Please describe the problem:
gint 
gdk_screen_get_monitor_at_window (GdkScreen      *screen,
				  GdkWindow	 *window)
{
    ...
    gdk_window_get_geometry (window, &win_rect.x, &win_rect.y, &win_rect.width,
			   &win_rect.height, NULL);
    gdk_window_get_origin (window, &win_rect.x, &win_rect.y);
    ...
    gdk_rectangle_intersect (&win_rect, &tmp_monitor, &intersect);
    ...
}
The implementation has a call gdk_window_get_origin(window, &win_rect.x, &win_rect.y) with just the same parameters win_rect, which are used above for another purpose, to keep window's coordinates.
These coordinates are being overrided. 

Steps to reproduce:
The test was developed under OpenSuse 10.2 with 2 monitors (number 0, number 1), which are connected horizontally. Monitor number 0 is on the left, number 1 is on the right side.
The most part of the window lies on the second monitor, i.e. expected return value is 1.



Actual results:
Here gdk_screen_get_monitor_at_window returns 0.

Expected results:
The expected value is 1.

Does this happen every time?
Yes

Other information:
I think this problem may be solved with the patch below described.

@@ -1,13 +1,13 @@
 gint gdk_screen_get_monitor_at_window (GdkScreen *screen, GdkWindow *window)
 {
        gint num_monitors, i, area = 0, screen_num = -1;
-       GdkRectangle win_rect;
+       GdkRectangle win_rect, orig_rect;
        g_return_val_if_fail (GDK_IS_SCREEN (screen), -1);

        gdk_window_get_geometry (window, &win_rect.x, &win_rect.y, &win_rect.width,
                            &win_rect.height, NULL);

-       gdk_window_get_origin (window, &win_rect.x, &win_rect.y);
+       gdk_window_get_origin (window, &orig_rect.x, &orig_rect.y);

        num_monitors = gdk_screen_get_n_monitors (screen);

@@ -27,6 +27,6 @@
        if (screen_num >= 0)
        return screen_num;
        else
-       return get_nearest_monitor (screen, win_rect.x + win_rect.width / 2,
-                                win_rect.y + win_rect.height / 2);
+       return get_nearest_monitor (screen, orig_rect.x + win_rect.width / 2,
+                                orig_rect.y + win_rect.height / 2);
 }