Audio indicator: cross platform drawing and animation

chrome/browser/ui/tabs/tab_audio_indicator.h

+// Copyright (c) 2013 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 CHROME_BROWSER_UI_TABS_TAB_AUDIO_INDICATOR_H_
+#define CHROME_BROWSER_UI_TABS_TAB_AUDIO_INDICATOR_H_
+
+#include <vector>
+
+#include "base/compiler_specific.h"
+#include "base/gtest_prod_util.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/base/animation/animation_delegate.h"
+
+namespace gfx {
+class Canvas;
+class Rect;
+}
+namespace ui {
+class Animation;
+class AnimationContainer;
+class LinearAnimation;
+}
+
+// This class is used to draw an animating tab audio indicator.
+class TabAudioIndicator : public ui::AnimationDelegate {
+ public:
+  class Delegate {
+   public:
+    virtual void ScheduleAudioIndicatorPaint() = 0;
+
+   protected:
+    virtual ~Delegate() {}
+  };
+
+  explicit TabAudioIndicator(Delegate* delegate);
+  virtual ~TabAudioIndicator();
+
+  void SetAnimationContainer(ui::AnimationContainer* animation_container);
+  void SetIsPlayingAudio(bool is_playing_audio);
+  bool IsAnimating();
+
+  void Paint(gfx::Canvas* canvas, const gfx::Rect& rect);
+
+ private:
+  enum State {
+    STATE_NOT_ANIMATING,
+    STATE_ANIMATING,
+    STATE_ANIMATION_ENDING,
+  };
+
+  FRIEND_TEST_ALL_PREFIXES(TabAudioIndicatorTest, AnimationState);
+  FRIEND_TEST_ALL_PREFIXES(TabAudioIndicatorTest, SchedulePaint);
+
+  // AnimationDelegate:
+  virtual void AnimationProgressed(const ui::Animation* animation) OVERRIDE;
+  virtual void AnimationEnded(const ui::Animation* animation) OVERRIDE;
+
+  // Gets the equalizer levels for all 3 columns. The values are tweened between
+  // the current and target frame.
+  std::vector<int> GetCurrentEqualizerLevels() const;
+
+  Delegate* delegate_;
+  scoped_ptr<ui::LinearAnimation> animation_;
+  scoped_refptr<ui::AnimationContainer> animation_container_;
+
+  // The equalizer frame that's currently being displayed.
+  size_t frame_index_;
+
+  // The equalizer levels that were last displayed. This is used to prevent
+  // unnecessary drawing when animation progress doesn't result in equalizer
+  // levels changing.
+  std::vector<int> last_displayed_equalizer_levels_;
+
+  State state_;
+
+  DISALLOW_COPY_AND_ASSIGN(TabAudioIndicator);
+};
+
+#endif  // CHROME_BROWSER_UI_TABS_TAB_AUDIO_INDICATOR_H_