Add EventForwarder for routing touch events

ui/android/view_android.h

Index: ui/android/view_android.h
diff --git a/ui/android/view_android.h b/ui/android/view_android.h
index 0abd77cdc40d55152a13aa423e46c79d90082f0c..18bd14094d927764f1bd79c0cecd5b1df3981468 100644
--- a/ui/android/view_android.h
+++ b/ui/android/view_android.h
@@ -8,6 +8,7 @@
 #include <list>
 
 #include "base/android/jni_weak_ref.h"
+#include "base/bind.h"
 #include "base/memory/ref_counted.h"
 #include "ui/android/ui_android_export.h"
 #include "ui/gfx/geometry/rect_f.h"
@@ -19,11 +20,18 @@ class Layer;
 }
 
 namespace ui {
-
+class EventForwarder;
+class MotionEventAndroid;
+class ViewClient;
 class WindowAndroid;
 
 // A simple container for a UI layer.
 // At the root of the hierarchy is a WindowAndroid, when attached.
+// Dispatches input/view events coming from Java layer. Hit testing against
+// those events is implemented so that the |ViewClient| will be invoked
+// when the event got hit on the area defined by |layout_params_|.
+// Hit testing is done in the order of parent -> child, and from top
+// of the stack to back among siblings.
 class UI_ANDROID_EXPORT ViewAndroid {
  public:
   // Stores an anchored view to delete itself at the end of its lifetime
@@ -56,9 +64,32 @@ class UI_ANDROID_EXPORT ViewAndroid {
     // 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);
+  // Layout parameters used to set the view's position and size.
+  // Position is in parent's coordinate space.
+  struct LayoutParams {
+    static LayoutParams MatchParent() { return {true, 0, 0, 0, 0}; }
+    static LayoutParams Normal(int x, int y, int width, int height) {
+      return {false, x, y, width, height};
+    };
+
+    bool match_parent;  // Bounds matches that of the parent if true.
+    int x;
+    int y;
+    int width;
+    int height;
+
+    LayoutParams(const LayoutParams& p) = default;
+
+   private:
+    LayoutParams(bool match_parent, int x, int y, int width, int height)
+        : match_parent(match_parent),
+          x(x),
+          y(y),
+          width(width),
+          height(height) {}
+  };
+
+  explicit ViewAndroid(ViewClient* view_client);
 
   ViewAndroid();
   virtual ~ViewAndroid();
@@ -83,12 +114,24 @@ class UI_ANDROID_EXPORT ViewAndroid {
 
   void SetDelegate(const base::android::JavaRef<jobject>& delegate);
 
-  // Adds this view as a child of another view.
+  // Gets (creates one if not present) Java object of the EventForwarder
+  // for a view tree in the view hierarchy including this node.
+  // Only one instance per the view tree is allowed.
+  base::android::ScopedJavaLocalRef<jobject> GetEventForwarder();
+
+  // Adds a child to this view.
   void AddChild(ViewAndroid* child);
 
+  // Moves the give child ViewAndroid to the front of the list so that it can be
+  // the first responder of events.
+  void MoveToFront(ViewAndroid* child);
+
   // Detaches this view from its parent.
   void RemoveFromParent();
 
+  // Sets the layout relative to parent. Used to do hit testing against events.
+  void SetLayout(LayoutParams params);
+
   bool StartDragAndDrop(const base::android::JavaRef<jstring>& jtext,
                         const base::android::JavaRef<jobject>& jimage);
 
@@ -106,12 +149,41 @@ class UI_ANDROID_EXPORT ViewAndroid {
   // This may return null.
   base::android::ScopedJavaLocalRef<jobject> GetContainerView();
 
+  float GetDipScale();
+
  protected:
   ViewAndroid* parent_;
 
  private:
+  friend class EventForwarder;
+  friend class ViewAndroidBoundsTest;
+
+  using ViewClientCallback =
+      const base::Callback<bool(ViewClient*, const MotionEventAndroid&)>;
+
+  bool OnTouchEvent(const MotionEventAndroid& event, bool for_touch_handle);
+  bool OnMouseEvent(const MotionEventAndroid& event);
+
   void RemoveChild(ViewAndroid* child);
 
+  bool HitTest(ViewClientCallback send_to_client,
+               const MotionEventAndroid& event);
+
+  static bool SendTouchEventToClient(bool for_touch_handle,
+                                     ViewClient* client,
+                                     const MotionEventAndroid& event);
+  static bool SendMouseEventToClient(ViewClient* client,
+                                     const MotionEventAndroid& event);
+
+  bool has_event_forwarder() const { return !!event_forwarder_; }
+
+  // Returns true if any node of the tree along the hierarchy (view's children
+  // and parents) already has |EventForwarder| attached to it.
+  static bool ViewTreeHasEventForwarder(ViewAndroid* view);
+
+  // Returns true if any children node (or self) has |EventForwarder|.
+  static bool SubtreeHasEventForwarder(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).
@@ -121,7 +193,15 @@ class UI_ANDROID_EXPORT ViewAndroid {
   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.
+  LayoutParams layout_params_;
+
+  gfx::Vector2dF content_offset_;  // in CSS pixel.
+  std::unique_ptr<EventForwarder> event_forwarder_;
 
   DISALLOW_COPY_AND_ASSIGN(ViewAndroid);
 };