Implement Pango RenderText for Linux.

ui/gfx/render_text_linux.cc

 // 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"
 
+#include <pango/pangocairo.h>
+
+#include <algorithm>
+
+#include "base/logging.h"
+#include "ui/gfx/canvas_skia.h"
+#include "ui/gfx/pango_util.h"
+#include "unicode/uchar.h"
+#include "unicode/ustring.h"
+
+namespace {
+
+// TODO(xji): instead of converting each R or G or B from 8-bit to 16-bit,
+// it should also massage A in the conversion.
+int ConvertColorFrom8BitTo16Bit(int c) {
+  return (c << 8) + c;
+}
+
+}

[msw, 2011/08/29 20:38:05]

}  // namespace

[xji, 2011/08/30 00:39:41]

Done.

+
+// TODO(xji): index saved in upper layer is utf16 index. Pango uses utf8 index.
+// Since caret_pos is used internally, we could save utf8 index for caret_pos
+// to avoid conversion.
+
 namespace gfx {
 
 RenderTextLinux::RenderTextLinux()
-    : RenderText() {
+    : layout_(NULL),
+      layout_line_(NULL) {
 }
 
 RenderTextLinux::~RenderTextLinux() {
+  ResetLayout();
 }
 
 RenderText* RenderText::CreateRenderText() {
   return new RenderTextLinux;
 }
 
+void RenderTextLinux::SetText(const string16& text) {
+  RenderText::SetText(text);
+  ResetLayout();
+}
+
+void RenderTextLinux::SetDisplayRect(const Rect&r) {
+  RenderText::SetDisplayRect(r);
+  ResetLayout();
+}
+
+void RenderTextLinux::SetCompositionRange(const ui::Range& composition_range) {
+  RenderText::SetCompositionRange(composition_range);
+  ResetLayout();
+}
+
+void RenderTextLinux::ApplyStyleRange(StyleRange style_range) {
+  RenderText::ApplyStyleRange(style_range);
+  ResetLayout();
+}
+
+void RenderTextLinux::ApplyDefaultStyle() {
+  RenderText::ApplyDefaultStyle();
+  ResetLayout();
+}
+
+base::i18n::TextDirection RenderTextLinux::GetTextDirection() {
+  EnsureLayout();
+
+  const char* layout_text = pango_layout_get_text(layout_);
+  PangoDirection base_dir =
+        pango_find_base_dir(layout_text, strlen(layout_text));
+  if (base_dir == PANGO_DIRECTION_RTL || base_dir == PANGO_DIRECTION_WEAK_RTL)
+    return base::i18n::RIGHT_TO_LEFT;
+  return base::i18n::LEFT_TO_RIGHT;
+}
+
+int RenderTextLinux::GetStringWidth() {
+  PangoLayout* layout = EnsureLayout();
+  int width, height;
+  pango_layout_get_pixel_size(layout, &width, &height);
+  return width;
+}
+
+void RenderTextLinux::Draw(Canvas* canvas) {
+  PangoLayout* layout = EnsureLayout();
+  Rect bounds(display_rect());
+
+  // Clip the canvas to the text display area.
+  CanvasSkia* canvas_skia = canvas->AsCanvasSkia();
+  canvas_skia->ClipRectInt(
+      bounds.x(), bounds.y(), bounds.width(), bounds.height());
+
+  // TODO(xji): use ScopedPlatformPaint.

[msw, 2011/08/29 20:38:05]

You should be able to do:
skia::ScopedPlatformPaint scoped_platform_paint(canvas);
cairo_t* cr = scoped_platform_paint.GetPlatformSurface();

[xji, 2011/08/30 00:39:41]

Done.

+  cairo_t* cr = skia::BeginPlatformPaint(canvas_skia);
+  cairo_save(cr);
+  cairo_rectangle(cr, bounds.x(), bounds.y(), bounds.width(), bounds.height());
+  cairo_clip(cr);
+
+  int text_width, text_height;
+  pango_layout_get_pixel_size(layout, &text_width, &text_height);
+  Point offset(ToViewPoint(Point()));
+  // Vertically centered.
+  int text_y = offset.y() + ((bounds.height() - text_height) / 2);
+  cairo_move_to(cr, offset.x(), text_y);
+  pango_cairo_show_layout(cr, layout);

[msw, 2011/08/29 20:38:05]

We ought to check with a Pango/Skia expert to determine if this is okay, we
might need to tweak this for acceleration, etc.

