Cache DrawStringParams in views::Label

ui/views/controls/label.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_VIEWS_CONTROLS_LABEL_H_
 #define UI_VIEWS_CONTROLS_LABEL_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 131 matching lines @@
   virtual gfx::Size GetTextSize() const;
 
   SkColor disabled_color() const { return actual_disabled_color_; }
 
   // View:
   void OnBoundsChanged(const gfx::Rect& previous_bounds) override;
   void OnPaint(gfx::Canvas* canvas) override;
   void OnNativeThemeChanged(const ui::NativeTheme* theme) override;
 
  private:
+  struct DrawStringParams {
+    DrawStringParams() : flags(0) {}
+
+    base::string16 text;
+    gfx::Rect bounds;
+    int flags;
+  };
+
   // These tests call CalculateDrawStringParams in order to verify the
   // calculations done for drawing text.
   FRIEND_TEST_ALL_PREFIXES(LabelTest, DrawSingleLineString);
   FRIEND_TEST_ALL_PREFIXES(LabelTest, DrawMultiLineString);
   FRIEND_TEST_ALL_PREFIXES(LabelTest, DrawSingleLineStringInRTL);
   FRIEND_TEST_ALL_PREFIXES(LabelTest, DrawMultiLineStringInRTL);
   FRIEND_TEST_ALL_PREFIXES(LabelTest, DirectionalityFromText);
   FRIEND_TEST_ALL_PREFIXES(LabelTest, DisableSubpixelRendering);
 
   // Sets both |text_| and |layout_text_| to appropriate values, taking
   // the label's 'obscured' status into account.
   void SetTextInternal(const base::string16& text);
 
   void Init(const base::string16& text, const gfx::FontList& font_list);
 
   void RecalculateColors();
 
   // Returns where the text is drawn, in the receivers coordinate system.
   gfx::Rect GetTextBounds() const;
 
   int ComputeDrawStringFlags() const;
 
   gfx::Rect GetAvailableRect() const;
 
-  // Returns parameters to be used for the DrawString call.
-  void CalculateDrawStringParams(base::string16* paint_text,
-                                 gfx::Rect* text_bounds,
-                                 int* flags) const;
+  // Returns parameters to be used for the DrawString call. Returned value is a
+  // weak pointer, owned by and scoped to the label.
+  const DrawStringParams* CalculateDrawStringParams() const;
 
   // Updates any colors that have not been explicitly set from the theme.
   void UpdateColorsFromTheme(const ui::NativeTheme* theme);
 
-  // Resets |cached_heights_| and |cached_heights_cursor_| and mark
-  // |text_size_valid_| as false.
-  void ResetCachedSize();
+  // Resets |cached_heights_|, |cached_heights_cursor_|, |cached_draw_params_|
+  // and mark |text_size_valid_| as false.
+  void ResetLayoutCache();
 
   bool ShouldShowDefaultTooltip() const;
 
   base::string16 text_;
   base::string16 layout_text_;
   gfx::FontList font_list_;
   SkColor requested_enabled_color_;
   SkColor actual_enabled_color_;
   SkColor requested_disabled_color_;
   SkColor actual_disabled_color_;
@@ skipping 17 matching lines @@
   base::string16 tooltip_text_;
   bool handles_tooltips_;
   // Whether to collapse the label when it's not visible.
   bool collapse_when_hidden_;
   gfx::ShadowValues shadows_;
 
   // The cached heights to avoid recalculation in GetHeightForWidth().
   mutable std::vector<gfx::Size> cached_heights_;
   mutable int cached_heights_cursor_;
 
+  // The cached results of CalculateDrawStringParams().
+  mutable DrawStringParams cached_draw_params_;
+
   // TODO(vadimt): Remove is_first_paint_text_ before crbug.com/431326 is
   // closed.
   bool is_first_paint_text_;
 
   DISALLOW_COPY_AND_ASSIGN(Label);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_LABEL_H_