb(u8 red, u8 green, u8 blue)
+        {
+            return from_rgba(red, green, blue, 0xff);
+        }
+    };
+
+    static constexpr Color WHITE = Color::from_rgb(0xff, 0xff, 0xff);
+    static constexpr Color BLACK = Color::from_rgb(0x00, 0x00, 0x00);
+    static constexpr Color GRAY = Color::from_rgb(0x80, 0x80, 0x80);
+
+    static constexpr Color BLUE = Color::from_rgb(0x00, 0x00, 0xff);
+    static constexpr Color GREEN = Color::from_rgb(0x00, 0xff, 0x00);
+    static constexpr Color RED = Color::from_rgb(0xff, 0x00, 0x00);
+
+    static constexpr Color CYAN = Color::from_rgb(0x00, 0xff, 0xff);
+};

libui/include/ui/Container.h

@@ -0,0 +1,34 @@
+/**
+ * @file Container.h
+ * @author apio (cloudapio.eu)
+ * @brief A container widget to pad and align objects inside it.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <ui/Alignment.h>
+#include <ui/Widget.h>
+
+namespace ui
+{
+    class Container : public Widget
+    {
+      public:
+        Container(Rect rect, VerticalAlignment valign, HorizontalAlignment halign);
+
+        void set_widget(Widget& widget);
+
+        Result<EventResult> handle_mouse_move(Point position) override;
+        Result<EventResult> handle_mouse_leave() override;
+        Result<EventResult> handle_mouse_down(Point position, int buttons) override;
+        Result<EventResult> handle_mouse_up(Point position, int buttons) override;
+        Result<void> draw(Canvas& canvas) override;
+
+      private:
+        Widget* m_widget;
+        VerticalAlignment m_valign;
+        HorizontalAlignment m_halign;
+    };
+}

libui/include/ui/Font.h

@@ -0,0 +1,120 @@
+/**
+ * @file Font.h
+ * @author apio (cloudapio.eu)
+ * @brief PSF font loading and rendering.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <luna/Buffer.h>
+#include <luna/SharedPtr.h>
+#include <os/Path.h>
+#include <ui/Canvas.h>
+
+#define PSF_FONT_MAGIC 0x864ab572
+
+namespace ui
+{
+    /**
+     * @brief A class holding PSF font data, used for direct rendering of glyphs into a canvas.
+     */
+    class Font : public Shareable
+    {
+      public:
+        /**
+         * @brief An enum used to select a font weight when loading a font.
+         */
+        enum FontWeight
+        {
+            Regular,
+            Bold,
+        };
+
+        /**
+         * @brief Load a Font object from a font file.
+         *
+         * @param path The full path to the font file.
+         * @return Result<SharedPtr<Font>> An error, or the loaded Font object.
+         */
+        static Result<SharedPtr<Font>> load(const os::Path& path);
+
+        /**
+         * @brief Load a system font by name.
+         *
+         * @param name The name of the font to load (the default system font is "Tamsyn").
+         * @param weight The weight of the font (regular or bold).
+         * @return Result<SharedPtr<Font>> An error, or the loaded Font object.
+         */
+        static Result<SharedPtr<Font>> load_builtin(StringView name, FontWeight weight);
+
+        /**
+         * @brief Return a pointer to the system's default font.
+         *
+         * @return SharedPtr<Font> The default font.
+         */
+        static SharedPtr<Font> default_font();
+
+        /**
+         * @brief Return a pointer to the system's default bold font.
+         *
+         * @return SharedPtr<Font> The default bold font.
+         */
+        static SharedPtr<Font> default_bold_font();
+
+        /**
+         * @brief Render a single Unicode code point onto a canvas, using this font's glyphs.
+         *
+         * @param codepoint The code point to render.
+         * @param color The color to draw the code point in.
+         * @param canvas The canvas to use.
+         */
+        void render(wchar_t codepoint, ui::Color color, ui::Canvas& canvas);
+
+        /**
+         * @brief Render a Unicode text string onto a canvas, using this font's glyphs.
+         *
+         * @param text The string to render (must be null-terminated).
+         * @param color The color to draw the code point in.
+         * @param canvas The canvas to use.
+         */
+        void render(const wchar_t* text, ui::Color color, ui::Canvas& canvas);
+
+        /**
+         * @brief Return the width of this font's glyphs.
+         *
+         * @return int The width.
+         */
+        int width() const
+        {
+            return m_psf_header.width;
+        }
+
+        /**
+         * @brief Return the height of this font's glyphs.
+         *
+         * @return int The height.
+         */
+        int height() const
+        {
+            return m_psf_header.height;
+        }
+
+      private:
+        struct PSFHeader
+        {
+            u32 magic;
+            u32 version; // zero
+            u32 headersize;
+            u32 flags; // 0 if there's no unicode table
+            u32 numglyph;
+            u32 bytesperglyph;
+            int height;
+            int width;
+        };
+
+        PSFHeader m_psf_header;
+        Buffer m_font_data;
+    };
+};

libui/include/ui/Image.h

@@ -0,0 +1,92 @@
+/**
+ * @file Image.h
+ * @author apio (cloudapio.eu)
+ * @brief TGA image loading and rendering.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <luna/Buffer.h>
+#include <luna/SharedPtr.h>
+#include <os/Path.h>
+#include <ui/Widget.h>
+
+namespace ui
+{
+    /**
+     * @brief An image in the TGA file format.
+     */
+    class Image : public Shareable
+    {
+      public:
+        /**
+         * @brief Load a new TGA image from a file.
+         *
+         * @param path The path to open.
+         * @return Result<SharedPtr<Image>> An error, or a new Image object.
+         */
+        static Result<SharedPtr<Image>> load(const os::Path& path);
+
+        /**
+         * @brief Return the array of pixels contained in the image.
+         *
+         * @return u32* The array of pixels.
+         */
+        u32* pixels()
+        {
+            return (u32*)m_image_data.data();
+        }
+
+        /**
+         * @brief Return the width of the image.
+         *
+         * @return u16 The width.
+         */
+        u16 width()
+        {
+            return m_tga_header.w;
+        }
+
+        /**
+         * @brief Return the height of the image.
+         *
+         * @return u16 The height.
+         */
+        u16 height()
+        {
+            return m_tga_header.h;
+        }
+
+      private:
+        struct [[gnu::packed]] TGAHeader
+        {
+            u8 idlen;
+            u8 colormap;
+            u8 encoding;
+            u16 cmaporig, cmaplen;
+            u8 cmapent;
+            u16 x;
+            u16 y;
+            u16 w;
+            u16 h;
+            u8 bpp;
+            u8 pixeltype;
+        };
+
+        TGAHeader m_tga_header;
+        Buffer m_image_data;
+    };
+
+    class ImageWidget final : public Widget
+    {
+      public:
+        static Result<OwnedPtr<ImageWidget>> load(const os::Path& path);
+
+        Result<void> draw(Canvas& canvas) override;
+
+      private:
+        SharedPtr<Image> m_image;
+    };
+}

libui/include/ui/Layout.h

@@ -0,0 +1,69 @@
+/**
+ * @file Layout.h
+ * @author apio (cloudapio.eu)
+ * @brief Layout widgets to organize content.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <luna/Vector.h>
+#include <ui/Widget.h>
+
+namespace ui
+{
+    enum class AdjustHeight
+    {
+        No,
+        Yes
+    };
+
+    enum class AdjustWidth
+    {
+        No,
+        Yes
+    };
+
+    class HorizontalLayout final : public Widget
+    {
+      public:
+        HorizontalLayout(AdjustHeight adjust_height = AdjustHeight::Yes, AdjustWidth adjust_width = AdjustWidth::Yes);
+
+        Result<EventResult> handle_mouse_move(Point position) override;
+        Result<EventResult> handle_mouse_leave() override;
+        Result<EventResult> handle_mouse_down(Point position, int buttons) override;
+        Result<EventResult> handle_mouse_up(Point position, int buttons) override;
+
+        Result<void> draw(Canvas& canvas) override;
+
+        Result<void> add_widget(Widget& widget);
+
+      private:
+        Vector<Widget*> m_widgets;
+        AdjustHeight m_adjust_height;
+        AdjustWidth m_adjust_width;
+        int m_used_width;
+    };
+
+    class VerticalLayout final : public Widget
+    {
+      public:
+        VerticalLayout(AdjustHeight adjust_height = AdjustHeight::Yes, AdjustWidth adjust_width = AdjustWidth::Yes);
+
+        Result<EventResult> handle_mouse_move(Point position) override;
+        Result<EventResult> handle_mouse_leave() override;
+        Result<EventResult> handle_mouse_down(Point position, int buttons) override;
+        Result<EventResult> handle_mouse_up(Point position, int buttons) override;
+
+        Result<void> draw(Canvas& canvas) override;
+
+        Result<void> add_widget(Widget& widget);
+
+      private:
+        Vector<Widget*> m_widgets;
+        AdjustHeight m_adjust_height;
+        AdjustWidth m_adjust_width;
+        int m_used_height;
+    };
+}

