Add gfx::RenderText and support code.

RenderText is NativeTextFieldViews' interface to platform-specific text rendering engines.

This change doesn't hook in any new Pango or Uniscribe functionality, it will just setup the necessary API.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=93840

Review URL: http://codereview.chromium.org/7265011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@93855 0039d316-1c4b-4281-b951-d872f2087c98

7 files changed, 1000 insertions, 0 deletions

diff --git a/ui/gfx/render_text.cc b/ui/gfx/render_text.cc
new file mode 100644
index 0000000..c656792
--- /dev/null
+++ b/ui/gfx/render_text.cc
@@ -0,0 +1,506 @@
+// Copyright (c) 2011 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.h"
+
+#include <algorithm>
+
+#include "base/i18n/break_iterator.h"
+#include "base/logging.h"
+#include "base/stl_util.h"
+#include "ui/gfx/canvas.h"
+#include "ui/gfx/canvas_skia.h"
+
+namespace {
+
+#ifndef NDEBUG
+// Check StyleRanges invariant conditions: sorted and non-overlapping ranges.
+void CheckStyleRanges(const gfx::StyleRanges& style_ranges, size_t length) {
+  if (length == 0) {
+    DCHECK(style_ranges.empty()) << "Style ranges exist for empty text.";
+    return;
+  }
+  for (gfx::StyleRanges::size_type i = 0; i < style_ranges.size() - 1; i++) {
+    const ui::Range& former = style_ranges[i].range;
+    const ui::Range& latter = style_ranges[i + 1].range;
+    DCHECK(!former.is_empty()) << "Empty range at " << i << ":" << former;
+    DCHECK(former.IsValid()) << "Invalid range at " << i << ":" << former;
+    DCHECK(!former.is_reversed()) << "Reversed range at " << i << ":" << former;
+    DCHECK(former.end() == latter.start()) << "Ranges gap/overlap/unsorted." <<
+        "former:" << former << ", latter:" << latter;
+  }
+  const gfx::StyleRange& end_style = *style_ranges.rbegin();
+  DCHECK(!end_style.range.is_empty()) << "Empty range at end.";
+  DCHECK(end_style.range.IsValid()) << "Invalid range at end.";
+  DCHECK(!end_style.range.is_reversed()) << "Reversed range at end.";
+  DCHECK(end_style.range.end() == length) << "Style and text length mismatch.";
+}
+#endif
+
+void ApplyStyleRangeImpl(gfx::StyleRanges& style_ranges,
+                         gfx::StyleRange style_range) {
+  const ui::Range& new_range = style_range.range;
+  // Follow StyleRanges invariant conditions: sorted and non-overlapping ranges.
+  gfx::StyleRanges::iterator i;
+  for (i = style_ranges.begin(); i != style_ranges.end();) {
+    if (i->range.end() < new_range.start()) {
+      i++;
+    } else if (i->range.start() == new_range.end()) {
+      break;
+    } else if (new_range.Contains(i->range)) {
+      i = style_ranges.erase(i);
+      if (i == style_ranges.end())
+        break;
+    } else if (i->range.start() < new_range.start() &&
+               i->range.end() > new_range.end()) {
+      // Split the current style into two styles.
+      gfx::StyleRange split_style = gfx::StyleRange(*i);
+      split_style.range.set_end(new_range.start());
+      i = style_ranges.insert(i, split_style) + 1;
+      i->range.set_start(new_range.end());
+      break;
+    } else if (i->range.start() < new_range.start()) {
+      i->range.set_end(new_range.start());
+      i++;
+    } else if (i->range.end() > new_range.end()) {
+      i->range.set_start(new_range.end());
+      break;
+    } else
+      NOTREACHED();
+  }
+  // Add the new range in its sorted location.
+  style_ranges.insert(i, style_range);
+}
+
+}  // namespace
+
+namespace gfx {
+
+StyleRange::StyleRange()
+    : font(),
+      foreground(SK_ColorBLACK),
+      strike(false),
+      underline(false),
+      range() {
+}
+
+void RenderText::SetText(const string16& text) {
+  size_t old_text_length = text_.length();
+  text_ = text;
+
+  // Update the style ranges as needed.
+  if (text_.empty()) {
+    style_ranges_.clear();
+  } else if (style_ranges_.empty()) {
+    ApplyDefaultStyle();
+  } else if (text_.length() > old_text_length) {
+    style_ranges_.back().range.set_end(text_.length());
+  } else if (text_.length() < old_text_length) {
+    StyleRanges::iterator i;
+    for (i = style_ranges_.begin(); i != style_ranges_.end(); i++) {
+      if (i->range.start() >= text_.length()) {
+        i = style_ranges_.erase(i);
+        if (i == style_ranges_.end())
+          break;
+      } else if (i->range.end() > text_.length()) {
+        i->range.set_end(text_.length());
+      }
+    }
+    style_ranges_.back().range.set_end(text_.length());
+  }
+#ifndef NDEBUG
+  CheckStyleRanges(style_ranges_, text_.length());
+#endif
+}
+
+size_t RenderText::GetCursorPosition() const {
+  return GetSelection().end();
+}
+
+void RenderText::SetCursorPosition(const size_t position) {
+  SetSelection(ui::Range(position, position));
+}
+
+void RenderText::MoveCursorLeft(BreakType break_type, bool select) {
+  if (break_type == LINE_BREAK) {
+    MoveCursorTo(0, select);
+    return;
+  }
+  size_t position = GetCursorPosition();
+  // Cancelling a selection moves to the edge of the selection.
