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

third_party/WebKit/Source/core/frame/LocalFrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 2579 matching lines @@
 
   frame_->Selection().DidLayout();
 
   DCHECK(frame_->GetDocument());
 
   FontFaceSet::DidLayout(*frame_->GetDocument());
   // Cursor update scheduling is done by the local root, which is the main frame
   // if there are no RemoteFrame ancestors in the frame tree. Use of
   // localFrameRoot() is discouraged but will change when cursor update
   // scheduling is moved from EventHandler to PageEventHandler.
-  GetFrame().LocalFrameRoot().GetEventHandler().ScheduleCursorUpdate();
+
+  // Fire a fake a mouse move event to update hover state and mouse cursor, and
+  // send the right mouse out/over events.
+  if (RuntimeEnabledFeatures::UpdateHoverPostLayoutEnabled()) {

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

If we are dragging a draggable object on the page and the page modifies the
layout say in drag event handler doesn't this cause mouse events being fired?
Then I guess we are contradicting the drag spec as it says we should not send
any input device events to the page. I believe when there is a drag operation
going on we do not update the hover states either (also it was mentioned in your
doc if I recall).

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

I tested that when we are starting the drag mode, this function does not get
called. I think we won't send any mouse events.

+    frame_->GetEventHandler().DispatchFakeMouseMoveEventSoon(
+        MouseEventManager::FakeMouseMoveReason::kPerFrame);
+  } else {
+    GetFrame().LocalFrameRoot().GetEventHandler().ScheduleCursorUpdate();
+  }
 
   UpdateGeometries();
 
   // Plugins could have torn down the page inside updateGeometries().
   if (GetLayoutViewItem().IsNull())
     return;
 
   ScheduleUpdatePluginsIfNecessary();
 
   if (ScrollingCoordinator* scrolling_coordinator =
@@ skipping 1550 matching lines @@
   scroll_offset_ = offset;
 
   if (!ScrollbarsSuppressed())
     pending_scroll_delta_ += scroll_delta;
 
   UpdateLayersAndCompositingAfterScrollIfNeeded();
 
   Document* document = frame_->GetDocument();
   document->EnqueueScrollEventForNode(document);
 
-  frame_->GetEventHandler().DispatchFakeMouseMoveEventSoon();
+  frame_->GetEventHandler().DispatchFakeMouseMoveEventSoon(
+      MouseEventManager::FakeMouseMoveReason::kDuringScroll);
   if (scroll_type == kUserScroll || scroll_type == kCompositorScroll) {
     Page* page = GetFrame().GetPage();
     if (page)
       page->GetChromeClient().ClearToolTip(*frame_);
   }
 
   LayoutViewItem layout_view_item = document->GetLayoutViewItem();
   if (!layout_view_item.IsNull()) {
     if (layout_view_item.UsesCompositing())
       layout_view_item.Compositor()->FrameViewDidScroll();
@@ skipping 1295 matching lines @@
 void LocalFrameView::SetAnimationHost(
     std::unique_ptr<CompositorAnimationHost> host) {
   animation_host_ = std::move(host);
 }
 
 LayoutUnit LocalFrameView::CaretWidth() const {
   return LayoutUnit(GetChromeClient()->WindowToViewportScalar(1));
 }
 
 }  // namespace blink