root/ui/gfx/render_text_win.cc

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DEFINITIONS

This source file includes following definitions.
  1. MetaFileEnumProc
  2. ChooseFallbackFont
  3. DeriveFontIfNecessary
  4. IsUnicodeBidiControlCharacter
  5. CharRangeToGlyphRange
  6. BreakRunAtWidth
  7. CheckLineIntegrity
  8. IsUnusualBlockCode
  9. script_cache
  10. GetGlyphXBoundary
  11. line_descent_
  12. AddRun
  13. Finalize
  14. SegmentFromHandle
  15. BreakRun
  16. UpdateRTLSegmentRanges
  17. AdvanceLine
  18. AddSegment
  19. needs_layout_
  20. GetStringSize
  21. FindCursorPosition
  22. GetFontSpansForTesting
  23. GetLayoutTextBaseline
  24. AdjacentCharSelectionModel
  25. AdjacentWordSelectionModel
  26. GetGlyphBounds
  27. GetSubstringBounds
  28. TextIndexToLayoutIndex
  29. LayoutIndexToTextIndex
  30. IsCursorablePosition
  31. ResetLayout
  32. EnsureLayout
  33. DrawVisualText
  34. ItemizeLogicalText
  35. LayoutVisualText
  36. LayoutTextRun
  37. ShapeTextRunWithFont
  38. CountCharsWithMissingGlyphs
  39. GetRunContainingCaret
  40. GetRunContainingXCoord
  41. FirstSelectionModelInsideRun
  42. LastSelectionModelInsideRun
  43. CreateInstance

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ui/gfx/render_text_win.h"

#include <algorithm>

#include "base/i18n/break_iterator.h"
#include "base/i18n/char_iterator.h"
#include "base/i18n/rtl.h"
#include "base/logging.h"
#include "base/strings/string_util.h"
#include "base/strings/utf_string_conversions.h"
#include "base/win/windows_version.h"
#include "third_party/icu/source/common/unicode/uchar.h"
#include "ui/gfx/canvas.h"
#include "ui/gfx/font_fallback_win.h"
#include "ui/gfx/font_smoothing_win.h"
#include "ui/gfx/platform_font_win.h"
#include "ui/gfx/utf16_indexing.h"

namespace gfx {

namespace {

// The maximum length of text supported for Uniscribe layout and display.
// This empirically chosen value should prevent major performance degradations.
// TODO(msw): Support longer text, partial layout/painting, etc.
const size_t kMaxUniscribeTextLength = 10000;

// The initial guess and maximum supported number of runs; arbitrary values.
// TODO(msw): Support more runs, determine a better initial guess, etc.
const int kGuessRuns = 100;
const size_t kMaxRuns = 10000;

// The maximum number of glyphs per run; ScriptShape fails on larger values.
const size_t kMaxGlyphs = 65535;

// Callback to |EnumEnhMetaFile()| to intercept font creation.
int CALLBACK MetaFileEnumProc(HDC hdc,
                              HANDLETABLE* table,
                              CONST ENHMETARECORD* record,
                              int table_entries,
                              LPARAM log_font) {
  if (record->iType == EMR_EXTCREATEFONTINDIRECTW) {
    const EMREXTCREATEFONTINDIRECTW* create_font_record =
        reinterpret_cast<const EMREXTCREATEFONTINDIRECTW*>(record);
    *reinterpret_cast<LOGFONT*>(log_font) = create_font_record->elfw.elfLogFont;
  }
  return 1;
}

// Finds a fallback font to use to render the specified |text| with respect to
// an initial |font|. Returns the resulting font via out param |result|. Returns
// |true| if a fallback font was found.
// Adapted from WebKit's |FontCache::GetFontDataForCharacters()|.
// TODO(asvitkine): This should be moved to font_fallback_win.cc.
bool ChooseFallbackFont(HDC hdc,
                        const Font& font,
                        const wchar_t* text,
                        int text_length,
                        Font* result) {
  // Use a meta file to intercept the fallback font chosen by Uniscribe.
  HDC meta_file_dc = CreateEnhMetaFile(hdc, NULL, NULL, NULL);
  if (!meta_file_dc)
    return false;

  SelectObject(meta_file_dc, font.GetNativeFont());

  SCRIPT_STRING_ANALYSIS script_analysis;
  HRESULT hresult =
      ScriptStringAnalyse(meta_file_dc, text, text_length, 0, -1,
                          SSA_METAFILE | SSA_FALLBACK | SSA_GLYPHS | SSA_LINK,
                          0, NULL, NULL, NULL, NULL, NULL, &script_analysis);

  if (SUCCEEDED(hresult)) {
    hresult = ScriptStringOut(script_analysis, 0, 0, 0, NULL, 0, 0, FALSE);
    ScriptStringFree(&script_analysis);
  }

  bool found_fallback = false;
  HENHMETAFILE meta_file = CloseEnhMetaFile(meta_file_dc);
  if (SUCCEEDED(hresult)) {
    LOGFONT log_font;
    log_font.lfFaceName[0] = 0;
    EnumEnhMetaFile(0, meta_file, MetaFileEnumProc, &log_font, NULL);
    if (log_font.lfFaceName[0]) {
      *result = Font(base::UTF16ToUTF8(log_font.lfFaceName),
                     font.GetFontSize());
      found_fallback = true;
    }
  }
  DeleteEnhMetaFile(meta_file);

  return found_fallback;
}

// Changes |font| to have the specified |font_size| (or |font_height| on Windows
// XP) and |font_style| if it is not the case already. Only considers bold and
// italic styles, since the underlined style has no effect on glyph shaping.
void DeriveFontIfNecessary(int font_size,
                           int font_height,
                           int font_style,
                           Font* font) {
  const int kStyleMask = (Font::BOLD | Font::ITALIC);
  const int target_style = (font_style & kStyleMask);

  // On Windows XP, the font must be resized using |font_height| instead of
  // |font_size| to match GDI behavior.
  if (base::win::GetVersion() < base::win::VERSION_VISTA) {
    PlatformFontWin* platform_font =
        static_cast<PlatformFontWin*>(font->platform_font());
    *font = platform_font->DeriveFontWithHeight(font_height, target_style);
    return;
  }

  const int current_style = (font->GetStyle() & kStyleMask);
  const int current_size = font->GetFontSize();
  if (current_style != target_style || current_size != font_size)
    *font = font->Derive(font_size - current_size, target_style);
}