+  if (!GetSelection().is_empty() && !select) {
+    // Use the selection start if it is left of the selection end.
+    if (GetCursorBounds(GetSelection().start(), false).x() <
+        GetCursorBounds(position, false).x())
+      position = GetSelection().start();
+    // If |move_by_word|, use the nearest word boundary left of the selection.
+    if (break_type == WORD_BREAK)
+      position = GetLeftCursorPosition(position, true);
+  } else {
+    position = GetLeftCursorPosition(position, break_type == WORD_BREAK);
+  }
+  MoveCursorTo(position, select);
+}
+
+void RenderText::MoveCursorRight(BreakType break_type, bool select) {
+  if (break_type == LINE_BREAK) {
+    MoveCursorTo(text().length(), select);
+    return;
+  }
+  size_t position = GetCursorPosition();
+  // Cancelling a selection moves to the edge of the selection.
+  if (!GetSelection().is_empty() && !select) {
+    // Use the selection start if it is right of the selection end.
+    if (GetCursorBounds(GetSelection().start(), false).x() >
+        GetCursorBounds(position, false).x())
+      position = GetSelection().start();
+    // If |move_by_word|, use the nearest word boundary right of the selection.
+    if (break_type == WORD_BREAK)
+      position = GetRightCursorPosition(position, true);
+  } else {
+    position = GetRightCursorPosition(position, break_type == WORD_BREAK);
+  }
+  MoveCursorTo(position, select);
+}
+
+bool RenderText::MoveCursorTo(size_t position, bool select) {
+  bool changed = GetCursorPosition() != position ||
+                 select == GetSelection().is_empty();
+  if (select)
+    SetSelection(ui::Range(GetSelection().start(), position));
+  else
+    SetSelection(ui::Range(position, position));
+  return changed;
+}
+
+bool RenderText::MoveCursorTo(const gfx::Point& point, bool select) {
+  // TODO(msw): Make this function support cursor placement via mouse near BiDi
+  //  level changes. The visual cursor appearance will depend on the location
+  //  clicked, not solely the resulting logical cursor position. See the TODO
+  //  note pertaining to selection_range_ for more information.
+  return MoveCursorTo(FindCursorPosition(point), select);
+}
+
+const ui::Range& RenderText::GetSelection() const {
+  return selection_range_;
+}
+
+void RenderText::SetSelection(const ui::Range& range) {
+  selection_range_.set_end(std::min(range.end(), text().length()));
+  selection_range_.set_start(std::min(range.start(), text().length()));
+
+  // Update |display_offset_| to ensure the current cursor is visible.
+  gfx::Rect cursor_bounds(GetCursorBounds(GetCursorPosition(), insert_mode()));
+  int display_width = display_rect_.width();
+  int string_width = GetStringWidth();
+  if (string_width < display_width) {
+    // Show all text whenever the text fits to the size.
+    display_offset_.set_x(0);
+  } else if ((display_offset_.x() + cursor_bounds.right()) > display_width) {
+    // Pan to show the cursor when it overflows to the right,
+     display_offset_.set_x(display_width - cursor_bounds.right());
+  } else if ((display_offset_.x() + cursor_bounds.x()) < 0) {
+    // Pan to show the cursor when it overflows to the left.
+    display_offset_.set_x(-cursor_bounds.x());
+  }
+}
+
+bool RenderText::IsPointInSelection(const gfx::Point& point) const {
+  size_t pos = FindCursorPosition(point);
+  return (pos >= GetSelection().GetMin() && pos < GetSelection().GetMax());
+}
+
+void RenderText::ClearSelection() {
+  SetCursorPosition(GetCursorPosition());
+}
+
+void RenderText::SelectAll() {
+  SetSelection(ui::Range(0, text().length()));
+}
+
+void RenderText::SelectWord() {
+  size_t selection_start = GetSelection().start();
+  size_t cursor_position = GetCursorPosition();
+  // First we setup selection_start_ and cursor_pos_. There are so many cases
+  // because we try to emulate what select-word looks like in a gtk textfield.
+  // See associated testcase for different cases.
+  if (cursor_position > 0 && cursor_position < text().length()) {
+    if (isalnum(text()[cursor_position])) {
+      selection_start = cursor_position;
+      cursor_position++;
+    } else
+      selection_start = cursor_position - 1;
+  } else if (cursor_position == 0) {
+    selection_start = cursor_position;
+    if (text().length() > 0)
+      cursor_position++;
+  } else {
+    selection_start = cursor_position - 1;
+  }
+
+  // Now we move selection_start_ to beginning of selection. Selection boundary
+  // is defined as the position where we have alpha-num character on one side
+  // and non-alpha-num char on the other side.
+  for (; selection_start > 0; selection_start--) {
+    if (IsPositionAtWordSelectionBoundary(selection_start))
+      break;
+  }
+
+  // Now we move cursor_pos_ to end of selection. Selection boundary
+  // is defined as the position where we have alpha-num character on one side
+  // and non-alpha-num char on the other side.
