implement the logic to set tile priorities based on current matrix

BUG=163060


Review URL: https://chromiumcodereview.appspot.com/11414238

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@170908 0039d316-1c4b-4281-b951-d872f2087c98

cc/cc.gyp

@@ -242,6 +242,7 @@
       'tile_draw_quad.h',
       'tile_manager.cc',
       'tile_manager.h',
+      'tile_priority.cc',
       'tile_priority.h',
       'tiled_layer.cc',
       'tiled_layer.h',

cc/cc_tests.gyp

@@ -52,6 +52,7 @@
       'texture_copier_unittest.cc',
       'texture_layer_unittest.cc',
       'texture_uploader_unittest.cc',
+      'tile_priority_unittest.cc',
       'tiled_layer_impl_unittest.cc',
       'tiled_layer_unittest.cc',
       'tree_synchronizer_unittest.cc',

cc/picture_layer_impl.cc

@@ -4,6 +4,7 @@
 
 #include "cc/picture_layer_impl.h"
 
+#include "base/time.h"
 #include "cc/append_quads_data.h"
 #include "cc/checkerboard_draw_quad.h"
 #include "cc/debug_border_draw_quad.h"
@@ -19,7 +20,8 @@ namespace cc {
 PictureLayerImpl::PictureLayerImpl(int id) :
     LayerImpl(id),
     tilings_(this),
-    pile_(PicturePileImpl::Create()) {
+    pile_(PicturePileImpl::Create()),
+    last_update_time_(0) {
 }
 
 PictureLayerImpl::~PictureLayerImpl() {
@@ -132,6 +134,30 @@ void PictureLayerImpl::didUpdateTransforms() {
     tilings_.AddTiling(contentsScaleX(), tile_size);
     // TODO(enne): handle invalidations, create new tiles
   }
+
+  gfx::Transform  current_screen_space_transform = screenSpaceTransform();
+  double current_time =
+      (base::TimeTicks::Now() - base::TimeTicks()).InSecondsF();
+  double time_delta = 0;
+  if (last_update_time_ != 0 && last_bounds_ == bounds() &&
+      last_content_bounds_ == contentBounds() &&
+      last_content_scale_x_ == contentsScaleX() &&
+      last_content_scale_y_ == contentsScaleY()) {
+    time_delta = current_time - last_update_time_;
+  }
+  tilings_.UpdateTilePriorities(layerTreeHostImpl()->deviceViewportSize(),
+                                contentsScaleX(),
+                                contentsScaleY(),
+                                last_screen_space_transform_,
+                                current_screen_space_transform,
+                                time_delta);
+
+  last_screen_space_transform_ = current_screen_space_transform;
+  last_update_time_ = current_time;
+  last_bounds_ = bounds();
+  last_content_bounds_ = contentBounds();
+  last_content_scale_x_ = contentsScaleX();
+  last_content_scale_y_ = contentsScaleY();
 }
 
 scoped_refptr<Tile> PictureLayerImpl::CreateTile(PictureLayerTiling*,

cc/picture_layer_impl.h

@@ -44,6 +44,13 @@ protected:
   PictureLayerTilingSet tilings_;
   scoped_refptr<PicturePileImpl> pile_;
 
+  gfx::Transform last_screen_space_transform_;
+  double last_update_time_;
+  gfx::Size last_bounds_;
+  gfx::Size last_content_bounds_;
+  float last_content_scale_x_;
+  float last_content_scale_y_;
+
   friend class PictureLayer;
   DISALLOW_COPY_AND_ASSIGN(PictureLayerImpl);
 };

cc/picture_layer_tiling.cc

@@ -3,6 +3,8 @@
 // found in the LICENSE file.
 
 #include "cc/picture_layer_tiling.h"
+
+#include "cc/math_util.h"
 #include "ui/gfx/rect_conversions.h"
 #include "ui/gfx/size_conversions.h"
 
@@ -266,4 +268,52 @@ gfx::Size PictureLayerTiling::Iterator::texture_size() const {
   return tiling_->tiling_data_.max_texture_size();
 }
 