// Returns true if |c| is a Unicode BiDi control character.
bool IsUnicodeBidiControlCharacter(base::char16 c) {
  return c == base::i18n::kRightToLeftMark ||
         c == base::i18n::kLeftToRightMark ||
         c == base::i18n::kLeftToRightEmbeddingMark ||
         c == base::i18n::kRightToLeftEmbeddingMark ||
         c == base::i18n::kPopDirectionalFormatting ||
         c == base::i18n::kLeftToRightOverride ||
         c == base::i18n::kRightToLeftOverride;
}

// Returns the corresponding glyph range of the given character range.
// |range| is in text-space (0 corresponds to |GetLayoutText()[0]|).
// Returned value is in run-space (0 corresponds to the first glyph in the run).
Range CharRangeToGlyphRange(const internal::TextRun& run,
                            const Range& range) {
  DCHECK(run.range.Contains(range));
  DCHECK(!range.is_reversed());
  DCHECK(!range.is_empty());
  const Range run_range(range.start() - run.range.start(),
                        range.end() - run.range.start());
  Range result;
  if (run.script_analysis.fRTL) {
    result = Range(run.logical_clusters[run_range.end() - 1],
        run_range.start() > 0 ? run.logical_clusters[run_range.start() - 1]
                              : run.glyph_count);
  } else {
    result = Range(run.logical_clusters[run_range.start()],
        run_range.end() < run.range.length() ?
            run.logical_clusters[run_range.end()] : run.glyph_count);
  }
  DCHECK(!result.is_reversed());
  DCHECK(Range(0, run.glyph_count).Contains(result));
  return result;
}

// Starting from |start_char|, finds a suitable line break position at or before
// |available_width| using word break info from |breaks|. If |empty_line| is
// true, this function will not roll back to |start_char| and |*next_char| will
// be greater than |start_char| (to avoid constructing empty lines). Returns
// whether to skip the line before |*next_char|.
// TODO(ckocagil): Do not break ligatures and diacritics.
//                 TextRun::logical_clusters might help.
// TODO(ckocagil): We might have to reshape after breaking at ligatures.
//                 See whether resolving the TODO above resolves this too.
// TODO(ckocagil): Do not reserve width for whitespace at the end of lines.
bool BreakRunAtWidth(const wchar_t* text,
                     const internal::TextRun& run,
                     const BreakList<size_t>& breaks,
                     size_t start_char,
                     int available_width,
                     bool empty_line,
                     int* width,
                     size_t* next_char) {
  DCHECK(run.range.Contains(Range(start_char, start_char + 1)));
  BreakList<size_t>::const_iterator word = breaks.GetBreak(start_char);
  BreakList<size_t>::const_iterator next_word = word + 1;
  // Width from |std::max(word->first, start_char)| to the current character.
  int word_width = 0;
  *width = 0;

  for (size_t i = start_char; i < run.range.end(); ++i) {
    if (U16_IS_SINGLE(text[i]) && text[i] == L'\n') {
      *next_char = i + 1;
      return true;
    }

    // |word| holds the word boundary at or before |i|, and |next_word| holds
    // the word boundary right after |i|. Advance both |word| and |next_word|
    // when |i| reaches |next_word|.
    if (next_word != breaks.breaks().end() && i >= next_word->first) {
      word = next_word++;
      word_width = 0;
    }

    Range glyph_range = CharRangeToGlyphRange(run, Range(i, i + 1));
    int char_width = 0;
    for (size_t j = glyph_range.start(); j < glyph_range.end(); ++j)
      char_width += run.advance_widths[j];

    *width += char_width;
    word_width += char_width;

    if (*width > available_width) {
      if (!empty_line || word_width < *width) {
        // Roll back one word.
        *width -= word_width;
        *next_char = std::max(word->first, start_char);
      } else if (char_width < *width) {
        // Roll back one character.
        *width -= char_width;
        *next_char = i;
      } else {
        // Continue from the next character.
        *next_char = i + 1;
      }

      return true;
    }
  }

  *next_char = run.range.end();
  return false;
}

// For segments in the same run, checks the continuity and order of |x_range|
// and |char_range| fields.
void CheckLineIntegrity(const std::vector<internal::Line>& lines,
                        const ScopedVector<internal::TextRun>& runs) {
  size_t previous_segment_line = 0;
  const internal::LineSegment* previous_segment = NULL;

  for (size_t i = 0; i < lines.size(); ++i) {
    for (size_t j = 0; j < lines[i].segments.size(); ++j) {
      const internal::LineSegment* segment = &lines[i].segments[j];
      internal::TextRun* run = runs[segment->run];

      if (!previous_segment) {
        previous_segment = segment;
      } else if (runs[previous_segment->run] != run) {
        previous_segment = NULL;
      } else {
        DCHECK_EQ(previous_segment->char_range.end(),
                  segment->char_range.start());
        if (!run->script_analysis.fRTL) {
          DCHECK_EQ(previous_segment->x_range.end(), segment->x_range.start());
        } else {
          DCHECK_EQ(segment->x_range.end(), previous_segment->x_range.start());
        }

        previous_segment = segment;
        previous_segment_line = i;
      }
    }
  }
}

// Returns true if characters of |block_code| may trigger font fallback.
bool IsUnusualBlockCode(const UBlockCode block_code) {
  return block_code == UBLOCK_GEOMETRIC_SHAPES ||
         block_code == UBLOCK_MISCELLANEOUS_SYMBOLS;
}

}  // namespace

namespace internal {

TextRun::TextRun()
  : font_style(0),
    strike(false),
    diagonal_strike(false),
    underline(false),
    width(0),
    preceding_run_widths(0),
    glyph_count(0),
    script_cache(NULL) {
  memset(&script_analysis, 0, sizeof(script_analysis));
  memset(&abc_widths, 0, sizeof(abc_widths));
}

TextRun::~TextRun() {
  ScriptFreeCache(&script_cache);
}

// Returns the X coordinate of the leading or |trailing| edge of the glyph
// starting at |index|, relative to the left of the text (not the view).
int GetGlyphXBoundary(const internal::TextRun* run,
                      size_t index,
                      bool trailing) {
  DCHECK_GE(index, run->range.start());
  DCHECK_LT(index, run->range.end() + (trailing ? 0 : 1));
  int x = 0;
  HRESULT hr = ScriptCPtoX(
      index - run->range.start(),
      trailing,
      run->range.length(),
      run->glyph_count,
      run->logical_clusters.get(),
      run->visible_attributes.get(),
      run->advance_widths.get(),
      &run->script_analysis,
      &x);
  DCHECK(SUCCEEDED(hr));
  return run->preceding_run_widths + x;
}