+  for (; cursor_position < text().length(); cursor_position++) {
+    if (IsPositionAtWordSelectionBoundary(cursor_position))
+      break;
+  }
+
+  SetSelection(ui::Range(selection_start, cursor_position));
+}
+
+const ui::Range& RenderText::GetCompositionRange() const {
+  return composition_range_;
+}
+
+void RenderText::SetCompositionRange(const ui::Range& composition_range) {
+  CHECK(!composition_range.IsValid() ||
+        ui::Range(0, text_.length()).Contains(composition_range));
+  composition_range_.set_end(composition_range.end());
+  composition_range_.set_start(composition_range.start());
+}
+
+void RenderText::ApplyStyleRange(StyleRange style_range) {
+  const ui::Range& new_range = style_range.range;
+  if (!new_range.IsValid() || new_range.is_empty())
+    return;
+  CHECK(!new_range.is_reversed());
+  CHECK(ui::Range(0, text_.length()).Contains(new_range));
+  ApplyStyleRangeImpl(style_ranges_, style_range);
+#ifndef NDEBUG
+  CheckStyleRanges(style_ranges_, text_.length());
+#endif
+}
+
+void RenderText::ApplyDefaultStyle() {
+  style_ranges_.clear();
+  StyleRange style = StyleRange(default_style_);
+  style.range.set_end(text_.length());
+  style_ranges_.push_back(style);
+}
+
+base::i18n::TextDirection RenderText::GetTextDirection() const {
+  // TODO(msw): Bidi implementation, intended to replace the functionality added
+  //  in crrev.com/91881 (discussed in codereview.chromium.org/7324011).
+  return base::i18n::LEFT_TO_RIGHT;
+}
+
+int RenderText::GetStringWidth() const {
+  return GetSubstringBounds(ui::Range(0, text_.length()))[0].width();
+}
+
+void RenderText::Draw(gfx::Canvas* canvas) {
+  // Clip the canvas to the text display area.
+  canvas->ClipRectInt(display_rect_.x(), display_rect_.y(),
+                      display_rect_.width(), display_rect_.height());
+
+  // Draw the selection.
+  std::vector<gfx::Rect> selection(GetSubstringBounds(GetSelection()));
+  SkColor selection_color =
+      focused() ? kFocusedSelectionColor : kUnfocusedSelectionColor;
+  for (std::vector<gfx::Rect>::const_iterator i = selection.begin();
+       i < selection.end(); ++i) {
+    gfx::Rect r(*i);
+    r.Offset(display_offset_);
+    canvas->FillRectInt(selection_color, r.x(), r.y(), r.width(), r.height());
+  }
+
+  // Create a temporary copy of the style ranges for composition and selection.
+  // TODO(msw): This pattern ought to be reconsidered; what about composition
+  //            and selection overlaps, retain existing local style features?
+  StyleRanges style_ranges(style_ranges_);
+  // Apply a composition style override to a copy of the style ranges.
+  if (composition_range_.IsValid() && !composition_range_.is_empty()) {
+    StyleRange composition_style(default_style_);
+    composition_style.underline = true;
+    composition_style.range.set_start(composition_range_.start());
+    composition_style.range.set_end(composition_range_.end());
+    ApplyStyleRangeImpl(style_ranges, composition_style);
+  }
+  // Apply a selection style override to a copy of the style ranges.
+  if (selection_range_.IsValid() && !selection_range_.is_empty()) {
+    StyleRange selection_style(default_style_);
+    selection_style.foreground = kSelectedTextColor;
+    selection_style.range.set_start(selection_range_.GetMin());
+    selection_style.range.set_end(selection_range_.GetMax());
+    ApplyStyleRangeImpl(style_ranges, selection_style);
+  }
+
+  // Draw the text.
+  gfx::Rect bounds(display_rect_);
+  bounds.Offset(display_offset_);
+  for (StyleRanges::const_iterator i = style_ranges.begin();
+       i < style_ranges.end(); ++i) {
+    Font font = !i->underline ? i->font :
+        i->font.DeriveFont(0, i->font.GetStyle() | Font::UNDERLINED);
+    string16 text = text_.substr(i->range.start(), i->range.length());
+    bounds.set_width(font.GetStringWidth(text));
+    canvas->DrawStringInt(text, font, i->foreground, bounds);
+
+    // Draw the strikethrough.
+    if (i->strike) {
+      SkPaint paint;
+      paint.setAntiAlias(true);
+      paint.setStyle(SkPaint::kFill_Style);
+      paint.setColor(i->foreground);
+      paint.setStrokeWidth(kStrikeWidth);
+      canvas->AsCanvasSkia()->drawLine(SkIntToScalar(bounds.x()),
+                                       SkIntToScalar(bounds.bottom()),
+                                       SkIntToScalar(bounds.right()),
+                                       SkIntToScalar(bounds.y()),
+                                       paint);
+    }
+
+    bounds.set_x(bounds.x() + bounds.width());
+  }
+
+  // Paint cursor. Replace cursor is drawn as rectangle for now.
