Keeping track of descendants that draw content instead of recalcualting

cc/layers/layer.cc

Index: cc/layers/layer.cc
diff --git a/cc/layers/layer.cc b/cc/layers/layer.cc
index 82978daa03633a23d52b405414b4be0ead50b08c..cfb93d4e82e64005692331daa5fa0aa4b3b11f3e 100644
--- a/cc/layers/layer.cc
+++ b/cc/layers/layer.cc
@@ -47,6 +47,7 @@ Layer::Layer()
       parent_(NULL),
       layer_tree_host_(NULL),
       scroll_clip_layer_id_(INVALID_ID),
+      num_descendants_that_draw_content_(0),
       should_scroll_on_main_thread_(false),
       have_wheel_event_handlers_(false),
       have_scroll_event_handlers_(false),
@@ -55,6 +56,7 @@ Layer::Layer()
       is_root_for_isolated_group_(false),
       is_container_for_fixed_position_layers_(false),
       is_drawable_(false),
+      draws_content_(false),
       hide_layer_and_subtree_(false),
       masks_to_bounds_(false),
       contents_opaque_(false),
@@ -250,6 +252,9 @@ void Layer::InsertChild(scoped_refptr<Layer> child, size_t index) {
 
   index = std::min(index, children_.size());
   children_.insert(children_.begin() + index, child);
+  AddDrawableDescendants(child->NumDescendantsThatDrawContent() +
+                         (child->DrawsContent() ? 1 : 0) +
+                         (child->HasDelegatedContent() ? 1000 : 0));
   SetNeedsFullTreeSync();
 }
 
@@ -280,6 +285,9 @@ void Layer::RemoveChildOrDependent(Layer* child) {
       continue;
 
     child->SetParent(NULL);
+    AddDrawableDescendants(-child->NumDescendantsThatDrawContent() -
+                           (child->DrawsContent() ? 1 : 0) -
+                           (child->HasDelegatedContent() ? 1000 : 0));

[danakj, 2014/07/14 20:22:02]

i don't think you need to do this here after you address comments below, it
should be in the NumDescendants* stuff.

Can you make sure we have tests to verify this is working right for delegated
layers, as we currently do for the delegated impl layers.

[awoloszyn, 2014/07/16 20:44:19]

Done.

     children_.erase(iter);
     SetNeedsFullTreeSync();
     return;
@@ -779,6 +787,7 @@ void Layer::SetIsDrawable(bool is_drawable) {
     return;
 
   is_drawable_ = is_drawable;
+  UpdateDrawsContent();
   SetNeedsCommit();
 }
 
@@ -900,6 +909,7 @@ void Layer::PushPropertiesTo(LayerImpl* layer) {
     layer->SetTransformAndInvertibility(transform_, transform_is_invertible_);
   DCHECK(!(TransformIsAnimating() && layer->TransformIsAnimatingOnImplOnly()));
   layer->Set3dSortingContextId(sorting_context_id_);
+  layer->SetNumDescendantsThatDrawContent(num_descendants_that_draw_content_);
 
   layer->SetScrollClipLayer(scroll_clip_layer_id_);
   layer->set_user_scrollable_horizontal(user_scrollable_horizontal_);
@@ -1006,7 +1016,36 @@ scoped_ptr<LayerImpl> Layer::CreateLayerImpl(LayerTreeImpl* tree_impl) {
 }
 
 bool Layer::DrawsContent() const {
-  return is_drawable_;
+  return draws_content_;
+}
+
+bool Layer::HasDrawableContent() const {
+  return true;
+}
+
+void Layer::UpdateDrawsContent() {
+  bool draws_content = is_drawable_ && HasDrawableContent();
+  if (draws_content == draws_content_)
+    return;
+  // As per the comment that was originally in
+  // LayerTreeHost::PrecalculateMetaInformation:
+  // Layers with delegated content need to be treated as if they have as

[danakj, 2014/07/14 20:22:02]

This isn't quite what we're doing yet. Right now you're saying if a layer has
delegated content, that its parent has 1000 children that draw content.

What we want is for the layer *with* delegated content to have 1000 children
that draw content. So we'll have to change this->num_descenda... in this method
here to add/subtract 1000.

[awoloszyn, 2014/07/16 20:44:19]

I moved this into NumDescendantsThatDrawContent(). This is consistent with the
old behavior where we counted the +1000 regardless of whether or not we drew
content.

+  // many children as the number of layers they own delegated quads for.
+  // Since we don't know this number right now, we choose one that acts like
+  // infinity for our purposes.
+
+  if (parent()) {
+    if (draws_content) {
+      parent()->AddDrawableDescendants(1 + (HasDelegatedContent() ? 1000 : 0));
+    } else {
+      parent()->AddDrawableDescendants(-1 - (HasDelegatedContent() ? 1000 : 0));
+    }
+  }
+  draws_content_ = draws_content;

[danakj, 2014/07/14 20:22:02]

SetNeedsCommit in here, please add this to the tests we have for setting
properties causing a commit and needs_push_props to be true.

[awoloszyn, 2014/07/16 20:44:20]

Done.

+}
+
+int Layer::NumDescendantsThatDrawContent() const {
+  return num_descendants_that_draw_content_;
 }
 
 void Layer::SavePaintProperties() {
@@ -1189,7 +1228,22 @@ void Layer::RemoveFromClipTree() {
   clip_parent_ = NULL;
 }
 
+void Layer::AddDrawableDescendants(int num) {
+  DCHECK_GE(num_descendants_that_draw_content_, 0);
+  DCHECK_GE(num_descendants_that_draw_content_ + num, 0);
+  if (num == 0)
+    return;
+  num_descendants_that_draw_content_ += num;
+  SetNeedsCommit();
+  if (parent())
+    parent()->AddDrawableDescendants(num);
+}
+
 void Layer::RunMicroBenchmark(MicroBenchmark* benchmark) {
   benchmark->RunOnLayer(this);
 }
+
+bool Layer::HasDelegatedContent() const {
+  return false;
+}
 }  // namespace cc

[danakj, 2014/07/14 20:22:02]

blank line above

[awoloszyn, 2014/07/16 20:44:20]

Done.