Introduce ViewRoot forwarding input/view events to native

ui/android/view_android.h

 // Copyright 2013 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.
 
 #ifndef UI_ANDROID_VIEW_ANDROID_H_
 #define UI_ANDROID_VIEW_ANDROID_H_
 
 #include <list>
 
 #include "base/android/jni_weak_ref.h"
 #include "base/memory/ref_counted.h"
 #include "ui/android/ui_android_export.h"
 #include "ui/gfx/geometry/rect_f.h"
 
 namespace cc {
 class Layer;
 }
 
 namespace ui {
 
 class ViewClient;
 class WindowAndroid;
 
 // A simple container for a UI layer.
-// At the root of the hierarchy is a WindowAndroid, when attached.
+// At the root of the hierarchy is a ViewRoot, a subclass of ViewAndroid.
 class UI_ANDROID_EXPORT ViewAndroid {
  public:
   // Stores an anchored view to delete itself at the end of its lifetime
   // automatically. This helps manage the lifecyle without the dependency
   // on |ViewAndroid|.
   class ScopedAnchorView {
    public:
     ScopedAnchorView(JNIEnv* env,
                      const base::android::JavaRef<jobject>& jview,
                      const base::android::JavaRef<jobject>& jdelegate);
@@ skipping 21 matching lines @@
 
   explicit ViewAndroid(ViewClient* client);
 
   ViewAndroid();
   virtual ~ViewAndroid();
 
   // Returns the window at the root of this hierarchy, or |null|
   // if disconnected.
   virtual WindowAndroid* GetWindowAndroid() const;
 
-  // Returns |ViewRoot| associated with the current ViewAndroid.
-  // Create one if not present.
-  base::android::ScopedJavaLocalRef<jobject> GetViewRoot();
+  // Set the root |WindowAndroid|. This is simply passed up to the root
+  // of the tree i.e. |ViewRoot| where the reference is held.
+  virtual void SetWindowAndroid(WindowAndroid* window);

[boliu, 2017/01/03 19:16:11]

This should not be needed.

First this seems to be a method that should be on ViewRoot only, not View.

For both chrome and webview, WindowAndroid and ViewRoot should be set *together*
everywhere. And the mapping from a ViewRoot to WindowAndroid should never have
to change. This applies to tab reparenting in chrome as well, ie when
reparenting to a new WindowAndroid, should start using a new ViewRoot as well.
So there should be no need for SetWindowAndroid in ViewRoot either.

[Jinsuk Kim, 2017/01/04 10:45:02]

Done. Is this suggestion about the immutable pairing between ViewRoot -
WindowAndroid to make it easy to track their relationship? 

[boliu, 2017/01/04 17:45:10]

Yeah. Also to keep things simple and avoid unnecessary complexity.

[Jinsuk Kim, 2017/01/05 11:03:12]

Acknowledged.

 
   // Used to return and set the layer for this view. May be |null|.
   cc::Layer* GetLayer() const;
   void SetLayer(scoped_refptr<cc::Layer> layer);
 
   void SetDelegate(const base::android::JavaRef<jobject>& delegate);
 
   // Adds this view as a child of another view.
   void AddChild(ViewAndroid* child);
 
   // Detaches this view from its parent.
   void RemoveFromParent();
 
   bool StartDragAndDrop(const base::android::JavaRef<jstring>& jtext,
                         const base::android::JavaRef<jobject>& jimage);
 
   ScopedAnchorView AcquireAnchorView();
   void SetAnchorRect(const base::android::JavaRef<jobject>& anchor,
                      const gfx::RectF& bounds);
 
   gfx::Size GetPhysicalBackingSize();
   void UpdateLayerBounds();
 
   // Internal implementation of ViewClient forwarding calls to the interface.
-  void OnPhysicalBackingSizeChanged(int width, int height);
+  void OnPhysicalBackingSizeChangedInternal(int width, int height);

[boliu, 2017/01/03 19:16:11]

the rename is to avoid name collision with ViewRoot, right?

maybe this should be protected then?

[Jinsuk Kim, 2017/01/04 10:45:02]

Done.

 
  protected:
+  // Returns the root of this hierarchy.

[boliu, 2017/01/03 19:16:11]

not quite, returns the ViewRoot of the hierarchy, but null if hierarchy isn't
attached to a ViewRoot

[Jinsuk Kim, 2017/01/04 10:45:02]

Done.

+  virtual ViewAndroid* GetViewRoot();
+
   ViewAndroid* parent_;
 
  private:
   void RemoveChild(ViewAndroid* child);
 
   // Checks if any ViewAndroid instance in the tree hierarchy (including
   // all the parents and the children) has |ViewRoot| already.
   bool HasViewRootInTreeHierarchy();
 
   // Checks if any children (plus this ViewAndroid itself) has |ViewRoot|.
   bool HasViewRootInSubtree();
 
   // Returns the Java delegate for this view. This is used to delegate work
   // up to the embedding view (or the embedder that can deal with the
   // implementation details).
   const base::android::ScopedJavaLocalRef<jobject>
       GetViewAndroidDelegate() const;
 
   // Creates a new |ViewRoot| for this ViewAndroid. No parent or child
   // should have |ViewRoot| for this ViewAndroid to have one.
   base::android::ScopedJavaLocalRef<jobject> CreateViewRoot();
 
-  bool HasViewRoot();
+  // Checks if this is the root of the view tree. Used to avoid ending up
+  // with multiple roots when modifying a tree.
+  bool IsViewRoot();
 
   std::list<ViewAndroid*> children_;
+
   scoped_refptr<cc::Layer> layer_;
   JavaObjectWeakGlobalRef delegate_;
-  JavaObjectWeakGlobalRef view_root_;
   ViewClient* const client_;
 
   int physical_width_pix_;
   int physical_height_pix_;
 
   DISALLOW_COPY_AND_ASSIGN(ViewAndroid);
 };
 
-bool RegisterViewRoot(JNIEnv* env);
-
 }  // namespace ui
 
 #endif  // UI_ANDROID_VIEW_ANDROID_H_