[gtk+] GL: Fix typo in gdk_gl_texture_from_surface

[Alexander Larsson <alexl src gnome org>]

commit 442adf6359867746f0d96887507a1cf87bdeba06
Author: Alexander Larsson <alexl redhat com>
Date:   Thu Nov 20 15:36:21 2014 +0100

    GL: Fix typo in gdk_gl_texture_from_surface
    
    Got a sign wrong in commit 800c712738f5666937e32d9f8cb32353513b9423

 gdk/gdkgl.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gdk/gdkgl.c b/gdk/gdkgl.c
index d693ca0..6c76e83 100644
--- a/gdk/gdkgl.c
+++ b/gdk/gdkgl.c
@@ -700,7 +700,7 @@ gdk_gl_texture_from_surface (cairo_surface_t *surface,
     {
       cairo_region_get_rectangle (region, i, &rect);
 
-      glScissor (rect.x * window_scale, unscaled_window_height - (rect.y - rect.height) * window_scale,
+      glScissor (rect.x * window_scale, unscaled_window_height - (rect.y + rect.height) * window_scale,
                  rect.width * window_scale, rect.height * window_scale);
 
       e = rect;