cc : Move screen space scale factor to root transform node

third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp

 // Copyright 2015 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 "platform/graphics/compositing/PaintArtifactCompositor.h"
 
 #include "cc/layers/content_layer_client.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/picture_layer.h"
 #include "cc/playback/display_item_list.h"
@@ skipping 436 matching lines @@
   };
   Vector<BlinkEffectAndCcIdPair> m_effectStack;
 
 #if DCHECK_IS_ON()
   HashSet<const EffectPaintPropertyNode*> m_effectNodesConverted;
   bool m_isFirstEffectEver;
 #endif
 };
 
 void PropertyTreeManager::setDeviceScaleFactor(float deviceScaleFactor) {
-  auto& rootTransformNode = *transformTree().Node(kSecondaryRootNodeId);
-  rootTransformNode.local.Scale(deviceScaleFactor, deviceScaleFactor);
+  auto& rootTransformNode = *transformTree().Node(kRealRootNodeId);
+  rootTransformNode.needs_surface_contents_scale = true;
+  rootTransformNode.surface_contents_scale =
+      gfx::Vector2dF(deviceScaleFactor, deviceScaleFactor);
+  // TODO(jaydasika) : We shouldn't set ToScreen and FromScreen of root

[weiliangc, 2016/10/13 21:16:18]

Why does this not work in cc right now?

[jaydasika, 2016/10/13 21:46:48]

It doesn't work. We only update transforms from node 1. In cc, you can see a
similar update for node 0 in SetScreenSpaceScale. I plan to remove them in a
follow-up.  

+  // transform node here. They should be set while updating transform tree in
+  // cc.
+  gfx::Transform toScreen;
+  toScreen.Scale(deviceScaleFactor, deviceScaleFactor);
+  transformTree().SetToScreen(rootTransformNode.id, toScreen);
+  gfx::Transform fromScreen;
+  if (!toScreen.GetInverse(&fromScreen))
+    rootTransformNode.ancestors_are_invertible = false;
+  transformTree().SetFromScreen(rootTransformNode.id, fromScreen);
+  transformTree().set_needs_update(true);
 }
 
 int PropertyTreeManager::compositorIdForTransformNode(
     const TransformPaintPropertyNode* transformNode) {
   if (!transformNode)
     return kSecondaryRootNodeId;
 
   auto it = m_transformNodeMap.find(transformNode);
   if (it != m_transformNodeMap.end())
     return it->value;
@@ skipping 293 matching lines @@
   }
   m_contentLayerClients.clear();
   m_contentLayerClients.swap(newContentLayerClients);
 
   // Mark the property trees as having been rebuilt.
   layerTree->property_trees()->sequence_number = kPropertyTreeSequenceNumber;
   layerTree->property_trees()->needs_rebuild = false;
 }
 
 }  // namespace blink