+void PictureLayerTiling::UpdateTilePriorities(
+    const gfx::Size& device_viewport,
+    float layer_content_scale_x,
+    float layer_content_scale_y,
+    const gfx::Transform& last_screen_transform,
+    const gfx::Transform& current_screen_transform,
+    double time_delta) {
+  gfx::Rect content_rect = ContentRect();
+  if (content_rect.IsEmpty())
+    return;
+
+  gfx::Rect view_rect(gfx::Point(), device_viewport);
+  int right = tiling_data_.TileXIndexFromSrcCoord(content_rect.width() - 1);
+  int bottom = tiling_data_.TileYIndexFromSrcCoord(content_rect.height() - 1);
+  for (TileMap::const_iterator it = tiles_.begin(); it != tiles_.end(); ++it) {
+    TileMapKey key = it->first;
+    TilePriority priority;
+    if (key.first > right || key.second > bottom) {
+      priority.distance_to_visible_in_pixels = std::numeric_limits<int>::max();
+      priority.time_to_visible_in_seconds =
+          TilePriority::kMaxTimeToVisibleInSeconds;
+      // TODO(qinmin): pass the correct tree to this function.
+      it->second->set_priority(ACTIVE_TREE, priority);
+      continue;
+    }
+
+    gfx::Rect tile_bound = tiling_data_.TileBounds(key.first, key.second);
+    gfx::RectF layer_content_rect = gfx::ScaleRect(
+        tile_bound,
+        layer_content_scale_x / contents_scale_,
+        layer_content_scale_y / contents_scale_);
+    gfx::RectF screen_rect = MathUtil::mapClippedRect(
+        current_screen_transform, layer_content_rect);
+    gfx::RectF previous_rect = MathUtil::mapClippedRect(
+        last_screen_transform, layer_content_rect);
+
+    priority.resolution = HIGH_RESOLUTION;
+    priority.time_to_visible_in_seconds =
+        TilePriority::TimeForBoundsToIntersect(
+            previous_rect, screen_rect, time_delta, view_rect);
+
+    priority.distance_to_visible_in_pixels =
+        TilePriority::manhattanDistance(screen_rect, view_rect);
+    // TODO(qinmin): pass the correct tree to this function.
+    it->second->set_priority(ACTIVE_TREE, priority);
+  }
+}
+
 }  // namespace cc

cc/picture_layer_tiling.h

@@ -86,6 +86,13 @@ class CC_EXPORT PictureLayerTiling {
 
   void Reset() { return tiles_.clear(); }
 
+  void UpdateTilePriorities(const gfx::Size& device_viewport,
+                            float layer_content_scale_x,
+                            float layer_content_scale_y,
+                            const gfx::Transform& last_screen_transform,
+                            const gfx::Transform& current_screen_transform,
+                            double time_delta);
+
  protected:
   typedef std::pair<int, int> TileMapKey;
   typedef base::hash_map<TileMapKey, scoped_refptr<Tile> > TileMap;

cc/picture_layer_tiling_set.cc

@@ -157,4 +157,18 @@ PictureLayerTilingSet::Iterator::operator bool() const {
       region_iter_.has_rect();
 }
 
+void PictureLayerTilingSet::UpdateTilePriorities(
+    const gfx::Size& device_viewport,
+    float layer_content_scale_x,
+    float layer_content_scale_y,
+    const gfx::Transform& last_screen_transform,
+    const gfx::Transform& current_screen_transform,
+    double time_delta) {
+  for (size_t i = 0; i < tilings_.size(); ++i) {
+    tilings_[i]->UpdateTilePriorities(
+        device_viewport, layer_content_scale_x, layer_content_scale_y,
+        last_screen_transform, current_screen_transform, time_delta);
+  }
+}
+
 }  // namespace cc

cc/picture_layer_tiling_set.h

@@ -28,6 +28,13 @@ class CC_EXPORT PictureLayerTilingSet {
   void AddTiling(float contents_scale, gfx::Size tile_size);
   size_t num_tilings() const { return tilings_.size(); }
 
+  void UpdateTilePriorities(const gfx::Size& device_viewport,
+                            float layer_content_scale_x,
+                            float layer_content_scale_y,
+                            const gfx::Transform& last_screen_transform,
+                            const gfx::Transform& current_screen_transform,
+                            double time_delta);
+
   // For a given rect, iterates through tiles that can fill it.  If no
   // set of tiles with resources can fill the rect, then it will iterate
   // through null tiles with valid geometry_rect() until the rect is full.