libui/include/ui/Mouse.h

@@ -0,0 +1,21 @@
+/**
+ * @file Mouse.h
+ * @author apio (cloudapio.eu)
+ * @brief Mouse buttons.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <moon/Mouse.h>
+
+namespace ui
+{
+    enum MouseButtons
+    {
+        LEFT = moon::Left,
+        MIDDLE = moon::Middle,
+        RIGHT = moon::Right,
+    };
+}

libui/include/ui/Point.h

@@ -0,0 +1,22 @@
+/**
+ * @file Point.h
+ * @author apio (cloudapio.eu)
+ * @brief 2D space points.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+
+namespace ui
+{
+    /**
+     * @brief A point in 2D space.
+     */
+    struct Point
+    {
+        int x { 0 };
+        int y { 0 };
+    };
+}

libui/include/ui/Rect.h

@@ -0,0 +1,81 @@
+/**
+ * @file Rect.h
+ * @author apio (cloudapio.eu)
+ * @brief A simple 2D rectangle representation.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <ui/Point.h>
+
+namespace ui
+{
+    /**
+     * @brief A simple rectangle.
+     */
+    struct Rect
+    {
+        Point pos;
+        int width;
+        int height;
+
+        /**
+         * @brief Check if a point is contained in this rectangle.
+         *
+         * @param point The point to check.
+         * @return true The point is contained inside the rectangle.
+         * @return false The point is not contained inside the rectangle.
+         */
+        bool contains(Point point);
+
+        /**
+         * @brief Check if another rectangle is contained in this one.
+         *
+         * @param point The rectangle to check.
+         * @return true The other rectangle is contained inside this one.
+         * @return false The other rectangle is not contained inside this one.
+         */
+        bool contains(Rect rect);
+
+        /**
+         * @brief Normalize a point to fit inside this rectangle.
+         *
+         * @param point The original point.
+         * @return Point The normalized point.
+         */
+        Point normalize(Point point);
+
+        /**
+         * @brief Transform an absolute position to a position relative to this rectangle.
+         *
+         * @param pos The original absolute position.
+         * @return Point The position relative to this rectangle.
+         */
+        Point relative(Point pos);
+
+        /**
+         * @brief Transform a position relative to this rectangle to an absolute position.
+         *
+         * @param pos The original relative position.
+         * @return Point The absolute position.
+         */
+        Point absolute(Point pos);
+
+        /**
+         * @brief Transform another rectangle relative to this one to an absolute rectangle.
+         *
+         * @param rect The original relative rectangle.
+         * @return Point The absolute rectangle.
+         */
+        Rect absolute(Rect rect);
+
+        /**
+         * @brief Return a copy of this rectangle with no negative values (normalized to 0).
+         *
+         * @return Rect The new rectangle.
+         */
+        Rect normalized();
+    };
+}

libui/include/ui/Widget.h

@@ -0,0 +1,87 @@
+/**
+ * @file Widget.h
+ * @author apio (cloudapio.eu)
+ * @brief Abstract widget class.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <luna/Ignore.h>
+#include <luna/Result.h>
+#include <ui/Canvas.h>
+#include <ui/Point.h>
+#include <ui/Rect.h>
+
+namespace ui
+{
+    class Window;
+
+    enum class EventResult
+    {
+        DidHandle,
+        DidNotHandle,
+    };
+
+    class Widget
+    {
+      public:
+        virtual Result<EventResult> handle_mouse_move(Point position)
+        {
+            ignore(position);
+            return EventResult::DidNotHandle;
+        }
+
+        virtual Result<EventResult> handle_mouse_down(Point position, int buttons)
+        {
+            ignore(position, buttons);
+            return EventResult::DidNotHandle;
+        }
+
+        virtual Result<EventResult> handle_mouse_up(Point position, int buttons)
+        {
+            ignore(position, buttons);
+            return EventResult::DidNotHandle;
+        }
+
+        virtual Result<EventResult> handle_mouse_leave()
+        {
+            return EventResult::DidNotHandle;
+        }
+
+        virtual Result<void> draw(Canvas& canvas);
+
+        void set_window(Window* window, Rect rect, Badge<Window>)
+        {
+            m_window = window;
+            m_rect = rect;
+        }
+
+        void set_parent(Widget* parent)
+        {
+            m_parent = parent;
+            m_window = parent->m_window;
+        }
+
+        Widget* parent()
+        {
+            return m_parent;
+        }
+
+        Window* window()
+        {
+            return m_window;
+        }
+
+        Rect& rect()
+        {
+            return m_rect;
+        }
+
+      protected:
+        Widget* m_parent { nullptr };
+        Window* m_window;
+        Rect m_rect { 0, 0, 50, 50 };
+    };
+}

libui/include/ui/Window.h

@@ -0,0 +1,67 @@
+/**
+ * @file Window.h
+ * @author apio (cloudapio.eu)
+ * @brief UI windows.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <luna/OwnedPtr.h>
+#include <luna/StringView.h>
+#include <ui/Canvas.h>
+#include <ui/Mouse.h>
+#include <ui/Rect.h>
+#include <ui/Widget.h>
+
+namespace ui
+{
+    class Window
+    {
+      public:
+        static Result<Window*> create(Rect rect, bool decorated = true);
+
+        void set_title(StringView title);
+
+        void set_background(Color color)
+        {
+            m_background = color;
+        }
+
+        void set_main_widget(Widget& widget)
+        {
+            check(!m_main_widget);
+            widget.set_window(this, m_canvas.rect(), {});
+            m_main_widget = &widget;
+        }
+
+        Canvas& canvas()
+        {
+            return m_canvas;
+        }
+
+        void update();
+
+        void close();
+
+        Result<void> draw();
+        Result<void> handle_mouse_leave();
+        Result<void> handle_mouse_move(ui::Point position);
+        Result<void> handle_mouse_buttons(ui::Point position, int buttons);
+
+        int id() const
+        {
+            return m_id;
+        }
+
+        ~Window();
+
+      private:
+        int m_id;
+        Canvas m_canvas;
+        Widget* m_main_widget { nullptr };
+        Color m_background { ui::BLACK };
+        Option<int> m_old_mouse_buttons;
+    };
+}

libui/include/ui/ipc/Client.h

@@ -0,0 +1,63 @@
+/**
+ * @file ipc/Client.h
+ * @author apio (cloudapio.eu)
+ * @brief IPC message definitions for UI messages sent to the client.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <os/IPC.h>
+#include <ui/Point.h>
+
+namespace ui
+{
+    enum ClientMessages : u8
+    {
+        IPC_ENUM_CLIENT(ui),
+        CREATE_WINDOW_RESPONSE_ID,
+        WINDOW_CLOSE_REQUEST_ID,
+        MOUSE_EVENT_REQUEST_ID,
+        MOUSE_LEAVE_REQUEST_ID,
+        GET_SCREEN_RECT_RESPONSE_ID
+    };
+
+    struct CreateWindowResponse
+    {
+        static constexpr u8 ID = CREATE_WINDOW_RESPONSE_ID;
+
+        int window;
+        IPC_STRING(shm_path);
+    };
+
+    struct WindowCloseRequest
+    {
+        static constexpr u8 ID = WINDOW_CLOSE_REQUEST_ID;
+
+        int window;
+    };
+
+    struct MouseEventRequest
+    {
+        static constexpr u8 ID = MOUSE_EVENT_REQUEST_ID;
+
+        int window;
+        Point position;
+        int buttons;
+    };
+
+    struct MouseLeaveRequest
+    {
+        static constexpr u8 ID = MOUSE_LEAVE_REQUEST_ID;
+
+        int window;
+    };
+
+    struct GetScreenRectResponse
+    {
+        static constexpr u8 ID = GET_SCREEN_RECT_RESPONSE_ID;
+
+        Rect rect;
+    };
+}

