[gtk+/native-layout] Track direct window cairo access and avoid tricks when used

[Tristan Van Berkom <tvb src gnome org>]

commit e9da5b95dec6dc055a0a9e93290d1cf4770aa2a3
Author: Alexander Larsson <alexl redhat com>
Date:   Tue Jan 19 14:44:52 2010 +0100

    Track direct window cairo access and avoid tricks when used
    
    When a cairo surface is requested for direct window access (i.e. not
    when double-buffering) we can't really track when the actual drawing happens
    as cairo drawing is not virtualized. This means we can't properly flush
    any outstanding window moves or implicit paints.
    
    This actually causes problems with e.g. abiword (bug #606009) where they
    draw without double-buffering. If you press down it scrolls the window
    and then draws the caret, but the caret drawing does not flush the
    outstanding move from the scroll, so the caret gets drawn on the wrong
    screen.
    
    We fix this by never allowing either implicit paints or outstanding window
    moves on impl-windows where any windows related to it has an outstanding
    direct cairo surface. Luckily this is not very common so in practice this
    doesn't matter much.

 gdk/gdkinternals.h |    1 +
 gdk/gdkwindow.c    |    9 +++++++--
 2 files changed, 8 insertions(+), 2 deletions(-)
---
diff --git a/gdk/gdkinternals.h b/gdk/gdkinternals.h
index 0681bdc..822335f 100644
--- a/gdk/gdkinternals.h
+++ b/gdk/gdkinternals.h
@@ -273,6 +273,7 @@ struct _GdkWindowObject
   GdkRegion *input_shape;
   
   cairo_surface_t *cairo_surface;
+  guint outstanding_surfaces; /* only set on impl window */
 };
 
 #define GDK_WINDOW_TYPE(d) (((GdkWindowObject*)(GDK_WINDOW (d)))->window_type)
diff --git a/gdk/gdkwindow.c b/gdk/gdkwindow.c
index 9e6b14a..5b39995 100644
--- a/gdk/gdkwindow.c
+++ b/gdk/gdkwindow.c
@@ -2622,6 +2622,9 @@ gdk_window_begin_implicit_paint (GdkWindow *window, GdkRectangle *rect)
       private->implicit_paint != NULL)
     return FALSE; /* Don't stack implicit paints */
 
+  if (private->outstanding_surfaces != 0)
+    return FALSE; /* May conflict with direct drawing to cairo surface */
+
   /* Never do implicit paints for foreign windows, they don't need
    * double buffer combination since they have no client side children,
    * and creating pixmaps for them is risky since they could disappear
@@ -3327,7 +3330,7 @@ move_region_on_impl (GdkWindowObject *impl_window,
       gdk_region_destroy (exposing);
     }
 
-  if (1) /* Enable flicker free handling of moves. */
+  if (impl_window->outstanding_surfaces == 0) /* Enable flicker free handling of moves. */
     append_move_region (impl_window, region, dx, dy);
   else
     do_move_region_bits_on_impl (impl_window,
@@ -4846,6 +4849,7 @@ gdk_window_cairo_surface_destroy (void *data)
   GdkWindowObject *private = (GdkWindowObject*) data;
 
   private->cairo_surface = NULL;
+  private->impl_window->outstanding_surfaces--;
 }
 
 static cairo_surface_t *
@@ -4889,11 +4893,12 @@ gdk_window_ref_cairo_surface (GdkDrawable *drawable)
 
 	  source = _gdk_drawable_get_source_drawable (drawable);
 
-	  /* TODO: Avoid the typecheck crap by adding virtual call */
 	  private->cairo_surface = _gdk_drawable_create_cairo_surface (source, width, height);
 
 	  if (private->cairo_surface)
 	    {
+	      private->impl_window->outstanding_surfaces++;
+
 	      cairo_surface_set_device_offset (private->cairo_surface,
 					       private->abs_x,
 					       private->abs_y);