+  if (cursor_visible() && focused()) {
+    bounds = GetCursorBounds(GetCursorPosition(), insert_mode());
+    bounds.Offset(display_offset_);
+    if (!bounds.IsEmpty())
+      canvas->DrawRectInt(kCursorColor,
+                          bounds.x(),
+                          bounds.y(),
+                          bounds.width(),
+                          bounds.height());
+  }
+}
+
+size_t RenderText::FindCursorPosition(const gfx::Point& point) const {
+  const gfx::Font& font = Font();
+  int left = 0;
+  int left_pos = 0;
+  int right = font.GetStringWidth(text());
+  int right_pos = text().length();
+
+  int x = point.x();
+  if (x <= left) return left_pos;
+  if (x >= right) return right_pos;
+  // binary searching the cursor position.
+  // TODO(oshima): use the center of character instead of edge.
+  // Binary search may not work for language like arabic.
+  while (std::abs(static_cast<long>(right_pos - left_pos) > 1)) {
+    int pivot_pos = left_pos + (right_pos - left_pos) / 2;
+    int pivot = font.GetStringWidth(text().substr(0, pivot_pos));
+    if (pivot < x) {
+      left = pivot;
+      left_pos = pivot_pos;
+    } else if (pivot == x) {
+      return pivot_pos;
+    } else {
+      right = pivot;
+      right_pos = pivot_pos;
+    }
+  }
+  return left_pos;
+}
+
+std::vector<gfx::Rect> RenderText::GetSubstringBounds(
+    const ui::Range& range) const {
+  size_t start = range.GetMin();
+  size_t end = range.GetMax();
+  gfx::Font font;
+  int start_x = font.GetStringWidth(text().substr(0, start));
+  int end_x = font.GetStringWidth(text().substr(0, end));
+  std::vector<gfx::Rect> bounds;
+  bounds.push_back(gfx::Rect(start_x, 0, end_x - start_x, font.GetHeight()));
+  return bounds;
+}
+
+gfx::Rect RenderText::GetCursorBounds(size_t cursor_pos,
+                                      bool insert_mode) const {
+  gfx::Font font;
+  int x = font.GetStringWidth(text_.substr(0U, cursor_pos));
+  DCHECK_GE(x, 0);
+  int h = std::min(display_rect_.height(), font.GetHeight());
+  gfx::Rect bounds(x, (display_rect_.height() - h) / 2, 1, h);
+  if (!insert_mode && text_.length() != cursor_pos)
+    bounds.set_width(font.GetStringWidth(text_.substr(0, cursor_pos + 1)) - x);
+  return bounds;
+}
+
+size_t RenderText::GetLeftCursorPosition(size_t position,
+                                         bool move_by_word) const {
+  if (!move_by_word)
+    return position == 0? position : position - 1;
+  // Notes: We always iterate words from the begining.
+  // 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.
+  base::i18n::BreakIterator iter(text(), base::i18n::BreakIterator::BREAK_WORD);
+  bool success = iter.Init();
+  DCHECK(success);
+  if (!success)
+    return position;
+  int last = 0;
+  while (iter.Advance()) {
+    if (iter.IsWord()) {
+      size_t begin = iter.pos() - iter.GetString().length();
+      if (begin == position) {
+        // The cursor is at the beginning of a word.
+        // Move to previous word.
+        break;
+      } else if(iter.pos() >= position) {
+        // The cursor is in the middle or at the end of a word.
+        // Move to the top of current word.
+        last = begin;
+        break;
+      } else {
+        last = iter.pos() - iter.GetString().length();
+      }
+    }
+  }
+
+  return last;
+}
+
+size_t RenderText::GetRightCursorPosition(size_t position,
+                                          bool move_by_word) const {
+  if (!move_by_word)
+    return std::min(position + 1, text().length());
+  base::i18n::BreakIterator iter(text(), base::i18n::BreakIterator::BREAK_WORD);
+  bool success = iter.Init();
+  DCHECK(success);
+  if (!success)
+    return position;
+  size_t pos = 0;
+  while (iter.Advance()) {
+    pos = iter.pos();
+    if (iter.IsWord() && pos > position) {
+      break;
+    }
+  }
+  return pos;
+}
+
+RenderText::RenderText()
+    : text_(),
+      selection_range_(),
+      cursor_visible_(false),
+      insert_mode_(true),
+      composition_range_(),
+      style_ranges_(),
+      default_style_(),
+      display_rect_(),
+      display_offset_() {
+}
+
+RenderText::~RenderText() {
+}
+
+bool RenderText::IsPositionAtWordSelectionBoundary(size_t pos) {
+  return pos == 0 || (isalnum(text()[pos - 1]) && !isalnum(text()[pos])) ||
+      (!isalnum(text()[pos - 1]) && isalnum(text()[pos]));
+}
+
+}  // namespace gfx
diff --git a/ui/gfx/render_text.h b/ui/gfx/render_text.h
new file mode 100644
index 0000000..e0cdc0b
--- /dev/null
+++ b/ui/gfx/render_text.h
@@ -0,0 +1,224 @@
+// Copyright (c) 2011 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.
+
+#ifndef UI_GFX_RENDER_TEXT_H_
+#define UI_GFX_RENDER_TEXT_H_
+#pragma once
+
+#include <vector>
+
+#include "base/gtest_prod_util.h"
+#include "base/i18n/rtl.h"
+#include "base/string16.h"
+#include "third_party/skia/include/core/SkColor.h"
+#include "ui/base/range/range.h"
+#include "ui/gfx/font.h"
+#include "ui/gfx/rect.h"
+#include "ui/gfx/point.h"
+
+namespace {
+
+// Strike line width.
