/*
 * 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 <X11/Xlib.h>
#include <GL/gl.h>
#include <GL/glx.h>

static void resize(int w, int h)
{
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glViewport(0, 0, w, h);
	glOrtho(0, 1, 0, 1, -1, 1);
	glMatrixMode(GL_MODELVIEW);
}

static 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)
{
	int rgb_attribs[] = {
		GLX_RGBA,
		GLX_RED_SIZE, 1,
		GLX_GREEN_SIZE, 1,
		GLX_BLUE_SIZE, 1,
		GLX_DOUBLEBUFFER,
		None
	};
	Display *dpy;
	XVisualInfo *vi;
	GLXContext ctx;
	Window win;
	XSetWindowAttributes attr;
	int screen_width, screen_height;
	int width = 300, height = 300;
	int x, y, w, h;
	int state = 0;
	int i;

	dpy = XOpenDisplay (NULL);
	vi = glXChooseVisual (dpy, DefaultScreen (dpy), rgb_attribs);

	screen_width = WidthOfScreen (ScreenOfDisplay(dpy, DefaultScreen (dpy)));
	screen_height = HeightOfScreen (ScreenOfDisplay(dpy, DefaultScreen (dpy)));

	x = y = 0;
	for (i = 1; i < argc; i++) {
		if (strcmp(argv[i], "--single") == 0) {
			rgb_attribs[7] = None;
		} else if (strcmp(argv[i], "--offset") == 0) {
			x = y = 1;
		}
	}

	attr.colormap = XCreateColormap (dpy,
					 RootWindow (dpy, vi->screen),
					 vi->visual,
					 AllocNone);
	attr.border_pixel = 0;
	attr.override_redirect = True;
	win = XCreateWindow (dpy, DefaultRootWindow (dpy),
			     x, y, width, height, 0,
			     vi->depth, InputOutput, vi->visual,
			     CWOverrideRedirect | CWBorderPixel | CWColormap,
			     &attr);
	XMapWindow (dpy, win);

	ctx = glXCreateContext (dpy, vi, NULL, True);
	XFree (vi);

	w = width, h = height;
	while (1) {
		glXMakeCurrent (dpy, win, ctx);
		resize(w, h);
		render();

		if (rgb_attribs[7])
			glXSwapBuffers (dpy, win);
		else
			glFinish();
		glXMakeCurrent (dpy, 0, 0);

		if ((state = !state))
			w = screen_width, h = screen_height;
		else
			w = width, h = height;
		XResizeWindow (dpy, win, w, h);
	}

	return 0;
}