cc: Use maximum tiling contents scales for picture layer scale

Due to the way the math works out for calculating which tiles to use for a
given content rect, the content scale for a picture layer has to be the maximum
of all the tilings on a layer.

Currently, each layer only has one tiling, but this change also creates the
infrastructure for adding different tilings over time and clamping contents
scales to a minimum.

NOTRY=true
R=danakj@chromium.org
BUG=155209


Review URL: https://chromiumcodereview.appspot.com/11777008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@175420 0039d316-1c4b-4281-b951-d872f2087c98

6 files changed, 105 insertions, 36 deletions

diff --git a/cc/layer_impl.cc b/cc/layer_impl.cc
index 4ab9989..c588fe2 100644
--- a/cc/layer_impl.cc
+++ b/cc/layer_impl.cc
@@ -713,6 +713,19 @@ void LayerImpl::setContentsScale(float contentsScaleX, float contentsScaleY)
     noteLayerPropertyChanged();
 }
 
+void LayerImpl::calculateContentsScale(
+    float idealContentsScale,
+    float* contentsScaleX,
+    float* contentsScaleY,
+    gfx::Size* contentBounds)
+{
+    // Base LayerImpl has all of its content scales and content bounds pushed
+    // from its Layer during commit and just reuses those values as-is.
+    *contentsScaleX = this->contentsScaleX();
+    *contentsScaleY = this->contentsScaleY();
+    *contentBounds = this->contentBounds();
+}
+
 void LayerImpl::setScrollOffset(gfx::Vector2d scrollOffset)
 {
     if (m_scrollOffset == scrollOffset)
diff --git a/cc/layer_impl.h b/cc/layer_impl.h
index 4320446..2219cf7 100644
--- a/cc/layer_impl.h
+++ b/cc/layer_impl.h
@@ -199,6 +199,12 @@ public:
     float contentsScaleY() const { return m_drawProperties.contents_scale_y; }
     void setContentsScale(float contentsScaleX, float contentsScaleY);
 
+    virtual void calculateContentsScale(
+        float idealContentsScale,
+        float* contentsScaleX,
+        float* contentsScaleY,
+        gfx::Size* contentBounds);
+
     gfx::Vector2d scrollOffset() const { return m_scrollOffset; }
     void setScrollOffset(gfx::Vector2d);
 
diff --git a/cc/layer_tree_host_common.cc b/cc/layer_tree_host_common.cc
index feba747..5af7a69 100644
--- a/cc/layer_tree_host_common.cc
+++ b/cc/layer_tree_host_common.cc
@@ -406,8 +406,41 @@ gfx::Transform computeScrollCompensationMatrixForChildren(LayerImpl* layer, cons
     return nextScrollCompensationMatrix;
 }
 
+template<typename LayerType>
+static inline void calculateContentsScale(LayerType* layer, float contentsScale)
+{
+    layer->calculateContentsScale(
+        contentsScale,
+        &layer->drawProperties().contents_scale_x,
+        &layer->drawProperties().contents_scale_y,
+        &layer->drawProperties().content_bounds);
+
+    LayerType* maskLayer = layer->maskLayer();
+    if (maskLayer)
+    {
+        maskLayer->calculateContentsScale(
+            contentsScale,
+            &maskLayer->drawProperties().contents_scale_x,
+            &maskLayer->drawProperties().contents_scale_y,
+            &maskLayer->drawProperties().content_bounds);
+    }
+
+    LayerType* replicaMaskLayer = layer->replicaLayer() ? layer->replicaLayer()->maskLayer() : 0;
+    if (replicaMaskLayer)
+    {
+        replicaMaskLayer->calculateContentsScale(
+            contentsScale,
+            &replicaMaskLayer->drawProperties().contents_scale_x,
+            &replicaMaskLayer->drawProperties().contents_scale_y,
+            &replicaMaskLayer->drawProperties().content_bounds);
+    }
+}
+
 static inline void updateLayerContentsScale(LayerImpl* layer, const gfx::Transform& combinedTransform, float deviceScaleFactor, float pageScaleFactor, bool animatingTransformToScreen)
 {
+    gfx::Vector2dF transformScale = MathUtil::computeTransform2dScaleComponents(combinedTransform, deviceScaleFactor * pageScaleFactor);
+    float contentsScale = std::max(transformScale.x(), transformScale.y());
+    calculateContentsScale(layer, contentsScale);
 }
 
 static inline void updateLayerContentsScale(Layer* layer, const gfx::Transform& combinedTransform, float deviceScaleFactor, float pageScaleFactor, bool animatingTransformToScreen)
@@ -433,31 +466,8 @@ static inline void updateLayerContentsScale(Layer* layer, const gfx::Transform&
     float contentsScale = rasterScale * deviceScaleFactor;
     if (!layer->boundsContainPageScale())
         contentsScale *= pageScaleFactor;
-    layer->calculateContentsScale(
-        contentsScale,
-        &layer->drawProperties().contents_scale_x,
-        &layer->drawProperties().contents_scale_y,
-        &layer->drawProperties().content_bounds);
-
-    Layer* maskLayer = layer->maskLayer();
-    if (maskLayer)
-    {
-        maskLayer->calculateContentsScale(
-            contentsScale,
-            &maskLayer->drawProperties().contents_scale_x,
-            &maskLayer->drawProperties().contents_scale_y,
-            &maskLayer->drawProperties().content_bounds);
-    }
 
