Add a flag to update hover effect when a layout is changed

third_party/WebKit/Source/core/input/MouseEventManager.cpp

 // Copyright 2016 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 "core/input/MouseEventManager.h"
 
 #include "core/clipboard/DataObject.h"
 #include "core/clipboard/DataTransfer.h"
 #include "core/dom/Element.h"
 #include "core/dom/ElementTraversal.h"
@@ skipping 38 matching lines @@
       Traversal<HTMLCanvasElement>::FirstAncestorOrSelf(*element);
   // In this case, the event target is canvas and mouse rerouting doesn't
   // happen.
   if (canvas == element)
     return String();
   return canvas->GetIdFromControl(element);
 }
 
 // The amount of time to wait before sending a fake mouse event triggered
 // during a scroll.
-const double kFakeMouseMoveInterval = 0.1;
+constexpr double kFakeMouseMoveIntervalDuringScroll = 0.1;
+
+// The amount of time to wait before sending a fake mouse event on style and
+// layout changes sets to 50Hz, same as common screen refresh rate.
+constexpr double kFakeMouseMoveIntervalPerFrame = 0.02;
 
 // TODO(crbug.com/653490): Read these values from the OS.
 #if OS(MACOSX)
 const int kDragThresholdX = 3;
 const int kDragThresholdY = 3;
 constexpr TimeDelta kTextDragDelay = TimeDelta::FromSecondsD(0.15);
 #else
 const int kDragThresholdX = 4;
 const int kDragThresholdY = 4;
 constexpr TimeDelta kTextDragDelay = TimeDelta::FromSecondsD(0.0);
@@ skipping 231 matching lines @@
             : EventTypeNames::auxclick,
         mev.Event(), mev.CanvasRegionId(), nullptr);
   }
 
   return WebInputEventResult::kNotHandled;
 }
 
 void MouseEventManager::FakeMouseMoveEventTimerFired(TimerBase* timer) {
   TRACE_EVENT0("input", "MouseEventManager::fakeMouseMoveEventTimerFired");
   DCHECK(timer == &fake_mouse_move_event_timer_);
-  DCHECK(!mouse_pressed_);
 
   if (is_mouse_position_unknown_)
     return;
 
   LocalFrameView* view = frame_->View();
   if (!view)
     return;
 
   if (!frame_->GetPage() || !frame_->GetPage()->GetFocusController().IsActive())
     return;
 
   // Don't dispatch a synthetic mouse move event if the mouse cursor is not
   // visible to the user.
   if (!frame_->GetPage()->IsCursorVisible())

[Navid Zolghadr, 2017/07/05 17:37:33]

Does this apply for layout change causing fake event case as well? So it's like
if the cursor is not visible and if the layout change we do not update the hover
state?

[lanwei, 2017/07/06 03:04:34]

I think we should not send the fake mouse move when the mouse cursor is not
visible when layout changes neither, because we should send any boundary events
or update hover states when the mouse is not visible. 

     return;
 
+  WebPointerEvent::Button button = WebPointerProperties::Button::kNoButton;
+  int modifiers = KeyboardEventManager::GetCurrentModifierState() |
+                  WebInputEvent::kRelativeMotionEvent;
+  if (mouse_pressed_) {
+    button = WebPointerProperties::Button::kLeft;

[Navid Zolghadr, 2017/07/05 17:37:33]

Shouldn't this still be kNoButton since we are sending a move event? Did that
cause any problem?

[lanwei, 2017/07/06 03:04:34]

Yes, I tested when we pressed a button and moved the mouse, we got the button of
WebPointerProperties::Button::kLeft, and also here, if the button is not
Button::kLeft, it will reset the mouse_pressed_ to false.
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/input/Mou...

+    modifiers |= WebInputEvent::kLeftButtonDown;
+  }
   WebMouseEvent fake_mouse_move_event(
       WebInputEvent::kMouseMove,
       WebFloatPoint(last_known_mouse_position_.X(),
                     last_known_mouse_position_.Y()),
       WebFloatPoint(last_known_mouse_global_position_.X(),
                     last_known_mouse_global_position_.Y()),
-      WebPointerProperties::Button::kNoButton, 0,
-      KeyboardEventManager::GetCurrentModifierState() |
-          WebInputEvent::Modifiers::kRelativeMotionEvent,
-      TimeTicks::Now().InSeconds());
+      button, 0, modifiers, TimeTicks::Now().InSeconds());
   // TODO(dtapuska): Update m_lastKnowMousePosition to be viewport coordinates.
   fake_mouse_move_event.SetFrameScale(1);
   Vector<WebMouseEvent> coalesced_events;
   frame_->GetEventHandler().HandleMouseMoveEvent(fake_mouse_move_event,
                                                  coalesced_events);
 }
 
 void MouseEventManager::CancelFakeMouseMoveEvent() {
   fake_mouse_move_event_timer_.Stop();
 }
@@ skipping 226 matching lines @@
 FloatPoint MouseEventManager::LastKnownMousePositionGlobal() {
   return last_known_mouse_global_position_;
 }
 
 void MouseEventManager::SetLastKnownMousePosition(const WebMouseEvent& event) {
   is_mouse_position_unknown_ = false;
   last_known_mouse_position_ = event.PositionInRootFrame();
   last_known_mouse_global_position_ = event.PositionInScreen();
 }
 