[xji, 2011/08/30 00:39:41]

talked with Mike Reed, who said that "The only way to get gpu accelerated via
skia is to not draw through cairo, but only through SkCanvas". since chrome's UI
drawing in Linux all use pango directly, he said that "we need to get all of
chrome to try to use SkCanvas for all of their drawing."

[msw, 2011/08/30 01:17:07]

Ok, that's definitely outside the scope of this change.

+
+  // Destructor.
+  cairo_restore(cr);
+  skia::EndPlatformPaint(canvas_skia);
+
+  // Paint cursor.
+  bounds = GetUpdatedCursorBounds();
+  if (cursor_visible() && focused() && !bounds.IsEmpty()) {
+    if (!bounds.IsEmpty())
+       canvas->DrawRectInt(kCursorColor,

[msw, 2011/08/29 20:38:05]

outdent this line by one space.

[xji, 2011/08/30 00:39:41]

Done.

+                          bounds.x(),
+                          bounds.y(),
+                          bounds.width(),
+                          bounds.height());
+  }
+}
+
+SelectionModel RenderTextLinux::FindCursorPosition(const Point& point) {
+  // TODO(xji): when points outside of text, return HOME/END position.
+  PangoLayout* layout = EnsureLayout();
+
+  if (text().empty())
+    return SelectionModel(0, 0, SelectionModel::LEADING);
+
+  Point p(ToTextPoint(point));
+  int caret_pos, trailing;
+  pango_layout_xy_to_index(layout, p.x() * PANGO_SCALE, p.y() * PANGO_SCALE,
+                           &caret_pos, &trailing);
+
+  size_t selection_end = caret_pos;
+  if (trailing > 0) {
+    const char* pango_text = pango_layout_get_text(layout);
+    const char* ch = g_utf8_offset_to_pointer(pango_text + caret_pos, trailing);
+    DCHECK_GE(ch, pango_text);
+    DCHECK_LE(ch, pango_text + strlen(pango_text));
+    selection_end = ch - pango_text;
+  }
+
+  return SelectionModel(
+      Utf8IndexToUtf16Index(selection_end),
+      Utf8IndexToUtf16Index(caret_pos),
+      trailing > 0 ? SelectionModel::TRAILING : SelectionModel::LEADING);
+}
+
+Rect RenderTextLinux::GetCursorBounds(const SelectionModel& selection,
+                                      bool insert_mode) {
+  PangoLayout* layout = EnsureLayout();
+
+  size_t caret_pos = insert_mode ? selection.caret_pos() :
+                                   selection.selection_end();
+  PangoRectangle pos;
+  pango_layout_index_to_pos(layout, Utf16IndexToUtf8Index(caret_pos), &pos);
+
+  SelectionModel::CaretPlacement caret_placement = selection.caret_placement();
+  int x = pos.x;
+  if ((insert_mode && caret_placement == SelectionModel::TRAILING) ||
+      (!insert_mode && pos.width < 0))
+    x += pos.width;
+  x = x / PANGO_SCALE;
+
+  int h = std::min(display_rect().height(), pos.height / PANGO_SCALE);
+  Rect bounds(x, (display_rect().height() - h) / 2, 0, h);
+  bounds.set_origin(ToViewPoint(bounds.origin()));
+
+  if (!insert_mode)
+    bounds.set_width(std::abs(pos.width));
+
+  return bounds;
+}
+
+SelectionModel RenderTextLinux::GetLeftSelectionModel(
+    const SelectionModel& current,
+    BreakType break_type) {
+  EnsureLayout();
+
+  if (break_type == LINE_BREAK || text().empty())
+    return LeftEndSelectionModel();
+  if (break_type == CHARACTER_BREAK)
+    return LeftSelectionModel(current);
+  // TODO(xji): not implemented yet.
+  return RenderText::GetLeftSelectionModel(current, break_type);
+}
+
+SelectionModel RenderTextLinux::GetRightSelectionModel(
+    const SelectionModel& current,
+    BreakType break_type) {
+  EnsureLayout();
+
+  if (break_type == LINE_BREAK || text().empty())
+    return RightEndSelectionModel();
+  if (break_type == CHARACTER_BREAK)
+    return RightSelectionModel(current);
+  // TODO(xji): not implemented yet.
+  return RenderText::GetRightSelectionModel(current, break_type);
+}
+
+size_t RenderTextLinux::GetIndexOfPreviousGrapheme(size_t position) {
+  EnsureLayout();
+  return Utf16IndexOfAdjacentGrapheme(position, PREVIOUS);
+}
+
+SelectionModel RenderTextLinux::LeftEndSelectionModel() {
+  if (GetTextDirection() == base::i18n::RIGHT_TO_LEFT) {
+    GSList* first_visual_run = layout_line_->runs;
+    if (first_visual_run) {
+      PangoItem* item =
+          reinterpret_cast<PangoLayoutRun*>(first_visual_run->data)->item;
+      if (item->analysis.level % 2 == 0) {  // LTR.
+        size_t caret = Utf8IndexToUtf16Index(item->offset);
+        return SelectionModel(text().length(), caret, SelectionModel::LEADING);