libui/include/ui/ipc/Server.h

@@ -0,0 +1,66 @@
+/**
+ * @file ipc/Server.h
+ * @author apio (cloudapio.eu)
+ * @brief IPC message definitions for UI messages sent to the server.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <os/IPC.h>
+#include <ui/Color.h>
+#include <ui/Rect.h>
+#include <ui/ipc/Client.h>
+
+namespace ui
+{
+    enum ServerMessages : u8
+    {
+        IPC_ENUM_SERVER(ui),
+        CREATE_WINDOW_ID,
+        SET_WINDOW_TITLE_ID,
+        INVALIDATE_ID,
+        CLOSE_WINDOW_ID,
+        GET_SCREEN_RECT_ID,
+    };
+
+    struct CreateWindowRequest
+    {
+        using ResponseType = CreateWindowResponse;
+        static constexpr u8 ID = CREATE_WINDOW_ID;
+
+        ui::Rect rect;
+        bool decorated;
+    };
+
+    struct SetWindowTitleRequest
+    {
+        static constexpr u8 ID = SET_WINDOW_TITLE_ID;
+
+        int window;
+        IPC_STRING(title);
+    };
+
+    struct InvalidateRequest
+    {
+        static constexpr u8 ID = INVALIDATE_ID;
+
+        int window;
+    };
+
+    struct CloseWindowRequest
+    {
+        static constexpr u8 ID = CLOSE_WINDOW_ID;
+
+        int window;
+    };
+
+    struct GetScreenRectRequest
+    {
+        using ResponseType = GetScreenRectResponse;
+        static constexpr u8 ID = GET_SCREEN_RECT_ID;
+
+        int _shadow; // Unused.
+    };
+}

libui/src/Alignment.cpp

@@ -0,0 +1,40 @@
+/**
+ * @file Alignment.cpp
+ * @author apio (cloudapio.eu)
+ * @brief UI component alignment.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <ui/Alignment.h>
+
+namespace ui
+{
+    Rect align(Rect container, Rect contained, VerticalAlignment valign, HorizontalAlignment halign)
+    {
+        Rect result;
+        result.width = contained.width;
+        result.height = contained.height;
+        result.pos.y = container.pos.y;
+        result.pos.x = container.pos.x;
+
+        switch (valign)
+        {
+        case VerticalAlignment::Top: break;
+        case VerticalAlignment::Center: result.pos.y += (container.height - contained.height) / 2; break;
+        case VerticalAlignment::Bottom: result.pos.y += container.height - contained.height; break;
+        default: break;
+        }
+
+        switch (halign)
+        {
+        case HorizontalAlignment::Left: break;
+        case HorizontalAlignment::Center: result.pos.x += (container.width - contained.width) / 2; break;
+        case HorizontalAlignment::Right: result.pos.x += container.width - contained.width; break;
+        default: break;
+        }
+
+        return result;
+    }
+}

libui/src/App.cpp

@@ -0,0 +1,136 @@
+/**
+ * @file App.cpp
+ * @author apio (cloudapio.eu)
+ * @brief UI application event loop.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <os/ArgumentParser.h>
+#include <os/File.h>
+#include <os/IPC.h>
+#include <ui/App.h>
+#include <ui/ipc/Client.h>
+#include <ui/ipc/Server.h>
+
+Result<void> handle_ipc_client_event(os::LocalClient&, u8 id)
+{
+    return ui::App::the().handle_ipc_event(id);
+}
+
+namespace ui
+{
+    App* App::s_app { nullptr };
+
+    App::App()
+    {
+        s_app = this;
+    }
+
+    App::~App()
+    {
+        s_app = nullptr;
+    }
+
+    Result<void> App::init(int argc, char** argv)
+    {
+        StringView socket_path = "/tmp/wind.sock";
+
+        os::ArgumentParser parser;
+        parser.add_description("A UI application."_sv);
+        parser.add_system_program_info(argv[0]);
+        parser.add_value_argument(socket_path, 's', "socket"_sv, "the path for the local IPC socket"_sv);
+        parser.parse(argc, argv);
+
+        m_client = TRY(os::LocalClient::connect(socket_path, true));
+
+        return {};
+    }
+
+    Result<int> App::run()
+    {
+        check(m_main_window);
+        while (!m_should_close) { TRY(os::IPC::check_for_messages(*m_client)); }
+        return 0;
+    }
+
+    App& App::the()
+    {
+        check(s_app);
+        return *s_app;
+    }
+
+    Rect App::screen_rect()
+    {
+        ui::GetScreenRectRequest request {};
+        auto response = os::IPC::send_sync<ui::GetScreenRectResponse>(*m_client, request).release_value();
+        return response.rect;
+    }
+
+    Result<void> App::register_window(OwnedPtr<Window>&& window, Badge<Window>)
+    {
+        int id = window->id();
+        check(TRY(m_windows.try_set(id, move(window))));
+        return {};
+    }
+
+    void App::unregister_window(Window* window, Badge<Window>)
+    {
+        int id = window->id();
+        check(m_windows.try_remove(id));
+    }
+
+    Window* App::find_window(int id)
+    {
+        auto* window = m_windows.try_get_ref(id);
+        check(window);
+        return window->ptr();
+    }
+
+#define READ_MESSAGE(request)                                                                                          \
+    do {                                                                                                               \
+        auto rc = m_client->recv_typed(request);                                                                       \
+        if (rc.has_error())                                                                                            \
+        {                                                                                                              \
+            if (rc.error() == EAGAIN) { continue; }                                                                    \
+            if (rc.error() == EINTR) { continue; }                                                                     \
+            else                                                                                                       \
+                return rc.release_error();                                                                             \
+        }                                                                                                              \
+        break;                                                                                                         \
+    } while (true)
+
+    Result<void> App::handle_ipc_event(u8 id)
+    {
+        switch (id)
+        {
+        case WINDOW_CLOSE_REQUEST_ID: {
+            WindowCloseRequest request;
+            READ_MESSAGE(request);
+            os::eprintln("ui: Window close request from server! Shall comply.");
+            auto* window = find_window(request.window);
+            window->close();
+            return {};
+        }
+        case MOUSE_EVENT_REQUEST_ID: {
+            MouseEventRequest request;
+            READ_MESSAGE(request);
+            auto* window = find_window(request.window);
+            window->handle_mouse_move(request.position);
+            window->handle_mouse_buttons(request.position, request.buttons);
+            window->draw();
+            return {};
+        }
+        case MOUSE_LEAVE_REQUEST_ID: {
+            MouseLeaveRequest request;
+            READ_MESSAGE(request);
+            auto* window = find_window(request.window);
+            window->handle_mouse_leave();
+            window->draw();
+            return {};
+        }
+        default: fail("Unexpected IPC request from server!");
+        }
+    }
+}

libui/src/Button.cpp

@@ -0,0 +1,68 @@
+/**
+ * @file Button.cpp
+ * @author apio (cloudapio.eu)
+ * @brief A clickable component that triggers an action when pressed.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <ui/Button.h>
+#include <ui/Mouse.h>
+
+namespace ui
+{
+    Button::Button(Rect rect)
+    {
+        m_rect = rect;
+    }
+
+    void Button::set_widget(Widget& widget)
+    {
+        widget.rect() = m_rect;
+        m_child = &widget;
+        widget.set_parent(this);
+    }
+
+    void Button::set_action(void (*action)(void))
+    {
+        m_action = action;
+    }
+
+    Result<EventResult> Button::handle_mouse_move(Point position)
+    {
+        m_hovered = true;
+        return m_child->handle_mouse_move(position);
+    }
+
+    Result<EventResult> Button::handle_mouse_leave()
+    {
+        m_hovered = m_clicked = false;
+        return m_child->handle_mouse_leave();
+    }
+
+    Result<EventResult> Button::handle_mouse_down(Point position, int buttons)
+    {
+        auto result = TRY(m_child->handle_mouse_down(position, buttons));
+        if (result == EventResult::DidNotHandle)
+        {
+            if (!m_clicked && (buttons == ui::MouseButtons::LEFT))
+            {
+                m_clicked = true;
+                m_action();
+            }
+        }
+        return EventResult::DidHandle;
+    }
+
+    Result<EventResult> Button::handle_mouse_up(Point position, int buttons)
+    {
+        if (buttons & ui::MouseButtons::LEFT) m_clicked = false;
+        return m_child->handle_mouse_up(position, buttons);
+    }
+
+    Result<void> Button::draw(Canvas& canvas)
+    {
+        return m_child->draw(canvas);
+    }
+}

