Do not send redundant selectionchange-events (decouple focus)

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

 /*
  * Copyright (C) 2004, 2005, 2006, 2007 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 356 matching lines @@
   const Node* result = nullptr;
   for (const Node* n = &node; n && hasEditableStyle(*n); n = n->parentNode()) {
     if (n->isElementNode())
       result = n;
     if (node.document().body() == n)
       break;
   }
   return toElement(const_cast<Node*>(result));
 }
 
+bool selectionHasFocus(const SelectionInFlatTree& selection) {
+  const Document* document = selection.base().document();

[yosin_UTC9, 2017/03/22 09:11:35]

Let's handle document == nullptr case, selection.isNone(), for ease of using
this function.

[hugoh_UTC2, 2017/03/22 09:19:14]

You mean when selection.isNone(), we return false? 

!selection.isNone() => document != nullptr ?

[yosin_UTC9, 2017/03/22 09:26:35]

Yes, just return false if selection.isNone(),

So, we can write

if (!document)
  return false;

Since there is no selection, it can not have focus.

[hugoh_UTC2, 2017/03/22 09:41:11]

Done. See PS26.

+  const Element* focus = document->focusedElement();
+  if (!focus) {
+    // No focused element means document root has focus.
+    focus = document->documentElement();
+  }
+
+  const Node* const nodeWhereSelectionStarts =
+      selection.base().computeContainerNode();
+  const Node* const nodeWhereSelectionEnds =
+      selection.extent().computeContainerNode();
+
+  return focus->containsIncludingHostElements(*nodeWhereSelectionStarts) ||
+         focus->containsIncludingHostElements(*nodeWhereSelectionEnds);
+}
+
 ContainerNode* highestEditableRoot(
     const Position& position,
     Element* (*rootEditableElementOf)(const Position&),
     bool (*hasEditableStyle)(const Node&)) {
   if (position.isNull())
     return 0;
 
   ContainerNode* highestRoot = rootEditableElementOf(position);
   if (!highestRoot)
     return 0;
@@ skipping 1786 matching lines @@
         return InputType::DeleteWordBackward;
       if (granularity == LineBoundary)
         return InputType::DeleteLineBackward;
       return InputType::DeleteContentBackward;
     default:
       return InputType::None;
   }
 }
 
 }  // namespace blink