Handle flushing implicit paint while there is a paint outstanding

If a native window or a window with a native subwindow is moved or resized
then the client window moves and implicit paints need to be flushed since
the native window move will copy/overwrite data. This may happen while there
is an outstanding paint if the move is inside an expose event (weird, but
flash embedded in webkit hit this).

Right now we're asserting here, but the right fix is to allow this but
to not flush the parts that are currently in a (non-implicit) paint. This
means we flush all results from previous not-yet-flushed exposes, but not
the ones being drawn.

diff --git a/gdk/gdkwindow.c b/gdk/gdkwindow.c
index d2798ba01e4b05ede16ee126497089c4e49ed045..d20cb44c4da359f2ba767cb29b145c86f71d285b 100644 (file)
--- a/gdk/gdkwindow.c
+++ b/gdk/gdkwindow.c
@@ -2031,7 +2031,8 @@ gdk_window_begin_implicit_paint (GdkWindow *window, GdkRectangle *rect)
 }
 
 /* Ensure that all content related to this (sub)window is pushed to the
-   native region */
+   native region. If there is an active paint then that area is not
+   pushed, in order to not show partially finished double buffers. */
 static void
 gdk_window_flush_implicit_paint (GdkWindow *window)
 {
@@ -2040,19 +2041,27 @@ gdk_window_flush_implicit_paint (GdkWindow *window)
   GdkWindowPaint *paint;
   GdkRegion *region;
   GdkGC *tmp_gc;
+  GSList *list;
 
-  /* Ensure that there is no explicit paint region. */
-  g_assert (private->paint_stack == NULL);
-  
   impl_window = gdk_window_get_impl_window (private);
   if (impl_window->implicit_paint == NULL)
     return;
 
   paint = impl_window->implicit_paint;
   region = gdk_region_copy (private->clip_region_with_children);
+
+  /* Don't flush active double buffers, as that may show partially done
+   * rendering */
+  for (list = private->paint_stack; list != NULL; list = list->next)
+    {
+      GdkWindowPaint *tmp_paint = list->data;
+
+      gdk_region_subtract (region, tmp_paint->region);
+    }
+
   gdk_region_offset (region, private->abs_x, private->abs_y);
   gdk_region_intersect (region, paint->region);
-  
+
   if (!gdk_region_empty (region))
     {
       /* Some regions are valid, push these to window now */