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;
+const 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.
+const double kFakeMouseMoveIntervalPerFrame = 0.02;

[dtapuska, 2017/06/28 19:15:17]

I believe constexpr is preferred

[lanwei, 2017/07/04 18:37:15]

Done.

 
 // 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 504 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() {
+void MouseEventManager::DispatchFakeMouseMoveEventSoon(
+    DispatchInterval dispatch_interval) {
   if (mouse_pressed_)

[dtapuska, 2017/06/28 19:15:18]

So if mouse is pressed or cursor isn't known then we don't update the cursor.
This is different than before. Do we need to take these into account?

[lanwei, 2017/07/04 18:37:15]

We should update hover states and mouse cursor when mouse is pressed, but we
cannot update them correctly when the mouse position is unknown. I will fix it
in another patch.

     return;
 
   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 = dispatch_interval == DispatchInterval::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(DispatchInterval::kDuringScroll);
 }
 
 WebInputEventResult MouseEventManager::HandleMousePressEvent(
     const MouseEventWithHitTestResults& event) {
   TRACE_EVENT0("blink", "MouseEventManager::handleMousePressEvent");
 
   ResetDragState();
   CancelFakeMouseMoveEvent();
 
   frame_->GetDocument()->UpdateStyleAndLayoutIgnorePendingStylesheets();
@@ skipping 472 matching lines @@
 }
 
 void MouseEventManager::SetClickCount(int click_count) {
   click_count_ = click_count;
 }
 
 bool MouseEventManager::MouseDownMayStartDrag() {
   return mouse_down_may_start_drag_;
 }
 
+bool MouseEventManager::FakeMouseMovePending() {
+  return fake_mouse_move_event_timer_.IsActive();
+}
+
 }  // namespace blink