Add EventForwarder for routing touch events

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"
 
 class GURL;
 
 namespace cc {
 class Layer;
 }
 
 namespace ui {
 
+class EventHandler;
+class ViewClient;
 class WindowAndroid;
+struct MotionEventData;
 
 // A simple container for a UI layer.
 // At the root of the hierarchy is a WindowAndroid, when attached.
 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:
@@ skipping 15 matching lines @@
    private:
     // TODO(jinsukkim): Following weak refs can be cast to strong refs which
     //     cannot be garbage-collected and leak memory. Rewrite not to use them.
     //     see comments in crrev.com/2103243002.
     JavaObjectWeakGlobalRef view_;
     JavaObjectWeakGlobalRef delegate_;
 
     // Default copy/assign disabled by move constructor.
   };
 
-  // A ViewAndroid may have its own delegate or otherwise will
-  // use the next available parent's delegate.
-  ViewAndroid(const base::android::JavaRef<jobject>& delegate);
+  explicit ViewAndroid(ViewClient* view_client);
 
   ViewAndroid();
   virtual ~ViewAndroid();
 
   // The content offset is in CSS pixels, and is used to translate
   // snapshots to the correct part of the view.
   void set_content_offset(const gfx::Vector2dF& content_offset) {
     content_offset_ = content_offset;
   }
 
   gfx::Vector2dF content_offset() const {
     return content_offset_;
   }
 
   // Returns the window at the root of this hierarchy, or |null|
   // if disconnected.
   virtual WindowAndroid* GetWindowAndroid() const;
 
   // 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.
+  // Creates |EventHandler| for a view tree below (not including) WindowAndroid.
+  // Only one instance per the view tree is allowed at its top VA.
+  EventHandler* CreateEventHandler();

[Khushal, 2017/03/02 21:46:15]

Why create a new instance each time? Shouldn't this be GetEventHandler that
lazily creates the object?

+
+  // Adds a child to this view.
   void AddChild(ViewAndroid* child);
 
+  // Move the give child ViewAndroid to the top of the list so that it can be
+  // the first responder of events.
+  void MoveToTop(ViewAndroid* child);
+
   // Detaches this view from its parent.
   void RemoveFromParent();
 
+  // Set the layout relative to parent. Used to do hit testing against events.
+  void SetLayout(int x, int y, int width, int height, bool match_parent);
+
   bool StartDragAndDrop(const base::android::JavaRef<jstring>& jtext,
                         const base::android::JavaRef<jobject>& jimage);
 
   void OnBackgroundColorChanged(unsigned int color);
   void OnTopControlsChanged(float top_controls_offset,
                             float top_content_offset);
   void OnBottomControlsChanged(float bottom_controls_offset,
                                float bottom_content_offset);
   void StartContentIntent(const GURL& content_url, bool is_main_frame);
 
   ScopedAnchorView AcquireAnchorView();
   void SetAnchorRect(const base::android::JavaRef<jobject>& anchor,
                      const gfx::RectF& bounds);
 
   // This may return null.
   base::android::ScopedJavaLocalRef<jobject> GetContainerView();
 
+  bool OnTouchEvent(const MotionEventData& event);
+  bool OnMouseEvent(const MotionEventData& event);
+
+  // Virtual for testing.
+  virtual float GetDipScale();
+
  protected:
   ViewAndroid* parent_;
 
  private:
+  // Returns the root of this ViewAndroid hierarchy from which events starts
+  // trickling down. Note that it may not be the actual top of the tree.
+  ViewAndroid* GetViewRoot();
+
   void RemoveChild(ViewAndroid* child);
 
+  bool has_event_handler() const { return !!event_handler_; }
+
+  static bool ViewTreeHasEventHandler(ViewAndroid* view);
+
   // 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;
 
   std::list<ViewAndroid*> children_;
   scoped_refptr<cc::Layer> layer_;
   JavaObjectWeakGlobalRef delegate_;
-  gfx::Vector2dF content_offset_;  // in CSS pixel
+
+  ViewClient* const client_;
+
+  // Basic view layout information. Used to do hit testing deciding whether
+  // the passed events should be processed by the view.
+  gfx::Point origin_;  // In parent's coordinate space.
+  gfx::Size size_;
+  bool match_parent_;  // Bounds matches that of the parent if true.
+
+  gfx::Vector2dF content_offset_;  // in CSS pixel.
+  std::unique_ptr<EventHandler> event_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(ViewAndroid);
 };
 
 }  // namespace ui
 
 #endif  // UI_ANDROID_VIEW_ANDROID_H_