Luna/kernel/src/video/TextConsole.cpp

#include "video/TextConsole.h"
#include "boot/bootboot.h"
#include "video/Framebuffer.h"
#include <luna/CString.h>
#include <luna/Format.h>
#include <luna/Result.h>
#include <luna/Utf8.h>
#include <stdarg.h>

extern const BOOTBOOT bootboot;

#include "video/BuiltinFont.h"

static constexpr u32 BLACK = 0xff000000;
static constexpr u32 WHITE = 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 u32 g_x_position = 0;
static u32 g_y_position = 0;

static Utf8StateDecoder decoder;

static void putwchar_at(wchar_t c, u32 x, u32 y)
{
    const u8* glyph = &font[c * 16];
    for (u32 i = 0; i < FONT_HEIGHT; i++)
    {
        for (u32 j = 0; j < FONT_WIDTH; j++)
        {
            volatile u8 mask = *glyph;
            if (mask & (0b10000000 >> j)) Framebuffer::pixel(x + j, y + i, g_foreground_color);
            else
                Framebuffer::pixel(x + j, y + i, g_background_color);
        }
        glyph++;
    }
}

static void erase_current_line()
{
    Framebuffer::rect(0, g_y_position, Framebuffer::width(), FONT_HEIGHT, BLACK);
}

static void scroll()
{
    memcpy(Framebuffer::ptr(), Framebuffer::ptr() + (Framebuffer::scanline() * FONT_HEIGHT),
           Framebuffer::size() - (Framebuffer::scanline() * FONT_HEIGHT));
    g_y_position -= FONT_HEIGHT;
    erase_current_line();
}

static bool should_scroll()
{
    return (g_y_position + FONT_HEIGHT) >= Framebuffer::height();
}

static void next_line()
{
    g_x_position = 0;
    g_y_position += FONT_HEIGHT;
}

static void next_char()
{
    g_x_position += FONT_WIDTH;
}

static void prev_char()
{
    g_x_position -= FONT_WIDTH;
}

static void erase_current_char()
{
    Framebuffer::rect(g_x_position, g_y_position, FONT_WIDTH, FONT_HEIGHT, BLACK);
}

static bool at_end_of_screen()
{
    return (g_x_position + FONT_WIDTH) > Framebuffer::width();
}

namespace TextConsole
{
    void putwchar(wchar_t c)
    {
        // Unprintable (not in the built-in font) characters get represented as a box
        if (c > (wchar_t)255) c = (wchar_t)256;

        switch (c)
        {
        case L'\n': {
            next_line();
            if (should_scroll()) scroll();
            break;
        }
        case L'\r': g_x_position = 0; break;
        case L'\b':
            if (g_x_position != 0)
            {
                prev_char();
                erase_current_char();
            }
            break;
        default: {
            putwchar_at(c, g_x_position, g_y_position);
            next_char();
            if (at_end_of_screen())
            {
                next_line();
                if (should_scroll()) scroll();
            }
            break;
        }
        }
    }

    // FIXME: Should this function propagate errors?
    void putchar(char c)
    {
        auto rc = decoder.feed(c);
        if (rc.has_error())
        {
            decoder.reset();
            return;
        }

        auto maybe_wchar = rc.value();
        if (maybe_wchar.has_value()) putwchar(maybe_wchar.value());
    }

    void set_foreground(u32 color)
    {
        g_foreground_color = color;
    }

    void set_background(u32 color)
    {
        g_background_color = color;
    }

    u32 foreground()
    {
        return g_foreground_color;
    }

    u32 background()
    {
        return g_background_color;
    }

    void move_to(u32 x, u32 y)
    {
        g_x_position = x;
        g_y_position = y;
    }

    void clear()
    {
        move_to(0, 0);
        Framebuffer::rect(0, 0, Framebuffer::width(), Framebuffer::height(), BLACK);
    }

    void print(const char* str)
    {
        while (*str) putchar(*str++);
    }

    void println(const char* str)
    {
        print(str);
        putchar('\n');
    }

    usize printf(const char* format, ...)
    {
        va_list ap;
        va_start(ap, format);
        auto rc = pure_cstyle_format(
            format, [](char c, void*) { putchar(c); }, nullptr, ap);
        va_end(ap);
        return rc;
    }
}