[gtk+] gdkwindow-x11: Correct math for filling in the _NET_WM_OPAQUE_REGION property

[Jasper St. Pierre <jstpierre src gnome org>]

commit f07d11309805dfe72fc0ded5af0aa135d3ef9003
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Sat Aug 31 13:21:09 2013 -0400

    gdkwindow-x11: Correct math for filling in the _NET_WM_OPAQUE_REGION property
    
    This fixes incorrect rendering under mutter and other WMs that implement
    _NET_WM_OPAQUE_REGION.

 gdk/x11/gdkwindow-x11.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/gdk/x11/gdkwindow-x11.c b/gdk/x11/gdkwindow-x11.c
index a88cf8e..e5b3ffe 100644
--- a/gdk/x11/gdkwindow-x11.c
+++ b/gdk/x11/gdkwindow-x11.c
@@ -5576,10 +5576,10 @@ gdk_x11_window_set_opaque_region (GdkWindow      *window,
         {
           cairo_rectangle_int_t rect;
           cairo_region_get_rectangle (region, i, &rect);
-          data[i+0] = rect.x;
-          data[i+1] = rect.y;
-          data[i+2] = rect.width;
-          data[i+3] = rect.height;
+          data[i*4+0] = rect.x;
+          data[i*4+1] = rect.y;
+          data[i*4+2] = rect.width;
+          data[i*4+3] = rect.height;
         }
     }
   else