Move character{After,Before}() for VisiblePosition to VisibleUnits.cpp

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:
  * 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 2341 matching lines @@
 
     // If this is not editable but |pos| has an editable root, skip to the end
     if (!highestRoot && highestRootOfPos)
         return VisiblePosition(Position(highestRootOfPos, PositionAnchorType::AfterAnchor).parentAnchoredEquivalent());
 
     // That must mean that |pos| is not editable. Return the next position after
     // |pos| that is in the same editable region as this position
     return firstEditableVisiblePositionAfterPositionInRoot(pos.deepEquivalent(), highestRoot);
 }
 
+UChar32 characterAfter(const VisiblePosition& visiblePosition)
+{
+    // We canonicalize to the first of two equivalent candidates, but the second
+    // of the two candidates is the one that will be inside the text node
+    // containing the character after this visible position.
+    Position pos = mostForwardCaretPosition(visiblePosition.deepEquivalent());
+    if (!pos.isOffsetInAnchor())
+        return 0;
+    Node* containerNode = pos.computeContainerNode();
+    if (!containerNode || !containerNode->isTextNode())
+        return 0;
+    unsigned offset = static_cast<unsigned>(pos.offsetInContainerNode());
+    Text* textNode = toText(containerNode);
+    unsigned length = textNode->length();
+    if (offset >= length)
+        return 0;
+
+    return textNode->data().characterStartingAt(offset);
+}
+
+UChar32 characterBefore(const VisiblePosition& visiblePosition)
+{
+    return characterAfter(previousPositionOf(visiblePosition));
+}
+
 VisiblePosition nextPositionOf(const VisiblePosition& visiblePosition, EditingBoundaryCrossingRule rule)
 {
     VisiblePosition next(nextVisuallyDistinctCandidate(visiblePosition.deepEquivalent()), visiblePosition.affinity());
 
     switch (rule) {
     case CanCrossEditingBoundary:
         return next;
     case CannotCrossEditingBoundary:
         return honorEditingBoundaryAtOrAfter(next, visiblePosition.deepEquivalent());
     case CanSkipOverEditingBoundary:
@@ skipping 53 matching lines @@
         return honorEditingBoundaryAtOrBefore(prev, visiblePosition.deepEquivalent());
     case CanSkipOverEditingBoundary:
         return skipToStartOfEditingBoundary(prev, visiblePosition.deepEquivalent());
     }
 
     ASSERT_NOT_REACHED();
     return honorEditingBoundaryAtOrBefore(prev, visiblePosition.deepEquivalent());
 }
 
 } // namespace blink