Introduce VisiblePosition::isValid

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

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 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.
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  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1319 matching lines @@
         absoluteBlockPoint -= FloatSize(containingBlock.scrolledContentOffset());
 
     if (root->block().isHorizontalWritingMode())
         return LayoutPoint(LayoutUnit(lineDirectionPoint - absoluteBlockPoint.x()), root->blockDirectionPointInLine());
 
     return LayoutPoint(root->blockDirectionPointInLine(), LayoutUnit(lineDirectionPoint - absoluteBlockPoint.y()));
 }
 
 VisiblePosition previousLinePosition(const VisiblePosition& visiblePosition, LayoutUnit lineDirectionPoint, EditableType editableType)
 {
+    DCHECK(visiblePosition.isValid());

[yosin_UTC9, 2016/09/20 13:55:51]

We should add |DCHECK(vp.isValid())| all functions take VP.
Since, we have gTest for |VP::isValid()|, is it better to add
|DCHECK(vp.isValid()| in another gigantic patch"?

[Xiaocheng, 2016/09/21 06:31:49]

Unfortunately we are not having such a gigantic patch...

I tried adding a |DCHECK(vp.isValid())| to all functions in VisibleUnits.cpp and
got massive hitting.

We may create a crbug for it and gradually add DCHECKs to all functions, though.

+
     Position p = visiblePosition.deepEquivalent();
     Node* node = p.anchorNode();
 
     if (!node)
         return VisiblePosition();
 
-    DCHECK(!node->document().needsLayoutTreeUpdate());
-
     LayoutObject* layoutObject = node->layoutObject();
     if (!layoutObject)
         return VisiblePosition();
 
     RootInlineBox* root = 0;
     InlineBox* box = computeInlineBoxPosition(visiblePosition).inlineBox;
     if (box) {
         root = box->root().prevRootBox();
         // We want to skip zero height boxes.
         // This could happen in case it is a TrailingFloatsRootInlineBox.
@@ skipping 25 matching lines @@
     // Move to the start of the content in this block, which effectively moves us
     // to the start of the line we're on.
     Element* rootElement = hasEditableStyle(*node, editableType) ? rootEditableElement(*node, editableType) : node->document().documentElement();
     if (!rootElement)
         return VisiblePosition();
     return VisiblePosition::firstPositionInNode(rootElement);
 }
 
 VisiblePosition nextLinePosition(const VisiblePosition& visiblePosition, LayoutUnit lineDirectionPoint, EditableType editableType)
 {
+    DCHECK(visiblePosition.isValid());
+
     Position p = visiblePosition.deepEquivalent();
     Node* node = p.anchorNode();
 
     if (!node)
         return VisiblePosition();
 
-    DCHECK(!node->document().needsLayoutTreeUpdate());
-
     LayoutObject* layoutObject = node->layoutObject();
     if (!layoutObject)
         return VisiblePosition();
 
     RootInlineBox* root = 0;
     InlineBox* box = computeInlineBoxPosition(visiblePosition).inlineBox;
     if (box) {
         root = box->root().nextRootBox();
         // We want to skip zero height boxes.
         // This could happen in case it is a TrailingFloatsRootInlineBox.
@@ skipping 1908 matching lines @@
 {
     return previousPositionOfAlgorithm<EditingStrategy>(visiblePosition, rule);
 }
 
 VisiblePositionInFlatTree previousPositionOf(const VisiblePositionInFlatTree& visiblePosition, EditingBoundaryCrossingRule rule)
 {
     return previousPositionOfAlgorithm<EditingInFlatTreeStrategy>(visiblePosition, rule);
 }
 
 } // namespace blink