Change return value of FrameSelection::modify() to prevent unnecessary window scrolling

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:
  * 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 54 matching lines @@
 #include "core/html/HTMLSelectElement.h"
 #include "core/input/EventHandler.h"
 #include "core/layout/HitTestRequest.h"
 #include "core/layout/HitTestResult.h"
 #include "core/layout/LayoutPart.h"
 #include "core/loader/DocumentLoader.h"
 #include "core/page/EditorClient.h"
 #include "core/page/FocusController.h"
 #include "core/page/FrameTree.h"
 #include "core/page/Page.h"
+#include "core/page/SpatialNavigation.h"
 #include "core/paint/PaintLayer.h"
 #include "platform/SecureTextInput.h"
 #include "platform/geometry/FloatQuad.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/text/UnicodeUtilities.h"
 #include "wtf/PtrUtil.h"
 #include "wtf/text/CString.h"
 #include <stdio.h>
 
 #define EDIT_DEBUG 0
@@ skipping 518 matching lines @@
 
 static DispatchEventResult dispatchSelectStart(const VisibleSelection& selection)
 {
     Node* selectStartTarget = selection.extent().computeContainerNode();
     if (!selectStartTarget)
         return DispatchEventResult::NotCanceled;
 
     return selectStartTarget->dispatchEvent(Event::createCancelableBubble(EventTypeNames::selectstart));
 }
 
+// The return value of |FrameSelection::modify()| is different based on
+// value of |userTriggered| parameter.
+// When |userTriggered| is |userTriggered|, |modify()| returns false if
+// "selectstart" event is dispatched and canceled, otherwise returns true.
+// When |userTriggered| is |NotUserTrigged|, return value specifies whether
+// selection is modified or not.
 bool FrameSelection::modify(EAlteration alter, SelectionDirection direction, TextGranularity granularity, EUserTriggered userTriggered)
 {
     SelectionModifier selectionModifier(*frame(), selection(), m_xPosForVerticalArrowNavigation);
     const bool modified = selectionModifier.modify(alter, direction, granularity);
     if (userTriggered == UserTriggered
         && selectionModifier.selection().isRange()
         && selection().isCaret()
         && dispatchSelectStart(selection()) != DispatchEventResult::NotCanceled) {
         return false;
     }
-    if (!modified)
-        return false;
+    if (!modified) {
+        if (userTriggered == NotUserTriggered)
+            return false;
+        // If spatial navigation enabled, focus navigator will move focus to
+        // another element. See snav-input.html and snav-textarea.html
+        if (isSpatialNavigationEnabled(m_frame))
+            return false;
+        // Even if selection isn't changed, we prevent to default action, e.g.
+        // scroll window when caret is at end of content editable.
+        return true;
+    }
 
     const SetSelectionOptions options = CloseTyping | ClearTypingStyle | userTriggered;
     setSelection(selectionModifier.selection(), options);
 
     if (granularity == LineGranularity || granularity == ParagraphGranularity)
         m_xPosForVerticalArrowNavigation = selectionModifier.xPosForVerticalArrowNavigation();
 
     if (userTriggered == UserTriggered)
         m_granularity = CharacterGranularity;
 
@@ skipping 737 matching lines @@
 
 void showTree(const blink::FrameSelection* sel)
 {
     if (sel)
         sel->showTreeForThis();
     else
         fprintf(stderr, "Cannot showTree for (nil) FrameSelection.\n");
 }
 
 #endif