libui/src/Canvas.cpp

@@ -0,0 +1,62 @@
+/**
+ * @file Canvas.cpp
+ * @author apio (cloudapio.eu)
+ * @brief Drawable surfaces.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <ui/Canvas.h>
+
+namespace ui
+{
+    Canvas Canvas::create(u8* ptr, int width, int height)
+    {
+        return Canvas { .width = width, .height = height, .stride = width, .ptr = ptr };
+    }
+
+    Canvas Canvas::subcanvas(Rect rect)
+    {
+        if (rect.pos.x < 0) rect.pos.x = 0;
+        if (rect.pos.y < 0) rect.pos.y = 0;
+        if (rect.pos.x + rect.width > width) rect.width = width - rect.pos.x;
+        if (rect.pos.y + rect.height > height) rect.height = height - rect.pos.y;
+
+        u8* p = ptr + rect.pos.x * sizeof(Color) + (rect.pos.y * sizeof(Color) * stride);
+
+        return Canvas { .width = rect.width, .height = rect.height, .stride = stride, .ptr = p };
+    }
+
+    void Canvas::fill(Color color)
+    {
+        u8* p = ptr;
+        for (int i = 0; i < height; i++)
+        {
+            u32* colorp = (u32*)p;
+            for (int j = 0; j < width; j++)
+            {
+                *colorp = color.raw;
+                colorp++;
+            }
+            p += stride * sizeof(Color);
+        }
+    }
+
+    void Canvas::fill(u32* pixels, int _stride)
+    {
+        u8* p = ptr;
+        for (int i = 0; i < height; i++)
+        {
+            u32* colorp = (u32*)p;
+            for (int j = 0; j < width; j++)
+            {
+                u32 pix = pixels[j];
+                if (Color::from_u32(pix).alpha() == 0xff) *colorp = pix;
+                colorp++;
+            }
+            pixels += _stride;
+            p += stride * sizeof(Color);
+        }
+    }
+}

libui/src/Container.cpp

@@ -0,0 +1,58 @@
+/**
+ * @file Container.cpp
+ * @author apio (cloudapio.eu)
+ * @brief A container widget to pad and align objects inside it.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <ui/Container.h>
+
+namespace ui
+{
+    Container::Container(Rect rect, VerticalAlignment valign, HorizontalAlignment halign)
+        : m_valign(valign), m_halign(halign)
+    {
+        m_rect = rect;
+    }
+
+    void Container::set_widget(Widget& widget)
+    {
+        m_widget = &widget;
+        widget.rect() = ui::align(m_rect, widget.rect(), m_valign, m_halign);
+        widget.set_parent(this);
+    }
+
+    Result<EventResult> Container::handle_mouse_move(Point position)
+    {
+        if (m_widget->rect().contains(position)) return m_widget->handle_mouse_move(position);
+        return ui::EventResult::DidNotHandle;
+    }
+
+    Result<EventResult> Container::handle_mouse_leave()
+    {
+        return m_widget->handle_mouse_leave();
+    }
+
+    Result<EventResult> Container::handle_mouse_down(Point position, int buttons)
+    {
+        if (m_widget->rect().contains(position)) return m_widget->handle_mouse_down(position, buttons);
+        return ui::EventResult::DidNotHandle;
+    }
+
+    Result<EventResult> Container::handle_mouse_up(Point position, int buttons)
+    {
+        if (m_widget->rect().contains(position)) return m_widget->handle_mouse_up(position, buttons);
+        return ui::EventResult::DidNotHandle;
+    }
+
+    Result<void> Container::draw(Canvas& canvas)
+    {
+        auto rect = ui::Rect { m_widget->rect().pos.x - m_rect.pos.x, m_widget->rect().pos.y - m_rect.pos.y,
+                               m_widget->rect().width, m_widget->rect().height };
+        auto subcanvas = canvas.subcanvas(rect);
+        return m_widget->draw(subcanvas);
+    }
+
+}

libui/src/Font.cpp

@@ -0,0 +1,121 @@
+/**
+ * @file Font.cpp
+ * @author apio (cloudapio.eu)
+ * @brief PSF font loading and rendering.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <luna/String.h>
+#include <os/File.h>
+#include <ui/Font.h>
+
+constexpr static int BYTES_PER_PIXEL = (int)sizeof(ui::Color);
+
+namespace ui
+{
+    Result<SharedPtr<Font>> Font::load(const os::Path& path)
+    {
+        auto font = TRY(make_shared<Font>());
+
+        auto file = TRY(os::File::open(path, os::File::ReadOnly));
+
+        TRY(file->read_typed(font->m_psf_header));
+
+        if (font->m_psf_header.magic != PSF_FONT_MAGIC)
+        {
+            os::eprintln("ui::Font::load(%s) failed: font magic does not match PSF2 magic", path.name().chars());
+            return err(ENOTSUP);
+        }
+
+        if (font->m_psf_header.version != 0)
+        {
+            os::eprintln("ui::Font::load(%s) failed: font version is unsupported", path.name().chars());
+            return err(ENOTSUP);
+        }
+
+        if (font->m_psf_header.flags)
+        {
+            os::eprintln("ui::Font::load(%s) warning: font has a unicode table, which we're ignoring",
+                         path.name().chars());
+            // todo(); // Font has a unicode table, oh no!
+        }
+
+        font->m_font_data = TRY(file->read_all()); // Read the rest of the file into the font data buffer.
+
+        return font;
+    }
+
+    Result<SharedPtr<Font>> Font::load_builtin(StringView name, FontWeight weight)
+    {
+        auto path = TRY(String::format("/usr/share/fonts/%s-%s.psf"_sv, name.chars(),
+                                       weight == FontWeight::Bold ? "Bold" : "Regular"));
+
+        return load(path.view());
+    }
+
+    SharedPtr<Font> Font::default_font()
+    {
+        static SharedPtr<ui::Font> s_default_font = {};
+        if (!s_default_font) s_default_font = load("/usr/share/fonts/Tamsyn-Regular.psf").release_value();
+        return s_default_font;
+    }
+
+    SharedPtr<Font> Font::default_bold_font()
+    {
+        static SharedPtr<ui::Font> s_default_bold_font = {};
+        if (!s_default_bold_font) s_default_bold_font = load("/usr/share/fonts/Tamsyn-Bold.psf").release_value();
+        return s_default_bold_font;
+    }
+
+    void Font::render(wchar_t codepoint, ui::Color color, ui::Canvas& canvas)
+    {
+        const wchar_t str[] = { codepoint, 0 };
+        render(str, color, canvas);
+    }
+
+    void Font::render(const wchar_t* text, ui::Color color, ui::Canvas& canvas)
+    {
+        usize len = wcslen(text);
+
+        int height = m_psf_header.height;
+        int width = m_psf_header.width;
+        int last_char_width = width;
+
+        if (canvas.width < (m_psf_header.width * static_cast<int>(len)))
+        {
+            len = (canvas.width / width) + 1;
+            last_char_width = canvas.width % width;
+        }
+
+        if (canvas.height < height) height = canvas.height;
+
+        const int bytes_per_line = (m_psf_header.width + 7) / 8;
+
+        for (usize i = 0; i < len; i++)
+        {
+            if (i + 1 == len) width = last_char_width;
+            wchar_t codepoint = text[i];
+
+            u8* glyph =
+                m_font_data.data() + (codepoint > 0 && codepoint < (wchar_t)m_psf_header.numglyph ? codepoint : 0) *
+                                         m_psf_header.bytesperglyph;
+
+            u32 offset = (u32)i * m_psf_header.width * BYTES_PER_PIXEL;
+            for (int y = 0; y < height; y++)
+            {
+                u32 line = offset;
+                int mask = 1 << (m_psf_header.width - 1);
+                for (int x = 0; x < width; x++)
+                {
+                    if (*((u32*)glyph) & mask) *(u32*)(canvas.ptr + line) = color.raw;
+                    mask >>= 1;
+                    line += BYTES_PER_PIXEL;
+                }
+                glyph += bytes_per_line;
+                offset += canvas.stride * BYTES_PER_PIXEL;
+            }
+        }
+    }
+}

