Fix for 424682: Draw correct repaint regions instead of a conservative bounding box

cc/debug/debug_rect_history.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/debug/debug_rect_history.h"
 
 #include "cc/base/math_util.h"
 #include "cc/layers/layer_impl.h"
 #include "cc/layers/layer_iterator.h"
 #include "cc/layers/layer_utils.h"
@@ skipping 50 matching lines @@
   if (debug_state.show_layer_animation_bounds_rects)
     SaveLayerAnimationBoundsRects(render_surface_layer_list);
 }
 
 void DebugRectHistory::SavePaintRects(LayerImpl* layer) {
   // We would like to visualize where any layer's paint rect (update rect) has
   // changed, regardless of whether this layer is skipped for actual drawing or
   // not. Therefore we traverse recursively over all layers, not just the render
   // surface list.
 
   if (!layer->update_rect().IsEmpty() && layer->DrawsContent()) {

[danakj, 2015/02/26 23:53:05]

Can this use the region too?

[daplatz, 2015/02/27 11:04:56]

I made the change; it makes sense; but for this i also had to slightly update
the PictureLayerImpl::GetInvalidationRegion method as it seems when there is a
twinlayer, the invalidations are only ever reset on that twin; not doing it made
the repaint rect on the hud not fade out but stay indefintively.

     float width_scale = layer->content_bounds().width() /
                         static_cast<float>(layer->bounds().width());
     float height_scale = layer->content_bounds().height() /
                          static_cast<float>(layer->bounds().height());
-    gfx::Rect update_content_rect = gfx::ScaleToEnclosingRect(
-        layer->update_rect(), width_scale, height_scale);
-    debug_rects_.push_back(
+
+    for (Region::Iterator it(layer->GetInvalidationRegion());
+        it.has_rect();
+        it.next()) {
+
+      gfx::Rect update_content_rect = gfx::ScaleToEnclosingRect(
+        it.rect(), width_scale, height_scale);
+      debug_rects_.push_back(
         DebugRect(PAINT_RECT_TYPE,
-                  MathUtil::MapEnclosingClippedRect(
-                      layer->screen_space_transform(), update_content_rect)));
+          MathUtil::MapEnclosingClippedRect(
+            layer->screen_space_transform(), update_content_rect)));
+    }
   }
 
   for (unsigned i = 0; i < layer->children().size(); ++i)
     SavePaintRects(layer->children()[i]);
 }
 
 void DebugRectHistory::SavePropertyChangedRects(
     const LayerImplList& render_surface_layer_list,
     LayerImpl* hud_layer) {
   for (int surface_index = render_surface_layer_list.size() - 1;
@@ skipping 171 matching lines @@
     debug_rects_.push_back(
         DebugRect(ANIMATION_BOUNDS_RECT_TYPE,
                   gfx::ToEnclosingRect(gfx::RectF(inflated_bounds.x(),
                                                   inflated_bounds.y(),
                                                   inflated_bounds.width(),
                                                   inflated_bounds.height()))));
   }
 }
 
 }  // namespace cc