cc: Ensure that large damage doesn't register as "frame has no damage"

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>
 
@@ skipping 11 matching lines @@
 
 std::unique_ptr<DamageTracker> DamageTracker::Create() {
   return base::WrapUnique(new DamageTracker());
 }
 
 DamageTracker::DamageTracker()
   : mailboxId_(0) {}
 
 DamageTracker::~DamageTracker() {}
 
-static inline void ExpandDamageRectInsideRectWithFilters(
-    gfx::Rect* damage_rect,
-    const gfx::Rect& pre_filter_rect,
-    const FilterOperations& filters) {
-  // Compute the pixels in the background of the surface that could be affected
-  // by the damage in the content below.
-  gfx::Rect expanded_damage_rect = filters.MapRect(*damage_rect, SkMatrix::I());
-
-  // Restrict it to the rectangle in which the background filter is shown.
-  expanded_damage_rect.Intersect(pre_filter_rect);
-
-  damage_rect->Union(expanded_damage_rect);
-}
-
 void DamageTracker::UpdateDamageTrackingState(
     const LayerImplList& layer_list,
     const RenderSurfaceImpl* target_surface,
     bool target_surface_property_changed_only_from_descendant,
     const gfx::Rect& target_surface_content_rect,
     LayerImpl* target_surface_mask_layer,
     const FilterOperations& filters) {
   //
   // This function computes the "damage rect" of a target surface, and updates
   // the state that is used to correctly track damage across frames. The damage
@@ skipping 59 matching lines @@
   //
   //      3. After the damage rect is computed, the leftover not marked regions
   //         in a map are used to compute are damaged by deleted layers and
   //         erased from map.
   //
 
   PrepareRectHistoryForUpdate();
   // These functions cannot be bypassed with early-exits, even if we know what
   // the damage will be for this frame, because we need to update the damage
   // tracker state to correctly track the next frame.
-  gfx::Rect damage_from_active_layers =
+  DamageAccumulator damage_from_active_layers =
       TrackDamageFromActiveLayers(layer_list, target_surface);
-  gfx::Rect damage_from_surface_mask =
+  DamageAccumulator damage_from_surface_mask =
       TrackDamageFromSurfaceMask(target_surface_mask_layer);
-  gfx::Rect damage_from_leftover_rects = TrackDamageFromLeftoverRects();
+  DamageAccumulator damage_from_leftover_rects = TrackDamageFromLeftoverRects();
 
-  gfx::Rect damage_rect_for_this_update;
+  DamageAccumulator damage_for_this_update;
 
   if (target_surface_property_changed_only_from_descendant) {
-    damage_rect_for_this_update = target_surface_content_rect;
+    damage_for_this_update.Union(target_surface_content_rect);
   } else {
     // TODO(shawnsingh): can we clamp this damage to the surface's content rect?
     // (affects performance, but not correctness)
-    damage_rect_for_this_update = damage_from_active_layers;
-    damage_rect_for_this_update.Union(damage_from_surface_mask);
-    damage_rect_for_this_update.Union(damage_from_leftover_rects);
-    damage_rect_for_this_update =
-        filters.MapRect(damage_rect_for_this_update,
-                        target_surface->FiltersTransform().matrix());
+    damage_for_this_update.Union(damage_from_active_layers);
+    damage_for_this_update.Union(damage_from_surface_mask);
+    damage_for_this_update.Union(damage_from_leftover_rects);
+
+    gfx::Rect damage_rect;
+    bool is_rect_valid = damage_for_this_update.GetAsRect(&damage_rect);
+    if (is_rect_valid) {
+      damage_rect = filters.MapRect(
+          damage_rect, target_surface->FiltersTransform().matrix());
+      damage_for_this_update = DamageAccumulator();
+      damage_for_this_update.Union(damage_rect);
+    }
   }
 
   // Damage accumulates until we are notified that we actually did draw on that
   // frame.
-  current_damage_rect_.Union(damage_rect_for_this_update);
+  current_damage_.Union(damage_for_this_update);
+}
+
+bool DamageTracker::GetDamageRectIfValid(gfx::Rect* rect) {
+  return current_damage_.GetAsRect(rect);
 }
 
 DamageTracker::LayerRectMapData& DamageTracker::RectDataForLayer(
     int layer_id,
     bool* layer_is_new) {
   LayerRectMapData data(layer_id);
 
   SortedRectMapForLayers::iterator it = std::lower_bound(
       rect_history_for_layers_.begin(), rect_history_for_layers_.end(), data);
 
@@ skipping 15 matching lines @@
                        rect_history_for_surfaces_.end(), data);
 
   if (it == rect_history_for_surfaces_.end() || it->surface_id_ != surface_id) {
     *surface_is_new = true;
     it = rect_history_for_surfaces_.insert(it, data);
   }
 
   return *it;
 }
 
-gfx::Rect DamageTracker::TrackDamageFromActiveLayers(
+DamageTracker::DamageAccumulator DamageTracker::TrackDamageFromActiveLayers(
     const LayerImplList& layer_list,
     const RenderSurfaceImpl* target_surface) {
-  gfx::Rect damage_rect;
+  DamageAccumulator damage;
 
   for (size_t layer_index = 0; layer_index < layer_list.size(); ++layer_index) {
     // Visit layers in back-to-front order.
     LayerImpl* layer = layer_list[layer_index];
 