+const int kStrikeWidth = 2;
+
+// Color settings for text, backgrounds and cursor.
+// These are tentative, and should be derived from theme, system
+// settings and current settings.
+// TODO(oshima): Change this to match the standard chrome
+// before dogfooding textfield views.
+const SkColor kSelectedTextColor = SK_ColorWHITE;
+const SkColor kFocusedSelectionColor = SK_ColorCYAN;
+const SkColor kUnfocusedSelectionColor = SK_ColorLTGRAY;
+const SkColor kCursorColor = SK_ColorBLACK;
+
+}  // namespace
+
+namespace gfx {
+
+class Canvas;
+class RenderTextTest;
+
+// A visual style applicable to a range of text.
+struct UI_API StyleRange {
+  StyleRange();
+
+  Font font;
+  SkColor foreground;
+  bool strike;
+  bool underline;
+  ui::Range range;
+};
+
+typedef std::vector<StyleRange> StyleRanges;
+
+// TODO(msw): Distinguish between logical character and glyph?
+enum BreakType {
+  CHARACTER_BREAK,
+  WORD_BREAK,
+  LINE_BREAK,
+};
+
+// TODO(msw): Implement RenderText[Win|Linux] for Uniscribe/Pango BiDi...
+
+// RenderText represents an abstract model of styled text and its corresponding
+// visual layout. Support is built in for a cursor, a selection, simple styling,
+// complex scripts, and bi-directional text. Implementations provide mechanisms
+// for rendering and translation between logical and visual data.
+class UI_API RenderText {
+
+ public:
+  virtual ~RenderText();
+
+  // Creates a platform-specific RenderText instance.
+  static RenderText* CreateRenderText();
+
+  const string16& text() const { return text_; }
+  virtual void SetText(const string16& text);
+
+  bool cursor_visible() const { return cursor_visible_; }
+  void set_cursor_visible(bool visible) { cursor_visible_ = visible; }
+
+  bool insert_mode() const { return insert_mode_; }
+  void toggle_insert_mode() { insert_mode_ = !insert_mode_; }
+
+  bool focused() const { return focused_; }
+  void set_focused(bool focused) { focused_ = focused; }
+
+  const StyleRange& default_style() const { return default_style_; }
+  void set_default_style(StyleRange style) { default_style_ = style; }
+
+  const gfx::Rect& display_rect() const { return display_rect_; }
+  void set_display_rect(const gfx::Rect& r) { display_rect_ = r; }
+
+  size_t GetCursorPosition() const;
+  void SetCursorPosition(const size_t position);
+
+  // Moves the cursor left or right. Cursor movement is visual, meaning that
+  // left and right are relative to screen, not the directionality of the text.
+  // If |select| is false, the selection range is emptied at the new position.
+  // If |break_type| is CHARACTER_BREAK, move to the neighboring character.
+  // If |break_type| is WORD_BREAK, move to the nearest word boundary.
+  // If |break_type| is LINE_BREAK, move to text edge as shown on screen.
+  void MoveCursorLeft(BreakType break_type, bool select);
+  void MoveCursorRight(BreakType break_type, bool select);
+
+  // Moves the cursor to the specified logical |position|.
+  // If |select| is false, the selection range is emptied at the new position.
+  // Returns true if the cursor position or selection range changed.
+  bool MoveCursorTo(size_t position, bool select);
+
+  // Move the cursor to the position associated with the clicked point.
+  // If |select| is false, the selection range is emptied at the new position.
+  bool MoveCursorTo(const gfx::Point& point, bool select);
+
+  const ui::Range& GetSelection() const;
+  void SetSelection(const ui::Range& range);
+
+  // Returns true if the local point is over selected text.
+  bool IsPointInSelection(const gfx::Point& point) const;
+
+  // Selects no text, all text, or the word at the current cursor position.
+  void ClearSelection();
+  void SelectAll();
+  void SelectWord();
+
+  const ui::Range& GetCompositionRange() const;
+  void SetCompositionRange(const ui::Range& composition_range);
+
+  // Apply |style_range| to the internal style model.
+  virtual void ApplyStyleRange(StyleRange style_range);
+
+  // Apply |default_style_| over the entire text range.
+  virtual void ApplyDefaultStyle();
+
+  base::i18n::TextDirection GetTextDirection() const;
+
+  // Get the width of the entire string.
+  int GetStringWidth() const;
+
+  virtual void Draw(gfx::Canvas* canvas);
+
+  // TODO(msw): Deprecate this function. Logical and visual cursors are not
+  //  mapped one-to-one. See the selection_range_ TODO for more information.
+  // Get the logical cursor position from a visual point in local coordinates.
+  virtual size_t FindCursorPosition(const gfx::Point& point) const;
+
+  // Get the visual bounds containing the logical substring within |range|.
+  // These bounds could be visually discontiguous if the logical selection range
+  // is split by an odd number of LTR/RTL level change.
