compositor: Ignore opaque region for shaded windows

Typically, the opaque region applies to the client window.

When shaded, the client window is unmapped and the frame shrunk to its
minimum height.

When shaded, the opaque regio nshould simply be ignored as the client
window is no longer visible.
Signed-off-by: Olivier Fourdan <fourdan@xfce.org>
Closes: #452

src/compositor.c

@@ -97,6 +97,7 @@
 #define WIN_IS_VISIBLE(cw)              (WIN_IS_VIEWABLE(cw) && WIN_HAS_DAMAGE(cw))
 #define WIN_IS_DAMAGED(cw)              (cw->damaged)
 #define WIN_IS_REDIRECTED(cw)           (cw->redirected)
+#define WIN_IS_SHADED(cw)               (WIN_HAS_CLIENT(cw) && FLAG_TEST (cw->c->flags, CLIENT_FLAG_SHADED))
 
 #ifndef TIMEOUT_REPAINT_PRIORITY
 #define TIMEOUT_REPAINT_PRIORITY   1
@@ -2168,6 +2169,12 @@ clip_opaque_region (CWindow *cw, XserverRegion region)
     g_return_if_fail (cw != NULL);
     TRACE ("window 0x%lx", cw->id);
 
+    if (cw->opaque_region == None)
+    {
+        TRACE ("window 0x%lx has no opaque region", cw->id);
+        return;
+    }
+
     screen_info = cw->screen_info;
     display_info = screen_info->display_info;
 
@@ -2314,7 +2321,7 @@ paint_all (ScreenInfo *screen_info, XserverRegion region, gushort buffer)
             XFixesCopyRegion (dpy, cw->borderClip, paint_region);
         }
 
-        if ((cw->opacity == NET_WM_OPAQUE) && (cw->opaque_region != None))
+        if ((cw->opacity == NET_WM_OPAQUE) && !WIN_IS_SHADED(cw))
         {
             clip_opaque_region (cw, paint_region);
         }