     // We skip damage from the HUD layer because (a) the HUD layer damages the
     // whole frame and (b) we don't want HUD layer damage to be shown by the
     // HUD damage rect visualization.
     if (layer == layer->layer_tree_impl()->hud_layer())
       continue;
 
     if (layer->render_surface() && layer->render_surface() != target_surface)
-      ExtendDamageForRenderSurface(layer->render_surface(), &damage_rect);
+      ExtendDamageForRenderSurface(layer->render_surface(), &damage);
     else
-      ExtendDamageForLayer(layer, &damage_rect);
+      ExtendDamageForLayer(layer, &damage);
   }
 
-  return damage_rect;
+  return damage;
 }
 
-gfx::Rect DamageTracker::TrackDamageFromSurfaceMask(
+DamageTracker::DamageAccumulator DamageTracker::TrackDamageFromSurfaceMask(
     LayerImpl* target_surface_mask_layer) {
-  gfx::Rect damage_rect;
+  DamageAccumulator damage;
 
   if (!target_surface_mask_layer)
-    return damage_rect;
+    return damage;
 
   // Currently, if there is any change to the mask, we choose to damage the
   // entire surface. This could potentially be optimized later, but it is not
   // expected to be a common case.
   if (target_surface_mask_layer->LayerPropertyChanged() ||
       !target_surface_mask_layer->update_rect().IsEmpty()) {
-    damage_rect = gfx::Rect(target_surface_mask_layer->bounds());
+    damage.Union(gfx::Rect(target_surface_mask_layer->bounds()));
   }
 
-  return damage_rect;
+  return damage;
 }
 
 void DamageTracker::PrepareRectHistoryForUpdate() {
   mailboxId_++;
 }
 
-gfx::Rect DamageTracker::TrackDamageFromLeftoverRects() {
+DamageTracker::DamageAccumulator DamageTracker::TrackDamageFromLeftoverRects() {
   // After computing damage for all active layers, any leftover items in the
   // current rect history correspond to layers/surfaces that no longer exist.
   // So, these regions are now exposed on the target surface.
 
-  gfx::Rect damage_rect;
+  DamageAccumulator damage;
   SortedRectMapForLayers::iterator layer_cur_pos =
       rect_history_for_layers_.begin();
   SortedRectMapForLayers::iterator layer_copy_pos = layer_cur_pos;
   SortedRectMapForSurfaces::iterator surface_cur_pos =
       rect_history_for_surfaces_.begin();
   SortedRectMapForSurfaces::iterator surface_copy_pos = surface_cur_pos;
 
   // Loop below basically implements std::remove_if loop with and extra
-  // processing (adding deleted rect to damage_rect) for deleted items.
+  // processing (adding deleted rect to damage) for deleted items.
   // cur_pos iterator runs through all elements of the vector, but copy_pos
   // always points to the element after the last not deleted element. If new
   // not deleted element found then it is copied to the *copy_pos and copy_pos
   // moved to the next position.
   // If there are no deleted elements then copy_pos iterator is in sync with
   // cur_pos and no copy happens.
   while (layer_cur_pos < rect_history_for_layers_.end()) {
     if (layer_cur_pos->mailboxId_ == mailboxId_) {
       if (layer_cur_pos != layer_copy_pos)
         *layer_copy_pos = *layer_cur_pos;
 
       ++layer_copy_pos;
     } else {
-      damage_rect.Union(layer_cur_pos->rect_);
+      damage.Union(layer_cur_pos->rect_);
     }
 
     ++layer_cur_pos;
   }
 
   while (surface_cur_pos < rect_history_for_surfaces_.end()) {
     if (surface_cur_pos->mailboxId_ == mailboxId_) {
       if (surface_cur_pos != surface_copy_pos)
         *surface_copy_pos = *surface_cur_pos;
 
       ++surface_copy_pos;
     } else {
-      damage_rect.Union(surface_cur_pos->rect_);
+      damage.Union(surface_cur_pos->rect_);
     }
 
     ++surface_cur_pos;
   }
 
   if (layer_copy_pos != rect_history_for_layers_.end())
     rect_history_for_layers_.erase(layer_copy_pos,
                                    rect_history_for_layers_.end());
   if (surface_copy_pos != rect_history_for_surfaces_.end())
     rect_history_for_surfaces_.erase(surface_copy_pos,
                                      rect_history_for_surfaces_.end());
 
   // If the vector has excessive storage, shrink it
   if (rect_history_for_layers_.capacity() > rect_history_for_layers_.size() * 4)
     SortedRectMapForLayers(rect_history_for_layers_)
         .swap(rect_history_for_layers_);
   if (rect_history_for_surfaces_.capacity() >
       rect_history_for_surfaces_.size() * 4)
     SortedRectMapForSurfaces(rect_history_for_surfaces_)
         .swap(rect_history_for_surfaces_);
 
