Add EventForwarder for routing touch events

ui/android/view_android.cc

Index: ui/android/view_android.cc
diff --git a/ui/android/view_android.cc b/ui/android/view_android.cc
index 1d5b146653458a83b93c58810f743f6df78e5c46..88ba8c0b5a681646df58e4c1180c1de9fb88fa68 100644
--- a/ui/android/view_android.cc
+++ b/ui/android/view_android.cc
@@ -8,11 +8,14 @@
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_string.h"
+#include "base/containers/adapters.h"
 #include "cc/layers/layer.h"
 #include "jni/ViewAndroidDelegate_jni.h"
+#include "ui/android/event_forwarder.h"
+#include "ui/android/view_client.h"
 #include "ui/android/window_android.h"
-#include "ui/display/display.h"
-#include "ui/display/screen.h"
+#include "ui/base/layout.h"
+#include "ui/events/android/motion_event_android.h"
 #include "url/gurl.h"
 
 namespace ui {
@@ -71,11 +74,12 @@ ViewAndroid::ScopedAnchorView::view() const {
   return view_.get(env);
 }
 
-ViewAndroid::ViewAndroid(const JavaRef<jobject>& delegate)
+ViewAndroid::ViewAndroid(ViewClient* view_client)
     : parent_(nullptr),
-      delegate_(base::android::AttachCurrentThread(), delegate.obj()) {}
+      client_(view_client),
+      layout_params_(LayoutParams::MatchParent()) {}
 
-ViewAndroid::ViewAndroid() : parent_(nullptr) {}
+ViewAndroid::ViewAndroid() : ViewAndroid(nullptr) {}
 
 ViewAndroid::~ViewAndroid() {
   RemoveFromParent();
@@ -88,21 +92,71 @@ ViewAndroid::~ViewAndroid() {
 }
 
 void ViewAndroid::SetDelegate(const JavaRef<jobject>& delegate) {
+  // A ViewAndroid may have its own delegate or otherwise will use the next
+  // available parent's delegate.
   JNIEnv* env = base::android::AttachCurrentThread();
   delegate_ = JavaObjectWeakGlobalRef(env, delegate);
 }
 
+float ViewAndroid::GetDipScale() {
+  return ui::GetScaleFactorForNativeView(this);
+}
+
+ScopedJavaLocalRef<jobject> ViewAndroid::GetEventForwarder() {
+  if (!event_forwarder_) {
+    DCHECK(!ViewTreeHasEventForwarder(this))
+        << "Root of the ViewAndroid can have at most one handler.";
+    event_forwarder_.reset(new EventForwarder(this));
+  }
+  return event_forwarder_->GetJavaObject();
+}
+
 void ViewAndroid::AddChild(ViewAndroid* child) {
   DCHECK(child);
   DCHECK(std::find(children_.begin(), children_.end(), child) ==
          children_.end());
+  DCHECK(!SubtreeHasEventForwarder(child) || !ViewTreeHasEventForwarder(this))
+      << "Only one event handler is allowed.";
 
+  // The new child goes to the top, which is the end of the list.
   children_.push_back(child);
   if (child->parent_)
     child->RemoveFromParent();
   child->parent_ = this;
 }
 
+// static
+bool ViewAndroid::ViewTreeHasEventForwarder(ViewAndroid* view) {
+  ViewAndroid* v = view;
+  do {
+    if (v->has_event_forwarder())
+      return true;
+    v = v->parent_;
+  } while (v);
+  return SubtreeHasEventForwarder(view);
+}
+
+// static
+bool ViewAndroid::SubtreeHasEventForwarder(ViewAndroid* view) {
+  if (view->has_event_forwarder())
+    return true;
+  for (auto* child : view->children_) {
+    if (SubtreeHasEventForwarder(child))
+      return true;
+  }
+  return false;
+}
+
+void ViewAndroid::MoveToFront(ViewAndroid* child) {
+  DCHECK(child);
+  auto it = std::find(children_.begin(), children_.end(), child);
+  DCHECK(it != children_.end());
+
+  // Top element is placed at the end of the list.
+  if (*it != children_.back())
+    children_.splice(children_.end(), children_, it);
+}
+
 void ViewAndroid::RemoveFromParent() {
   if (parent_)
     parent_->RemoveChild(this);
@@ -124,15 +178,13 @@ void ViewAndroid::SetAnchorRect(const JavaRef<jobject>& anchor,
   if (delegate.is_null())
     return;
 
