Force use of and cache render surface.

cc/trees/damage_tracker.cc

 // Copyright 2011 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/trees/damage_tracker.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
 #include "base/memory/ptr_util.h"
 #include "cc/base/filter_operations.h"
 #include "cc/base/math_util.h"
 #include "cc/layers/heads_up_display_layer_impl.h"
 #include "cc/layers/layer_impl.h"
 #include "cc/layers/render_surface_impl.h"
 #include "cc/trees/effect_node.h"
 #include "cc/trees/layer_tree_host_common.h"
 #include "cc/trees/layer_tree_impl.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 
 namespace cc {
 
 std::unique_ptr<DamageTracker> DamageTracker::Create() {
   return base::WrapUnique(new DamageTracker());
 }
 
-DamageTracker::DamageTracker()
-  : mailboxId_(0) {}
+DamageTracker::DamageTracker() : mailboxId_(0) {}
 
 DamageTracker::~DamageTracker() {}
 
 void DamageTracker::UpdateDamageTracking(
     LayerTreeImpl* layer_tree_impl,
     const RenderSurfaceList& render_surface_list) {
   //
   // This function computes the "damage rect" of each target surface, and
   // updates the state that is used to correctly track damage across frames. The
   // damage rect is the region of the surface that may have changed and needs to
@@ skipping 317 matching lines @@
   //
   //   2. Repaint/update: If a region of the layer that was repainted/updated,
   //      that region damages the surface.
   //
   // Property changes take priority over update rects.
   //
   // This method is called when we want to consider how a layer contributes to
   // its target RenderSurface, even if that layer owns the target RenderSurface
   // itself. To consider how a layer's target surface contributes to the
   // ancestor surface, ExtendDamageForRenderSurface() must be called instead.
-
   bool layer_is_new = false;
   LayerRectMapData& data = RectDataForLayer(layer->id(), &layer_is_new);
   gfx::Rect old_rect_in_target_space = data.rect_;
 
   gfx::Rect rect_in_target_space = layer->GetEnclosingRectInTargetSpace();
   data.Update(rect_in_target_space, mailboxId_);
 
   if (layer_is_new || layer->LayerPropertyChanged()) {
     // If a layer is new or has changed, then its entire layer rect affects the
     // target surface.
     damage_for_this_update_.Union(rect_in_target_space);
 
     // The layer's old region is now exposed on the target surface, too.
     // Note old_rect_in_target_space is already in target space.
     damage_for_this_update_.Union(old_rect_in_target_space);
-    return;
+  } else {
+    // If the layer properties haven't changed, then the the target surface is
+    // only affected by the layer's damaged area, which could be empty.
+    gfx::Rect damage_rect =
+        gfx::UnionRects(layer->update_rect(), layer->damage_rect());
+    damage_rect.Intersect(gfx::Rect(layer->bounds()));
+    if (!damage_rect.IsEmpty()) {
+      gfx::Rect damage_rect_in_target_space = MathUtil::MapEnclosingClippedRect(
+          layer->DrawTransform(), damage_rect);
+      damage_for_this_update_.Union(damage_rect_in_target_space);
+    }
   }
 
-  // If the layer properties haven't changed, then the the target surface is
-  // only affected by the layer's damaged area, which could be empty.
-  gfx::Rect damage_rect =
-      gfx::UnionRects(layer->update_rect(), layer->damage_rect());
-  damage_rect.Intersect(gfx::Rect(layer->bounds()));
-  if (!damage_rect.IsEmpty()) {
-    gfx::Rect damage_rect_in_target_space =
-        MathUtil::MapEnclosingClippedRect(layer->DrawTransform(), damage_rect);
-    damage_for_this_update_.Union(damage_rect_in_target_space);
-  }
+  if (layer_is_new || !layer->LayerPropertyChanged())

[wutao, 2017/06/09 19:19:10]

This might need special check:
If the layer is the target of itself, then we did not include this layer's
property change.
However, if the layer is subtree of the target surface, we should include the
layer's property change.

+    has_damage_from_contributing_content_ |= !damage_for_this_update_.IsEmpty();
 }
 
 void DamageTracker::AccumulateDamageFromRenderSurface(
     RenderSurfaceImpl* render_surface) {
   // There are two ways a "descendant surface" can damage regions of the "target
   // surface":
   //   1. Property change:
   //        - a surface's geometry can change because of
   //            - changes to descendants (i.e. the subtree) that affect the
   //              surface's content rect
@@ skipping 43 matching lines @@
   // layer. We expand the damage from this layer too, as we need to readback
   // those pixels from the surface with only the contents of layers below this
   // one in them. This means we need to redraw any pixels in the surface being
   // used for the blur in this layer this frame.
   const FilterOperations& background_filters =
       render_surface->BackgroundFilters();
   if (background_filters.HasFilterThatMovesPixels()) {
     ExpandDamageInsideRectWithFilters(surface_rect_in_target_space,
                                       background_filters);
   }
+
+  if (surface_is_new || !render_surface->SurfacePropertyChanged())
+    has_damage_from_contributing_content_ |= !damage_for_this_update_.IsEmpty();
 }
 
 bool DamageTracker::DamageAccumulator::GetAsRect(gfx::Rect* rect) {
   if (!is_valid_rect_)
     return false;
 
   base::CheckedNumeric<int> width = right_;
   width -= x_;
   base::CheckedNumeric<int> height = bottom_;
   height -= y_;
   if (!width.IsValid() || !height.IsValid()) {
     is_valid_rect_ = false;
     return false;
   }
 
   rect->set_x(x_);
   rect->set_y(y_);
   rect->set_width(width.ValueOrDie());
   rect->set_height(height.ValueOrDie());
   return true;
 }
 
 }  // namespace cc