libui/src/Image.cpp

@@ -0,0 +1,48 @@
+/**
+ * @file Image.cpp
+ * @author apio (cloudapio.eu)
+ * @brief TGA image loading and rendering.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <os/File.h>
+#include <ui/Alignment.h>
+#include <ui/Image.h>
+
+namespace ui
+{
+    Result<SharedPtr<Image>> Image::load(const os::Path& path)
+    {
+        auto image = TRY(make_shared<Image>());
+        auto file = TRY(os::File::open(path, os::File::ReadOnly));
+
+        TRY(file->read_typed(image->m_tga_header));
+
+        if (image->m_tga_header.encoding != 2) todo();
+        if (image->m_tga_header.bpp != 32) todo();
+
+        Buffer image_id;
+        TRY(file->read(image_id, image->m_tga_header.idlen));
+
+        TRY(file->read(image->m_image_data,
+                       image->m_tga_header.w * image->m_tga_header.h * (image->m_tga_header.bpp / 8)));
+
+        return image;
+    }
+
+    Result<OwnedPtr<ImageWidget>> ImageWidget::load(const os::Path& path)
+    {
+        auto widget = TRY(make_owned<ImageWidget>());
+        widget->m_image = TRY(Image::load(path));
+        widget->m_rect = { 0, 0, widget->m_image->width(), widget->m_image->height() };
+        return widget;
+    }
+
+    Result<void> ImageWidget::draw(Canvas& canvas)
+    {
+        canvas.subcanvas({ 0, 0, m_image->width(), m_image->height() }).fill(m_image->pixels(), m_image->width());
+        return {};
+    }
+}

libui/src/Layout.cpp

@@ -0,0 +1,192 @@
+/**
+ * @file Layout.cpp
+ * @author apio (cloudapio.eu)
+ * @brief Layout widgets to organize content.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <stdlib.h>
+#include <ui/Layout.h>
+
+namespace ui
+{
+    HorizontalLayout::HorizontalLayout(AdjustHeight adjust_height, AdjustWidth adjust_width)
+        : m_adjust_height(adjust_height), m_adjust_width(adjust_width)
+    {
+    }
+
+    Result<EventResult> HorizontalLayout::handle_mouse_move(Point position)
+    {
+        EventResult result = ui::EventResult::DidNotHandle;
+
+        for (auto widget : m_widgets)
+        {
+            if (widget->rect().contains(position)) result = TRY(widget->handle_mouse_move(position));
+            else
+                TRY(widget->handle_mouse_leave());
+        }
+
+        return result;
+    }
+
+    Result<EventResult> HorizontalLayout::handle_mouse_leave()
+    {
+        for (auto widget : m_widgets) TRY(widget->handle_mouse_leave());
+
+        return ui::EventResult::DidNotHandle;
+    }
+
+    Result<EventResult> HorizontalLayout::handle_mouse_up(Point position, int buttons)
+    {
+        for (auto widget : m_widgets)
+        {
+            if (widget->rect().contains(position)) return widget->handle_mouse_up(position, buttons);
+        }
+
+        return ui::EventResult::DidNotHandle;
+    }
+
+    Result<EventResult> HorizontalLayout::handle_mouse_down(Point position, int buttons)
+    {
+        for (auto widget : m_widgets)
+        {
+            if (widget->rect().contains(position)) return widget->handle_mouse_down(position, buttons);
+        }
+
+        return ui::EventResult::DidNotHandle;
+    }
+
+    Result<void> HorizontalLayout::draw(Canvas& canvas)
+    {
+        for (auto widget : m_widgets)
+        {
+            ui::Rect rect = { m_rect.relative(widget->rect().pos), widget->rect().width, widget->rect().height };
+            auto subcanvas = canvas.subcanvas(rect);
+            TRY(widget->draw(subcanvas));
+        }
+
+        return {};
+    }
+
+    Result<void> HorizontalLayout::add_widget(Widget& widget)
+    {
+        TRY(m_widgets.try_append(&widget));
+
+        if (m_adjust_width == AdjustWidth::No)
+        {
+            widget.rect().pos.x = m_rect.pos.x + m_used_width;
+            m_used_width += widget.rect().width;
+        }
+        else
+        {
+            int used_width = 0;
+            div_t result = div(m_rect.width, (int)m_widgets.size());
+            for (auto w : m_widgets)
+            {
+                w->rect().pos.x = m_rect.pos.x + used_width;
+                w->rect().width = result.quot;
+                used_width += result.quot;
+            }
+            m_widgets[m_widgets.size() - 1]->rect().width += result.rem;
+        }
+
+        widget.rect().pos.y = m_rect.pos.y;
+
+        if (m_adjust_height == AdjustHeight::Yes) { widget.rect().height = m_rect.height; }
+
+        widget.set_parent(this);
+
+        return {};
+    }
+
+    VerticalLayout::VerticalLayout(AdjustHeight adjust_height, AdjustWidth adjust_width)
+        : m_adjust_height(adjust_height), m_adjust_width(adjust_width)
+    {
+    }
+
+    Result<EventResult> VerticalLayout::handle_mouse_move(Point position)
+    {
+        EventResult result = ui::EventResult::DidNotHandle;
+
+        for (auto widget : m_widgets)
+        {
+            if (widget->rect().contains(position)) result = TRY(widget->handle_mouse_move(position));
+            else
+                TRY(widget->handle_mouse_leave());
+        }
+
+        return result;
+    }
+
+    Result<EventResult> VerticalLayout::handle_mouse_leave()
+    {
+        for (auto widget : m_widgets) TRY(widget->handle_mouse_leave());
+
+        return ui::EventResult::DidNotHandle;
+    }
+
+    Result<EventResult> VerticalLayout::handle_mouse_up(Point position, int buttons)
+    {
+        for (auto widget : m_widgets)
+        {
+            if (widget->rect().contains(position)) return widget->handle_mouse_up(position, buttons);
+        }
+
+        return ui::EventResult::DidNotHandle;
+    }
+
+    Result<EventResult> VerticalLayout::handle_mouse_down(Point position, int buttons)
+    {
+        for (auto widget : m_widgets)
+        {
+            if (widget->rect().contains(position)) return widget->handle_mouse_down(position, buttons);
+        }
+
+        return ui::EventResult::DidNotHandle;
+    }
+
+    Result<void> VerticalLayout::draw(Canvas& canvas)
+    {
+        for (auto widget : m_widgets)
+        {
+            ui::Rect rect = { m_rect.relative(widget->rect().pos), widget->rect().width, widget->rect().height };
+            auto subcanvas = canvas.subcanvas(rect);
+            TRY(widget->draw(subcanvas));
+        }
+
+        return {};
+    }
+
+    Result<void> VerticalLayout::add_widget(Widget& widget)
+    {
+        TRY(m_widgets.try_append(&widget));
+
+        if (m_adjust_height == AdjustHeight::No)
+        {
+            widget.rect().pos.y = m_rect.pos.y + m_used_height;
+            m_used_height += widget.rect().height;
+        }
+        else
+        {
+            int used_height = 0;
+            div_t result = div(m_rect.height, (int)m_widgets.size());
+            for (auto w : m_widgets)
+            {
+                w->rect().pos.y = m_rect.pos.y + used_height;
+                w->rect().height = result.quot;
+                used_height += result.quot;
+            }
+            m_widgets[m_widgets.size() - 1]->rect().height += result.rem;
+        }
+
+        widget.rect().pos.x = m_rect.pos.x;
+
+        if (m_adjust_width == AdjustWidth::Yes) { widget.rect().width = m_rect.width; }
+
+        widget.set_parent(this);
+
+        return {};
+    }
+}

