/*
 * Copyright (C) 2010 Nick Bowler
 *
 * License WTFPL2: Do What The Fuck You Want To Public License, version 2.
 * This is free software: you are free to do what the fuck you want to.
 * There is NO WARRANTY, to the extent permitted by law.
 *
 * In case the above is not acceptable, you may alternately choose the terms
 * of the MIT license: http://opensource.org/licenses/mit-license.php.
 */
#include <stdio.h>
#include <string.h>

#include <gdk/gdk.h>
#include <gdk/gdkgl.h>
#include <GL/gl.h>

void resize(GdkGLDrawable *drawable)
{
	gint w, h;

	gdk_gl_drawable_get_size(drawable, &w, &h);

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glViewport(0, 0, w, h);
	glOrtho(0, 1, 0, 1, -1, 1);
	glMatrixMode(GL_MODELVIEW);
}

void render(void)
{
	glClear(GL_COLOR_BUFFER_BIT);

	glBegin(GL_LINE_LOOP);
	glVertex2d(0.1, 0.1);
	glVertex2d(0.9, 0.1);
	glVertex2d(0.9, 0.9);
	glVertex2d(0.1, 0.9);
	glEnd();
}

int main(int argc, char **argv)
{
	GdkWindow  *root, *win;
	GdkGLWindow *glwin;
	GdkGLConfig *config;
	GdkGLDrawable *drawable;
	GdkGLContext *context;
	gint screen_w, screen_h;
	int i, state = 0, mode = GDK_GL_MODE_RGB | GDK_GL_MODE_DOUBLE;

	GdkWindowAttr attrs = {
		.window_type = GDK_WINDOW_TOPLEVEL,
		.wclass = GDK_INPUT_OUTPUT,
		.x = 0, .y = 0,
		.width  = 300,
		.height = 300,
		.override_redirect = 1,
	};

	gdk_init(&argc, &argv);
	gdk_gl_init(&argc, &argv);

	for (i = 1; i < argc; i++) {
		if (strcmp(argv[i], "--single") == 0) {
			mode &= ~GDK_GL_MODE_DOUBLE;
		} else if (strcmp(argv[i], "--offset") == 0) {
			attrs.x = attrs.y = 1;
		}
	}

	root = gdk_get_default_root_window();
	gdk_window_get_geometry(root, NULL, NULL, &screen_w, &screen_h, NULL);
	printf("screen size: %dx%d\n", screen_w, screen_h);

	config = gdk_gl_config_new_by_mode(mode);
	win = gdk_window_new(NULL, &attrs, GDK_WA_X|GDK_WA_Y|GDK_WA_NOREDIR);
	glwin = gdk_window_set_gl_capability(win, config, NULL);
	drawable = gdk_window_get_gl_drawable(win);
	context  = gdk_gl_context_new(drawable, NULL, 1, GDK_GL_RGBA_TYPE);

	if (gdk_gl_drawable_is_double_buffered(drawable))
		puts("using double buffering");
	else
		puts("using single buffering");

	gdk_window_show(win);

	while (1) {
		gdk_gl_drawable_make_current(drawable, context);
		resize(drawable);
		render();
		if (gdk_gl_drawable_is_double_buffered(drawable))
			gdk_gl_drawable_swap_buffers(drawable);
		else
			glFinish();
		gdk_gl_drawable_gl_end(drawable);

		if (state = !state)
			gdk_window_resize(win, screen_w, screen_h);
		else
			gdk_window_resize(win, attrs.width, attrs.height);
	}

	return 0;
}