Change Font::offsetForPositionForComplexText to use CachingWordShapeIterator

Source/platform/fonts/shaping/HarfBuzzShaper.cpp

 /*
  * Copyright (c) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 BlackBerry Limited. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 428 matching lines @@
         toX = direction == RTL ? 0 : totalWidth;
 
     // None of our runs is part of the selection, possibly invalid arguments.
     if (!foundToX && !foundFromX)
         fromX = toX = 0;
     if (fromX < toX)
         return FloatRect(point.x() + fromX, point.y(), toX - fromX, height);
     return FloatRect(point.x() + toX, point.y(), fromX - toX, height);
 }
 
+int ShapeResult::offsetForPosition(Vector<RefPtr<ShapeResult>>& results,
+    const TextRun& run, float targetX)
+{
+    RefPtr<ShapeResult> wordResult;

[brucedawson, 2015/08/11 19:01:06]

This variable is never used and should be deleted.

This was detected, perversely enough, through a variable shadowing warning from
the two declarations of 'wordResult' in inner scopes.

+    unsigned totalOffset;
+    if (run.rtl()) {
+        totalOffset = run.length();
+        for (auto& wordResult : results) {
+            if (!wordResult)
+                continue;
+            totalOffset -= wordResult->numCharacters();
+            if (targetX >= 0 && targetX <= wordResult->width()) {
+                int offsetForWord = wordResult->offsetForPosition(targetX);
+                return totalOffset + offsetForWord;
+            }
+            targetX -= wordResult->width();
+        }
+    } else {
+        totalOffset = 0;
+        for (auto& wordResult : results) {
+            if (!wordResult)
+                continue;
+            int offsetForWord = wordResult->offsetForPosition(targetX);
+            ASSERT(offsetForWord >= 0);
+            totalOffset += offsetForWord;
+            if (targetX >= 0 && targetX <= wordResult->width())
+                return totalOffset;
+            targetX -= wordResult->width();
+        }
+    }
+    return totalOffset;
+}
+
 int ShapeResult::offsetForPosition(float targetX)
 {
     int charactersSoFar = 0;
     float currentX = 0;
 
     if (m_direction == RTL) {
         charactersSoFar = m_numCharacters;
         for (unsigned i = 0; i < m_runs.size(); ++i) {
             if (!m_runs[i])
                 continue;
@@ skipping 698 matching lines @@
             return spacing;
     }
 
     // Don't need to check m_textRun.allowsTrailingExpansion() since it's covered by !m_expansionOpportunityCount above
     spacing += nextExpansionPerOpportunity();
     m_isAfterExpansion = true;
     return spacing;
 }
 
 } // namespace blink