[AiS] for desktop, two lines and font sytles

ui/gfx/render_text.cc

 // 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.h"
 
 #include <algorithm>
 #include <climits>
 
 #include "base/command_line.h"
@@ skipping 427 matching lines @@
 
 // static
 RenderText* RenderText::CreateInstanceForEditing() {
   return new RenderTextHarfBuzz;
 }
 
 void RenderText::SetText(const base::string16& text) {
   DCHECK(!composition_range_.IsValid());
   if (text_ == text)
     return;
-  text_ = text;
+  text_.clear();
+  DoAppendText(text);
 
-  // Adjust ranged styles, baselines, and colors to accommodate a new text
-  // length. Clear style ranges as they might break new text graphemes and apply
+  // Clear style ranges as they might break new text graphemes and apply
   // the first style to the whole text instead.
-  const size_t text_length = text_.length();
-  colors_.SetMax(text_length);
+  colors_.SetValue(colors_.breaks().begin()->second);
   baselines_.SetValue(baselines_.breaks().begin()->second);
-  baselines_.SetMax(text_length);
-  for (size_t style = 0; style < NUM_TEXT_STYLES; ++style) {
-    BreakList<bool>& break_list = styles_[style];
-    break_list.SetValue(break_list.breaks().begin()->second);
-    break_list.SetMax(text_length);
-  }
-  cached_bounds_and_offset_valid_ = false;
+  for (size_t style = 0; style < NUM_TEXT_STYLES; ++style)
+    styles_[style].SetValue(styles_[style].breaks().begin()->second);
 
   // Reset selection model. SetText should always followed by SetSelectionModel
   // or SetCursorPosition in upper layer.
   SetSelectionModel(SelectionModel());
 
   // Invalidate the cached text direction if it depends on the text contents.
   if (directionality_mode_ == DIRECTIONALITY_FROM_TEXT)
     text_direction_ = base::i18n::UNKNOWN_DIRECTION;
 
-  obscured_reveal_index_ = -1;
   OnTextAttributeChanged();
 }
 
+void RenderText::AppendText(const base::string16& text) {
+  DoAppendText(text);
+  OnTextAttributeChanged();
+}
+
 void RenderText::SetHorizontalAlignment(HorizontalAlignment alignment) {
   if (horizontal_alignment_ != alignment) {
     horizontal_alignment_ = alignment;
     display_offset_ = Vector2d();
     cached_bounds_and_offset_valid_ = false;
   }
 }
 
 void RenderText::SetFontList(const FontList& font_list) {
   font_list_ = font_list;
@@ skipping 748 matching lines @@
 size_t RenderText::TextIndexToGivenTextIndex(const base::string16& given_text,
                                              size_t index) {
   DCHECK(given_text == layout_text() || given_text == display_text());
   DCHECK_LE(index, text().length());
   ptrdiff_t i = obscured() ? UTF16IndexToOffset(text(), 0, index) : index;
   CHECK_GE(i, 0);
   // Clamp indices to the length of the given layout or display text.
   return std::min<size_t>(given_text.length(), i);
 }
 
+void RenderText::DoAppendText(const base::string16& text) {
+  text_ += text;
+  // Adjust ranged styles and colors to accommodate a new text length.
+  const size_t text_length = text_.length();
+  colors_.SetMax(text_length);
+  baselines_.SetMax(text_length);
+  for (size_t style = 0; style < NUM_TEXT_STYLES; ++style)
+    styles_[style].SetMax(text_length);
+  cached_bounds_and_offset_valid_ = false;

[msw, 2015/03/18 20:20:16]

Sorry, I changed my mind here a bit. I think it'd be more appropriate if this
function limited its behavior to just extending the breaklists, and call it
something like "UpdateStyleLengths". The callers should either assign or append
to |text_|, set |cached_bounds_and_offset_valid_| and |obscured_reveal_index_|,
and call OnTextAttributeChanged()... Otherwise, I fear that this function might
be misconstrued as a sufficient and self-contained mechanism to extend the text
content and leave the RenderText in a good state; it isn't.

+  obscured_reveal_index_ = -1;
+}
+
 // static
 bool RenderText::RangeContainsCaret(const Range& range,
                                     size_t caret_pos,
                                     LogicalCursorDirection caret_affinity) {
   // NB: exploits unsigned wraparound (WG14/N1124 section 6.2.5 paragraph 9).
   size_t adjacent = (caret_affinity == CURSOR_BACKWARD) ?
       caret_pos - 1 : caret_pos + 1;
   return range.Contains(Range(caret_pos, adjacent));
 }
 
@@ skipping 242 matching lines @@
 
   SetDisplayOffset(display_offset_.x() + delta_x);
 }
 
 void RenderText::DrawSelection(Canvas* canvas) {
   for (const Rect& s : GetSubstringBounds(selection()))
     canvas->FillRect(s, selection_background_focused_color_);
 }
 
 }  // namespace gfx