cc: Change TileManager iterators to be queues.

cc/resources/eviction_tile_priority_queue.cc

+// Copyright 2014 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/resources/eviction_tile_priority_queue.h"
+
+namespace cc {
+
+namespace {
+
+class EvictionOrderComparator {
+ public:
+  explicit EvictionOrderComparator(TreePriority tree_priority)
+      : tree_priority_(tree_priority) {}
+
+  bool operator()(EvictionTilePriorityQueue::PairedPictureLayerQueue& a,
+                  EvictionTilePriorityQueue::PairedPictureLayerQueue& b) const {
+    if (a.IsEmpty())
+      return true;
+
+    if (b.IsEmpty())
+      return false;
+
+    PictureLayerImpl::LayerEvictionTileIterator* a_iterator =
+        a.NextTileIterator(tree_priority_);
+    PictureLayerImpl::LayerEvictionTileIterator* b_iterator =
+        b.NextTileIterator(tree_priority_);
+
+    Tile* a_tile = **a_iterator;
+    Tile* b_tile = **b_iterator;
+
+    const TilePriority& a_priority =
+        a_tile->priority_for_tree_priority(tree_priority_);
+    const TilePriority& b_priority =
+        b_tile->priority_for_tree_priority(tree_priority_);
+    bool prioritize_low_res = tree_priority_ == SMOOTHNESS_TAKES_PRIORITY;
+
+    // Now we have to return true iff b is lower priority than a.
+
+    // If the priority bin differs, b is lower priority if it has the higher
+    // priority bin.
+    if (a_priority.priority_bin != b_priority.priority_bin)
+      return b_priority.priority_bin > a_priority.priority_bin;
+
+    // Otherwise if the resolution differs, then the order will be determined by
+    // whether we prioritize low res or not.
+    // TODO(vmpstr): Remove this when TilePriority is no longer a member of Tile
+    // class but instead produced by the iterators.
+    if (b_priority.resolution != a_priority.resolution) {
+      // Non ideal resolution should be sorted higher than other resolutions.
+      if (a_priority.resolution == NON_IDEAL_RESOLUTION)
+        return false;
+
+      if (b_priority.resolution == NON_IDEAL_RESOLUTION)
+        return true;
+
+      if (prioritize_low_res)
+        return a_priority.resolution == LOW_RESOLUTION;
+
+      return a_priority.resolution == HIGH_RESOLUTION;
+    }
+
+    // Otherwise if the occlusion differs, b is lower priority if it is
+    // occluded.
+    bool a_is_occluded = a_tile->is_occluded_for_tree_priority(tree_priority_);
+    bool b_is_occluded = b_tile->is_occluded_for_tree_priority(tree_priority_);
+    if (a_is_occluded != b_is_occluded)
+      return b_is_occluded;
+
+    // b is lower priorty if it is farther from visible.