// Internal class to generate Line structures. If |multiline| is true, the text
// is broken into lines at |words| boundaries such that each line is no longer
// than |max_width|. If |multiline| is false, only outputs a single Line from
// the given runs. |min_baseline| and |min_height| are the minimum baseline and
// height for each line.
// TODO(ckocagil): Expose the interface of this class in the header and test
//                 this class directly.
class LineBreaker {
 public:
  LineBreaker(int max_width,
              int min_baseline,
              int min_height,
              bool multiline,
              const wchar_t* text,
              const BreakList<size_t>* words,
              const ScopedVector<TextRun>& runs)
      : max_width_(max_width),
        min_baseline_(min_baseline),
        min_height_(min_height),
        multiline_(multiline),
        text_(text),
        words_(words),
        runs_(runs),
        text_x_(0),
        line_x_(0),
        line_ascent_(0),
        line_descent_(0) {
    AdvanceLine();
  }

  // Breaks the run at given |run_index| into Line structs.
  void AddRun(int run_index) {
    const TextRun* run = runs_[run_index];
    bool run_fits = !multiline_;
    if (multiline_ && line_x_ + run->width <= max_width_) {
      DCHECK(!run->range.is_empty());
      const wchar_t first_char = text_[run->range.start()];
      // Uniscribe always puts newline characters in their own runs.
      if (!U16_IS_SINGLE(first_char) || first_char != L'\n')
        run_fits = true;
    }

    if (!run_fits)
      BreakRun(run_index);
    else
      AddSegment(run_index, run->range, run->width);
  }

  // Finishes line breaking and outputs the results. Can be called at most once.
  void Finalize(std::vector<Line>* lines, Size* size) {
    DCHECK(!lines_.empty());
    // Add an empty line to finish the line size calculation and remove it.
    AdvanceLine();
    lines_.pop_back();
    *size = total_size_;
    lines->swap(lines_);
  }

 private:
  // A (line index, segment index) pair that specifies a segment in |lines_|.
  typedef std::pair<size_t, size_t> SegmentHandle;

  LineSegment* SegmentFromHandle(const SegmentHandle& handle) {
    return &lines_[handle.first].segments[handle.second];
  }

  // Breaks a run into segments that fit in the last line in |lines_| and adds
  // them. Adds a new Line to the back of |lines_| whenever a new segment can't
  // be added without the Line's width exceeding |max_width_|.
  void BreakRun(int run_index) {
    DCHECK(words_);
    const TextRun* const run = runs_[run_index];
    int width = 0;
    size_t next_char = run->range.start();

    // Break the run until it fits the current line.
    while (next_char < run->range.end()) {
      const size_t current_char = next_char;
      const bool skip_line = BreakRunAtWidth(text_, *run, *words_, current_char,
          max_width_ - line_x_, line_x_ == 0, &width, &next_char);
      AddSegment(run_index, Range(current_char, next_char), width);
      if (skip_line)
        AdvanceLine();
    }
  }

  // RTL runs are broken in logical order but displayed in visual order. To find
  // the text-space coordinate (where it would fall in a single-line text)
  // |x_range| of RTL segments, segment widths are applied in reverse order.
  // e.g. {[5, 10], [10, 40]} will become {[35, 40], [5, 35]}.
  void UpdateRTLSegmentRanges() {
    if (rtl_segments_.empty())
      return;
    int x = SegmentFromHandle(rtl_segments_[0])->x_range.start();
    for (size_t i = rtl_segments_.size(); i > 0; --i) {
      LineSegment* segment = SegmentFromHandle(rtl_segments_[i - 1]);
      const size_t segment_width = segment->x_range.length();
      segment->x_range = Range(x, x + segment_width);
      x += segment_width;
    }
    rtl_segments_.clear();
  }

  // Finishes the size calculations of the last Line in |lines_|. Adds a new
  // Line to the back of |lines_|.
  void AdvanceLine() {
    if (!lines_.empty()) {
      Line* line = &lines_.back();
      // TODO(ckocagil): Determine optimal multiline height behavior.
      if (line_ascent_ + line_descent_ == 0) {
        line_ascent_ = min_baseline_;
        line_descent_ = min_height_ - min_baseline_;
      }
      // Set the single-line mode Line's metrics to be at least
      // |RenderText::font_list()| to not break the current single-line code.
      line_ascent_ = std::max(line_ascent_, min_baseline_);
      line_descent_ = std::max(line_descent_, min_height_ - min_baseline_);

      line->baseline = line_ascent_;
      line->size.set_height(line_ascent_ + line_descent_);
      line->preceding_heights = total_size_.height();
      total_size_.set_height(total_size_.height() + line->size.height());
      total_size_.set_width(std::max(total_size_.width(), line->size.width()));
    }
    line_x_ = 0;
    line_ascent_ = 0;
    line_descent_ = 0;
    lines_.push_back(Line());
  }

  // Adds a new segment with the given properties to |lines_.back()|.
  void AddSegment(int run_index, Range char_range, int width) {
    if (char_range.is_empty()) {
      DCHECK_EQ(width, 0);
      return;
    }
    const TextRun* run = runs_[run_index];
    line_ascent_ = std::max(line_ascent_, run->font.GetBaseline());
    line_descent_ = std::max(line_descent_,
                             run->font.GetHeight() - run->font.GetBaseline());

    LineSegment segment;
    segment.run = run_index;
    segment.char_range = char_range;
    segment.x_range = Range(text_x_, text_x_ + width);

    Line* line = &lines_.back();
    line->segments.push_back(segment);
    line->size.set_width(line->size.width() + segment.x_range.length());
    if (run->script_analysis.fRTL) {
      rtl_segments_.push_back(SegmentHandle(lines_.size() - 1,
                                            line->segments.size() - 1));
      // If this is the last segment of an RTL run, reprocess the text-space x
      // ranges of all segments from the run.
      if (char_range.end() == run->range.end())
        UpdateRTLSegmentRanges();
    }
    text_x_ += width;
    line_x_ += width;
  }

  const int max_width_;
  const int min_baseline_;
  const int min_height_;
  const bool multiline_;
  const wchar_t* text_;
  const BreakList<size_t>* const words_;
  const ScopedVector<TextRun>& runs_;

  // Stores the resulting lines.
  std::vector<Line> lines_;

  // Text space and line space x coordinates of the next segment to be added.
  int text_x_;
  int line_x_;

  // Size of the multiline text, not including the currently processed line.
  Size total_size_;

  // Ascent and descent values of the current line, |lines_.back()|.
  int line_ascent_;
  int line_descent_;

