gistfile1.h

#include <stdlib.h>

#include <gtk/gtk.h>

struct MainWindow {
    GtkWidget *window;
    gboolean draw;
    GAsyncQueue *draw_queue;
    cairo_surface_t *surface;
} *main_window;


gpointer main_window_painter(gpointer data)
{
    int w = 10, h = 20, flip = 0;

    while (1) {
        g_usleep(1000);
        cairo_t *c = cairo_create(main_window->surface);
        if (w > 400) {
            w = 10; h = 20;
            cairo_set_source_rgb(c, 1, 1, 1);
            cairo_rectangle(c, 0, 0, 640, 480);
            cairo_fill(c);
        }
        cairo_set_source_rgb(c, 0.3, 0.7, 0.2);
        cairo_rectangle(c, 0, 0, w++, h++);
        cairo_fill(c);
        cairo_destroy(c);
    }

    return NULL;
}

gboolean main_window_exposer(gpointer data)
{
    gtk_widget_queue_draw(main_window->window);
    return TRUE;
}

gboolean main_window_expose(GtkWidget *widget, GdkEventExpose *e)
{

    cairo_t *c = gdk_cairo_create(widget->window);

    cairo_set_source_surface(c, main_window->surface, 0, 0);
    cairo_rectangle(c, 0, 0, 640, 480);
    cairo_fill(c);

    cairo_destroy(c);
    return TRUE;
}

void main_window_new()
{
    main_window = g_malloc(sizeof(*main_window));
    main_window->draw = FALSE;
    main_window->window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    main_window->surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 640, 480);

    gtk_window_set_title(GTK_WINDOW(main_window->window), "Animation example");
    gtk_window_set_default_size(GTK_WINDOW(main_window->window), 640, 480);

    /* Refresh at 25 fps */
    g_timeout_add(40, main_window_exposer, NULL);

    g_signal_connect(G_OBJECT(main_window->window), "expose-event", G_CALLBACK(main_window_expose), NULL);

    gtk_widget_show_all(main_window->window);
}

int main(int argc, char **argv)
{
    GError *error = NULL;
    g_thread_init(NULL);
    gdk_threads_init();
    gdk_threads_enter();
    gtk_init(&argc, &argv);

    g_thread_create(main_window_painter, NULL, FALSE, &error);
    main_window_new();

    gtk_main();
    gdk_threads_leave();
    return EXIT_SUCCESS;
}