[msw, 2011/08/29 20:38:05]

Why do you set the cursor to text().length() here?
Shouldn't it also be at the position corresponding to item->offset?

[xji, 2011/08/30 00:39:41]

pango's text direction is determined by its first strong directionality
character's direction. In this case, the text begins with a RTL character and
ends in LTR character.
such as "ABCdef" visually display as "defCBA". 
In RTL context, the left end is logical END. and the cursor should be
text().length(). (it is the same as you set cursor as text().length() when
base::i18n::isRTL()).

In this case, it should be equivalent to the utf16 index of (item->offset +
item->length). but using text().length() directly is clear and saves one
conversion.

[msw, 2011/08/30 01:17:07]

Ah, you're right. Sorry, this behavior can just be a little confusing at times.
So when the user winds up at LeftEndSelectionModel, they see "|defCBA" with the
logical cursor at "ABCdef|". Then typing 'G' makes sense, yielding "|GdefCBA".
And typing 'g' sorta makes sense, making the caret jump and yielding "defg|CBA".

[xji, 2011/08/30 04:39:39]

Yes. that is right.

+      } else {  // RTL.
+        // TODO(xji): Utf8IndexToUtf16Index conversion should be able to avoid.
+        size_t caret = Utf8IndexToUtf16Index(item->offset + item->length);
+        caret = Utf16IndexOfAdjacentGrapheme(caret, PREVIOUS);
+        return SelectionModel(text().length(), caret, SelectionModel::TRAILING);

[msw, 2011/08/29 20:38:05]

Shouldn't this cursor be at position corresponding to item->offset +
item->length?

[xji, 2011/08/30 00:39:41]

same reason as above. in RTL context, Left end is logical end, cursor should be
text.length. equivalent to (item->offset + item->length())'s utf16 conversion.
but I think text().length() is clearer.

+      }
+    }
+  }
+  return SelectionModel(0, 0, SelectionModel::LEADING);
+}
+
+SelectionModel RenderTextLinux::RightEndSelectionModel() {
+  if (GetTextDirection() == base::i18n::LEFT_TO_RIGHT) {
+    GSList* last_visual_run = GetLastRun();
+    if (last_visual_run) {
+      PangoItem* item =
+          reinterpret_cast<PangoLayoutRun*>(last_visual_run->data)->item;
+      if (item->analysis.level % 2 == 0) {  // LTR.
+        // TODO(xji): Utf8IndexToUtf16Index conversion should be able to avoid.
+        size_t caret = Utf8IndexToUtf16Index(item->offset + item->length);
+        caret = Utf16IndexOfAdjacentGrapheme(caret, PREVIOUS);
+        return SelectionModel(text().length(), caret, SelectionModel::TRAILING);

[msw, 2011/08/29 20:38:05]

Shouldn't this cursor be at item->offset + item->length?

[xji, 2011/08/30 00:39:41]

ditto.
in LTR context, right end is logical end, cursor should be text().length().
equivalent to (item->offset + item->length).
but text().length() is clearer.

+      } else {  // RTL.
+        size_t caret = Utf8IndexToUtf16Index(item->offset);
+        return SelectionModel(text().length(), caret, SelectionModel::LEADING);

[msw, 2011/08/29 20:38:05]

shouldn't this cursor be at item->offset?

[xji, 2011/08/30 00:39:41]

ditto.
in LTR context, right end is logical end, cursor should be text().length().
equivalent to (item->offset + item->length).

