kernel: Start clearing caches when free memory is lower than 1MiB

This is done to avoid returning ENOMEM errors when cache memory can still be reclaimed.

apps/about.cpp

@@ -5,6 +5,8 @@
 #include <ui/Label.h>
 #include <ui/Layout.h>
 
+static constexpr ui::Color BACKGROUND_COLOR = ui::Color::from_rgb(89, 89, 89);
+
 Result<int> luna_main(int argc, char** argv)
 {
     ui::App app;
@@ -14,7 +16,7 @@ Result<int> luna_main(int argc, char** argv)
     app.set_main_window(window);
 
     window->set_title("About");
-    window->set_background(ui::CYAN);
+    window->set_background(BACKGROUND_COLOR);
 
     utsname info;
     uname(&info);
@@ -22,7 +24,7 @@ Result<int> luna_main(int argc, char** argv)
     ui::VerticalLayout main_layout;
     window->set_main_widget(main_layout);
 
-    ui::Label title("About Luna", ui::VerticalAlignment::Center, ui::HorizontalAlignment::Center,
+    ui::Label title("About Luna", ui::WHITE, ui::VerticalAlignment::Center, ui::HorizontalAlignment::Center,
                     ui::Font::default_bold_font());
     main_layout.add_widget(title);
 

apps/taskbar.cpp

@@ -8,6 +8,8 @@
 #include <ui/Image.h>
 #include <ui/Layout.h>
 
+static constexpr ui::Color TASKBAR_COLOR = ui::Color::from_rgb(83, 83, 83);
+
 void sigchld_handler(int)
 {
     wait(nullptr);
@@ -26,7 +28,7 @@ Result<int> luna_main(int argc, char** argv)
 
     auto window = TRY(ui::Window::create(bar, false));
     app.set_main_window(window);
-    window->set_background(ui::GRAY);
+    window->set_background(TASKBAR_COLOR);
 
     ui::HorizontalLayout layout(ui::AdjustHeight::Yes, ui::AdjustWidth::No);
     window->set_main_widget(layout);

kernel/src/memory/MemoryManager.cpp

@@ -157,6 +157,13 @@ namespace MemoryManager
         used_mem += ARCH_PAGE_SIZE;
         free_mem -= ARCH_PAGE_SIZE;
 
+        if (free_mem < 1024 * 1024)
+        {
+            // Less than 1 MiB of free memory! Let's start clearing caches...
+            kwarnln("Less than 1 MiB of free memory, clearing caches to try to gain extra memory");
+            Scheduler::signal_oom_thread();
+        }
+
         return index * ARCH_PAGE_SIZE;
     }
 

libui/include/ui/Label.h

@@ -22,7 +22,7 @@ namespace ui
     class Label final : public Widget
     {
       public:
-        Label(StringView text, VerticalAlignment valign = VerticalAlignment::Center,
+        Label(StringView text, ui::Color color = ui::WHITE, VerticalAlignment valign = VerticalAlignment::Center,
               HorizontalAlignment halign = HorizontalAlignment::Center, SharedPtr<Font> font = Font::default_font());
 
         void set_text(StringView text)
@@ -36,6 +36,7 @@ namespace ui
         StringView m_text;
         VerticalAlignment m_valign;
         HorizontalAlignment m_halign;
+        ui::Color m_color;
         SharedPtr<Font> m_font;
     };
 }

libui/src/Label.cpp

@@ -12,8 +12,9 @@
 
 namespace ui
 {
-    Label::Label(StringView text, VerticalAlignment valign, HorizontalAlignment halign, SharedPtr<Font> font)
+    Label::Label(StringView text, ui::Color color, VerticalAlignment valign, HorizontalAlignment halign,
-        : m_text(text), m_valign(valign), m_halign(halign), m_font(font)
+                 SharedPtr<Font> font)
+        : m_text(text), m_valign(valign), m_halign(halign), m_color(color), m_font(font)
     {
     }
 
@@ -30,7 +31,7 @@ namespace ui
         wchar_t buf[4096];
         TRY(decoder.decode(buf, sizeof(buf)));
 
-        m_font->render(buf, ui::BLACK, subcanvas);
+        m_font->render(buf, m_color, subcanvas);
         return {};
     }
 }

terminal/TerminalWidget.cpp

@@ -88,7 +88,11 @@ Result<void> TerminalWidget::init(char* const* args)
 
 Result<ui::EventResult> TerminalWidget::handle_key_event(const ui::KeyEventRequest& request)
 {
+    // Avoid handling "key released" events
     if (!request.pressed) return ui::EventResult::DidNotHandle;
+    // Non-printable key or key that has no special character (unlike Tab or Enter). We exit early to avoid inserting an
+    // invalid zero byte into the terminal input (this would also happen on Shift or Ctrl keypresses).
+    if (request.letter == '\0') return ui::EventResult::DidNotHandle;
 
     query_termios();
 

wind/Window.cpp

@@ -7,6 +7,8 @@
 
 LinkedList<Window> g_windows;
 
+static constexpr ui::Color TITLEBAR_COLOR = ui::Color::from_rgb(53, 53, 53);
+
 void Window::draw(ui::Canvas& screen)
 {
     dirty = false;
@@ -21,10 +23,10 @@ void Window::draw(ui::Canvas& screen)
     auto font = ui::Font::default_font();
 
     auto titlebar_canvas = window.subcanvas(titlebar);
-    titlebar_canvas.fill(ui::GRAY);
+    titlebar_canvas.fill(TITLEBAR_COLOR);
 
     auto textarea = titlebar_canvas.subcanvas(ui::Rect { 10, 10, titlebar_canvas.width - 10, titlebar_canvas.height });
-    font->render(buffer, ui::BLACK, textarea);
+    font->render(buffer, ui::WHITE, textarea);
 
     static SharedPtr<ui::Image> g_close_icon;