-    Layer* replicaMaskLayer = layer->replicaLayer() ? layer->replicaLayer()->maskLayer() : 0;
-    if (replicaMaskLayer)
-    {
-        replicaMaskLayer->calculateContentsScale(
-            contentsScale,
-            &replicaMaskLayer->drawProperties().contents_scale_x,
-            &replicaMaskLayer->drawProperties().contents_scale_y,
-            &replicaMaskLayer->drawProperties().content_bounds);
-    }
+    calculateContentsScale(layer, contentsScale);
 }
 
 template<typename LayerType, typename LayerList>
diff --git a/cc/picture_layer_impl.cc b/cc/picture_layer_impl.cc
index d5a44c7..161fd83 100644
--- a/cc/picture_layer_impl.cc
+++ b/cc/picture_layer_impl.cc
@@ -15,6 +15,7 @@
 #include "cc/solid_color_draw_quad.h"
 #include "cc/tile_draw_quad.h"
 #include "ui/gfx/quad_f.h"
+#include "ui/gfx/size_conversions.h"
 
 namespace cc {
 
@@ -129,18 +130,6 @@ void PictureLayerImpl::dumpLayerProperties(std::string*, int indent) const {
 }
 
 void PictureLayerImpl::didUpdateTransforms() {
-  if (drawsContent()) {
-    // TODO(enne): Add tilings during pinch zoom
-    // TODO(enne): Consider culling old tilings after pinch finishes.
-    if (!tilings_.num_tilings()) {
-      AddTiling(contentsScaleX(), TileSize());
-      // TODO(enne): Add a low-res tiling as well.
-    }
-  } else {
-    // TODO(enne): This should be unnecessary once there are two trees.
-    tilings_.Reset();
-  }
-
   gfx::Transform current_screen_space_transform =
       screenSpaceTransform();
   double current_time =
@@ -170,6 +159,36 @@ void PictureLayerImpl::didUpdateTransforms() {
   last_content_scale_y_ = contentsScaleY();
 }
 
+void PictureLayerImpl::calculateContentsScale(
+    float ideal_contents_scale,
+    float* contents_scale_x,
+    float* contents_scale_y,
+    gfx::Size* content_bounds) {
+  if (!drawsContent()) {
+    DCHECK(!tilings_.num_tilings());
+    return;
+  }
+
+  ManageTilings(ideal_contents_scale);
+
+  // The content scale and bounds for a PictureLayerImpl is somewhat fictitious.
+  // There are (usually) several tilings at different scales.  However, the
+  // content bounds is the (integer!) space in which quads are generated.
+  // In order to guarantee that we can fill this integer space with any set of
+  // tilings (and then map back to floating point texture coordinates), the
+  // contents scale must be at least as large as the largest of the tilings.
+  float max_contents_scale = 1.f;
+  for (size_t i = 0; i < tilings_.num_tilings(); ++i) {
+    const PictureLayerTiling* tiling = tilings_.tiling_at(i);
+    max_contents_scale = std::max(max_contents_scale, tiling->contents_scale());
+  }
+
+  *contents_scale_x = max_contents_scale;
+  *contents_scale_y = max_contents_scale;
+  *content_bounds = gfx::ToCeiledSize(
+      gfx::ScaleSize(bounds(), max_contents_scale, max_contents_scale));
+}
+
 scoped_refptr<Tile> PictureLayerImpl::CreateTile(PictureLayerTiling* tiling,
                                                  gfx::Rect rect) {
   TileManager* tile_manager = layerTreeImpl()->tile_manager();
@@ -260,4 +279,18 @@ gfx::Size PictureLayerImpl::TileSize() const {
   return layerTreeImpl()->settings().defaultTileSize;
 }
 
+void PictureLayerImpl::ManageTilings(float ideal_contents_scale) {
+  if (drawsContent()) {
+    // TODO(enne): Add tilings during pinch zoom
+    // TODO(enne): Consider culling old tilings after pinch finishes.
+    if (!tilings_.num_tilings()) {
+      AddTiling(ideal_contents_scale, TileSize());
+      // TODO(enne): Add a low-res tiling as well.
+    }
+  } else {
+    // TODO(enne): This should be unnecessary once there are two trees.
+    tilings_.Reset();
+  }
+}
+
 }  // namespace cc
diff --git a/cc/picture_layer_impl.h b/cc/picture_layer_impl.h
index c7fbf6e..60e2c8d 100644
--- a/cc/picture_layer_impl.h
+++ b/cc/picture_layer_impl.h
@@ -30,6 +30,11 @@ public:
   virtual void appendQuads(QuadSink&, AppendQuadsData&) OVERRIDE;
   virtual void dumpLayerProperties(std::string*, int indent) const OVERRIDE;
   virtual void didUpdateTransforms() OVERRIDE;
+  virtual void calculateContentsScale(
+      float ideal_contents_scale,
+      float* contents_scale_x,
+      float* contents_scale_y,
+      gfx::Size* content_bounds) OVERRIDE;
 
   // PictureLayerTilingClient overrides.
   virtual scoped_refptr<Tile> CreateTile(PictureLayerTiling*,
@@ -48,6 +53,7 @@ protected:
   void AddTiling(float contents_scale, gfx::Size tile_size);
   void SyncFromActiveLayer(const PictureLayerImpl* other);
   gfx::Size TileSize() const;
+  void ManageTilings(float ideal_contents_scale);
 
   PictureLayerTilingSet tilings_;
   scoped_refptr<PicturePileImpl> pile_;
diff --git a/cc/picture_layer_tiling_set.h b/cc/picture_layer_tiling_set.h
index 11e2796..383884e 100644
--- a/cc/picture_layer_tiling_set.h
+++ b/cc/picture_layer_tiling_set.h
@@ -30,6 +30,7 @@ class CC_EXPORT PictureLayerTilingSet {
       float contents_scale,
       gfx::Size tile_size);
   size_t num_tilings() const { return tilings_.size(); }
+  PictureLayerTiling* tiling_at(size_t idx) { return tilings_[idx]; }
 
   void Reset();