Do not send redundant selectionchange-events (decouple focus)

third_party/WebKit/Source/core/editing/PendingSelection.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 88 matching lines @@
                                      ? TextAffinity::Upstream
                                      : affinity);
   if (visibleEnd.isNull())
     return SelectionInFlatTree();
   SelectionInFlatTree::Builder builder;
   builder.collapse(visibleStart.toPositionWithAffinity());
   builder.extend(visibleEnd.deepEquivalent());
   return builder.build();
 }
 
+static bool selectionHasFocus(const LayoutView& layoutView,
+                              const VisibleSelectionInFlatTree& selection) {
+  if (!isSelectionInDocument(selection, layoutView.document()))
+    return false;
+
+  const LocalFrame* const frame = layoutView.document().frame();
+  const Element* focus = frame->document()->focusedElement();
+  if (!focus) {
+    // No focused element means document has focus.
+    focus = layoutView.document().documentElement();

[hugoh_UTC2, 2017/03/10 10:10:37]

I use document().documentElement(), not document.body() so non HTML-documents
(here SVG documents) also can have selected text.

+  }
+
+  const Node* const nodeWhereSelectionStarts =
+      selection.base().computeContainerNode();
+  const Node* const nodeWhereSelectionEnds =
+      selection.extent().computeContainerNode();
+
+  return focus->containsIncludingHostElements(*nodeWhereSelectionStarts) ||
+         focus->containsIncludingHostElements(*nodeWhereSelectionEnds);
+}
+
 void PendingSelection::commit(LayoutView& layoutView) {
   if (!hasPendingSelection())
     return;
   DCHECK(!layoutView.needsLayout());
   m_hasPendingSelection = false;
 
   const VisibleSelectionInFlatTree& originalSelection =
       m_frameSelection->computeVisibleSelectionInFlatTree();
 
   // Skip if pending VisibilePositions became invalid before we reach here.
   if (!isSelectionInDocument(originalSelection, layoutView.document()))
     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(originalSelection));
 
-  if (!selection.isRange()) {
+  if (!selection.isRange() || !selectionHasFocus(layoutView, selection)) {
     layoutView.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 21 matching lines @@
   DCHECK(layoutView == endLayoutObject->view());
   layoutView.setSelection(startLayoutObject, startPos.computeEditingOffset(),
                           endLayoutObject, endPos.computeEditingOffset());
 }
 
 DEFINE_TRACE(PendingSelection) {
   visitor->trace(m_frameSelection);
 }
 
 }  // namespace blink