GUI development¶

The graphical interface of xelix is handled by gfxcompd (Graphics compositor daemon), which lives in land/gfxcompd in the source tree. It uses FreeType for text rendering and Cairo for general drawing and compositing.

It currently exposes a very simple API though libxelixgfx / xelixgfx.h that can be used to create windows and draw arbitrary pixels inside them. There is currently no support for input events.

libxelixgfx reference¶

gfx_open¶

int gfx_open();

Opens a communication channel to gfxcompd though /dev/gfxbus and creates a shared memory region for the framebuffer. Returns 0 on success, a negative integer on failure.

gfx_close¶

int gfx_close();

Closes the communication channel and framebuffer. Returns 0 on success, a negative integer on failure.

struct gfx_window¶

struct gfx_window {
    uint32_t* addr;
    uint32_t bpp;
    uint32_t width;
    uint32_t height;
    uint32_t pitch;
    uint32_t size;
    uint32_t wid;
};

The primary representation of a GUI window.

addr

A pointer to an ARGB32 framebuffer of size 32-bit words – one for each pixel. Note that changes to this framebuffer will not be displayed until gfx_window_blit or gfx_window_blit_full are called.

bpp

Bits per pixel - Currently always 32.

width, height

Width and height of the framebuffer/paintable window area in pixels.

pitch

Bytes required to advance the y position by one, i.e. the width of the framebuffer in memory. This may differ from width for better memory alignment.

size

Total framebuffer size in bytes. This is equal to pitch * (height * bpp/4).

wid

Window ID

gfx_window_new¶

int gfx_window_new(struct gfx_window* win, const char* title, size_t width, size_t height);

Creates a new window and initializes the struct gfx_window in win. title will be used as the window title displayed to the user, width and height are a window size request. Returns 0 on success, a negative integer on failure.

gfx_window_blit¶

int gfx_window_blit(struct gfx_window* win, size_t x, size_t y, size_t width, size_t height);

Draws the area of the framebuffer starting at x, y and with size width, height to the screen.

gfx_window_blit_full¶

int gfx_window_blit_full(struct gfx_window* win);

Draws the entire framebuffer to the screen.

Sample program¶

#include <stdlib.h>
#include <xelixgfx.h>

struct gfx_window window;

int main() {
    if(gfx_open() < 0) {
        perror("Could not initialize gfx handle");
        exit(EXIT_FAILURE);
    }

    if(gfx_window_new(&window, "Example program", 800, 600) < 0) {
        perror("Could not initialize gfx window");
        exit(EXIT_FAILURE);
    }

    while(1) {
        do_stuff();

        // Put some pixels in the framebuffer
        memset32(window.addr, 0xffffffff, window.size / 4);

        // Blit framebuffer
        gfx_window_blit_full(&window);
    }

    gfx_close();
}

Compile with i786-pc-xelix-gcc -o testgui testgui.c -lxelixgfx -lm