  // The current RTL run segments, to be applied by |UpdateRTLSegmentRanges()|.
  std::vector<SegmentHandle> rtl_segments_;

  DISALLOW_COPY_AND_ASSIGN(LineBreaker);
};

}  // namespace internal

// static
HDC RenderTextWin::cached_hdc_ = NULL;

// static
std::map<std::string, Font> RenderTextWin::successful_substitute_fonts_;

RenderTextWin::RenderTextWin()
    : RenderText(),
      needs_layout_(false) {
  set_truncate_length(kMaxUniscribeTextLength);

  memset(&script_control_, 0, sizeof(script_control_));
  memset(&script_state_, 0, sizeof(script_state_));

  MoveCursorTo(EdgeSelectionModel(CURSOR_LEFT));
}

RenderTextWin::~RenderTextWin() {
}

Size RenderTextWin::GetStringSize() {
  EnsureLayout();
  return multiline_string_size_;
}

SelectionModel RenderTextWin::FindCursorPosition(const Point& point) {
  if (text().empty())
    return SelectionModel();

  EnsureLayout();
  // Find the run that contains the point and adjust the argument location.
  int x = ToTextPoint(point).x();
  size_t run_index = GetRunContainingXCoord(x);
  if (run_index >= runs_.size())
    return EdgeSelectionModel((x < 0) ? CURSOR_LEFT : CURSOR_RIGHT);
  internal::TextRun* run = runs_[run_index];

  int position = 0, trailing = 0;
  HRESULT hr = ScriptXtoCP(x - run->preceding_run_widths,
                           run->range.length(),
                           run->glyph_count,
                           run->logical_clusters.get(),
                           run->visible_attributes.get(),
                           run->advance_widths.get(),
                           &(run->script_analysis),
                           &position,
                           &trailing);
  DCHECK(SUCCEEDED(hr));
  DCHECK_GE(trailing, 0);
  position += run->range.start();
  const size_t cursor = LayoutIndexToTextIndex(position + trailing);
  DCHECK_LE(cursor, text().length());
  return SelectionModel(cursor, trailing ? CURSOR_BACKWARD : CURSOR_FORWARD);
}

std::vector<RenderText::FontSpan> RenderTextWin::GetFontSpansForTesting() {
  EnsureLayout();

  std::vector<RenderText::FontSpan> spans;
  for (size_t i = 0; i < runs_.size(); ++i) {
    spans.push_back(RenderText::FontSpan(runs_[i]->font,
        Range(LayoutIndexToTextIndex(runs_[i]->range.start()),
              LayoutIndexToTextIndex(runs_[i]->range.end()))));
  }

  return spans;
}

int RenderTextWin::GetLayoutTextBaseline() {
  EnsureLayout();
  return lines()[0].baseline;
}

SelectionModel RenderTextWin::AdjacentCharSelectionModel(
    const SelectionModel& selection,
    VisualCursorDirection direction) {
  DCHECK(!needs_layout_);
  internal::TextRun* run;
  size_t run_index = GetRunContainingCaret(selection);
  if (run_index >= runs_.size()) {
    // The cursor is not in any run: we're at the visual and logical edge.
    SelectionModel edge = EdgeSelectionModel(direction);
    if (edge.caret_pos() == selection.caret_pos())
      return edge;
    int visual_index = (direction == CURSOR_RIGHT) ? 0 : runs_.size() - 1;
    run = runs_[visual_to_logical_[visual_index]];
  } else {
    // If the cursor is moving within the current run, just move it by one
    // grapheme in the appropriate direction.
    run = runs_[run_index];
    size_t caret = selection.caret_pos();
    bool forward_motion =
        run->script_analysis.fRTL == (direction == CURSOR_LEFT);
    if (forward_motion) {
      if (caret < LayoutIndexToTextIndex(run->range.end())) {
        caret = IndexOfAdjacentGrapheme(caret, CURSOR_FORWARD);
        return SelectionModel(caret, CURSOR_BACKWARD);
      }
    } else {
      if (caret > LayoutIndexToTextIndex(run->range.start())) {
        caret = IndexOfAdjacentGrapheme(caret, CURSOR_BACKWARD);
        return SelectionModel(caret, CURSOR_FORWARD);
      }
    }
    // The cursor is at the edge of a run; move to the visually adjacent run.
    int visual_index = logical_to_visual_[run_index];
    visual_index += (direction == CURSOR_LEFT) ? -1 : 1;
    if (visual_index < 0 || visual_index >= static_cast<int>(runs_.size()))
      return EdgeSelectionModel(direction);
    run = runs_[visual_to_logical_[visual_index]];
  }
  bool forward_motion = run->script_analysis.fRTL == (direction == CURSOR_LEFT);
  return forward_motion ? FirstSelectionModelInsideRun(run) :
                          LastSelectionModelInsideRun(run);
}

// TODO(msw): Implement word breaking for Windows.
SelectionModel RenderTextWin::AdjacentWordSelectionModel(
    const SelectionModel& selection,
    VisualCursorDirection direction) {
  if (obscured())
    return EdgeSelectionModel(direction);

  base::i18n::BreakIterator iter(text(), base::i18n::BreakIterator::BREAK_WORD);
  bool success = iter.Init();
  DCHECK(success);
  if (!success)
    return selection;

  size_t pos;
  if (direction == CURSOR_RIGHT) {
    pos = std::min(selection.caret_pos() + 1, text().length());
    while (iter.Advance()) {
      pos = iter.pos();
      if (iter.IsWord() && pos > selection.caret_pos())
        break;
    }
  } else {  // direction == CURSOR_LEFT
    // Notes: We always iterate words from the beginning.
    // This is probably fast enough for our usage, but we may
    // want to modify WordIterator so that it can start from the
    // middle of string and advance backwards.
    pos = std::max<int>(selection.caret_pos() - 1, 0);
    while (iter.Advance()) {
      if (iter.IsWord()) {
        size_t begin = iter.pos() - iter.GetString().length();
        if (begin == selection.caret_pos()) {
          // The cursor is at the beginning of a word.
          // Move to previous word.
          break;
        } else if (iter.pos() >= selection.caret_pos()) {
          // The cursor is in the middle or at the end of a word.
          // Move to the top of current word.
          pos = begin;
          break;
        } else {
          pos = iter.pos() - iter.GetString().length();
        }
      }
    }
  }
  return SelectionModel(pos, CURSOR_FORWARD);
}