-void MouseEventManager::DispatchFakeMouseMoveEventSoon() {
-  if (mouse_pressed_)
+void MouseEventManager::DispatchFakeMouseMoveEventSoon(
+    MouseEventManager::FakeMouseMoveReason fake_mouse_move_reason) {
+  if (fake_mouse_move_reason ==
+          MouseEventManager::FakeMouseMoveReason::kDuringScroll &&
+      mouse_pressed_)
     return;
 
+  // When the mouse position is unknown, we do not send the fake mousemove
+  // event for now, so we cannot update the hover states and mouse cursor.
+  // We will fix it soon by keeping the last mouse position somehwhere in
+  // browser.
   if (is_mouse_position_unknown_)
     return;
 
   // Reschedule the timer, to prevent dispatching mouse move events
   // during a scroll. This avoids a potential source of scroll jank.
-  fake_mouse_move_event_timer_.StartOneShot(kFakeMouseMoveInterval,
-                                            BLINK_FROM_HERE);
+  // Or dispatch a fake mouse move to update hover states when the layout
+  // changes.
+  double interval =
+      fake_mouse_move_reason ==
+              MouseEventManager::FakeMouseMoveReason::kDuringScroll
+          ? kFakeMouseMoveIntervalDuringScroll
+          : kFakeMouseMoveIntervalPerFrame;
+  fake_mouse_move_event_timer_.StartOneShot(interval, BLINK_FROM_HERE);
 }
 
 void MouseEventManager::DispatchFakeMouseMoveEventSoonInQuad(
     const FloatQuad& quad) {
   LocalFrameView* view = frame_->View();
   if (!view)
     return;
 
   if (!quad.ContainsPoint(
           view->RootFrameToContents(last_known_mouse_position_)))
     return;
 
-  DispatchFakeMouseMoveEventSoon();
+  DispatchFakeMouseMoveEventSoon(
+      MouseEventManager::FakeMouseMoveReason::kDuringScroll);
 }
 
 WebInputEventResult MouseEventManager::HandleMousePressEvent(
     const MouseEventWithHitTestResults& event) {
   TRACE_EVENT0("blink", "MouseEventManager::handleMousePressEvent");
 
   ResetDragState();
   CancelFakeMouseMoveEvent();
 
   frame_->GetDocument()->UpdateStyleAndLayoutIgnorePendingStylesheets();
@@ skipping 128 matching lines @@
   //    never sees the mouse release event, which is supposed to reset
   //    m_mousePressed... so m_mousePressed ends up remaining true until the
   //    event handler finally gets another mouse released event. Oops.
   // 2. Dragging doesn't start until after a mouse press event, but a drag
   //    that ends as a result of a mouse release does not send a mouse release
   //    event. As a result, m_mousePressed also ends up remaining true until
   //    the next mouse release event seen by the EventHandler.
   // 3. When pressing Esc key while dragging and the object is outside of the
   //    we get a mouse leave event here
   if (event.Event().button != WebPointerProperties::Button::kLeft ||
-      event.Event().GetType() == WebInputEvent::kMouseLeave)
+      event.Event().GetType() == WebInputEvent::kMouseLeave) {
     mouse_pressed_ = false;
+  }
 
   if (!mouse_pressed_)
     return WebInputEventResult::kNotHandled;
 
   if (event.Event().pointer_type ==
       blink::WebPointerProperties::PointerType::kPen)
     return WebInputEventResult::kNotHandled;
 
   if (HandleDrag(event, DragInitiator::kMouse))
     return WebInputEventResult::kHandledSystem;
@@ skipping 322 matching lines @@
 }
 
 void MouseEventManager::SetClickCount(int click_count) {
   click_count_ = click_count;
 }
 
 bool MouseEventManager::MouseDownMayStartDrag() {
   return mouse_down_may_start_drag_;
 }
 
+bool MouseEventManager::FakeMouseMovePending() const {
+  return fake_mouse_move_event_timer_.IsActive();
+}
+
 }  // namespace blink