#include <X11/Xlib.h>
#include <X11/extensions/Xcomposite.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>

static int comp_event;
static int comp_error;

/* This program demonstrates that moving a redirected window around
 * when it is completely covered by a non-redirected one causes drawing
 * to happen in the wrong place.
 */
static void
disaster (const char *what)
{
    fprintf (stderr, "Error: %s\n", what);
    exit (0);
}

static void
dump_events (Display *dpy, const char *header)
{
    XSync (dpy, False);
    
    if (header)
	printf ("%s", header);
    
    while (XPending (dpy))
    {
	XEvent event;
	
	XNextEvent (dpy, &event);

	if (header)
	    printf ("  event: %d  (%lx)\n", event.type, event.xany.window);
    }
}

static void
paint_window (Display *dpy, Window window, unsigned long pixel)
{
    XGCValues gc_values;
    GC gc;

    gc_values.foreground = pixel;
    gc = XCreateGC (dpy, window, GCForeground, &gc_values);

    XFillRectangle (dpy, window, gc, 0, 0, 32000, 32000);

    XFreeGC (dpy, gc);
}

int
main (int argc, char **argv)
{
    Display *dpy;
    Window main_window;
    Window redirected_window;
    Window non_redirected_window;
    XGCValues gc_values;
    GC gc;

    dpy = XOpenDisplay (NULL);

    /* Create main window */
    
    main_window = XCreateSimpleWindow (dpy, XDefaultRootWindow (dpy),
				       100, 100, 600, 400, 0, 0, 0xffffffff);
    XMapWindow (dpy, main_window);

    if (!XCompositeQueryExtension (dpy, &comp_event, &comp_error))
	disaster ("No composite extension found\n");
    
    XCompositeRedirectSubwindows (dpy,
				  main_window,
				  CompositeRedirectManual);
    
    /* (1) Create redirected subwindow with a blue background */

    redirected_window = XCreateSimpleWindow (dpy, main_window,
					     50, 50, 500, 300,
					     0, 0, 0x000000ff);
    XSelectInput (dpy, redirected_window, ExposureMask);
    XMapWindow (dpy, redirected_window);

    /* (2) Create unredirected subwindow, completely covering
     * the redirected one
     */
    non_redirected_window = XCreateSimpleWindow (dpy, main_window,
						 25, 25, 550, 350,
						 0, 0, 0xaaaaaaaa);
    XMapWindow (dpy, non_redirected_window);

    XCompositeUnredirectWindow (dpy, non_redirected_window,
				CompositeRedirectManual);

    /* Discard events caused by unredirect */
    dump_events (dpy, NULL);

    /* (4) paint the non-redirected window pink */
    paint_window (dpy, non_redirected_window, 0x00ff00ff); /* pink */
    
    /* (5) Paint the redirected window green */
    paint_window (dpy, redirected_window, 0x0000ff00); /* green */

    /* (6) Move the redirected window (10, 10) pixels (from 50,50 to 60,60) */
    XMoveWindow (dpy, redirected_window, 60, 60);

    /* (7) Paint the redirected window yellow, eradicating all
     * traces of green
     */
    paint_window (dpy, redirected_window, 0x00ffff00); /* yellow */

    /* (8) Copy all of the redirected window to the non-redirected one.
     */
    gc = XCreateGC (dpy, redirected_window, 0L, NULL);
    XCopyArea (dpy, redirected_window, non_redirected_window, gc,
	       0, 0, 500, 300, 0, 0);

    /* (9) Draw a black rectangle around the area where we copied the
     * redirected window
     */
    XDrawRectangle (dpy, non_redirected_window, gc, 0, 0, 500, 300);

    /* 
     * At this point, the non-redirected window should be mostly yellow
     * with a pink L-shaped region in the lower right corner.
     * There should be no trace of green since that was completely painted
     * over in step (7).
     *
     * However, we _do_ see an L-shaped, 10 pixels wide strip of green,
     * because somehow the borderClip didn't get updated correctly by the
     * MoveWindow request.
     */
    XFlush (dpy);
    
    sleep (100);
}