cc/tile_priority.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/tile_priority.h"
+
+namespace {
+
+// TODO(qinmin): modify ui/range/Range.h to support template so that we
+// don't need to define this.
+struct Range {
+  Range(double start, double end) : start_(start), end_(end) {}
+  Range Intersects(const Range& other);
+  bool IsEmpty();
+  double start_;
+  double end_;
+};
+
+Range Range::Intersects(const Range& other) {
+  start_ = std::max(start_, other.start_);
+  end_ = std::min(end_, other.end_);
+  return Range(start_, end_);
+}
+
+bool Range::IsEmpty() {
+  return start_ >= end_;
+}
+
+// Calculate a time range that |value| will be larger than |threshold|
+// given the velocity of its change.
+Range TimeRangeValueLargerThanThreshold(
+    int value, int threshold, double velocity) {
+  double minimum_time = 0;
+  double maximum_time = cc::TilePriority::kMaxTimeToVisibleInSeconds;
+
+  if (velocity > 0) {
+    if (value < threshold)
+      minimum_time = std::min(cc::TilePriority::kMaxTimeToVisibleInSeconds,
+                              (threshold - value) / velocity);
+  } else if (velocity <= 0) {
+    if (value < threshold)
+      minimum_time = cc::TilePriority::kMaxTimeToVisibleInSeconds;
+    else if (velocity != 0)
+      maximum_time = std::min(maximum_time, (threshold - value) / velocity);
+  }
+
+  return Range(minimum_time, maximum_time);
+}
+
+}  // namespace
+
+namespace cc {
+
+const double TilePriority::kMaxTimeToVisibleInSeconds = 1000;
+
+int TilePriority::manhattanDistance(const gfx::RectF& a, const gfx::RectF& b) {
+  gfx::RectF c = gfx::UnionRects(a, b);
+  // Rects touching the edge of the screen should not be considered visible.
+  // So we add 1 pixel here to avoid that situation.
+  int x = static_cast<int>(
+      std::max(0.0f, c.width() - a.width() - b.width() + 1));
+  int y = static_cast<int>(
+      std::max(0.0f, c.height() - a.height() - b.height() + 1));
+  return (x + y);
+}
+
+double TilePriority::TimeForBoundsToIntersect(gfx::RectF previous_bounds,
+                                              gfx::RectF current_bounds,
+                                              double time_delta,
+                                              gfx::RectF target_bounds) {
+  if (current_bounds.Intersects(target_bounds))
+    return 0;
+
+  if (previous_bounds.Intersects(target_bounds) || time_delta == 0)
+    return kMaxTimeToVisibleInSeconds;
+
+  // As we are trying to solve the case of both scaling and scrolling, using
+  // a single coordinate with velocity is not enough. The logic here is to
+  // calculate the velocity for each edge. Then we calculate the time range that
+  // each edge will stay on the same side of the target bounds. If there is an
+  // overlap between these time ranges, the bounds must have intersect with
+  // each other during that period of time.
+  double velocity =
+      (current_bounds.right() - previous_bounds.right()) / time_delta;
+  Range range = TimeRangeValueLargerThanThreshold(
+      current_bounds.right(), target_bounds.x(), velocity);
+
+  velocity = (current_bounds.x() - previous_bounds.x()) / time_delta;
+  range = range.Intersects(TimeRangeValueLargerThanThreshold(
+      -current_bounds.x(), -target_bounds.right(), -velocity));
+
+
+  velocity = (current_bounds.y() - previous_bounds.y()) / time_delta;
+  range = range.Intersects(TimeRangeValueLargerThanThreshold(
+      -current_bounds.y(), -target_bounds.bottom(), -velocity));
+
+  velocity = (current_bounds.bottom() - previous_bounds.bottom()) / time_delta;
+  range = range.Intersects(TimeRangeValueLargerThanThreshold(
+      current_bounds.bottom(), target_bounds.y(), velocity));
+
+  return range.IsEmpty() ? kMaxTimeToVisibleInSeconds : range.start_;
+}
+
+}  // namespace cc

cc/tile_priority.h

@@ -5,6 +5,8 @@
 #ifndef CC_TILE_PRIORITY_H_
 #define CC_TILE_PRIORITY_H_
 
+#include <limits>
+
 #include "base/memory/ref_counted.h"
 #include "cc/picture_pile.h"
 #include "ui/gfx/rect.h"
@@ -25,7 +27,7 @@ enum TileResolution {
   NON_IDEAL_RESOLUTION = 2
 };
 
