Support targeting for gestures in ViewTargeter

ui/views/view_targeter.cc

 // Copyright 2014 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 "ui/views/view_targeter.h"
 
 #include "ui/events/event_target.h"
 #include "ui/views/focus/focus_manager.h"
 #include "ui/views/view.h"
 #include "ui/views/view_targeter_delegate.h"
+#include "ui/views/views_switches.h"
+#include "ui/views/widget/root_view.h"
+#include "ui/views/widget/widget.h"
 
 namespace views {
 
 ViewTargeter::ViewTargeter(ViewTargeterDelegate* delegate)
     : delegate_(delegate) {
   DCHECK(delegate_);
 }
 
 ViewTargeter::~ViewTargeter() {}
 
@@ skipping 11 matching lines @@
   View* view = static_cast<View*>(root);
 
   if (event->IsKeyEvent())
     return FindTargetForKeyEvent(view, *static_cast<ui::KeyEvent*>(event));
 
   if (event->IsScrollEvent()) {
     return FindTargetForScrollEvent(view,
                                     *static_cast<ui::ScrollEvent*>(event));
   }
 
+  if (event->IsGestureEvent())
+    return FindTargetForGestureEvent(view, *(event->AsGestureEvent()));
+
   NOTREACHED() << "ViewTargeter does not yet support this event type.";
   return NULL;
 }
 
 ui::EventTarget* ViewTargeter::FindNextBestTarget(
     ui::EventTarget* previous_target,
     ui::Event* event) {
+  if (!previous_target)
+    return NULL;
+
+  if (event->IsGestureEvent()) {
+    View* root =
+        static_cast<View*>(previous_target)->GetWidget()->GetRootView();
+    internal::RootView* root_view = static_cast<internal::RootView*>(root);
+
+    // If the default gesture handler was already established prior to |event|,
+    // only GESTURE_SCROLL_BEGIN events may be re-targeted.
+    if (root_view->dispatch_to_gesture_handler_ &&
+        event->type() != ui::ET_GESTURE_SCROLL_BEGIN) {
+      return NULL;
+    }
+
+    // If |gesture_handler_| is NULL, it is either because the view was removed
+    // from the tree by the previous dispatch of |event| or because |event| is
+    // the GESTURE_END event corresponding to the removal of the last touch
+    // point. In either case, no further re-targeting of |event| should be
+    // permitted.
+    if (!root_view->gesture_handler_)
+      return NULL;
+  }
+
   return previous_target->GetParentTarget();
 }
 
 bool ViewTargeter::SubtreeCanAcceptEvent(
     ui::EventTarget* target,
     const ui::LocatedEvent& event) const {
   NOTREACHED();
   return false;
 }
 
 bool ViewTargeter::EventLocationInsideBounds(
     ui::EventTarget* target,
     const ui::LocatedEvent& event) const {
   NOTREACHED();
   return false;
 }
 
 View* ViewTargeter::FindTargetForKeyEvent(View* root, const ui::KeyEvent& key) {
   if (root->GetFocusManager())
     return root->GetFocusManager()->GetFocusedView();
   return NULL;
 }
 
 View* ViewTargeter::FindTargetForScrollEvent(View* root,
                                              const ui::ScrollEvent& scroll) {
   gfx::Rect rect(scroll.location(), gfx::Size(1, 1));
   return root->GetEffectiveViewTargeter()->TargetForRect(root, rect);
 }
 
+View* ViewTargeter::FindTargetForGestureEvent(View* root,
+                                              const ui::GestureEvent& gesture) {
+  CHECK(!root->parent());
+  internal::RootView* root_view = static_cast<internal::RootView*>(root);

[sadrul, 2014/08/26 16:21:44]

This is pretty ugly.

How about have a RootViewTargeter, that knows about the RootView upon
construction, and this FindTargetForGestureEvent() CHECK_EQ(root_view_, root);?

[tdanderson, 2014/08/26 20:21:14]

Done.

+
+  // Return the default gesture handler if one is already set.
+  if (root_view->gesture_handler_) {
+    CHECK(root_view->dispatch_to_gesture_handler_);
+    return root_view->gesture_handler_;
+  }
+
+  // If rect-based targeting is enabled, use the gesture's bounding box to
+  // determine the target. Otherwise use the center point of the gesture's
+  // bounding box to determine the target.
+  gfx::Rect rect(gesture.location(), gfx::Size(1, 1));
+  if (views::switches::IsRectBasedTargetingEnabled() &&
+      !gesture.details().bounding_box().IsEmpty()) {
+    // TODO(tdanderson): Pass in the bounding box to GetEventHandlerForRect()
+    // once crbug.com/313392 is resolved.
+    rect = gfx::Rect(gesture.details().bounding_box());
+    rect.set_origin(gesture.location());
+    rect.Offset(-rect.width() / 2, -rect.height() / 2);
+  }
+
+  return root->GetEffectiveViewTargeter()->TargetForRect(root, rect);
+}
+
 }  // namespace views