Range RenderTextWin::GetGlyphBounds(size_t index) {
  const size_t run_index =
      GetRunContainingCaret(SelectionModel(index, CURSOR_FORWARD));
  // Return edge bounds if the index is invalid or beyond the layout text size.
  if (run_index >= runs_.size())
    return Range(string_width_);
  internal::TextRun* run = runs_[run_index];
  const size_t layout_index = TextIndexToLayoutIndex(index);
  return Range(GetGlyphXBoundary(run, layout_index, false),
               GetGlyphXBoundary(run, layout_index, true));
}

std::vector<Rect> RenderTextWin::GetSubstringBounds(const Range& range) {
  DCHECK(!needs_layout_);
  DCHECK(Range(0, text().length()).Contains(range));
  Range layout_range(TextIndexToLayoutIndex(range.start()),
                     TextIndexToLayoutIndex(range.end()));
  DCHECK(Range(0, GetLayoutText().length()).Contains(layout_range));

  std::vector<Rect> rects;
  if (layout_range.is_empty())
    return rects;
  std::vector<Range> bounds;

  // Add a Range for each run/selection intersection.
  // TODO(msw): The bounds should probably not always be leading the range ends.
  for (size_t i = 0; i < runs_.size(); ++i) {
    const internal::TextRun* run = runs_[visual_to_logical_[i]];
    Range intersection = run->range.Intersect(layout_range);
    if (intersection.IsValid()) {
      DCHECK(!intersection.is_reversed());
      Range range_x(GetGlyphXBoundary(run, intersection.start(), false),
                    GetGlyphXBoundary(run, intersection.end(), false));
      if (range_x.is_empty())
        continue;
      range_x = Range(range_x.GetMin(), range_x.GetMax());
      // Union this with the last range if they're adjacent.
      DCHECK(bounds.empty() || bounds.back().GetMax() <= range_x.GetMin());
      if (!bounds.empty() && bounds.back().GetMax() == range_x.GetMin()) {
        range_x = Range(bounds.back().GetMin(), range_x.GetMax());
        bounds.pop_back();
      }
      bounds.push_back(range_x);
    }
  }
  for (size_t i = 0; i < bounds.size(); ++i) {
    std::vector<Rect> current_rects = TextBoundsToViewBounds(bounds[i]);
    rects.insert(rects.end(), current_rects.begin(), current_rects.end());
  }
  return rects;
}

size_t RenderTextWin::TextIndexToLayoutIndex(size_t index) const {
  DCHECK_LE(index, text().length());
  ptrdiff_t i = obscured() ? gfx::UTF16IndexToOffset(text(), 0, index) : index;
  CHECK_GE(i, 0);
  // Clamp layout indices to the length of the text actually used for layout.
  return std::min<size_t>(GetLayoutText().length(), i);
}

size_t RenderTextWin::LayoutIndexToTextIndex(size_t index) const {
  if (!obscured())
    return index;

  DCHECK_LE(index, GetLayoutText().length());
  const size_t text_index = gfx::UTF16OffsetToIndex(text(), 0, index);
  DCHECK_LE(text_index, text().length());
  return text_index;
}

bool RenderTextWin::IsCursorablePosition(size_t position) {
  if (position == 0 || position == text().length())
    return true;
  EnsureLayout();

  // Check that the index is at a valid code point (not mid-surrgate-pair),
  // that it is not truncated from layout text (its glyph is shown on screen),
  // and that its glyph has distinct bounds (not mid-multi-character-grapheme).
  // An example of a multi-character-grapheme that is not a surrogate-pair is:
  // \x0915\x093f - (ki) - one of many Devanagari biconsonantal conjuncts.
  return gfx::IsValidCodePointIndex(text(), position) &&
         position < LayoutIndexToTextIndex(GetLayoutText().length()) &&
         GetGlyphBounds(position) != GetGlyphBounds(position - 1);
}

void RenderTextWin::ResetLayout() {
  // Layout is performed lazily as needed for drawing/metrics.
  needs_layout_ = true;
}

void RenderTextWin::EnsureLayout() {
  if (needs_layout_) {
    // TODO(msw): Skip complex processing if ScriptIsComplex returns false.
    ItemizeLogicalText();
    if (!runs_.empty())
      LayoutVisualText();
    needs_layout_ = false;
    std::vector<internal::Line> lines;
    set_lines(&lines);
  }

  // Compute lines if they're not valid. This is separate from the layout steps
  // above to avoid text layout and shaping when we resize |display_rect_|.
  if (lines().empty()) {
    DCHECK(!needs_layout_);
    std::vector<internal::Line> lines;
    internal::LineBreaker line_breaker(display_rect().width() - 1,
                                       font_list().GetBaseline(),
                                       font_list().GetHeight(), multiline(),
                                       GetLayoutText().c_str(),
                                       multiline() ? &GetLineBreaks() : NULL,
                                       runs_);
    for (size_t i = 0; i < runs_.size(); ++i)
      line_breaker.AddRun(visual_to_logical_[i]);
    line_breaker.Finalize(&lines, &multiline_string_size_);
    DCHECK(!lines.empty());
#ifndef NDEBUG
    CheckLineIntegrity(lines, runs_);
#endif
    set_lines(&lines);
  }
}

void RenderTextWin::DrawVisualText(Canvas* canvas) {
  DCHECK(!needs_layout_);
  DCHECK(!lines().empty());

  std::vector<SkPoint> pos;

  internal::SkiaTextRenderer renderer(canvas);
  ApplyFadeEffects(&renderer);
  ApplyTextShadows(&renderer);

  bool smoothing_enabled;
  bool cleartype_enabled;
  GetCachedFontSmoothingSettings(&smoothing_enabled, &cleartype_enabled);
  // Note that |cleartype_enabled| corresponds to Skia's |enable_lcd_text|.
  renderer.SetFontSmoothingSettings(
      smoothing_enabled, cleartype_enabled && !background_is_transparent(),
      smoothing_enabled /* subpixel_positioning */);

  ApplyCompositionAndSelectionStyles();

  for (size_t i = 0; i < lines().size(); ++i) {
    const internal::Line& line = lines()[i];
    const Vector2d line_offset = GetLineOffset(i);