+      }
+    }
+  }
+  return SelectionModel(0, 0, SelectionModel::LEADING);
+}
+
+GSList* RenderTextLinux::GetRunContainingPosition(size_t position) const {
+  GSList* run = layout_line_->runs;
+  while (run) {
+    PangoItem* box = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
+    size_t run_start = Utf8IndexToUtf16Index(box->offset);
+    size_t run_end = Utf8IndexToUtf16Index(box->offset + box->length);
+
+    if (position >= run_start && position < run_end)
+      return run;
+    run = run->next;
+  }
+  return NULL;
+}
+
+size_t RenderTextLinux::Utf8IndexOfAdjacentGrapheme(
+    size_t utf16_index_of_current_grapheme,
+    RelativeLogicalPosition pos) const {

[msw, 2011/08/29 20:38:05]

I implemented a similar function:
size_t IndexOfAdjacentGrapheme(size_t index, bool next) const;
We'll devise a common signature as we consolidate code.

+  PangoLogAttr* log_attrs;
+  gint n_attrs;
+  pango_layout_get_log_attrs(layout_, &log_attrs, &n_attrs);
+
+  const char* layout_text = pango_layout_get_text(layout_);
+  const char* ch = layout_text +
+      Utf16IndexToUtf8Index(utf16_index_of_current_grapheme);
+  int char_offset = static_cast<int>(g_utf8_pointer_to_offset(layout_text, ch));
+
+  if (pos == PREVIOUS) {
+    if (ch > layout_text) {
+      do {
+        ch = g_utf8_find_prev_char(layout_text, ch);
+        --char_offset;
+      } while (ch && *ch && !log_attrs[char_offset].is_cursor_position);
+      if (!ch)
+        ch = layout_text;
+    }
+  } else {
+    if (ch < layout_text + strlen(layout_text)) {
+      do {
+        ch = g_utf8_find_next_char(ch, NULL);
+        ++char_offset;
+      } while (ch && *ch && !log_attrs[char_offset].is_cursor_position);
+      if (!ch || ch >= layout_text + strlen(layout_text))
+        ch = layout_text + strlen(layout_text);
+    }
+  }
+
+  size_t utf8_index = static_cast<size_t>(ch - layout_text);
+  g_free(log_attrs);
+  return utf8_index;
+}
+
+size_t RenderTextLinux::Utf16IndexOfAdjacentGrapheme(
+    size_t utf16_index_of_current_grapheme,
+    RelativeLogicalPosition pos) const {
+  size_t utf8_index = Utf8IndexOfAdjacentGrapheme(
+      utf16_index_of_current_grapheme, pos);
+  return Utf8IndexToUtf16Index(utf8_index);
+}
+
+SelectionModel RenderTextLinux::FirstSelectionModelInsideRun(
+    const PangoItem* run) const {
+  // TODO(xji): Utf8IndexToUtf16Index conversion should be able to avoid.
+  size_t caret = Utf8IndexToUtf16Index(run->offset);
+  size_t cursor = Utf16IndexOfAdjacentGrapheme(caret, NEXT);
+  return SelectionModel(cursor, caret, SelectionModel::TRAILING);
+}
+
+SelectionModel RenderTextLinux::LastSelectionModelInsideRun(
+    const PangoItem* run) const {
+  // TODO(xji): Utf8IndexToUtf16Index conversion should be able to avoid.
+  size_t caret = Utf8IndexToUtf16Index(run->offset + run->length);
+  caret = Utf16IndexOfAdjacentGrapheme(caret, PREVIOUS);
+  return SelectionModel(caret, caret, SelectionModel::LEADING);
+}
+
+// Assume caret_pos in |current| is n, 'l' represents leading in
+// caret_placement and 't' represents trailing in caret_placement. Following
+// is the calculation from (caret_pos, caret_placement) in |current| to
+// (selection_end, caret_pos, caret_placement) when moving cursor left by
+// one grapheme (for simplicity, assume each grapheme is one character).
+// If n is in LTR run,
+// (n, t) ---> (n, n, l).
+// (n, l) ---> (n-1, n-1, l) if n is inside run (not at boundary).
+// (n, l) ---> goto across run case if n is at run boundary.
+// If n is in RTL run,
+// (n, l) --> (n+1, n, t).
+// (n, t) --> (n+2, n+1, t) if n is inside run.
+// (n, t) --> goto across run case if n is at run boundary.
+// If n is at run boundary, get its visually left run,
+// If left run is LTR run,
+// (n, t) --> (left run's end, left run's end, l).
+// If left run is RTL run,
+// (n, t) --> (left run's begin + 1, left run's begin, t).
+SelectionModel RenderTextLinux::LeftSelectionModel(
+    const SelectionModel& selection) {
+  size_t caret = selection.caret_pos();
+  SelectionModel::CaretPlacement caret_placement = selection.caret_placement();
+  GSList* run = GetRunContainingPosition(caret);
+  DCHECK(run);
+
+  PangoItem* box = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
+  size_t run_start = Utf8IndexToUtf16Index(box->offset);
+  size_t run_end = Utf8IndexToUtf16Index(box->offset + box->length);
+
+  if (box->analysis.level % 2 == 0) {  // LTR run.
+    if (caret_placement == SelectionModel::TRAILING)
+      return SelectionModel(caret, caret, SelectionModel::LEADING);
+    else if (caret > run_start) {
+      caret = Utf16IndexOfAdjacentGrapheme(caret, PREVIOUS);
+      return SelectionModel(caret, caret, SelectionModel::LEADING);
+    }
+  } else {  // RTL run.
+    if (caret_placement == SelectionModel::LEADING) {
+      size_t cursor = Utf16IndexOfAdjacentGrapheme(caret, NEXT);
+      return SelectionModel(cursor, caret, SelectionModel::TRAILING);
+    } else if (selection.selection_end() < run_end) {
+      caret = Utf16IndexOfAdjacentGrapheme(caret, NEXT);
+      size_t cursor = Utf16IndexOfAdjacentGrapheme(caret, NEXT);
+      return SelectionModel(cursor, caret, SelectionModel::TRAILING);
+    }
+  }
+
+  // The character is at the begin of its run; advance to the previous visual
+  // run.
+  GSList* prev_run = GetPreviousRun(run);
+  if (!prev_run)  // TODO(xji): check whether this is expected.