libui/src/Rect.cpp

@@ -0,0 +1,62 @@
+/**
+ * @file Rect.cpp
+ * @author apio (cloudapio.eu)
+ * @brief A simple 2D rectangle representation.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <ui/Rect.h>
+
+namespace ui
+{
+    bool Rect::contains(Point point)
+    {
+        return (point.x >= pos.x) && (point.y >= pos.y) && (point.x <= (pos.x + width)) &&
+               (point.y <= (pos.y + height));
+    }
+
+    bool Rect::contains(Rect rect)
+    {
+        if (!contains(rect.pos)) return false;
+        Point rel = relative(rect.pos);
+        if ((rel.x + rect.width) > width) return false;
+        if ((rel.y + rect.height) > height) return false;
+        return true;
+    }
+
+    Point Rect::normalize(Point point)
+    {
+        if (point.x < pos.x) point.x = pos.x;
+        if (point.y < pos.y) point.y = pos.y;
+        if (point.x > pos.x + width) point.x = pos.x + width;
+        if (point.y > pos.y + height) point.y = pos.y + height;
+        return point;
+    }
+
+    Point Rect::relative(Point point)
+    {
+        point = normalize(point);
+        point.x -= pos.x;
+        point.y -= pos.y;
+        return point;
+    }
+
+    Point Rect::absolute(Point point)
+    {
+        point.x += pos.x;
+        point.y += pos.y;
+        return point;
+    }
+
+    Rect Rect::absolute(Rect rect)
+    {
+        return Rect { absolute(rect.pos), rect.width, rect.height };
+    }
+
+    Rect Rect::normalized()
+    {
+        return Rect { ui::Point { pos.x < 0 ? 0 : pos.x, pos.y < 0 ? 0 : pos.y }, width, height };
+    }
+};

libui/src/Window.cpp

@@ -0,0 +1,110 @@
+/**
+ * @file Window.cpp
+ * @author apio (cloudapio.eu)
+ * @brief UI windows.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <luna/String.h>
+#include <os/SharedMemory.h>
+#include <sys/mman.h>
+#include <ui/App.h>
+#include <ui/Window.h>
+#include <ui/ipc/Server.h>
+
+namespace ui
+{
+    Result<Window*> Window::create(Rect rect, bool decorated)
+    {
+        auto window = TRY(make_owned<Window>());
+
+        ui::CreateWindowRequest request;
+        request.rect = rect;
+        request.decorated = decorated;
+        auto response = TRY(os::IPC::send_sync<ui::CreateWindowResponse>(App::the().client(), request));
+
+        auto path = COPY_IPC_STRING(response.shm_path);
+
+        u32* pixels = (u32*)TRY(os::SharedMemory::adopt(path.view(), rect.height * rect.width * 4));
+
+        window->m_canvas = ui::Canvas { rect.width, rect.height, rect.width, (u8*)pixels };
+        window->m_id = response.window;
+
+        Window* p = window.ptr();
+
+        App::the().register_window(move(window), {});
+
+        return p;
+    }
+
+    Window::~Window()
+    {
+        if (m_canvas.ptr) munmap(m_canvas.ptr, ((usize)m_canvas.width) * ((usize)m_canvas.height) * 4);
+    }
+
+    void Window::set_title(StringView title)
+    {
+        ui::SetWindowTitleRequest request;
+        request.window = m_id;
+        SET_IPC_STRING(request.title, title.chars());
+        os::IPC::send_async(App::the().client(), request);
+    }
+
+    void Window::update()
+    {
+        ui::InvalidateRequest request;
+        request.window = m_id;
+        os::IPC::send_async(App::the().client(), request);
+    }
+
+    void Window::close()
+    {
+        App& app = App::the();
+
+        ui::CloseWindowRequest request;
+        request.window = m_id;
+        os::IPC::send_async(app.client(), request);
+
+        if (this == app.main_window()) app.set_should_close(true);
+
+        app.unregister_window(this, {});
+    }
+
+    Result<void> Window::draw()
+    {
+        m_canvas.fill(m_background);
+        if (m_main_widget) return m_main_widget->draw(m_canvas);
+        update();
+        return {};
+    }
+
+    Result<void> Window::handle_mouse_leave()
+    {
+        if (!m_main_widget) return {};
+        TRY(m_main_widget->handle_mouse_leave());
+        return {};
+    }
+
+    Result<void> Window::handle_mouse_move(ui::Point position)
+    {
+        if (!m_main_widget) return {};
+        TRY(m_main_widget->handle_mouse_move(position));
+        return {};
+    }
+
+    Result<void> Window::handle_mouse_buttons(ui::Point position, int buttons)
+    {
+        if (!m_main_widget) return {};
+        if (buttons) TRY(m_main_widget->handle_mouse_down(position, buttons));
+        if (m_old_mouse_buttons.has_value())
+        {
+            int old_buttons = m_old_mouse_buttons.value();
+            int diff = old_buttons & ~buttons;
+            if (diff) TRY(m_main_widget->handle_mouse_up(position, diff));
+        }
+        m_old_mouse_buttons = buttons;
+        return {};
+    }
+}

shell/main.cpp

@@ -133,7 +133,8 @@ Result<int> luna_main(int argc, char** argv)
         if (interactive)
         {
             auto cwd = TRY(os::FileSystem::working_directory());
-            os::print("%s@%s:%s%c ", username, hostname, cwd.chars(), prompt_end);
+            os::print("\x1b[%dm%s\x1b[m@\x1b[36m%s\x1b[m:\x1b[1;34m%s\x1b[m%c ", getuid() == 0 ? 31 : 35, username,
+                      hostname, cwd.chars(), prompt_end);
         }
 
         auto maybe_cmd = input_file->read_line();

tools/install-headers.sh

@@ -8,10 +8,12 @@ cd $LUNA_ROOT
 mkdir -p $LUNA_BASE
 mkdir -p $LUNA_BASE/usr/include
 mkdir -p $LUNA_BASE/usr/include/luna
+mkdir -p $LUNA_BASE/usr/include/ui
 mkdir -p $LUNA_BASE/usr/include/os
 mkdir -p $LUNA_BASE/usr/include/moon
 
 cp --preserve=timestamps -RT libc/include/ $LUNA_BASE/usr/include
 cp --preserve=timestamps -RT libluna/include/luna/ $LUNA_BASE/usr/include/luna
+cp --preserve=timestamps -RT libui/include/ui/ $LUNA_BASE/usr/include/ui
 cp --preserve=timestamps -RT libos/include/os/ $LUNA_BASE/usr/include/os
 cp --preserve=timestamps -RT kernel/src/api/ $LUNA_BASE/usr/include/moon

tools/sources.sh

@@ -4,7 +4,7 @@ source $(dirname $0)/env.sh
 
 cd $LUNA_ROOT
 
-FOLDERS=(kernel libc libos libluna apps shell tests)
+FOLDERS=(kernel libc libos libui libluna apps shell tests)
 
 SOURCES=($(find ${FOLDERS[@]} -type f -name "*.cpp"))
 SOURCES+=($(find ${FOLDERS[@]} -type f -name "*.h"))

wind/CMakeLists.txt

@@ -0,0 +1,19 @@
+set(SOURCES
+    main.cpp
+    Screen.h
+    Screen.cpp
+    Mouse.h
+    Mouse.cpp
+    Window.h
+    Window.cpp
+    IPC.cpp
+    IPC.h
+    Client.h
+)
+
+add_executable(wind ${SOURCES})
+target_compile_options(wind PRIVATE -Os ${COMMON_FLAGS} -Wno-write-strings -fno-threadsafe-statics)
+add_dependencies(wind libc)
+target_include_directories(wind PRIVATE ${LUNA_BASE}/usr/include ${CMAKE_CURRENT_LIST_DIR})
+target_link_libraries(wind PRIVATE os ui)
+install(TARGETS wind DESTINATION ${LUNA_BASE}/usr/bin)

wind/Client.h

@@ -0,0 +1,18 @@
+#pragma once
+#include "Window.h"
+#include <os/LocalServer.h>
+
+struct Client
+{
+    os::LocalServer::Client conn;
+    Vector<Window*> windows;
+    bool rpc_in_progress { false };
+    u8 rpc_id { 0 };
+
+    Client(os::LocalServer::Client&& client)
+#ifdef CLIENT_IMPLEMENTATION
+        : conn(move(client)), windows() {}
+#else
+        ;
+#endif
+};