+    return b_priority.distance_to_visible > a_priority.distance_to_visible;
+  }
+
+ private:
+  TreePriority tree_priority_;
+};
+
+}  // namespace
+
+EvictionTilePriorityQueue::EvictionTilePriorityQueue() {
+}
+
+EvictionTilePriorityQueue::~EvictionTilePriorityQueue() {
+}
+
+void EvictionTilePriorityQueue::Build(
+    const std::vector<PictureLayerImpl::Pair>& paired_layers,
+    TreePriority tree_priority) {
+  tree_priority_ = tree_priority;
+
+  for (std::vector<PictureLayerImpl::Pair>::const_iterator it =
+           paired_layers.begin();
+       it != paired_layers.end();
+       ++it) {
+    PairedPictureLayerQueue paired_queue;
+    if (it->active) {
+      paired_queue.active_iterator =
+          PictureLayerImpl::LayerEvictionTileIterator(it->active,
+                                                      tree_priority_);
+    }
+
+    if (it->pending) {
+      paired_queue.pending_iterator =
+          PictureLayerImpl::LayerEvictionTileIterator(it->pending,
+                                                      tree_priority_);
+    }
+
+    paired_queues_.push_back(paired_queue);
+  }
+
+  std::make_heap(paired_queues_.begin(),
+                 paired_queues_.end(),
+                 EvictionOrderComparator(tree_priority_));
+}
+
+void EvictionTilePriorityQueue::Reset() {
+  paired_queues_.clear();
+}
+
+void EvictionTilePriorityQueue::Pop() {
+  DCHECK(!IsEmpty());
+
+  std::pop_heap(paired_queues_.begin(),
+                paired_queues_.end(),
+                EvictionOrderComparator(tree_priority_));
+  PairedPictureLayerQueue& paired_queue = paired_queues_.back();
+  paired_queue.Pop(tree_priority_);
+  std::push_heap(paired_queues_.begin(),
+                 paired_queues_.end(),
+                 EvictionOrderComparator(tree_priority_));
+}
+
+bool EvictionTilePriorityQueue::IsEmpty() const {
+  return paired_queues_.empty() || paired_queues_.front().IsEmpty();
+}
+
+Tile* EvictionTilePriorityQueue::Top() {
+  DCHECK(!IsEmpty());
+  return paired_queues_.front().Top(tree_priority_);
+}
+
+EvictionTilePriorityQueue::PairedPictureLayerQueue::PairedPictureLayerQueue() {
+}
+
+EvictionTilePriorityQueue::PairedPictureLayerQueue::~PairedPictureLayerQueue() {
+}
+
+Tile* EvictionTilePriorityQueue::PairedPictureLayerQueue::Top(
+    TreePriority tree_priority) {
+  DCHECK(!IsEmpty());
+
+  PictureLayerImpl::LayerEvictionTileIterator* next_iterator =
+      NextTileIterator(tree_priority);
+  DCHECK(*next_iterator);
+
+  Tile* tile = **next_iterator;
+  DCHECK(std::find(returned_shared_tiles.begin(),
+                   returned_shared_tiles.end(),
+                   tile) == returned_shared_tiles.end());
+  return tile;
+}
+
+bool EvictionTilePriorityQueue::PairedPictureLayerQueue::IsEmpty() const {
+  return !active_iterator && !pending_iterator;
+}
+
+void EvictionTilePriorityQueue::PairedPictureLayerQueue::Pop(
+    TreePriority tree_priority) {
+  DCHECK(!IsEmpty());
+
+  PictureLayerImpl::LayerEvictionTileIterator* next_iterator =
+      NextTileIterator(tree_priority);
+  DCHECK(*next_iterator);
+  returned_shared_tiles.push_back(**next_iterator);
+  ++(*next_iterator);
+
+  if (IsEmpty())
+    return;
+
+  next_iterator = NextTileIterator(tree_priority);
+  while (std::find(returned_shared_tiles.begin(),
+                   returned_shared_tiles.end(),
+                   **next_iterator) != returned_shared_tiles.end()) {
+    ++(*next_iterator);
+    if (IsEmpty())
+      break;
+    next_iterator = NextTileIterator(tree_priority);
+  }
+}
+
+PictureLayerImpl::LayerEvictionTileIterator*
+EvictionTilePriorityQueue::PairedPictureLayerQueue::NextTileIterator(
+    TreePriority tree_priority) {
+  DCHECK(!IsEmpty());
+
+  // If we only have one iterator with tiles, return it.
+  if (!active_iterator)
+    return &pending_iterator;
+  if (!pending_iterator)
+    return &active_iterator;
+
+  Tile* active_tile = *active_iterator;
+  Tile* pending_tile = *pending_iterator;
+  if (active_tile == pending_tile)
+    return &active_iterator;
+
+  const TilePriority& active_priority =
+      active_tile->priority_for_tree_priority(tree_priority);
+  const TilePriority& pending_priority =
+      pending_tile->priority_for_tree_priority(tree_priority);
+
+  if (pending_priority.IsHigherPriorityThan(active_priority))
+    return &active_iterator;
+  return &pending_iterator;
+}
+
+}  // namespace cc