Workaround X11 clipping bug

It turns out that XCopyArea handling of obscured source regions is
buggy. It clears the destination area even outside the GC clip
region. We work around this for the pixmap->window case as that
can happen in gtk+ and is easy to work around.

X Bug report at:
http://lists.freedesktop.org/archives/xorg/2009-February/043318.html

diff --git a/gdk/x11/gdkdrawable-x11.c b/gdk/x11/gdkdrawable-x11.c
index 2e53041bb2c87df62d4da037bc92d07e193b3db0..e6ea4f1853e206bf5bb0a61f6ef7e47dd7a7d579 100644 (file)
--- a/gdk/x11/gdkdrawable-x11.c
+++ b/gdk/x11/gdkdrawable-x11.c
@@ -634,13 +634,50 @@ gdk_x11_draw_drawable (GdkDrawable *drawable,
 
   if (GDK_IS_DRAWABLE_IMPL_X11 (src))
     src_impl = GDK_DRAWABLE_IMPL_X11 (src);
+  else if (GDK_IS_WINDOW (src))
+    src_impl = GDK_DRAWABLE_IMPL_X11(((GdkWindowObject *)src)->impl);
   else
-    src_impl = NULL;
+    src_impl = GDK_DRAWABLE_IMPL_X11(((GdkPixmapObject *)src)->impl);
+
+  if (GDK_IS_WINDOW_IMPL_X11 (impl) &&
+      GDK_IS_PIXMAP_IMPL_X11 (src_impl))
+    {
+      GdkPixmapImplX11 *src_pixmap = GDK_PIXMAP_IMPL_X11 (src_impl);
+      /* Work around an Xserver bug where non-visible areas from
+       * a pixmap to a window will clear the window background
+       * in destination areas that are supposed to be clipped out.
+       * This is a problem with client side windows as this means
+       * things may draw outside the virtual windows. This could
+       * also happen for window to window copies, but I don't
+       * think we generate any calls like that.
+       *
+       * See: 
+       * http://lists.freedesktop.org/archives/xorg/2009-February/043318.html
+       */
+      if (xsrc < 0)
+       {
+         width += xsrc;
+         xdest -= xsrc;
+         xsrc = 0;
+       }
+      
+      if (ysrc < 0)
+       {
+         height += ysrc;
+         ydest -= ysrc;
+         ysrc = 0;
+       }
+
+      if (xsrc + width > src_pixmap->width)
+       width = src_pixmap->width - xsrc;
+      if (ysrc + height > src_pixmap->height)
+       height = src_pixmap->height - ysrc;
+    }
   
   if (src_depth == 1)
     {
       XCopyArea (GDK_SCREEN_XDISPLAY (impl->screen),
-                 src_impl ? src_impl->xid : GDK_DRAWABLE_XID (src),
+                 src_impl->xid,
                 impl->xid,
                 GDK_GC_GET_XGC (gc),
                 xsrc, ysrc,
@@ -650,7 +687,7 @@ gdk_x11_draw_drawable (GdkDrawable *drawable,
   else if (dest_depth != 0 && src_depth == dest_depth)
     {
       XCopyArea (GDK_SCREEN_XDISPLAY (impl->screen),
-                 src_impl ? src_impl->xid : GDK_DRAWABLE_XID (src),
+                 src_impl->xid,
                 impl->xid,
                 GDK_GC_GET_XGC (gc),
                 xsrc, ysrc,