/* gcc `pkg-config --cflags --libs cairo-xlib` -o slice slice.c
 *
 * Test case demonstrating cairo bug #10508:
 *
 *	Transformed image source surfaces sometimes misrender to xlib surface target
 *	https://bugs.freedesktop.org/show_bug.cgi?id=10508
 *
 * This test case draws a transformed image to a window by continually
 * drawing the image over and over in single-pixel columns. The
 * results should be a static image showing four quadrants of
 * different colors, (with expected fading on the edges).
 *
 * The bug manifests itself by vertical mis-colored lines that appear
 * to sweep across the image as it redraws. The bug is intermittent,
 * but making your X server busy, (by, say, moving a window around),
 * appears to make it occur more regularly.
 */
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>

#include <cairo.h>
#include <cairo-xlib.h>
#include <X11/Xutil.h> /* for Region */

static void
expose (Display *dpy,
	Window window,
	int window_width,
	int window_height,
	cairo_surface_t *image,
	int extents_x,
	int extents_y,
	int extents_width,
	int extents_height)
{
    Pixmap pixmap;
    cairo_surface_t *backing;
    cairo_t *cr;
    cairo_matrix_t matrix;
    cairo_pattern_t *pattern;
    XGCValues gcv;
    GC gc;

    gcv.function = GXcopy;
    gcv.foreground = WhitePixel (dpy, DefaultScreen (dpy));
    gc = XCreateGC (dpy, window, GCFunction | GCForeground, &gcv);

    pixmap = XCreatePixmap (dpy, window, extents_width, extents_height,
			    DefaultDepth (dpy, DefaultScreen (dpy)));
    /* Clear background to white. */
    XFillRectangle (dpy, pixmap, gc, 0, 0, extents_width, extents_height);

    backing = cairo_xlib_surface_create (dpy, pixmap,
					 DefaultVisual (dpy, DefaultScreen (dpy)),
					 extents_width, extents_height);

    cr = cairo_create (backing);

    /* Draw the scaled image surface */
    cairo_translate (cr, - extents_x, - extents_y);
    cairo_scale (cr, 20, 20);

    pattern = cairo_pattern_create_for_surface (image);
    cairo_matrix_init_translate (&matrix, - 0.5, - 0.5);
    cairo_pattern_set_matrix (pattern, &matrix);
    cairo_set_source (cr, pattern);

    cairo_identity_matrix (cr);
    cairo_paint (cr);

    cairo_pattern_destroy (pattern);

    cairo_destroy (cr);
    cairo_surface_destroy (backing);

    XCopyArea (dpy, pixmap, window, gc, 0, 0,
	       extents_width, extents_height,
	       extents_x, extents_y);

    XFreePixmap (dpy, pixmap);
    XFreeGC (dpy, gc);
}

int
main (void)
{
    Display *dpy;
    Window root, window;
    int screen;
    int window_width = 100, window_height = 100;
    cairo_surface_t *source;
    KeyCode quit_code;
    XEvent xev;
    int i;

#define SOURCE_SIZE 4
    static uint32_t data[SOURCE_SIZE * SOURCE_SIZE] = {
	0xffffffff, 0xffffffff,		0xffff0000, 0xffff0000,
	0xffffffff, 0xffffffff,		0xffff0000, 0xffff0000,

	0xff00ff00, 0xff00ff00,		0xff0000ff, 0xff0000ff,
	0xff00ff00, 0xff00ff00,		0xff0000ff, 0xff0000ff
    };

    source = cairo_image_surface_create_for_data ((unsigned char *) data,
						  CAIRO_FORMAT_RGB24,
						  SOURCE_SIZE,
						  SOURCE_SIZE,
						  SOURCE_SIZE * 4);

    dpy = XOpenDisplay(0);
    if (dpy == NULL) {
	fprintf(stderr, "Failed to open display\n");
	return 1;
    }

    XSynchronize (dpy, 1);

    root = DefaultRootWindow(dpy);
    screen = DefaultScreen(dpy);

    window = XCreateSimpleWindow(dpy, root, 0, 0,
				 window_width, window_height, 0,
				 BlackPixel(dpy, screen), BlackPixel(dpy, screen));

    quit_code = XKeysymToKeycode(dpy, XStringToKeysym("Q"));

    XSelectInput(dpy, window,
		 KeyPressMask
		 |ExposureMask
		 |ButtonPressMask);

    XMapWindow(dpy, window);

    /* Wait for first expose xev. */
    XWindowEvent(dpy, window, ExposureMask, &xev);

    /* Draw to demonstrate bug. */
    expose (dpy, window,
	    window_width, window_height,
	    source,
	    0, 0, 100, 100);

    while (1) {
	for (i = 0; i < 100; i ++) {
	    /* Quit on any key/button press to exit */
	    if (XCheckWindowEvent(dpy, window, KeyPressMask|ButtonPressMask, &xev))
		goto DONE;
	    expose (dpy, window,
		    window_width, window_height,
		    source,
		    i, 0, 1, 100);
	    usleep (10000);
	}
    }
  DONE:

    cairo_surface_destroy (source);
    XCloseDisplay (dpy);
    cairo_debug_reset_static_data ();

    return 0;
}