wind/IPC.cpp

@@ -0,0 +1,181 @@
+#include "IPC.h"
+#include "Screen.h"
+#include <luna/Alignment.h>
+#include <luna/String.h>
+#include <os/File.h>
+#include <os/SharedMemory.h>
+#include <time.h>
+
+#define TRY_OR_IPC_ERROR(expr)                                                                                         \
+    ({                                                                                                                 \
+        auto _expr_rc = (expr);                                                                                        \
+        if (!_expr_rc.has_value())                                                                                     \
+        {                                                                                                              \
+            g_windows.remove(window);                                                                                  \
+            delete window;                                                                                             \
+            os::IPC::send_error(client.conn, _expr_rc.error());                                                        \
+            return {};                                                                                                 \
+        }                                                                                                              \
+        _expr_rc.release_value();                                                                                      \
+    })
+
+#define READ_MESSAGE(request)                                                                                          \
+    do {                                                                                                               \
+        auto rc = client.conn.recv_typed(request);                                                                     \
+        if (rc.has_error())                                                                                            \
+        {                                                                                                              \
+            if (rc.error() == EAGAIN)                                                                                  \
+            {                                                                                                          \
+                client.rpc_in_progress = true;                                                                         \
+                client.rpc_id = decltype(request)::ID;                                                                 \
+                return {};                                                                                             \
+            }                                                                                                          \
+            if (rc.error() == EINTR)                                                                                   \
+            {                                                                                                          \
+                client.rpc_in_progress = true;                                                                         \
+                client.rpc_id = decltype(request)::ID;                                                                 \
+                return {};                                                                                             \
+            }                                                                                                          \
+            else                                                                                                       \
+                return rc.release_error();                                                                             \
+        }                                                                                                              \
+    } while (0)
+
+#define CHECK_WINDOW_ID(request)                                                                                       \
+    do {                                                                                                               \
+        if ((usize)request.window >= client.windows.size() || !client.windows[request.window])                         \
+        {                                                                                                              \
+            os::eprintln("wind: Window id is invalid!");                                                               \
+            return {};                                                                                                 \
+        }                                                                                                              \
+    } while (0)
+
+static Result<void> handle_create_window_message(Client& client)
+{
+    ui::CreateWindowRequest request;
+    READ_MESSAGE(request);
+
+    if (request.decorated)
+    {
+        request.rect.height +=
+            Window::titlebar_height(); // Make sure we provide the full contents rect that was asked for.
+        request.rect.pos.y -= Window::titlebar_height(); // Adjust it so the contents begin at the expected coordinates.
+    }
+
+    request.rect = request.rect.normalized();
+
+    auto name = TRY(String::from_cstring("Window"));
+
+    auto shm_path = TRY(String::format("/wind-shm-%d-%lu"_sv, client.conn.fd(), time(NULL)));
+
+    auto* window = new (std::nothrow) Window(request.rect, move(name), request.decorated);
+    if (!window)
+    {
+        os::IPC::send_error(client.conn, ENOMEM);
+        return {};
+    }
+
+    window->pixels = (u32*)TRY_OR_IPC_ERROR(
+        os::SharedMemory::create(shm_path.view(), window->contents.height * window->contents.width * 4));
+
+    TRY_OR_IPC_ERROR(client.windows.try_append(window));
+    int id = static_cast<int>(client.windows.size() - 1);
+
+    window->client = &client;
+    window->id = id;
+
+    ui::CreateWindowResponse response;
+    response.window = id;
+    SET_IPC_STRING(response.shm_path, shm_path.chars());
+    os::IPC::send_async(client.conn, response);
+    return {};
+}
+
+static Result<void> handle_set_window_title_message(Client& client)
+{
+    ui::SetWindowTitleRequest request;
+    READ_MESSAGE(request);
+
+    auto name = COPY_IPC_STRING(request.title);
+
+    os::println("wind: SetWindowTitle(\"%s\") for window %d", name.chars(), request.window);
+
+    CHECK_WINDOW_ID(request);
+
+    client.windows[request.window]->name = move(name);
+
+    return {};
+}
+
+static Result<void> handle_invalidate_message(Client& client)
+{
+    ui::InvalidateRequest request;
+    READ_MESSAGE(request);
+
+    CHECK_WINDOW_ID(request);
+
+    client.windows[request.window]->dirty = true;
+
+    return {};
+}
+
+static Result<void> handle_close_window_message(Client& client)
+{
+    ui::CloseWindowRequest request;
+    READ_MESSAGE(request);
+
+    CHECK_WINDOW_ID(request);
+
+    auto* window = client.windows[request.window];
+    client.windows[request.window] = nullptr;
+    g_windows.remove(window);
+    delete window;
+
+    return {};
+}
+
+static Result<void> handle_get_screen_rect_message(Client& client)
+{
+    ui::GetScreenRectRequest request;
+    READ_MESSAGE(request); // Kinda pointless, but required.
+
+    ui::GetScreenRectResponse response;
+    response.rect = Screen::the().canvas().rect();
+    os::IPC::send_async(client.conn, response);
+
+    return {};
+}
+
+namespace wind
+{
+    Result<void> handle_ipc_message(Client& client, u8 id)
+    {
+        client.rpc_in_progress = false;
+        switch (id)
+        {
+        case ui::CREATE_WINDOW_ID: return handle_create_window_message(client);
+        case ui::SET_WINDOW_TITLE_ID: return handle_set_window_title_message(client);
+        case ui::INVALIDATE_ID: return handle_invalidate_message(client);
+        case ui::CLOSE_WINDOW_ID: return handle_close_window_message(client);
+        case ui::GET_SCREEN_RECT_ID: return handle_get_screen_rect_message(client);
+        default: os::eprintln("wind: Invalid IPC message from client!"); return err(EINVAL);
+        }
+    }
+
+    Result<void> handle_ipc(Client& client)
+    {
+        if (client.rpc_in_progress) return handle_ipc_message(client, client.rpc_id);
+
+        u8 id;
+        auto rc = client.conn.recv_typed(id);
+        if (rc.has_error())
+        {
+            if (rc.error() == EAGAIN) { return {}; }
+            if (rc.error() == EINTR) { return {}; }
+            else
+                return rc.release_error();
+        }
+
+        return handle_ipc_message(client, id);
+    }
+}

wind/IPC.h

@@ -0,0 +1,10 @@
+#pragma once
+#include "Client.h"
+#include <ui/ipc/Server.h>
+
+namespace wind
+{
+    Result<void> handle_ipc_message(Client& client, u8 id);
+
+    Result<void> handle_ipc(Client& client);
+}