    // Skip painting empty lines or lines outside the display rect area.
    if (!display_rect().Intersects(Rect(PointAtOffsetFromOrigin(line_offset),
                                        line.size)))
      continue;

    const Vector2d text_offset = line_offset + Vector2d(0, line.baseline);
    int preceding_segment_widths = 0;

    for (size_t j = 0; j < line.segments.size(); ++j) {
      const internal::LineSegment* segment = &line.segments[j];
      const int segment_width = segment->x_range.length();
      const internal::TextRun* run = runs_[segment->run];
      DCHECK(!segment->char_range.is_empty());
      DCHECK(run->range.Contains(segment->char_range));
      Range glyph_range = CharRangeToGlyphRange(*run, segment->char_range);
      DCHECK(!glyph_range.is_empty());
      // Skip painting segments outside the display rect area.
      if (!multiline()) {
        const Rect segment_bounds(PointAtOffsetFromOrigin(line_offset) +
                                      Vector2d(preceding_segment_widths, 0),
                                  Size(segment_width, line.size.height()));
        if (!display_rect().Intersects(segment_bounds)) {
          preceding_segment_widths += segment_width;
          continue;
        }
      }

      // |pos| contains the positions of glyphs. An extra terminal |pos| entry
      // is added to simplify width calculations.
      int segment_x = preceding_segment_widths;
      pos.resize(glyph_range.length() + 1);
      for (size_t k = glyph_range.start(); k < glyph_range.end(); ++k) {
        pos[k - glyph_range.start()].set(
            SkIntToScalar(text_offset.x() + run->offsets[k].du + segment_x),
            SkIntToScalar(text_offset.y() + run->offsets[k].dv));
        segment_x += run->advance_widths[k];
      }
      pos.back().set(SkIntToScalar(text_offset.x() + segment_x),
                     SkIntToScalar(text_offset.y()));

      renderer.SetTextSize(run->font.GetFontSize());
      renderer.SetFontFamilyWithStyle(run->font.GetFontName(), run->font_style);

      for (BreakList<SkColor>::const_iterator it =
               colors().GetBreak(segment->char_range.start());
           it != colors().breaks().end() &&
               it->first < segment->char_range.end();
           ++it) {
        const Range intersection =
            colors().GetRange(it).Intersect(segment->char_range);
        const Range colored_glyphs = CharRangeToGlyphRange(*run, intersection);
        DCHECK(glyph_range.Contains(colored_glyphs));
        DCHECK(!colored_glyphs.is_empty());
        const SkPoint& start_pos =
            pos[colored_glyphs.start() - glyph_range.start()];
        const SkPoint& end_pos =
            pos[colored_glyphs.end() - glyph_range.start()];

        renderer.SetForegroundColor(it->second);
        renderer.DrawPosText(&start_pos, &run->glyphs[colored_glyphs.start()],
                             colored_glyphs.length());
        renderer.DrawDecorations(start_pos.x(), text_offset.y(),
                                 SkScalarCeilToInt(end_pos.x() - start_pos.x()),
                                 run->underline, run->strike,
                                 run->diagonal_strike);
      }

      preceding_segment_widths += segment_width;
    }

    renderer.EndDiagonalStrike();
  }

  UndoCompositionAndSelectionStyles();
}

void RenderTextWin::ItemizeLogicalText() {
  runs_.clear();
  string_width_ = 0;
  multiline_string_size_ = Size();

  // Set Uniscribe's base text direction.
  script_state_.uBidiLevel =
      (GetTextDirection() == base::i18n::RIGHT_TO_LEFT) ? 1 : 0;

  const base::string16& layout_text = GetLayoutText();
  if (layout_text.empty())
    return;

  HRESULT hr = E_OUTOFMEMORY;
  int script_items_count = 0;
  std::vector<SCRIPT_ITEM> script_items;
  const size_t layout_text_length = layout_text.length();
  // Ensure that |kMaxRuns| is attempted and the loop terminates afterward.
  for (size_t runs = kGuessRuns; hr == E_OUTOFMEMORY && runs <= kMaxRuns;
       runs = std::max(runs + 1, std::min(runs * 2, kMaxRuns))) {
    // Derive the array of Uniscribe script items from the logical text.
    // ScriptItemize always adds a terminal array item so that the length of
    // the last item can be derived from the terminal SCRIPT_ITEM::iCharPos.
    script_items.resize(runs);
    hr = ScriptItemize(layout_text.c_str(), layout_text_length, runs - 1,
                       &script_control_, &script_state_, &script_items[0],
                       &script_items_count);
  }
  DCHECK(SUCCEEDED(hr));
  if (!SUCCEEDED(hr) || script_items_count <= 0)
    return;

  // Temporarily apply composition underlines and selection colors.
  ApplyCompositionAndSelectionStyles();

  // Build the list of runs from the script items and ranged styles. Use an
  // empty color BreakList to avoid breaking runs at color boundaries.
  BreakList<SkColor> empty_colors;
  empty_colors.SetMax(layout_text_length);
  internal::StyleIterator style(empty_colors, styles());
  SCRIPT_ITEM* script_item = &script_items[0];
  const size_t max_run_length = kMaxGlyphs / 2;
  for (size_t run_break = 0; run_break < layout_text_length;) {
    internal::TextRun* run = new internal::TextRun();
    run->range.set_start(run_break);
    run->font = font_list().GetPrimaryFont();
    run->font_style = (style.style(BOLD) ? Font::BOLD : 0) |
                      (style.style(ITALIC) ? Font::ITALIC : 0);
    DeriveFontIfNecessary(run->font.GetFontSize(), run->font.GetHeight(),
                          run->font_style, &run->font);
    run->strike = style.style(STRIKE);
    run->diagonal_strike = style.style(DIAGONAL_STRIKE);
    run->underline = style.style(UNDERLINE);
    run->script_analysis = script_item->a;

    // Find the next break and advance the iterators as needed.
    const size_t script_item_break = (script_item + 1)->iCharPos;
    run_break = std::min(script_item_break,
                         TextIndexToLayoutIndex(style.GetRange().end()));

    // Clamp run lengths to avoid exceeding the maximum supported glyph count.
    if ((run_break - run->range.start()) > max_run_length) {
      run_break = run->range.start() + max_run_length;
      if (!IsValidCodePointIndex(layout_text, run_break))
        --run_break;
    }

    // Break runs adjacent to character substrings in certain code blocks.
    // This avoids using their fallback fonts for more characters than needed,
    // in cases like "\x25B6 Media Title", etc. http://crbug.com/278913
    if (run_break > run->range.start()) {
      const size_t run_start = run->range.start();
      const int32 run_length = static_cast<int32>(run_break - run_start);
      base::i18n::UTF16CharIterator iter(layout_text.c_str() + run_start,
                                         run_length);
      const UBlockCode first_block_code = ublock_getCode(iter.get());
      const bool first_block_unusual = IsUnusualBlockCode(first_block_code);
      while (iter.Advance() && iter.array_pos() < run_length) {
        const UBlockCode current_block_code = ublock_getCode(iter.get());
        if (current_block_code != first_block_code &&
            (first_block_unusual || IsUnusualBlockCode(current_block_code))) {
          run_break = run_start + iter.array_pos();
          break;
        }
      }
    }

