// 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_render_params.h"
#include "ui/gfx/geometry/size_conversions.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;

// 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;
}

// Returns the index of the first unusual character after a usual character or
// vice versa. Unusual characters are defined by |IsUnusualBlockCode|.
size_t FindUnusualCharacter(const base::string16& text,
                            size_t run_start,
                            size_t run_break) {
  const int32 run_length = static_cast<int32>(run_break - run_start);
  base::i18n::UTF16CharIterator iter(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))) {
      return run_start + iter.array_pos();
    }
  }
  return run_break;
}

}  // 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();
      const Size line_size(ToCeiledSize(line->size));
      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) {
  EnsureLayout();
  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() ? 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 = UTF16OffsetToIndex(text(), 0, index);
  DCHECK_LE(text_index, text().length());
  return text_index;
}

bool RenderTextWin::IsValidCursorIndex(size_t index) {
  if (index == 0 || index == text().length())
    return true;
  if (!IsValidLogicalIndex(index))
    return false;
  EnsureLayout();
  // Disallow indices amid multi-character graphemes by checking glyph bounds.
  // These characters are not surrogate-pairs, but may yield a single glyph:
  //   \x0915\x093f - (ki) - one of many Devanagari biconsonantal conjuncts.
  //   \x0e08\x0e33 - (cho chan + sara am) - a Thai consonant and vowel pair.
  return GetGlyphBounds(index) != GetGlyphBounds(index - 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);

  renderer.SetFontRenderParams(
      font_list().GetPrimaryFont().GetFontRenderParams(),
      background_is_transparent());

  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),
                                        ToCeiledSize(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);
        // The range may be empty if a portion of a multi-character grapheme is
        // selected, yielding two colors for a single glyph. For now, this just
        // paints the glyph with a single style, but it should paint it twice,
        // clipped according to selection bounds. See http://crbug.com/366786
        if (colored_glyphs.is_empty())
          continue;
        DCHECK(glyph_range.Contains(colored_glyphs));
        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()) {
      run_break =
          FindUnusualCharacter(layout_text, run->range.start(), run_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;

  run->logical_clusters.reset(new WORD[run_length]);

  // Try shaping with |original_font|.
  Font current_font = original_font;
  int missing_count = CountCharsWithMissingGlyphs(run,
      ShapeTextRunWithFont(run, current_font));
  if (missing_count == 0)
    return;

  // 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 = missing_count;
  Font best_partial_font = current_font;

  // Try to shape with the cached font from previous runs, if any.
  std::map<std::string, Font>::const_iterator it =
      successful_substitute_fonts_.find(original_font.GetFontName());
  if (it != successful_substitute_fonts_.end()) {
    current_font = it->second;
    missing_count = CountCharsWithMissingGlyphs(run,
        ShapeTextRunWithFont(run, current_font));
    if (missing_count == 0)
      return;
    if (missing_count < best_partial_font_missing_char_count) {
      best_partial_font_missing_char_count = missing_count;
      best_partial_font = current_font;
    }
  }

  // Try finding a fallback font using a meta file.
  // TODO(msw|asvitkine): Support RenderText's font_list()?
  if (GetUniscribeFallbackFont(original_font, run_text, run_length,
                               &current_font)) {
    missing_count = CountCharsWithMissingGlyphs(run,
        ShapeTextRunWithFont(run, current_font));
    if (missing_count == 0) {
      successful_substitute_fonts_[original_font.GetFontName()] = current_font;
      return;
    }
    if (missing_count < best_partial_font_missing_char_count) {
      best_partial_font_missing_char_count = missing_count;
      best_partial_font = current_font;
    }
  }

  // Try fonts in the fallback list except the first, which is |original_font|.
  std::vector<std::string> fonts =
      GetFallbackFontFamilies(original_font.GetFontName());
  for (size_t i = 1; i < fonts.size(); ++i) {
    missing_count = CountCharsWithMissingGlyphs(run,
        ShapeTextRunWithFont(run, Font(fonts[i], original_font.GetFontSize())));
    if (missing_count == 0) {
      successful_substitute_fonts_[original_font.GetFontName()] = current_font;
      return;
    }
    if (missing_count < best_partial_font_missing_char_count) {
      best_partial_font_missing_char_count = missing_count;
      best_partial_font = current_font;
    }
  }

  // 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,
                                               HRESULT shaping_result) const {
  if (shaping_result != S_OK) {
    DCHECK_EQ(shaping_result, USP_E_SCRIPT_NOT_IN_FONT);
    return INT_MAX;
  }

  // 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
  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::CreateNativeInstance() {
  return new RenderTextWin;
}

}  // namespace gfx