-  float scale = display::Screen::GetScreen()
-                    ->GetDisplayNearestWindow(this)
-                    .device_scale_factor();
-  int left_margin = std::round(bounds.x() * scale);
-  int top_margin = std::round((content_offset().y() + bounds.y()) * scale);
+  float dip_scale = GetDipScale();
+  int left_margin = std::round(bounds.x() * dip_scale);
+  int top_margin = std::round((content_offset().y() + bounds.y()) * dip_scale);
   JNIEnv* env = base::android::AttachCurrentThread();
   Java_ViewAndroidDelegate_setViewPosition(
       env, delegate, anchor, bounds.x(), bounds.y(), bounds.width(),
-      bounds.height(), scale, left_margin, top_margin);
+      bounds.height(), dip_scale, left_margin, top_margin);
 }
 
 ScopedJavaLocalRef<jobject> ViewAndroid::GetContainerView() {
@@ -177,6 +229,10 @@ void ViewAndroid::SetLayer(scoped_refptr<cc::Layer> layer) {
   layer_ = layer;
 }
 
+void ViewAndroid::SetLayout(ViewAndroid::LayoutParams params) {
+  layout_params_ = params;
+}
+
 bool ViewAndroid::StartDragAndDrop(const JavaRef<jstring>& jtext,
                                    const JavaRef<jobject>& jimage) {
   ScopedJavaLocalRef<jobject> delegate(GetViewAndroidDelegate());
@@ -227,4 +283,51 @@ void ViewAndroid::StartContentIntent(const GURL& content_url,
                                                 is_main_frame);
 }
 
+bool ViewAndroid::OnTouchEvent(const MotionEventAndroid& event,
+                               bool for_touch_handle) {
+  return HitTest(
+      base::Bind(&ViewAndroid::SendTouchEventToClient, for_touch_handle),
+      event);
+}
+
+bool ViewAndroid::SendTouchEventToClient(bool for_touch_handle,
+                                         ViewClient* client,
+                                         const MotionEventAndroid& event) {
+  return client->OnTouchEvent(event, for_touch_handle);
+}
+
+bool ViewAndroid::OnMouseEvent(const MotionEventAndroid& event) {
+  return HitTest(base::Bind(&ViewAndroid::SendMouseEventToClient), event);
+}
+
+bool ViewAndroid::SendMouseEventToClient(ViewClient* client,
+                                         const MotionEventAndroid& event) {
+  return client->OnMouseEvent(event);
+}
+
+bool ViewAndroid::HitTest(ViewClientCallback send_to_client,
+                          const MotionEventAndroid& event) {
+  if (client_ && send_to_client.Run(client_, event))
+    return true;
+
+  if (!children_.empty()) {
+    std::unique_ptr<MotionEventAndroid> e(
+        event.Offset(-layout_params_.x, -layout_params_.y));
+
+    // Match from back to front for hit testing.
+    for (auto* child : base::Reversed(children_)) {
+      bool matched = child->layout_params_.match_parent;
+      if (!matched) {
+        gfx::Rect bound(child->layout_params_.x, child->layout_params_.y,
+                        child->layout_params_.width,
+                        child->layout_params_.height);
+        matched = bound.Contains(e->GetX(0), e->GetY(0));
+      }
+      if (matched && child->HitTest(send_to_client, *e))
+        return true;
+    }
+  }
+  return false;
+}
+
 }  // namespace ui