    DCHECK(IsValidCodePointIndex(layout_text, run_break));

    style.UpdatePosition(LayoutIndexToTextIndex(run_break));
    if (script_item_break == run_break)
      script_item++;
    run->range.set_end(run_break);
    runs_.push_back(run);
  }

  // Undo the temporarily applied composition underlines and selection colors.
  UndoCompositionAndSelectionStyles();
}

void RenderTextWin::LayoutVisualText() {
  DCHECK(!runs_.empty());

  if (!cached_hdc_)
    cached_hdc_ = CreateCompatibleDC(NULL);

  HRESULT hr = E_FAIL;
  // Ensure ascent and descent are not smaller than ones of the font list.
  // Keep them tall enough to draw often-used characters.
  // For example, if a text field contains a Japanese character, which is
  // smaller than Latin ones, and then later a Latin one is inserted, this
  // ensures that the text baseline does not shift.
  int ascent = font_list().GetBaseline();
  int descent = font_list().GetHeight() - font_list().GetBaseline();
  for (size_t i = 0; i < runs_.size(); ++i) {
    internal::TextRun* run = runs_[i];
    LayoutTextRun(run);

    ascent = std::max(ascent, run->font.GetBaseline());
    descent = std::max(descent,
                       run->font.GetHeight() - run->font.GetBaseline());

    if (run->glyph_count > 0) {
      run->advance_widths.reset(new int[run->glyph_count]);
      run->offsets.reset(new GOFFSET[run->glyph_count]);
      hr = ScriptPlace(cached_hdc_,
                       &run->script_cache,
                       run->glyphs.get(),
                       run->glyph_count,
                       run->visible_attributes.get(),
                       &(run->script_analysis),
                       run->advance_widths.get(),
                       run->offsets.get(),
                       &(run->abc_widths));
      DCHECK(SUCCEEDED(hr));
    }
  }

  // Build the array of bidirectional embedding levels.
  scoped_ptr<BYTE[]> levels(new BYTE[runs_.size()]);
  for (size_t i = 0; i < runs_.size(); ++i)
    levels[i] = runs_[i]->script_analysis.s.uBidiLevel;

  // Get the maps between visual and logical run indices.
  visual_to_logical_.reset(new int[runs_.size()]);
  logical_to_visual_.reset(new int[runs_.size()]);
  hr = ScriptLayout(runs_.size(),
                    levels.get(),
                    visual_to_logical_.get(),
                    logical_to_visual_.get());
  DCHECK(SUCCEEDED(hr));

  // Precalculate run width information.
  size_t preceding_run_widths = 0;
  for (size_t i = 0; i < runs_.size(); ++i) {
    internal::TextRun* run = runs_[visual_to_logical_[i]];
    run->preceding_run_widths = preceding_run_widths;
    const ABC& abc = run->abc_widths;
    run->width = abc.abcA + abc.abcB + abc.abcC;
    preceding_run_widths += run->width;
  }
  string_width_ = preceding_run_widths;
}

void RenderTextWin::LayoutTextRun(internal::TextRun* run) {
  const size_t run_length = run->range.length();
  const wchar_t* run_text = &(GetLayoutText()[run->range.start()]);
  Font original_font = run->font;
  LinkedFontsIterator fonts(original_font);
  bool tried_cached_font = false;
  bool tried_fallback = false;
  // Keep track of the font that is able to display the greatest number of
  // characters for which ScriptShape() returned S_OK. This font will be used
  // in the case where no font is able to display the entire run.
  int best_partial_font_missing_char_count = INT_MAX;
  Font best_partial_font = original_font;
  Font current_font;

  run->logical_clusters.reset(new WORD[run_length]);
  while (fonts.NextFont(&current_font)) {
    HRESULT hr = ShapeTextRunWithFont(run, current_font);

    bool glyphs_missing = false;
    if (hr == USP_E_SCRIPT_NOT_IN_FONT) {
      glyphs_missing = true;
    } else if (hr == S_OK) {
      // If |hr| is S_OK, there could still be missing glyphs in the output.
      // http://msdn.microsoft.com/en-us/library/windows/desktop/dd368564.aspx
      const int missing_count = CountCharsWithMissingGlyphs(run);
      // Track the font that produced the least missing glyphs.
      if (missing_count < best_partial_font_missing_char_count) {
        best_partial_font_missing_char_count = missing_count;
        best_partial_font = run->font;
      }
      glyphs_missing = (missing_count != 0);
    } else {
      NOTREACHED() << hr;
    }

    // Use the font if it had glyphs for all characters.
    if (!glyphs_missing) {
      // Save the successful fallback font that was chosen.
      if (tried_fallback)
        successful_substitute_fonts_[original_font.GetFontName()] = run->font;
      return;
    }

    // First, try the cached font from previous runs, if any.
    if (!tried_cached_font) {
      tried_cached_font = true;

      std::map<std::string, Font>::const_iterator it =
          successful_substitute_fonts_.find(original_font.GetFontName());
      if (it != successful_substitute_fonts_.end()) {
        fonts.SetNextFont(it->second);
        continue;
      }
    }

    // If there are missing glyphs, first try finding a fallback font using a
    // meta file, if it hasn't yet been attempted for this run.
    // TODO(msw|asvitkine): Support RenderText's font_list()?
    if (!tried_fallback) {
      tried_fallback = true;

      Font fallback_font;
      if (ChooseFallbackFont(cached_hdc_, run->font, run_text, run_length,
                             &fallback_font)) {
        fonts.SetNextFont(fallback_font);
        continue;
      }
    }
  }

  // If a font was able to partially display the run, use that now.
  if (best_partial_font_missing_char_count < static_cast<int>(run_length)) {
    // Re-shape the run only if |best_partial_font| differs from the last font.
    if (best_partial_font.GetNativeFont() != run->font.GetNativeFont())
      ShapeTextRunWithFont(run, best_partial_font);
    return;
  }

  // If no font was able to partially display the run, replace all glyphs
  // with |wgDefault| from the original font to ensure to they don't hold
  // garbage values.
  // First, clear the cache and select the original font on the HDC.
  ScriptFreeCache(&run->script_cache);
  run->font = original_font;
  SelectObject(cached_hdc_, run->font.GetNativeFont());

  // Now, get the font's properties.
  SCRIPT_FONTPROPERTIES properties;
  memset(&properties, 0, sizeof(properties));
  properties.cBytes = sizeof(properties);
  HRESULT hr = ScriptGetFontProperties(cached_hdc_, &run->script_cache,
                                       &properties);

