Cache gfx::RenderText instances in views::Label.

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 <algorithm>
 #include <cstring>
 #include <string>
@@ skipping 34 matching lines @@
 namespace internal {
 
 // Internal helper class used by derived classes to draw text through Skia.
 class SkiaTextRenderer {
  public:
   explicit SkiaTextRenderer(Canvas* canvas);
   ~SkiaTextRenderer();
 
   void SetDrawLooper(SkDrawLooper* draw_looper);
   void SetFontRenderParams(const FontRenderParams& params,
-                           bool background_is_transparent);
+                           bool subpixel_rendering_enabled);
   void SetTypeface(SkTypeface* typeface);
   void SetTextSize(SkScalar size);
   void SetFontFamilyWithStyle(const std::string& family, int font_style);
   void SetForegroundColor(SkColor foreground);
   void SetShader(SkShader* shader);
   // Sets underline metrics to use if the text will be drawn with an underline.
   // If not set, default values based on the size of the text will be used. The
   // two metrics must be set together.
   void SetUnderlineMetrics(SkScalar thickness, SkScalar position);
   void DrawSelection(const std::vector<Rect>& selection, SkColor color);
@@ skipping 108 matching lines @@
   int baseline;
 };
 
 // Creates an SkTypeface from a font |family| name and a |gfx::Font::FontStyle|.
 // May return NULL.
 skia::RefPtr<SkTypeface> CreateSkiaTypeface(const std::string& family,
                                             int style);
 
 // Applies the given FontRenderParams to a Skia |paint|.
 void ApplyRenderParams(const FontRenderParams& params,
-                       bool background_is_transparent,
+                       bool subpixel_rendering_enabled,
                        SkPaint* paint);
 
 }  // namespace internal
 
 // 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 GFX_EXPORT RenderText {
  public:
@@ skipping 54 matching lines @@
   // 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 currently only supported on
   // Windows. Support other platforms.
   bool multiline() const { return multiline_; }
   void SetMultiline(bool multiline);
 
+  // Returns true if this supports multiline rendering.
+  virtual bool MultilineSupported() const = 0;
+
   // TODO(ckocagil): Add vertical alignment and line spacing support instead.
   int min_line_height() const { return min_line_height_; }
   void SetMinLineHeight(int line_height);
 
   // Set the maximum length of the layout text, not the actual text.
   // A |length| of 0 forgoes a hard limit, but does not guarantee proper
   // functionality of very long strings. Applies to subsequent SetText calls.
   // WARNING: Only use this for system limits, it lacks complex text support.
   void set_truncate_length(size_t length) { truncate_length_ = length; }
 
   // The layout text will be elided to fit |display_rect| using this behavior.
   void SetElideBehavior(ElideBehavior elide_behavior);
   ElideBehavior elide_behavior() const { return elide_behavior_; }
 
   const Rect& display_rect() const { return display_rect_; }
   void SetDisplayRect(const Rect& r);
 
-  bool background_is_transparent() const { return background_is_transparent_; }
-  void set_background_is_transparent(bool transparent) {
-    background_is_transparent_ = transparent;
+  bool subpixel_rendering_enabled() const {
+    return subpixel_rendering_enabled_;
+  }
+  void set_subpixel_rendering_enabled(bool enabled) {
+    subpixel_rendering_enabled_ = enabled;
   }
 
   const SelectionModel& selection_model() const { return selection_model_; }
 
   const Range& selection() const { return selection_model_.selection(); }
 
   size_t cursor_position() const { return selection_model_.caret_pos(); }
   void SetCursorPosition(size_t position);
 
   // Moves the cursor left or right. Cursor movement is visual, meaning that
@@ skipping 130 matching lines @@
   // supplied index is already at the boundary of the string.
   size_t IndexOfAdjacentGrapheme(size_t index,
                                  LogicalCursorDirection direction);
 
   // Return a SelectionModel with the cursor at the current selection's start.
   // The returned value represents a cursor/caret position without a selection.
   SelectionModel GetSelectionModelForSelectionStart();
 
   // Sets shadows to drawn with text.
   void set_shadows(const ShadowValues& shadows) { shadows_ = shadows; }
-  const ShadowValues& shadows() { return shadows_; }
+  const ShadowValues& shadows() const { return shadows_; }
 
   typedef std::pair<Font, Range> FontSpan;
   // For testing purposes, returns which fonts were chosen for which parts of
   // the text by returning a vector of Font and Range pairs, where each range
   // specifies the character range for which the corresponding font has been
   // chosen.
   virtual std::vector<FontSpan> GetFontSpansForTesting() = 0;
 
   // Gets the horizontal bounds (relative to the left of the text, not the view)
   // of the glyph starting at |index|. If the glyph is RTL then the returned
@@ skipping 285 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_;
 
   // Is the background transparent (either partially or fully)?

[msw, 2015/02/17 22:16:45]

nit: update comment.

-  bool background_is_transparent_;
+  bool subpixel_rendering_enabled_;
 
   // The local display area for rendering the text.
   Rect display_rect_;
 
   // Flag to work around a Skia bug with the PDF path (http://crbug.com/133548)
   // that results in incorrect clipping when drawing to the document margins.
   // This field allows disabling clipping to work around the issue.
   // TODO(asvitkine): Remove this when the underlying Skia bug is fixed.
   bool clip_to_display_rect_;
 
@@ skipping 19 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_