Add ShapeResult::positionForOffset method

third_party/WebKit/Source/platform/fonts/shaping/ShapeResult.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 163 matching lines @@
 ShapeResult::~ShapeResult() {}
 
 size_t ShapeResult::byteSize() const {
   size_t selfByteSize = sizeof(this);
   for (unsigned i = 0; i < m_runs.size(); ++i) {
     selfByteSize += m_runs[i]->byteSize();
   }
   return selfByteSize;
 }
 
-int ShapeResult::offsetForPosition(float targetX,
-                                   bool includePartialGlyphs) const {
-  int charactersSoFar = 0;
+unsigned ShapeResult::offsetForPosition(float targetX,
+                                        bool includePartialGlyphs) const {
+  unsigned charactersSoFar = 0;
   float currentX = 0;
 
   if (rtl()) {
     charactersSoFar = m_numCharacters;
     for (unsigned i = 0; i < m_runs.size(); ++i) {
       if (!m_runs[i])
         continue;
       charactersSoFar -= m_runs[i]->m_numCharacters;
       float nextX = currentX + m_runs[i]->m_width;
       float offsetForRun = targetX - currentX;
@@ skipping 17 matching lines @@
         return charactersSoFar + index;
       }
       charactersSoFar += m_runs[i]->m_numCharacters;
       currentX = nextX;
     }
   }
 
   return charactersSoFar;
 }
 
+float ShapeResult::positionForOffset(unsigned absoluteOffset) const {

[eae, 2017/03/09 05:16:32]

This is similar to how ShapeResultBuffer::getCharacterRange but only iterates
over a single ShapeResult and only uses one offset. Once we have this a number
of callers to getCharacterRange can use this simpler and faster method instead.
It should also allow us to remove one of the two versions of the
getCharacterRange method.

+  float x = 0;
+  float offsetX = 0;
+
+  // The absoluteOffset argument represents the offset for the entire
+  // ShapeResult while offset is continuously updated to be relative to the
+  // current run.
+  unsigned offset = absoluteOffset;
+
+  if (rtl()) {
+    // Convert logical offsets to visual offsets, because results are in
+    // logical order while runs are in visual order.
+    x = m_width;
+    if (offset < numCharacters())
+      offset = numCharacters() - offset - 1;
+    x -= width();
+  }
+
+  for (unsigned i = 0; i < m_runs.size(); i++) {
+    if (!m_runs[i])
+      continue;
+    DCHECK_EQ(rtl(), m_runs[i]->rtl());
+    unsigned numCharacters = m_runs[i]->m_numCharacters;
+
+    if (!offsetX && offset < numCharacters) {
+      offsetX = m_runs[i]->xPositionForVisualOffset(offset, AdjustToEnd) + x;
+      break;
+    }
+
+    offset -= numCharacters;
+    x += m_runs[i]->m_width;
+  }
+
+  if (rtl())
+    x -= width();
+
+  // The position in question might be just after the text.
+  if (!offsetX && absoluteOffset == numCharacters())
+    return rtl() ? 0 : m_width;
+
+  return offsetX;
+}
+
 void ShapeResult::fallbackFonts(
     HashSet<const SimpleFontData*>* fallback) const {
   ASSERT(fallback);
   ASSERT(m_primaryFont);
   for (unsigned i = 0; i < m_runs.size(); ++i) {
     if (m_runs[i] && m_runs[i]->m_fontData &&
         m_runs[i]->m_fontData != m_primaryFont &&
         !m_runs[i]->m_fontData->isTextOrientationFallbackOf(
             m_primaryFont.get())) {
       fallback->insert(m_runs[i]->m_fontData.get());
@@ skipping 167 matching lines @@
   result->m_width = run->m_width;
   result->m_numGlyphs = count;
   DCHECK_EQ(result->m_numGlyphs, count);  // no overflow
   result->m_hasVerticalOffsets =
       fontData->platformData().isVerticalAnyUpright();
   result->m_runs.push_back(std::move(run));
   return result.release();
 }
 
 }  // namespace blink