+  virtual std::vector<gfx::Rect> GetSubstringBounds(
+      const ui::Range& range) const;
+
+  // Get the visual bounds describing the cursor at |position|. These bounds
+  // typically represent a vertical line, but if |insert_mode| is true they
+  // contain the bounds of the associated glyph.
+  virtual gfx::Rect GetCursorBounds(size_t position, bool insert_mode) const;
+
+ protected:
+  RenderText();
+
+  const StyleRanges& style_ranges() const { return style_ranges_; }
+
+  const gfx::Point& display_offset() const { return display_offset_; }
+
+  // Get the cursor position that visually neighbors |position|.
+  // If |move_by_word| is true, return the neighboring word delimiter position.
+  virtual size_t GetLeftCursorPosition(size_t position,
+                                       bool move_by_word) const;
+  virtual size_t GetRightCursorPosition(size_t position,
+                                        bool move_by_word) const;
+
+ private:
+  friend class RenderTextTest;
+
+  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, DefaultStyle);
+  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, CustomDefaultStyle);
+  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, ApplyStyleRange);
+  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, StyleRangesAdjust);
+
+  // Clear out |style_ranges_|.
+  void ClearStyleRanges();
+
+  bool IsPositionAtWordSelectionBoundary(size_t pos);
+
+  // Logical UTF-16 string data to be drawn.
+  string16 text_;
+
+  // TODO(msw): A single logical cursor position doesn't support two potential
+  //  visual cursor positions. For example, clicking right of 'c' & 'D' yeilds:
+  //  (visually: 'abc|FEDghi' and 'abcFED|ghi', both logically: 'abc|DEFghi').
+  //  Similarly, one visual position may have two associated logical positions.
+  //  For example, clicking the right side of 'D' and left side of 'g' yields:
+  //  (both visually: 'abcFED|ghi', logically: 'abc|DEFghi' and 'abcDEF|ghi').
+  //  Update the cursor model with a leading/trailing flag, a level association,
+  //  or a disjoint visual position to satisfy the proposed visual behavior.
+  // Logical selection range; the range end is also the logical cursor position.
+  ui::Range selection_range_;
+
+  // The cursor visibility and insert mode.
+  bool cursor_visible_;
+  bool insert_mode_;
+
+  // The focus state of the text.
+  bool focused_;
+
+  // Composition text range.
+  ui::Range composition_range_;
+
+  // List of style ranges. Elements in the list never overlap each other.
+  StyleRanges style_ranges_;
+  // The default text style.
+  StyleRange default_style_;
+
+  // The local display area for rendering the text.
+  gfx::Rect display_rect_;
+  // The offset for the text to be drawn, relative to the display area.
+  gfx::Point display_offset_;
+
+  DISALLOW_COPY_AND_ASSIGN(RenderText);
+};
+
+}  // namespace gfx
+
+#endif  // UI_GFX_RENDER_TEXT_H_
diff --git a/ui/gfx/render_text_linux.cc b/ui/gfx/render_text_linux.cc
new file mode 100644
index 0000000..21b3ac4
--- /dev/null
+++ b/ui/gfx/render_text_linux.cc
@@ -0,0 +1,20 @@
+// Copyright (c) 2011 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_linux.h"
+
+namespace gfx {
+
+RenderTextLinux::RenderTextLinux()
+    : RenderText() {
+}
+
+RenderTextLinux::~RenderTextLinux() {
+}
+
+RenderText* RenderText::CreateRenderText() {
+  return new RenderTextLinux;
+}
+
+}  // namespace gfx
diff --git a/ui/gfx/render_text_linux.h b/ui/gfx/render_text_linux.h
new file mode 100644
index 0000000..2709bea
--- /dev/null
+++ b/ui/gfx/render_text_linux.h
@@ -0,0 +1,25 @@
+// Copyright (c) 2011 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.
+
+#ifndef UI_GFX_RENDER_TEXT_LINUX_H_
+#define UI_GFX_RENDER_TEXT_LINUX_H_
+#pragma once
+
+#include "ui/gfx/render_text.h"
+
+namespace gfx {
+
+// RenderTextLinux is the Linux implementation of RenderText using Pango.
+class RenderTextLinux : public RenderText {
+ public:
+  RenderTextLinux();
+  virtual ~RenderTextLinux();
+
+private:
+  DISALLOW_COPY_AND_ASSIGN(RenderTextLinux);
+};
+
+}  // namespace gfx;
+
+#endif  // UI_GFX_RENDER_TEXT_LINUX_H_
diff --git a/ui/gfx/render_text_unittest.cc b/ui/gfx/render_text_unittest.cc
new file mode 100644
index 0000000..e809d41
--- /dev/null
+++ b/ui/gfx/render_text_unittest.cc
@@ -0,0 +1,180 @@
+// Copyright (c) 2011 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.h"
+
+#include "base/utf_string_conversions.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace gfx {
+
+class RenderTextTest : public testing::Test {
+};
+
+TEST_F(RenderTextTest, DefaultStyle) {
+  // Defaults to empty text with no styles.
+  gfx::RenderText* render_text = gfx::RenderText::CreateRenderText();
+  EXPECT_TRUE(render_text->text().empty());
+  EXPECT_TRUE(render_text->style_ranges().empty());
+
+  // Test that the built-in default style is applied for new text.