wind/Mouse.cpp

@@ -0,0 +1,112 @@
+#include "Mouse.h"
+#include "Client.h"
+#include <os/File.h>
+#include <os/IPC.h>
+#include <ui/Image.h>
+#include <ui/ipc/Client.h>
+
+static SharedPtr<ui::Image> g_mouse_cursor;
+
+Mouse::Mouse(ui::Canvas& screen)
+{
+    m_position.x = screen.width / 2;
+    m_position.y = screen.height / 2;
+    m_screen_rect = screen.rect();
+
+    g_mouse_cursor = ui::Image::load("/usr/share/cursors/default.tga").value_or({});
+}
+
+void Mouse::draw(ui::Canvas& screen)
+{
+    if (!g_mouse_cursor) return;
+    auto canvas = screen.subcanvas(ui::Rect { m_position, g_mouse_cursor->width(), g_mouse_cursor->height() });
+    canvas.fill(g_mouse_cursor->pixels(), g_mouse_cursor->width());
+}
+
+void Mouse::update(const moon::MousePacket& packet)
+{
+    m_position.x += packet.xdelta;
+    m_position.y -= packet.ydelta;
+    m_position = m_screen_rect.normalize(m_position);
+
+    if (m_dragging_window && !(packet.buttons & moon::MouseButton::Left))
+    {
+        os::println("Stopped drag: window at (%d,%d,%d,%d) with offset (%d,%d)", m_dragging_window->surface.pos.x,
+                    m_dragging_window->surface.pos.y, m_dragging_window->surface.width,
+                    m_dragging_window->surface.height, this->m_initial_drag_position.x,
+                    this->m_initial_drag_position.y);
+        m_dragging_window = nullptr;
+    }
+
+    if (m_dragging_window)
+    {
+        m_dragging_window->surface.pos =
+            ui::Point { m_position.x - m_initial_drag_position.x, m_position.y - m_initial_drag_position.y };
+        m_dragging_window->surface = m_dragging_window->surface.normalized();
+    }
+
+    else if ((packet.buttons & moon::MouseButton::Left) && !m_dragging_window)
+    {
+        // Iterate from the end of the list, since windows at the beginning are stacked at the bottom and windows at the
+        // top are at the end.
+        for (Window* window = g_windows.last().value_or(nullptr); window;
+             window = g_windows.previous(window).value_or(nullptr))
+        {
+            if (window->surface.absolute(window->close_button).contains(m_position))
+            {
+                ui::WindowCloseRequest request;
+                request.window = window->id;
+                auto& client = *window->client;
+                os::IPC::send_async(client.conn, request);
+                break;
+            }
+            else if (window->surface.absolute(window->titlebar).contains(m_position))
+            {
+                m_dragging_window = window;
+                m_initial_drag_position = window->surface.relative(m_position);
+                os::println("Started drag: window at (%d,%d,%d,%d) with offset (%d,%d)", window->surface.pos.x,
+                            window->surface.pos.y, window->surface.width, window->surface.height,
+                            m_initial_drag_position.x, m_initial_drag_position.y);
+                window->focus();
+                break;
+            }
+            else if (window->surface.absolute(window->contents).contains(m_position))
+            {
+                window->focus();
+                break; // We don't want to continue iterating, otherwise this would take into account windows whose
+                       // titlebar is underneath another window's contents!
+            }
+        }
+    }
+
+    Window* new_active_window = nullptr;
+
+    for (Window* window = g_windows.last().value_or(nullptr); window;
+         window = g_windows.previous(window).value_or(nullptr))
+    {
+        auto titlebar = window->surface.absolute(window->titlebar);
+        auto contents = window->surface.absolute(window->contents);
+        if (titlebar.contains(m_position)) break;
+        if (contents.contains(m_position))
+        {
+            ui::MouseEventRequest request;
+            request.window = window->id;
+            request.position = contents.relative(m_position);
+            request.buttons = packet.buttons;
+            os::IPC::send_async(window->client->conn, request);
+            new_active_window = window;
+            break;
+        }
+    }
+
+    if (m_active_window != new_active_window)
+    {
+        if (m_active_window)
+        {
+            ui::MouseLeaveRequest request;
+            request.window = m_active_window->id;
+            os::IPC::send_async(m_active_window->client->conn, request);
+        }
+        m_active_window = new_active_window;
+    }
+}

wind/Mouse.h

@@ -0,0 +1,24 @@
+#pragma once
+#include "Screen.h"
+#include "Window.h"
+#include <moon/Mouse.h>
+#include <ui/Canvas.h>
+
+class Mouse
+{
+  public:
+    Mouse(ui::Canvas& screen);
+
+    void update(const moon::MousePacket& packet);
+
+    void draw(ui::Canvas& screen);
+
+  private:
+    ui::Point m_position;
+    ui::Rect m_screen_rect;
+
+    Window* m_dragging_window = nullptr;
+    ui::Point m_initial_drag_position;
+
+    Window* m_active_window = nullptr;
+};

wind/Screen.cpp

@@ -0,0 +1,36 @@
+#include "Screen.h"
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+Screen Screen::s_the;
+
+Result<void> Screen::open()
+{
+    int fd = ::open("/dev/fb0", O_RDWR);
+    if (fd < 0) return err(errno);
+
+    int width = ioctl(fd, FB_GET_WIDTH);
+    int height = ioctl(fd, FB_GET_HEIGHT);
+
+    void* p = mmap(nullptr, width * height * BYTES_PER_PIXEL, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+    close(fd);
+
+    if (p == MAP_FAILED) { return err(errno); }
+
+    Screen screen;
+
+    screen.m_canvas = ui::Canvas::create((u8*)p, width, height);
+    screen.m_size = width * height * BYTES_PER_PIXEL;
+
+    s_the = screen;
+
+    return {};
+}
+
+void Screen::sync()
+{
+    msync(m_canvas.ptr, size(), MS_SYNC);
+}

wind/Screen.h

@@ -0,0 +1,34 @@
+#pragma once
+#include <luna/OwnedPtr.h>
+#include <ui/Canvas.h>
+
+constexpr int BYTES_PER_PIXEL = 4;
+
+class Screen
+{
+  public:
+    static Result<void> open();
+
+    ui::Canvas& canvas()
+    {
+        return m_canvas;
+    }
+
+    int size() const
+    {
+        return m_size;
+    }
+
+    static Screen& the()
+    {
+        return s_the;
+    }
+
+    void sync();
+
+  private:
+    ui::Canvas m_canvas;
+    int m_size;
+
+    static Screen s_the;
+};

wind/Window.cpp

@@ -0,0 +1,67 @@
+#include "Window.h"
+#include <luna/Utf8.h>
+#include <os/File.h>
+#include <sys/mman.h>
+#include <ui/Font.h>
+#include <ui/Image.h>
+
+LinkedList<Window> g_windows;
+
+void Window::draw(ui::Canvas& screen)
+{
+    dirty = false;
+
+    auto window = screen.subcanvas(surface);
+    window.subcanvas(contents).fill(pixels, contents.width);
+
+    wchar_t buffer[4096];
+    Utf8StringDecoder decoder(name.chars());
+    decoder.decode(buffer, sizeof(buffer)).release_value();
+
+    auto font = ui::Font::default_font();
+
+    auto titlebar_canvas = window.subcanvas(titlebar);
+    titlebar_canvas.fill(ui::GRAY);
+
+    auto textarea = titlebar_canvas.subcanvas(ui::Rect { 10, 10, titlebar_canvas.width - 10, titlebar_canvas.height });
+    font->render(buffer, ui::BLACK, textarea);
+
+    static SharedPtr<ui::Image> g_close_icon;
+
+    if (!g_close_icon) g_close_icon = ui::Image::load("/usr/share/icons/16x16/app-close.tga").release_value();
+
+    auto close_area = window.subcanvas(close_button);
+    close_area.fill(g_close_icon->pixels(), g_close_icon->width());
+}
+
+void Window::focus()
+{
+    // Bring the window to the front of the list.
+    g_windows.remove(this);
+    g_windows.append(this);
+}
+
+Window::Window(ui::Rect r, String&& n, bool d) : surface(r), name(move(n)), decorated(d)
+{
+    auto font = ui::Font::default_font();
+    if (decorated && surface.width < 36) surface.width = 36;
+    if (decorated && surface.height < (font->height() + 20)) surface.height = font->height() + 20;
+    titlebar = decorated ? ui::Rect { 0, 0, surface.width, font->height() + 20 } : ui::Rect { 0, 0, 0, 0 };
+    close_button = decorated ? ui::Rect { surface.width - 26, 10, 16, 16 } : ui::Rect { 0, 0, 0, 0 };
+    contents = decorated ? ui::Rect { 0, font->height() + 20, surface.width, surface.height - (font->height() + 20) }
+                         : ui::Rect { 0, 0, surface.width, surface.height };
+    g_windows.append(this);
+}
+
+int Window::titlebar_height()
+{
+    auto font = ui::Font::default_font();
+    return font->height() + 20;
+}
+
+Window::~Window()
+{
+    usize size = contents.width * contents.height * 4;
+
+    munmap(pixels, size);
+}

wind/Window.h

@@ -0,0 +1,33 @@
+#pragma once
+#include <luna/LinkedList.h>
+#include <luna/String.h>
+#include <ui/Canvas.h>
+#include <ui/Color.h>
+#include <ui/Rect.h>
+
+struct Client;
+
+struct Window : public LinkedListNode<Window>
+{
+    ui::Rect surface;
+    ui::Rect titlebar;
+    ui::Rect close_button;
+    ui::Rect contents;
+    u32* pixels;
+    String name;
+    bool dirty { false };
+    Client* client;
+    int id;
+    bool decorated;
+
+    static int titlebar_height();
+
+    Window(ui::Rect, String&&, bool);
+    ~Window();
+
+    void focus();
+
+    void draw(ui::Canvas& screen);
+};
+
+extern LinkedList<Window> g_windows;