[WIP: not for review] Reduce re-layout

ui/gfx/render_text.h

 // 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.
 
 #ifndef UI_GFX_RENDER_TEXT_H_
 #define UI_GFX_RENDER_TEXT_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 193 matching lines @@
  public:
   virtual ~RenderText();
 
   // Creates a platform-specific or cross-platform RenderText instance.
   static RenderText* CreateInstance();
   static RenderText* CreateInstanceForEditing();
 
   // Creates another instance of the same concrete class.
   virtual std::unique_ptr<RenderText> CreateInstanceOfSameType() const = 0;
 
+  // Like above but copies all style settings too.
+  std::unique_ptr<RenderText> CreateInstanceOfSameStyle(
+      const base::string16& text) const;
+
   const base::string16& text() const { return text_; }
   void SetText(const base::string16& text);
   void AppendText(const base::string16& text);
 
   HorizontalAlignment horizontal_alignment() const {
     return horizontal_alignment_;
   }
   void SetHorizontalAlignment(HorizontalAlignment alignment);
 
   const FontList& font_list() const { return font_list_; }
@@ skipping 35 matching lines @@
   // a UTF16 text index. If there is a previous revealed index, the previous one
   // is cleared and only the last set index will be revealed. If |index| is -1
   // or out of range, no char will be revealed. The revealed index is also
   // cleared when SetText or SetObscured is called.
   void SetObscuredRevealIndex(int index);
 
   // TODO(ckocagil): Multiline text rendering is not supported on Mac.
   bool multiline() const { return multiline_; }
   void SetMultiline(bool multiline);
 
+  // If multiline, a non-zero value will cap the number of lines rendered,
+  // and elide the rest (currently only ELIDE_TAIL supported.)
+  void SetMaxLines(size_t max_lines);
+  size_t max_lines() const { return max_lines_; }
+  size_t GetNumLines();
+
   // TODO(mukai): ELIDE_LONG_WORDS is not supported.
   WordWrapBehavior word_wrap_behavior() const { return word_wrap_behavior_; }
   void SetWordWrapBehavior(WordWrapBehavior behavior);
 
   // Set whether newline characters should be replaced with newline symbols.
   void SetReplaceNewlineCharsWithSymbols(bool replace);
 
   // Returns true if this instance supports multiline rendering.
   virtual bool MultilineSupported() const = 0;
 
@@ skipping 492 matching lines @@
   // True if the text is elided given the current behavior and display area.
   bool text_elided_;
 
   // The minimum height a line should have.
   int min_line_height_;
 
   // Whether the text should be broken into multiple lines. Uses the width of
   // |display_rect_| as the width cap.
   bool multiline_;
 
+  // If multiple lines, the maximum number of lines to render, or 0.
+  size_t max_lines_;
+
   // The wrap behavior when the text is broken into lines. Do nothing unless
   // |multiline_| is set. The default value is IGNORE_LONG_WORDS.
   WordWrapBehavior word_wrap_behavior_;
 
   // Whether newline characters should be replaced with newline symbols.
   bool replace_newline_chars_with_symbols_;
 
   // Set to true to suppress subpixel rendering due to non-font reasons (eg.
   // if the background is transparent). The default value is false.
   bool subpixel_rendering_suppressed_;
@@ skipping 29 matching lines @@
   // Lines computed by EnsureLayout. These should be invalidated upon
   // OnLayoutTextAttributeChanged and OnDisplayTextAttributeChanged calls.
   std::vector<internal::Line> lines_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderText);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_H_