+  render_text->SetText(ASCIIToUTF16("abc"));
+  EXPECT_EQ(1U, render_text->style_ranges().size());
+  gfx::StyleRange style;
+  EXPECT_EQ(style.font.GetFontName(),
+            render_text->style_ranges()[0].font.GetFontName());
+  EXPECT_EQ(style.foreground, render_text->style_ranges()[0].foreground);
+  EXPECT_EQ(ui::Range(0, 3), render_text->style_ranges()[0].range);
+  EXPECT_EQ(style.strike, render_text->style_ranges()[0].strike);
+  EXPECT_EQ(style.underline, render_text->style_ranges()[0].underline);
+
+  // Test that clearing the text also clears the styles.
+  render_text->SetText(string16());
+  EXPECT_TRUE(render_text->text().empty());
+  EXPECT_TRUE(render_text->style_ranges().empty());
+}
+
+TEST_F(RenderTextTest, CustomDefaultStyle) {
+  // Test a custom default style.
+  gfx::RenderText* render_text = gfx::RenderText::CreateRenderText();
+  gfx::StyleRange color;
+  color.foreground = SK_ColorRED;
+  render_text->set_default_style(color);
+  render_text->SetText(ASCIIToUTF16("abc"));
+  EXPECT_EQ(1U, render_text->style_ranges().size());
+  EXPECT_EQ(color.foreground, render_text->style_ranges()[0].foreground);
+
+  // Test that the custom default style persists across clearing text.
+  render_text->SetText(string16());
+  EXPECT_TRUE(render_text->style_ranges().empty());
+  render_text->SetText(ASCIIToUTF16("abc"));
+  EXPECT_EQ(1U, render_text->style_ranges().size());
+  EXPECT_EQ(color.foreground, render_text->style_ranges()[0].foreground);
+
+  // Test ApplyDefaultStyle after setting a new default.
+  gfx::StyleRange strike;
+  strike.strike = true;
+  render_text->set_default_style(strike);
+  render_text->ApplyDefaultStyle();
+  EXPECT_EQ(1U, render_text->style_ranges().size());
+  EXPECT_EQ(true, render_text->style_ranges()[0].strike);
+  EXPECT_EQ(strike.foreground, render_text->style_ranges()[0].foreground);
+}
+
+TEST_F(RenderTextTest, ApplyStyleRange) {
+  gfx::RenderText* render_text = gfx::RenderText::CreateRenderText();
+  render_text->SetText(ASCIIToUTF16("01234"));
+  EXPECT_EQ(1U, render_text->style_ranges().size());
+
+  // Test ApplyStyleRange (no-op on empty range).
+  gfx::StyleRange empty;
+  empty.range = ui::Range(1, 1);
+  render_text->ApplyStyleRange(empty);
+  EXPECT_EQ(1U, render_text->style_ranges().size());
+
+  // Test ApplyStyleRange (no-op on invalid range).
+  gfx::StyleRange invalid;
+  invalid.range = ui::Range::InvalidRange();
+  render_text->ApplyStyleRange(invalid);
+  EXPECT_EQ(1U, render_text->style_ranges().size());
+
+  // Apply a style with a range contained by an existing range.
+  gfx::StyleRange underline;
+  underline.underline = true;
+  underline.range = ui::Range(2, 3);
+  render_text->ApplyStyleRange(underline);
+  EXPECT_EQ(3U, render_text->style_ranges().size());
+  EXPECT_EQ(ui::Range(0, 2), render_text->style_ranges()[0].range);
+  EXPECT_FALSE(render_text->style_ranges()[0].underline);
+  EXPECT_EQ(ui::Range(2, 3), render_text->style_ranges()[1].range);
+  EXPECT_TRUE(render_text->style_ranges()[1].underline);
+  EXPECT_EQ(ui::Range(3, 5), render_text->style_ranges()[2].range);
+  EXPECT_FALSE(render_text->style_ranges()[2].underline);
+
+  // Apply a style with a range equal to another range.
+  gfx::StyleRange color;
+  color.foreground = SK_ColorWHITE;
+  color.range = ui::Range(2, 3);
+  render_text->ApplyStyleRange(color);
+  EXPECT_EQ(3U, render_text->style_ranges().size());
+  EXPECT_EQ(ui::Range(0, 2), render_text->style_ranges()[0].range);
+  EXPECT_NE(SK_ColorWHITE, render_text->style_ranges()[0].foreground);
+  EXPECT_FALSE(render_text->style_ranges()[0].underline);
+  EXPECT_EQ(ui::Range(2, 3), render_text->style_ranges()[1].range);
+  EXPECT_EQ(SK_ColorWHITE, render_text->style_ranges()[1].foreground);
+  EXPECT_FALSE(render_text->style_ranges()[1].underline);
+  EXPECT_EQ(ui::Range(3, 5), render_text->style_ranges()[2].range);
+  EXPECT_NE(SK_ColorWHITE, render_text->style_ranges()[2].foreground);
+  EXPECT_FALSE(render_text->style_ranges()[2].underline);
+
+  // Apply a style with a range containing an existing range.
+  // This new style also overlaps portions of neighboring ranges.
