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

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

Index: third_party/WebKit/Source/core/input/MouseEventManager.cpp
diff --git a/third_party/WebKit/Source/core/input/MouseEventManager.cpp b/third_party/WebKit/Source/core/input/MouseEventManager.cpp
index e4a1ec7df78bfad490fc49ea7b359e7fa48cdcce..158528c82ff9c56c87296a50c55e0ec917d1494d 100644
--- a/third_party/WebKit/Source/core/input/MouseEventManager.cpp
+++ b/third_party/WebKit/Source/core/input/MouseEventManager.cpp
@@ -56,7 +56,11 @@ String CanvasRegionId(Node* node, const WebMouseEvent& mouse_event) {
 
 // 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)
@@ -308,7 +312,6 @@ WebInputEventResult MouseEventManager::DispatchMouseClickIfNeeded(
 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;
@@ -325,16 +328,20 @@ void MouseEventManager::FakeMouseMoveEventTimerFired(TimerBase* timer) {
   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;
@@ -581,17 +588,30 @@ void MouseEventManager::SetLastKnownMousePosition(const WebMouseEvent& event) {
   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(
@@ -604,7 +624,8 @@ void MouseEventManager::DispatchFakeMouseMoveEventSoonInQuad(
           view->RootFrameToContents(last_known_mouse_position_)))
     return;
 
-  DispatchFakeMouseMoveEventSoon();
+  DispatchFakeMouseMoveEventSoon(
+      MouseEventManager::FakeMouseMoveReason::kDuringScroll);
 }
 
 WebInputEventResult MouseEventManager::HandleMousePressEvent(
@@ -753,8 +774,9 @@ WebInputEventResult MouseEventManager::HandleMouseDraggedEvent(
   // 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;
@@ -1097,4 +1119,8 @@ bool MouseEventManager::MouseDownMayStartDrag() {
   return mouse_down_may_start_drag_;
 }
 
+bool MouseEventManager::FakeMouseMovePending() const {
+  return fake_mouse_move_event_timer_.IsActive();
+}
+
 }  // namespace blink