[msw, 2011/08/29 20:38:05]

If the caret is at the beginning of the first run, this will be hit. I think it
is doing the correct thing even with RTL UI and/or text.

[xji, 2011/08/30 00:39:41]

Given an example, logical text "ABCdef", visually "defCBA".
when click left of 'd', selection model is (3, 3, leading).

The question is what happen when arrow-left.
should the selection model remain unchanged, it should it change to left-end as
(6, 3, leading).

I do not seem to get relies from our native speakers after I send out the
question. That is why the TODO.

+    return LeftEndSelectionModel();
+
+  box = reinterpret_cast<PangoLayoutRun*>(prev_run->data)->item;
+  return (box->analysis.level % 2) ? FirstSelectionModelInsideRun(box) :
+                                     LastSelectionModelInsideRun(box);
+}
+
+// Assume caret_pos in |current| is n, 'l' represents leading in
+// caret_placement and 't' represents trailing in caret_placement. Following
+// is the calculation from (caret_pos, caret_placement) in |current| to
+// (selection_end, caret_pos, caret_placement) when moving cursor right by
+// one grapheme (for simplicity, assume each grapheme is one character).
+// If n is in LTR run,
+// (n, l) ---> (n+1, n, t).
+// (n, t) ---> (n+2, n+1, t) if n is inside run (not at boundary).
+// (n, t) ---> goto across run case if n is at run boundary.
+// If n is in RTL run,
+// (n, t) --> (n, n, l).
+// (n, l) --> (n-1, n-1, l) if n is inside run.
+// (n, l) --> goto across run case if n is at run boundary.
+// If n is at run boundary, get its visually right run,
+// If right run is LTR run,
+// (n, t) --> (right run's begin + 1, right run's begin, t).
+// If right run is RTL run,
+// (n, t) --> (right run's end, right run's end, l).
+SelectionModel RenderTextLinux::RightSelectionModel(
+    const SelectionModel& selection) {
+  size_t caret = selection.caret_pos();
+  SelectionModel::CaretPlacement caret_placement = selection.caret_placement();
+  GSList* run = GetRunContainingPosition(caret);
+  DCHECK(run);
+
+  PangoItem* box = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
+  size_t run_start = Utf8IndexToUtf16Index(box->offset);
+  size_t run_end = Utf8IndexToUtf16Index(box->offset + box->length);
+
+  if (box->analysis.level % 2 == 0) {  // LTR run.
+    if (caret_placement == SelectionModel::LEADING) {
+      size_t cursor = Utf16IndexOfAdjacentGrapheme(caret, NEXT);
+      return SelectionModel(cursor, caret, SelectionModel::TRAILING);
+    } else if (selection.selection_end() < run_end) {
+      caret = Utf16IndexOfAdjacentGrapheme(caret, NEXT);
+      size_t cursor = Utf16IndexOfAdjacentGrapheme(caret, NEXT);
+      return SelectionModel(cursor, caret, SelectionModel::TRAILING);
+    }
+  } else {  // RTL run.
+    if (caret_placement == SelectionModel::TRAILING)
+      return SelectionModel(caret, caret, SelectionModel::LEADING);
+    else if (caret > run_start) {
+      caret = Utf16IndexOfAdjacentGrapheme(caret, PREVIOUS);
+      return SelectionModel(caret, caret, SelectionModel::LEADING);
+    }
+  }
+
+  // The character is at the end of its run; advance to the next visual run.
+  GSList* next_run = run->next;
+  if (!next_run)  // TODO(xji): what is the expected behavior?