  // The initial values for the "missing" glyph and the space glyph are taken
  // from the recommendations section of the OpenType spec:
  // https://www.microsoft.com/typography/otspec/recom.htm
  WORD missing_glyph = 0;
  WORD space_glyph = 3;
  if (hr == S_OK) {
    missing_glyph = properties.wgDefault;
    space_glyph = properties.wgBlank;
  }

  // Finally, initialize |glyph_count|, |glyphs|, |visible_attributes| and
  // |logical_clusters| on the run (since they may not have been set yet).
  run->glyph_count = run_length;
  memset(run->visible_attributes.get(), 0,
         run->glyph_count * sizeof(SCRIPT_VISATTR));
  for (int i = 0; i < run->glyph_count; ++i)
    run->glyphs[i] = IsWhitespace(run_text[i]) ? space_glyph : missing_glyph;
  for (size_t i = 0; i < run_length; ++i) {
    run->logical_clusters[i] = run->script_analysis.fRTL ?
        run_length - 1 - i : i;
  }

  // TODO(msw): Don't use SCRIPT_UNDEFINED. Apparently Uniscribe can
  //            crash on certain surrogate pairs with SCRIPT_UNDEFINED.
  //            See https://bugzilla.mozilla.org/show_bug.cgi?id=341500
  //            And http://maxradi.us/documents/uniscribe/
  run->script_analysis.eScript = SCRIPT_UNDEFINED;
}

HRESULT RenderTextWin::ShapeTextRunWithFont(internal::TextRun* run,
                                            const Font& font) {
  // Update the run's font only if necessary. If the two fonts wrap the same
  // PlatformFontWin object, their native fonts will have the same value.
  if (run->font.GetNativeFont() != font.GetNativeFont()) {
    const int font_size = run->font.GetFontSize();
    const int font_height = run->font.GetHeight();
    run->font = font;
    DeriveFontIfNecessary(font_size, font_height, run->font_style, &run->font);
    ScriptFreeCache(&run->script_cache);
  }

  // Select the font desired for glyph generation.
  SelectObject(cached_hdc_, run->font.GetNativeFont());

  HRESULT hr = E_OUTOFMEMORY;
  const size_t run_length = run->range.length();
  const wchar_t* run_text = &(GetLayoutText()[run->range.start()]);
  // Guess the expected number of glyphs from the length of the run.
  // MSDN suggests this at http://msdn.microsoft.com/en-us/library/dd368564.aspx
  size_t max_glyphs = static_cast<size_t>(1.5 * run_length + 16);
  while (hr == E_OUTOFMEMORY && max_glyphs <= kMaxGlyphs) {
    run->glyph_count = 0;
    run->glyphs.reset(new WORD[max_glyphs]);
    run->visible_attributes.reset(new SCRIPT_VISATTR[max_glyphs]);
    hr = ScriptShape(cached_hdc_, &run->script_cache, run_text, run_length,
                     max_glyphs, &run->script_analysis, run->glyphs.get(),
                     run->logical_clusters.get(), run->visible_attributes.get(),
                     &run->glyph_count);
    // Ensure that |kMaxGlyphs| is attempted and the loop terminates afterward.
    max_glyphs = std::max(max_glyphs + 1, std::min(max_glyphs * 2, kMaxGlyphs));
  }
  return hr;
}

int RenderTextWin::CountCharsWithMissingGlyphs(internal::TextRun* run) const {
  int chars_not_missing_glyphs = 0;
  SCRIPT_FONTPROPERTIES properties;
  memset(&properties, 0, sizeof(properties));
  properties.cBytes = sizeof(properties);
  ScriptGetFontProperties(cached_hdc_, &run->script_cache, &properties);

  const wchar_t* run_text = &(GetLayoutText()[run->range.start()]);
  for (size_t char_index = 0; char_index < run->range.length(); ++char_index) {
    const int glyph_index = run->logical_clusters[char_index];
    DCHECK_GE(glyph_index, 0);
    DCHECK_LT(glyph_index, run->glyph_count);

    if (run->glyphs[glyph_index] == properties.wgDefault)
      continue;

    // Windows Vista sometimes returns glyphs equal to wgBlank (instead of
    // wgDefault), with fZeroWidth set. Treat such cases as having missing
    // glyphs if the corresponding character is not whitespace.
    // See: http://crbug.com/125629
    if (run->glyphs[glyph_index] == properties.wgBlank &&
        run->visible_attributes[glyph_index].fZeroWidth &&
        !IsWhitespace(run_text[char_index]) &&
        !IsUnicodeBidiControlCharacter(run_text[char_index])) {
      continue;
    }

    ++chars_not_missing_glyphs;
  }

  DCHECK_LE(chars_not_missing_glyphs, static_cast<int>(run->range.length()));
  return run->range.length() - chars_not_missing_glyphs;
}

size_t RenderTextWin::GetRunContainingCaret(const SelectionModel& caret) const {
  DCHECK(!needs_layout_);
  size_t layout_position = TextIndexToLayoutIndex(caret.caret_pos());
  LogicalCursorDirection affinity = caret.caret_affinity();
  for (size_t run = 0; run < runs_.size(); ++run)
    if (RangeContainsCaret(runs_[run]->range, layout_position, affinity))
      return run;
  return runs_.size();
}

size_t RenderTextWin::GetRunContainingXCoord(int x) const {
  DCHECK(!needs_layout_);
  // Find the text run containing the argument point (assumed already offset).
  for (size_t run = 0; run < runs_.size(); ++run) {
    if ((runs_[run]->preceding_run_widths <= x) &&
        ((runs_[run]->preceding_run_widths + runs_[run]->width) > x))
      return run;
  }
  return runs_.size();
}

SelectionModel RenderTextWin::FirstSelectionModelInsideRun(
    const internal::TextRun* run) {
  size_t position = LayoutIndexToTextIndex(run->range.start());
  position = IndexOfAdjacentGrapheme(position, CURSOR_FORWARD);
  return SelectionModel(position, CURSOR_BACKWARD);
}

SelectionModel RenderTextWin::LastSelectionModelInsideRun(
    const internal::TextRun* run) {
  size_t position = LayoutIndexToTextIndex(run->range.end());
  position = IndexOfAdjacentGrapheme(position, CURSOR_BACKWARD);
  return SelectionModel(position, CURSOR_FORWARD);
}

RenderText* RenderText::CreateInstance() {
  return new RenderTextWin;
}

}  // namespace gfx

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