-  return damage_rect;
+  return damage;
+}
+
+void DamageTracker::ExpandDamageInsideRectWithFilters(
+    const gfx::Rect& pre_filter_rect,
+    const FilterOperations& filters,
+    DamageAccumulator* damage) {
+  gfx::Rect damage_rect;
+  bool is_valid_rect = damage->GetAsRect(&damage_rect);
+  // If the input isn't a valid rect, then there is no point in trying to make
+  // it bigger.
+  if (!is_valid_rect)
+    return;
+
+  // Compute the pixels in the background of the surface that could be affected
+  // by the damage in the content below.
+  gfx::Rect expanded_damage_rect = filters.MapRect(damage_rect, SkMatrix::I());
+
+  // Restrict it to the rectangle in which the background filter is shown.
+  expanded_damage_rect.Intersect(pre_filter_rect);
+
+  damage->Union(expanded_damage_rect);
 }
 
 void DamageTracker::ExtendDamageForLayer(LayerImpl* layer,
-                                         gfx::Rect* target_damage_rect) {
+                                         DamageAccumulator* target_damage) {
   // There are two ways that a layer can damage a region of the target surface:
   //   1. Property change (e.g. opacity, position, transforms):
   //        - the entire region of the layer itself damages the surface.
   //        - the old layer region also damages the surface, because this region
   //          is now exposed.
   //        - note that in many cases the old and new layer rects may overlap,
   //          which is fine.
   //
   //   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.
-    target_damage_rect->Union(rect_in_target_space);
+    target_damage->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.
-    target_damage_rect->Union(old_rect_in_target_space);
+    target_damage->Union(old_rect_in_target_space);
     return;
   }
 
   // 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);
-    target_damage_rect->Union(damage_rect_in_target_space);
+    target_damage->Union(damage_rect_in_target_space);
   }
 }
 
 void DamageTracker::ExtendDamageForRenderSurface(
     RenderSurfaceImpl* render_surface,
-    gfx::Rect* target_damage_rect) {
+    DamageAccumulator* target_damage) {
   // 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
   //            - changes to ancestor layers that propagate their property
   //              changes to their entire subtree.
   //        - just like layers, both the old surface rect and new surface rect
   //          will damage the target surface in this case.
   //
   //   2. Damage rect: This surface may have been damaged by its own layer_list
   //      as well, and that damage should propagate to the target surface.
   //
 
   bool surface_is_new = false;
   SurfaceRectMapData& data =
       RectDataForSurface(render_surface->id(), &surface_is_new);
   gfx::Rect old_surface_rect = data.rect_;
 
   gfx::Rect surface_rect_in_target_space =
       gfx::ToEnclosingRect(render_surface->DrawableContentRect());
   data.Update(surface_rect_in_target_space, mailboxId_);
 
   if (surface_is_new || render_surface->SurfacePropertyChanged()) {
     // The entire surface contributes damage.
-    target_damage_rect->Union(surface_rect_in_target_space);
+    target_damage->Union(surface_rect_in_target_space);
 
     // The surface's old region is now exposed on the target surface, too.
-    target_damage_rect->Union(old_surface_rect);
+    target_damage->Union(old_surface_rect);
   } else {
     // Only the surface's damage_rect will damage the target surface.
-    gfx::Rect damage_rect_in_local_space =
-        render_surface->damage_tracker()->current_damage_rect();
-
-    // If there was damage, transform it to target space, and possibly
-    // contribute its reflection if needed.
-    if (!damage_rect_in_local_space.IsEmpty()) {
+    gfx::Rect damage_rect_in_local_space;
+    bool is_valid_rect = render_surface->damage_tracker()->GetDamageRectIfValid(
+        &damage_rect_in_local_space);
+    if (is_valid_rect && !damage_rect_in_local_space.IsEmpty()) {
+      // If there was damage, transform it to target space, and possibly
+      // contribute its reflection if needed.
       const gfx::Transform& draw_transform = render_surface->draw_transform();
       gfx::Rect damage_rect_in_target_space = MathUtil::MapEnclosingClippedRect(
           draw_transform, damage_rect_in_local_space);
-      target_damage_rect->Union(damage_rect_in_target_space);
+      target_damage->Union(damage_rect_in_target_space);
+    } else if (!is_valid_rect) {
+      target_damage->Union(surface_rect_in_target_space);
     }
   }
 
   // If the layer has a background filter, this may cause pixels in our surface
   // to be expanded, so we will need to expand any damage at or below this
   // 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()) {
-    ExpandDamageRectInsideRectWithFilters(
-        target_damage_rect, surface_rect_in_target_space, background_filters);
+    ExpandDamageInsideRectWithFilters(surface_rect_in_target_space,
+                                      background_filters, target_damage);
   }
 }
 
+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