-struct TilePriority {
+struct CC_EXPORT TilePriority {
   TilePriority()
      : resolution(NON_IDEAL_RESOLUTION),
        time_to_visible_in_seconds(std::numeric_limits<float>::max()),
@@ -58,6 +60,18 @@ struct TilePriority {
                     time_to_ideal_resolution_in_seconds);
   }
 
+  static const double kMaxTimeToVisibleInSeconds;
+
+  static int manhattanDistance(const gfx::RectF& a, const gfx::RectF& b);
+
+  // Calculate the time for the |current_bounds| to intersect with the
+  // |target_bounds| given its previous location and time delta.
+  // This function should work for both scaling and scrolling case.
+  static double TimeForBoundsToIntersect(gfx::RectF previous_bounds,
+                                         gfx::RectF current_bounds,
+                                         double time_delta,
+                                         gfx::RectF target_bounds);
+
   TileResolution resolution;
   float time_to_visible_in_seconds;
   float time_to_ideal_resolution_in_seconds;

cc/tile_priority_unittest.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/tile_priority.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace cc {
+
+TEST(TilePriorityTest, TimeForBoundsToIntersectWithScroll) {
+  gfx::Rect target(0, 0, 800, 600);
+  gfx::Rect current(100, 100, 100, 100);
+  EXPECT_EQ(0, TilePriority::TimeForBoundsToIntersect(
+      gfx::Rect(-200, 0, 100, 100), current, 1, target));
+  EXPECT_EQ(0, TilePriority::TimeForBoundsToIntersect(
+      gfx::Rect(-100, 0, 100, 100), current, 1, target));
+  EXPECT_EQ(0, TilePriority::TimeForBoundsToIntersect(
+      gfx::Rect(400, 400, 100, 100), current, 1, target));
+
+  current = gfx::Rect(-300, -300, 100, 100);
+  EXPECT_EQ(1000, TilePriority::TimeForBoundsToIntersect(
+      gfx::Rect(0, 0, 100, 100), current, 1, target));
+  EXPECT_EQ(1000, TilePriority::TimeForBoundsToIntersect(
+      gfx::Rect(-200, -200, 100, 100), current, 1, target));
+  EXPECT_EQ(2, TilePriority::TimeForBoundsToIntersect(
+      gfx::Rect(-400, -400, 100, 100), current, 1, target));
+}
+
+TEST(TilePriorityTest, TimeForBoundsToIntersectWithScale) {
+  gfx::Rect target(0, 0, 800, 600);
+  gfx::Rect current(100, 100, 100, 100);
+  EXPECT_EQ(0, TilePriority::TimeForBoundsToIntersect(
+      gfx::Rect(-200, 0, 200, 200), current, 1, target));
+  EXPECT_EQ(0, TilePriority::TimeForBoundsToIntersect(
+      gfx::Rect(-100, 0, 50, 50), current, 1, target));
+  EXPECT_EQ(0, TilePriority::TimeForBoundsToIntersect(
+      gfx::Rect(400, 400, 400, 400), current, 1, target));
+
+  current = gfx::Rect(-300, -300, 100, 100);
+  EXPECT_EQ(1000, TilePriority::TimeForBoundsToIntersect(
+      gfx::Rect(-400, -400, 300, 300), current, 1, target));
+  EXPECT_EQ(8, TilePriority::TimeForBoundsToIntersect(
+      gfx::Rect(-275, -275, 50, 50), current, 1, target));
+  EXPECT_EQ(1, TilePriority::TimeForBoundsToIntersect(
+      gfx::Rect(-450, -450, 50, 50), current, 1, target));
+}
+
+TEST(TilePriorityTest, ManhattanDistanceBetweenRects) {
+  EXPECT_EQ(0, TilePriority::manhattanDistance(
+      gfx::RectF(0, 0, 400, 400), gfx::RectF(0, 0, 100, 100)));
+
+  EXPECT_EQ(2, TilePriority::manhattanDistance(
+      gfx::Rect(0, 0, 400, 400), gfx::Rect(-100, -100, 100, 100)));
+
+  EXPECT_EQ(1, TilePriority::manhattanDistance(
+      gfx::Rect(0, 0, 400, 400), gfx::Rect(0, -100, 100, 100)));
+
+  EXPECT_EQ(202, TilePriority::manhattanDistance(
+      gfx::Rect(0, 0, 100, 100), gfx::Rect(200, 200, 100, 100)));
+}
+
+}  // namespace cc