[msw, 2011/08/29 20:38:05]

If the caret happens to be greater than or equal to text().length() (which we
currently consider out-of-bounds and try to prevent), then this will move it
within bounds on the right side, which seems reasonable.

[xji, 2011/08/30 00:39:41]

ditto as above reason.
consider case "abcDEF" visually as "abcFED", 
when click right of 'D', then click right arrow, what should be expected?
specifically the logical position (selection_end)?

+    return RightEndSelectionModel();
+
+  box = reinterpret_cast<PangoLayoutRun*>(next_run->data)->item;
+  return (box->analysis.level % 2) ? LastSelectionModelInsideRun(box) :
+                                     FirstSelectionModelInsideRun(box);
+}
+
+PangoLayout* RenderTextLinux::EnsureLayout() {
+  if (layout_ == NULL) {
+    CanvasSkia canvas(display_rect().width(), display_rect().height(), false);
+    // TODO(xji): can use ScopedPlatformPaint ?

[msw, 2011/08/29 20:38:05]

You should be able to do:
skia::ScopedPlatformPaint scoped_platform_paint(canvas);
cairo_t* cr = scoped_platform_paint.GetPlatformSurface();

[xji, 2011/08/30 00:39:41]

Done.

+    cairo_t* cr = skia::BeginPlatformPaint(&canvas);
+
+    layout_ = pango_cairo_create_layout(cr);
+    SetupPangoLayout(
+        layout_,
+        text(),
+        default_style().font,
+        display_rect().width(),
+        base::i18n::GetFirstStrongCharacterDirection(text()),
+        CanvasSkia::DefaultCanvasTextAlignment());
+
+    pango_layout_set_height(layout_, display_rect().height() * PANGO_SCALE);
+    SetupPangoAttributes(layout_);
+
+    skia::EndPlatformPaint(&canvas);
+
+    layout_line_ = pango_layout_get_line_readonly(layout_, 0);
+    pango_layout_line_ref(layout_line_);
+  }
+  return layout_;
+}
+
+void RenderTextLinux::ResetLayout() {
+  // set_cached_bounds_and_offset_valid(false) is done in RenderText for every
+  // operation that trigger ResetLayout().

[msw, 2011/08/29 20:38:05]

trigger*s*, and we should probably add some common layout invalidation API as we
begin to consolidate Win and Linux.

[xji, 2011/08/30 00:39:41]

Done. agree on the consolidation part.

