Do not send redundant selectionchange-events (decouple focus)

third_party/WebKit/Source/core/editing/FrameSelection.cpp

 /*
  * Copyright (C) 2004, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
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  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 232 matching lines @@
     // "FocusIn", |m_frame| may associate to another document.
     if (!IsAvailable() || GetDocument() != current_document) {
       // Once we get test case to reach here, we should change this
       // if-statement to |DCHECK()|.
       NOTREACHED();
       return;
     }
   }
 
   frame_caret_->StopCaretBlinkTimer();
-  UpdateAppearance();
+  UpdateAppearance(LayoutSelection::PaintHint::kPaint);
 
   // Always clear the x position used for vertical arrow navigation.
   // It will be restored by the vertical arrow navigation code if necessary.
   x_pos_for_vertical_arrow_navigation_ = NoXPosForVerticalArrowNavigation();
 
   // TODO(yosin): Can we move this to at end of this function?
   // This may dispatch a synchronous focus-related events.
   if (!(options & kDoNotSetFocus)) {
     SelectFrameElementInParentIfFullySelected();
     if (!IsAvailable() || GetDocument() != current_document) {
@@ skipping 64 matching lines @@
   // TODO(yosin): We should move to call |TypingCommand::closeTyping()| to
   // |Editor| class.
   if (!GetDocument().IsRunningExecCommand())
     TypingCommand::CloseTyping(frame_);
 }
 
 void FrameSelection::DidChangeFocus() {
   // Hits in
   // virtual/gpu/compositedscrolling/scrollbars/scrollbar-miss-mousemove-disabled.html
   DisableCompositingQueryAsserts disabler;
-  UpdateAppearance();
+
+  const Element* focus = GetDocument().FocusedElement();

[yosin_UTC9, 2017/04/13 09:31:50]

Since Document::FocusedElement() is simple getter.

We can write

const Element* const focus = GetDocument().FocusedElement() ?
GetDocument().FocusedElement() : GetDOcument.documentElement();
if (!focus) {
  // No focused element means document root has focus.
  return;
}

[hugoh_UTC2, 2017/04/14 01:34:47]

Done. (But the comment must go above the ternary operator).

+  if (!focus) {
+    // No focused element means document root has focus.
+    focus = GetDocument().documentElement();
+    if (!focus)
+      return;

[yosin_UTC9, 2017/04/13 09:31:50]

We still need to call
frame_caret_->ScheduleVisualUpdateForPaintInvalidationIfNeeded();

We should rest |text_control_focus_| to false.

[hugoh_UTC2, 2017/04/14 01:34:47]

Done.
Done. We need this early return to protect us from
LayoutTests/editing/selection/selection-crash.html (I've now added a comment
about that), in all other cases I've tried, focus has been an Element (or
documentElement). So I was thinking this exceptional case should rather "keep
current value". But let's reset it to false for consistency if you prefer. 

+  }
+  // Hide the selection when focus goes away from a text-field and into
+  // something that is not a text-field. When focus enters another text-field we
+  // do not need to update appearance; the appearance is updated when the new
+  // selection is set.
+  if (text_control_focus_ && !focus->IsTextControl())
+    UpdateAppearance(LayoutSelection::PaintHint::kHide);
+  text_control_focus_ = focus->IsTextControl();
 }
 
 static DispatchEventResult DispatchSelectStart(
     const VisibleSelection& selection) {
   Node* select_start_target = selection.Extent().ComputeContainerNode();
   if (!select_start_target)
     return DispatchEventResult::kNotCanceled;
 
   return select_start_target->DispatchEvent(
       Event::CreateCancelableBubble(EventTypeNames::selectstart));
@@ skipping 417 matching lines @@
 
 bool FrameSelection::IsAppearanceDirty() const {
   return layout_selection_->HasPendingSelection();
 }
 
 void FrameSelection::CommitAppearanceIfNeeded(LayoutView& layout_view) {
   return layout_selection_->Commit(layout_view);
 }
 
 void FrameSelection::DidLayout() {
-  UpdateAppearance();
+  // Upon relayout, a hidden selection must be kept hidden and a visible
+  // selection must be kept visible.
+  UpdateAppearance(LayoutSelection::PaintHint::kKeep);
 }
 
-void FrameSelection::UpdateAppearance() {
+void FrameSelection::UpdateAppearance(LayoutSelection::PaintHint hint) {
   DCHECK(!frame_->ContentLayoutItem().IsNull());
   frame_caret_->ScheduleVisualUpdateForPaintInvalidationIfNeeded();
-  layout_selection_->SetHasPendingSelection();
+  layout_selection_->SetHasPendingSelection(hint);
 }
 
 void FrameSelection::NotifyLayoutObjectOfSelectionChange(
     EUserTriggered user_triggered) {
   TextControlElement* text_control =
       EnclosingTextControl(GetSelectionInDOMTree().Base());
   if (!text_control)
     return;
   text_control->SelectionChanged(user_triggered == kUserTriggered);
 }
@@ skipping 170 matching lines @@
 
   Position start = ComputeVisibleSelectionInDOMTreeDeprecated().Start();
   DCHECK(start.AnchorNode());
   if (start.AnchorNode() && start.AnchorNode()->GetLayoutObject()) {
     // FIXME: This code only handles scrolling the startContainer's layer, but
     // the selection rect could intersect more than just that.
     if (DocumentLoader* document_loader = frame_->Loader().GetDocumentLoader())
       document_loader->GetInitialScrollState().was_scrolled_by_user = true;
     if (start.AnchorNode()->GetLayoutObject()->ScrollRectToVisible(
             rect, alignment, alignment))
-      UpdateAppearance();
+      UpdateAppearance(LayoutSelection::PaintHint::kPaint);
   }
 }
 
 void FrameSelection::SetSelectionFromNone() {
   // Put a caret inside the body if the entire frame is editable (either the
   // entire WebView is editable or designMode is on for this document).
 
   Document* document = frame_->GetDocument();
   if (!ComputeVisibleSelectionInDOMTreeDeprecated().IsNone() ||
       !(blink::HasEditableStyle(*document)))
@@ skipping 178 matching lines @@
 }
 
 void showTree(const blink::FrameSelection* sel) {
   if (sel)
     sel->ShowTreeForThis();
   else
     LOG(INFO) << "Cannot showTree for <null> FrameSelection.";
 }
 
 #endif