+  gfx::StyleRange strike;
+  strike.strike = true;
+  strike.range = ui::Range(1, 4);
+  render_text->ApplyStyleRange(strike);
+  EXPECT_EQ(3U, render_text->style_ranges().size());
+  EXPECT_EQ(ui::Range(0, 1), render_text->style_ranges()[0].range);
+  EXPECT_FALSE(render_text->style_ranges()[0].strike);
+  EXPECT_EQ(ui::Range(1, 4), render_text->style_ranges()[1].range);
+  EXPECT_TRUE(render_text->style_ranges()[1].strike);
+  EXPECT_EQ(ui::Range(4, 5), render_text->style_ranges()[2].range);
+  EXPECT_FALSE(render_text->style_ranges()[2].strike);
+
+  // Apply a style overlapping all ranges.
+  gfx::StyleRange strike_underline;
+  strike_underline.strike = true;
+  strike_underline.underline = true;
+  strike_underline.range = ui::Range(0, render_text->text().length());
+  render_text->ApplyStyleRange(strike_underline);
+  EXPECT_EQ(1U, render_text->style_ranges().size());
+  EXPECT_EQ(ui::Range(0, 5), render_text->style_ranges()[0].range);
+  EXPECT_TRUE(render_text->style_ranges()[0].underline);
+  EXPECT_TRUE(render_text->style_ranges()[0].strike);
+
+  // Apply the default style.
+  render_text->ApplyDefaultStyle();
+  EXPECT_EQ(1U, render_text->style_ranges().size());
+  EXPECT_EQ(ui::Range(0, 5), render_text->style_ranges()[0].range);
+  EXPECT_FALSE(render_text->style_ranges()[0].underline);
+  EXPECT_FALSE(render_text->style_ranges()[0].strike);
+}
+
+TEST_F(RenderTextTest, StyleRangesAdjust) {
+  // Test that style ranges adjust to the text size.
+  gfx::RenderText* render_text = gfx::RenderText::CreateRenderText();
+  render_text->SetText(ASCIIToUTF16("abcdef"));
+  EXPECT_EQ(1U, render_text->style_ranges().size());
+  EXPECT_EQ(ui::Range(0, 6), render_text->style_ranges()[0].range);
+
+  // Test that the range is clipped to the length of shorter text.
+  render_text->SetText(ASCIIToUTF16("abc"));
+  EXPECT_EQ(1U, render_text->style_ranges().size());
+  EXPECT_EQ(ui::Range(0, 3), render_text->style_ranges()[0].range);
+
+  // Test that the last range extends to the length of longer text.
+  gfx::StyleRange strike;
+  strike.strike = true;
+  strike.range = ui::Range(2, 3);
+  render_text->ApplyStyleRange(strike);
+  render_text->SetText(ASCIIToUTF16("abcdefghi"));
+  EXPECT_EQ(2U, render_text->style_ranges().size());
+  EXPECT_EQ(ui::Range(0, 2), render_text->style_ranges()[0].range);
+  EXPECT_EQ(ui::Range(2, 9), render_text->style_ranges()[1].range);
+  EXPECT_TRUE(render_text->style_ranges()[1].strike);
+
+  // Test that ranges are removed if they're outside the range of shorter text.
+  render_text->SetText(ASCIIToUTF16("ab"));
+  EXPECT_EQ(1U, render_text->style_ranges().size());
+  EXPECT_EQ(ui::Range(0, 2), render_text->style_ranges()[0].range);
+  EXPECT_FALSE(render_text->style_ranges()[0].strike);
+
+  // Test that previously removed ranges don't return.
+  render_text->SetText(ASCIIToUTF16("abcdef"));
+  EXPECT_EQ(1U, render_text->style_ranges().size());
+  EXPECT_EQ(ui::Range(0, 6), render_text->style_ranges()[0].range);
+  EXPECT_FALSE(render_text->style_ranges()[0].strike);
+}
+
+}  // namespace gfx
diff --git a/ui/gfx/render_text_win.cc b/ui/gfx/render_text_win.cc
new file mode 100644
index 0000000..9f47946
--- /dev/null
+++ b/ui/gfx/render_text_win.cc
@@ -0,0 +1,20 @@
+// Copyright (c) 2011 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"
+
+namespace gfx {
+
+RenderTextWin::RenderTextWin()
+    : RenderText() {
+}
+
+RenderTextWin::~RenderTextWin() {
+}
+
+RenderText* RenderText::CreateRenderText() {
+  return new RenderTextWin;
+}
+
+}  // namespace gfx
diff --git a/ui/gfx/render_text_win.h b/ui/gfx/render_text_win.h
new file mode 100644
index 0000000..829888b
--- /dev/null
+++ b/ui/gfx/render_text_win.h
@@ -0,0 +1,25 @@
+// Copyright (c) 2011 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.
+
+#ifndef UI_GFX_RENDER_TEXT_WIN_H_
+#define UI_GFX_RENDER_TEXT_WIN_H_
+#pragma once
+
+#include "ui/gfx/render_text.h"
+
+namespace gfx {
+
+// RenderTextWin is the Windows implementation of RenderText using Uniscribe.
+class RenderTextWin : public RenderText {
+ public:
+  RenderTextWin();
+  virtual ~RenderTextWin();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(RenderTextWin);
+};
+
+}  // namespace gfx;
+
+#endif  // UI_GFX_RENDER_TEXT_WIN_H_