+  if (layout_) {
+    g_object_unref(layout_);
+    layout_ = NULL;
+  }
+  if (layout_line_) {
+    pango_layout_line_unref(layout_line_);
+    layout_line_ = NULL;
+  }
+}
+
+void RenderTextLinux::SetupPangoAttributes(PangoLayout* layout) {
+  PangoAttrList* attrs = pango_attr_list_new();
+  // Set selection background color.
+  SkColor selection_color =
+      focused() ? kFocusedSelectionColor : kUnfocusedSelectionColor;
+  size_t start = std::min(MinOfSelection(), text().length());
+  size_t end = std::min(MaxOfSelection(), text().length());
+  PangoAttribute* pango_attr;
+  if (end > start) {
+    pango_attr = pango_attr_background_new(
+        ConvertColorFrom8BitTo16Bit(SkColorGetR(selection_color)),
+        ConvertColorFrom8BitTo16Bit(SkColorGetG(selection_color)),
+        ConvertColorFrom8BitTo16Bit(SkColorGetB(selection_color)));
+    AppendPangoAttribute(start, end, pango_attr, attrs);
+  }
+
+  StyleRanges ranges_of_style(style_ranges());
+  ApplyCompositionAndSelectionStyles(&ranges_of_style);
+
+  for (StyleRanges::const_iterator i = ranges_of_style.begin();
+       i < ranges_of_style.end(); ++i) {
+    start = std::min(i->range.start(), text().length());
+    end = std::min(i->range.end(), text().length());
+    if (start >= end)
+      continue;
+
+    const Font& font = !i->underline ? i->font :
+        i->font.DeriveFont(0, i->font.GetStyle() | Font::UNDERLINED);
+    PangoFontDescription* desc = font.GetNativeFont();
+    pango_attr = pango_attr_font_desc_new(desc);
+    AppendPangoAttribute(start, end, pango_attr, attrs);
+    pango_font_description_free(desc);
+
+    SkColor foreground = i->foreground;
+    pango_attr = pango_attr_foreground_new(
+        ConvertColorFrom8BitTo16Bit(SkColorGetR(foreground)),
+        ConvertColorFrom8BitTo16Bit(SkColorGetG(foreground)),
+        ConvertColorFrom8BitTo16Bit(SkColorGetB(foreground)));
+    AppendPangoAttribute(start, end, pango_attr, attrs);
+
+    if (i->strike) {
+      pango_attr = pango_attr_strikethrough_new(true);
+      AppendPangoAttribute(start, end, pango_attr, attrs);
+    }
+  }
+
+  pango_layout_set_attributes(layout, attrs);
+  pango_attr_list_unref(attrs);
+}
+
+void RenderTextLinux::AppendPangoAttribute(size_t start,
+                                           size_t end,
+                                           PangoAttribute* pango_attr,
+                                           PangoAttrList* attrs) {
+  pango_attr->start_index = Utf16IndexToUtf8Index(start);

[msw, 2011/08/29 20:38:05]

This function is private, and all the callers check their start and end input
values, so you can probably either eliminate the external checks and also check
start in here (my recommendation), or eliminate the end check in this function.

[xji, 2011/08/30 00:39:41]

I am removing the 'end' check here.
it should check in external calls. in case start >= end, no pango attribute will
be created which eliminates memory leak and time cost.

+  size_t e = std::min(end, text().length());
+  pango_attr->end_index = Utf16IndexToUtf8Index(e);
+  pango_attr_list_insert(attrs, pango_attr);
+}
+
+GSList* RenderTextLinux::GetPreviousRun(GSList* run) const {
+  GSList* current = layout_line_->runs;
+  GSList* prev = NULL;
+  while (current) {
+    if (current == run)
+      return prev;
+    prev = current;
+    current = current->next;
+  }
+  return NULL;
+}
+
+GSList* RenderTextLinux::GetLastRun() const {
+  GSList* current = layout_line_->runs;
+  while (current && current->next) {
+    current = current->next;
+  }
+  return current;
+}
+
+size_t RenderTextLinux::Utf16IndexToUtf8Index(size_t index) const {
+  int32_t utf8_index = 0;
+  UErrorCode ec = U_ZERO_ERROR;
+  u_strToUTF8(NULL, 0, &utf8_index, text().data(), index, &ec);
+  // Even given a destination buffer as NULL and destination capacity as 0,
+  // if the output length is equal to or greater than the capacity, then the
+  // UErrorCode is set to U_STRING_NOT_TERMINATED_WARNING or
+  // U_BUFFER_OVERFLOW_ERROR respectively.
+  // Please refer to
+  // http://userguide.icu-project.org/strings#TOC-Using-C-Strings:-NUL-Terminated-vs
+  // for detail (search for "Note that" below "Preflighting").
+  DCHECK(ec == U_BUFFER_OVERFLOW_ERROR ||
+         ec == U_STRING_NOT_TERMINATED_WARNING);
+  return utf8_index;
+}
+
+size_t RenderTextLinux::Utf8IndexToUtf16Index(size_t index) const {
+  int32_t utf16_index = 0;
+  UErrorCode ec = U_ZERO_ERROR;
+  const char* layout_text = pango_layout_get_text(layout_);
+  u_strFromUTF8(NULL, 0, &utf16_index, layout_text, index, &ec);
+  DCHECK(ec == U_BUFFER_OVERFLOW_ERROR ||
+         ec == U_STRING_NOT_TERMINATED_WARNING);
+  return utf16_index;
+}
+
 }  // namespace gfx