#include <gdk/gdkkeysyms.h>
#include <gtk/gtk.h>
#include <math.h>

#define WIN_WIDTH 256
#define WIN_HEIGHT 256

cairo_t*	 g_pCairoContext;

gboolean on_key_press (GtkWidget	*	pWidget,
					   GdkEventKey*	pKey,
					   gpointer		userData)
{
	if (pKey->type == GDK_KEY_PRESS)
	{
		switch (pKey->keyval)
		{
			case GDK_Escape :
				gtk_main_quit ();
			break;
		}
	}

	return FALSE;
}

void render (int width, int height)
{
	cairo_pattern_t* pPattern;

	cairo_scale (g_pCairoContext, (double) width / 1.0f, (double) height / 1.0f);
	
	pPattern = cairo_pattern_create_radial (0.55f,
											0.55f,
											0.25f,
											0.5f,
											1.0f,
											0.525f);
	cairo_pattern_add_color_stop_rgba (pPattern,
									   0.0f,
									   0.0f,
									   0.0f,
									   1.0f,
									   0.811f);
	cairo_pattern_add_color_stop_rgba (pPattern,
									   0.64f,
									   0.345f,
									   0.345f,
									   1.0f,
									   0.317f);
	cairo_pattern_add_color_stop_rgba (pPattern,
									   0.84f,
									   0.713f,
									   0.713f,
									   1.0f,
									   0.137f);
	cairo_pattern_add_color_stop_rgba (pPattern,	
									   1.0f,
									   1.0f,
									   1.0f,
									   1.0f,
									   0.0f);
	cairo_pattern_set_filter (pPattern, CAIRO_FILTER_BILINEAR);
	cairo_set_source (g_pCairoContext, pPattern);
	cairo_arc (g_pCairoContext, 0.5f, 0.5f, 142.0f/150.0f, 0.0f, M_PI * 2.0f);
	cairo_fill (g_pCairoContext);
	cairo_pattern_destroy (pPattern);
}

static gboolean on_window_expose (GtkWidget*	 pWidget,
								  GdkEventExpose* pExpose)
{
	g_pCairoContext = gdk_cairo_create (pWidget->window);
	render (WIN_WIDTH, WIN_HEIGHT);
	cairo_destroy (g_pCairoContext);

	return FALSE;
}

int main(int argc, char **argv)
{
	GtkWidget *window;

	gtk_init (&argc, &argv);

	window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
	gtk_window_set_resizable (GTK_WINDOW(window), FALSE);
	gtk_widget_set_size_request (window, WIN_WIDTH, WIN_HEIGHT);
	gtk_window_set_title (GTK_WINDOW (window), "pattern example");
	gtk_widget_set_app_paintable (window, TRUE);

	g_signal_connect (G_OBJECT (window),
					  "destroy",
					  G_CALLBACK (gtk_main_quit),
					  NULL);

	g_signal_connect (G_OBJECT (window),
					  "key-press-event",
					  G_CALLBACK (on_key_press),
					  NULL);

	g_signal_connect (G_OBJECT (window),
					  "expose-event",
					  G_CALLBACK (on_window_expose),
					  NULL);

	gtk_widget_show (window);

	g_pCairoContext = gdk_cairo_create (window->window);

	gtk_main ();

	return 0;
}