From c40155c8e6336a3ef1ef4105b478598caca362af Mon Sep 17 00:00:00 2001
From: Alexander Larsson <alexl@redhat.com>
Date: Tue, 25 Jun 2013 10:07:49 +0200
Subject: [PATCH] gdkwindow: Don't recurse into clipped children when updating

We don't want to recurse into children that are clipped, as that is
wasted work. We handle this by moving the empty check to the top
of the function and only using the clipped region everywhere.
---
 gdk/gdkwindow.c | 81 ++++++++++++++++++++++++++-----------------------
 1 file changed, 43 insertions(+), 38 deletions(-)

diff --git a/gdk/gdkwindow.c b/gdk/gdkwindow.c
index d874ff5f84..823e6fe463 100644
--- a/gdk/gdkwindow.c
+++ b/gdk/gdkwindow.c
@@ -3322,63 +3322,61 @@ gdk_window_schedule_update (GdkWindow *window)
                                    GDK_FRAME_CLOCK_PHASE_PAINT);
 }
 
-void
-_gdk_window_process_updates_recurse (GdkWindow *window,
-				     cairo_region_t *expose_region)
+static void
+_gdk_window_process_updates_recurse_helper (GdkWindow *window,
+                                            cairo_region_t *expose_region,
+                                            int dx, int dy)
 {
   GdkWindow *child;
   cairo_region_t *clipped_expose_region;
   GdkRectangle clip_box;
   GList *l, *children;
 
-  if (cairo_region_is_empty (expose_region))
-    return;
+  clipped_expose_region = cairo_region_copy (expose_region);
+  cairo_region_translate (clipped_expose_region, dx, dy);
+  cairo_region_intersect (clipped_expose_region, window->clip_region);
+
+  if (cairo_region_is_empty (clipped_expose_region) || window->destroyed)
+    goto out;
 
   if (gdk_window_is_offscreen (window->impl_window) &&
       gdk_window_has_impl (window))
-    _gdk_window_add_damage ((GdkWindow *) window->impl_window, expose_region);
+    _gdk_window_add_damage ((GdkWindow *) window->impl_window, clipped_expose_region);
 
   if (window->alpha != 255 && !gdk_window_has_impl (window))
     {
       if (window->alpha == 0)
-	return;
+        goto out;
 
-      cairo_region_get_extents (expose_region, &clip_box);
+      cairo_region_get_extents (clipped_expose_region, &clip_box);
       clip_box.x += window->abs_x;
       clip_box.y += window->abs_y;
       /* TODO: How do we now do subwindow alphas */
     }
 
   /* Paint the window before the children, clipped to the window region */
-  clipped_expose_region = cairo_region_copy (expose_region);
-  cairo_region_intersect (clipped_expose_region, window->clip_region);
 
-  if (!cairo_region_is_empty (clipped_expose_region) &&
-      !window->destroyed)
+  /* While gtk+ no longer handles exposes on anything but native
+     window we still have to send them to all windows that have the
+     event mask set for backwards compat. We also need to send
+     it to all native windows, even if they don't specify the
+     expose mask, because they may have non-native children that do. */
+  if (gdk_window_has_impl (window) ||
+      window->event_mask & GDK_EXPOSURE_MASK)
     {
-      /* While gtk+ no longer handles exposes on anything but native
-	 window we still have to send them to all windows that have the
-	 event mask set for backwards compat. We also need to send
-	 it to all native windows, even if they don't specify the
-	 expose mask, because they may have non-native children that do. */
-      if (gdk_window_has_impl (window) ||
-	  window->event_mask & GDK_EXPOSURE_MASK)
-	{
-	  GdkEvent event;
+      GdkEvent event;
 
-	  event.expose.type = GDK_EXPOSE;
-	  event.expose.window = g_object_ref (window);
-	  event.expose.send_event = FALSE;
-	  event.expose.count = 0;
-	  event.expose.region = clipped_expose_region;
-	  cairo_region_get_extents (clipped_expose_region, &event.expose.area);
+      event.expose.type = GDK_EXPOSE;
+      event.expose.window = g_object_ref (window);
+      event.expose.send_event = FALSE;
+      event.expose.count = 0;
+      event.expose.region = clipped_expose_region;
+      cairo_region_get_extents (clipped_expose_region, &event.expose.area);
 
-          _gdk_event_emit (&event);
+      _gdk_event_emit (&event);
 
-	  g_object_unref (window);
-	}
+      g_object_unref (window);
     }
-  cairo_region_destroy (clipped_expose_region);
 
   /* Make this reentrancy safe for expose handlers freeing windows */
   children = g_list_copy (window->children);
@@ -3390,25 +3388,32 @@ _gdk_window_process_updates_recurse (GdkWindow *window,
       child = l->data;
 
       if (child->destroyed || !GDK_WINDOW_IS_MAPPED (child) || child->input_only || child->composited)
-	continue;
+        continue;
 
       /* Ignore offscreen children, as they don't draw in their parent and
        * don't take part in the clipping */
       if (gdk_window_is_offscreen (child))
-	continue;
+        continue;
 
       /* Client side child, expose */
       if (child->impl == window->impl)
-	{
-	  cairo_region_translate (expose_region, -child->x, -child->y);
-	  _gdk_window_process_updates_recurse ((GdkWindow *)child, expose_region);
-	  cairo_region_translate (expose_region, child->x, child->y);
-	}
+        _gdk_window_process_updates_recurse_helper ((GdkWindow *)child, clipped_expose_region, -child->x, -child->y);
     }
 
   g_list_free_full (children, g_object_unref);
+
+ out:
+  cairo_region_destroy (clipped_expose_region);
 }
 
+void
+_gdk_window_process_updates_recurse (GdkWindow *window,
+                                     cairo_region_t *expose_region)
+{
+  _gdk_window_process_updates_recurse_helper (window, expose_region, 0, 0);
+}
+
+
 static void
 gdk_window_update_native_shapes (GdkWindow *window)
 {
-- 
2.30.2