Do not send redundant selectionchange-events (decouple focus)

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights
  * reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 16 matching lines @@
 #include "core/editing/VisiblePosition.h"
 #include "core/editing/VisibleUnits.h"
 #include "core/html/TextControlElement.h"
 #include "core/layout/LayoutView.h"
 
 namespace blink {
 
 LayoutSelection::LayoutSelection(FrameSelection& frame_selection)
     : frame_selection_(&frame_selection),
       has_pending_selection_(false),
+      force_hide_(false),
       selection_start_(nullptr),
       selection_end_(nullptr),
       selection_start_pos_(-1),
       selection_end_pos_(-1) {}
 
 const VisibleSelection& LayoutSelection::GetVisibleSelection() const {
   return frame_selection_->ComputeVisibleSelectionInDOMTree();
 }
 
 static bool IsSelectionInDocument(
@@ skipping 57 matching lines @@
                ? TextAffinity::kUpstream
                : affinity);
   if (visible_end.IsNull())
     return SelectionInFlatTree();
   SelectionInFlatTree::Builder builder;
   builder.Collapse(visible_start.ToPositionWithAffinity());
   builder.Extend(visible_end.DeepEquivalent());
   return builder.Build();
 }
 
+void LayoutSelection::SetHasPendingSelection(PaintHint hint) {
+  has_pending_selection_ = true;
+  if (hint == PaintHint::kHide)

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

How about

if (hint == PaintHint::kKeep)
  return;
force_hide_ = hint == PaintHint::kHide;

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

Acknowledged. Semantically the same so this is a matter of taste. Hmm. :) I
think current logic is easier to read (no == operator to calculate).

[yosin_UTC9, 2017/04/14 02:29:16]

Blink prefers early-return style, though.

+    force_hide_ = true;
+  else if (hint == PaintHint::kPaint)
+    force_hide_ = false;
+}
+
 void LayoutSelection::Commit(LayoutView& layout_view) {
   if (!HasPendingSelection())
     return;
   DCHECK(!layout_view.NeedsLayout());
   has_pending_selection_ = false;
 
   const VisibleSelectionInFlatTree& original_selection =
       frame_selection_->ComputeVisibleSelectionInFlatTree();
 
   // Skip if pending VisibilePositions became invalid before we reach here.
   if (!IsSelectionInDocument(original_selection, layout_view.GetDocument()))
     return;
 
   // Construct a new VisibleSolution, since visibleSelection() is not
   // necessarily valid, and the following steps assume a valid selection. See
   // <https://bugs.webkit.org/show_bug.cgi?id=69563> and
   // <rdar://problem/10232866>.
   const VisibleSelectionInFlatTree& selection =
       CreateVisibleSelection(CalcVisibleSelection(original_selection));
 
-  if (!selection.IsRange()) {
+  if (!selection.IsRange() || force_hide_) {
     ClearSelection();
     return;
   }
 
   // Use the rightmost candidate for the start of the selection, and the
   // leftmost candidate for the end of the selection. Example: foo <a>bar</a>.
   // Imagine that a line wrap occurs after 'foo', and that 'bar' is selected.
   // If we pass [foo, 3] as the start of the selection, the selection painting
   // code will think that content on the line containing 'foo' is selected
   // and will fill the gap before 'bar'.
@@ skipping 18 matching lines @@
   if (!start_layout_object || !end_layout_object)
     return;
   DCHECK(layout_view == start_layout_object->View());
   DCHECK(layout_view == end_layout_object->View());
   SetSelection(start_layout_object, start_pos.ComputeEditingOffset(),
                end_layout_object, end_pos.ComputeEditingOffset());
 }
 
 void LayoutSelection::OnDocumentShutdown() {
   has_pending_selection_ = false;
+  force_hide_ = false;
   selection_start_ = nullptr;
   selection_end_ = nullptr;
   selection_start_pos_ = -1;
   selection_end_pos_ = -1;
 }
 
 DEFINE_TRACE(LayoutSelection) {
   visitor->Trace(frame_selection_);
 }
 
 }  // namespace blink