Reland of "Apply Shelf/Dock opacity animations for the Material Design style."

ash/common/shelf/shelf_background_animator.h

Index: ash/common/shelf/shelf_background_animator.h
diff --git a/ash/common/shelf/shelf_background_animator.h b/ash/common/shelf/shelf_background_animator.h
new file mode 100644
index 0000000000000000000000000000000000000000..31ad4e1566e08329c9a05fc6586497f86a7b4e2d
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+++ b/ash/common/shelf/shelf_background_animator.h
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+// Copyright 2016 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 ASH_COMMON_SHELF_SHELF_BACKGROUND_ANIMATOR_H_
+#define ASH_COMMON_SHELF_SHELF_BACKGROUND_ANIMATOR_H_
+
+#include <vector>
+
+#include "ash/ash_export.h"
+#include "ash/common/shelf/shelf_types.h"
+#include "ash/common/shelf/wm_shelf_observer.h"
+#include "ash/common/wm/background_animator.h"
+#include "base/macros.h"
+#include "base/observer_list.h"
+
+namespace ash {
+
+class ShelfBackgroundAnimatorObserver;
+class ShelfBackgroundAnimatorTestApi;
+class WmShelf;
+
+// Central controller for the Shelf and Dock opacity animations.
+//
+// The ShelfBackgroundAnimator is capable of observing a WmShelf instance for
+// background type changes or clients can call PaintBackground() directly.
+//
+// The Shelf uses 3 surfaces for the animations:
+//
+//  Non-Material Design:
+//    1. Shelf button backgrounds
+//    2. Opaque overlay for the SHELF_BACKGROUND_MAXIMIZED state.
+//    3. Shelf and Dock assets for the SHELF_BACKGROUND_OVERLAP state.
+//  Material Design:
+//    1. Shelf button backgrounds
+//    2. Opaque overlay for the SHELF_BACKGROUND_OVERLAP and
+//       SHELF_BACKGROUND_MAXIMIZED states.
+class ASH_EXPORT ShelfBackgroundAnimator : public WmShelfObserver,
+                                           public BackgroundAnimatorDelegate {
+ public:
+  // Initializes this with the given |background_type|. This will observe the
+  // |wm_shelf| for background type changes if |wm_shelf| is not null.
+  ShelfBackgroundAnimator(ShelfBackgroundType background_type,
+                          WmShelf* wm_shelf);
+  ~ShelfBackgroundAnimator() override;
+
+  ShelfBackgroundType target_background_type() const {
+    return target_background_type_;
+  }
+
+  // Initializes |observer| with current values using the Initialize() function.
+  void AddObserver(ShelfBackgroundAnimatorObserver* observer);
+  void RemoveObserver(ShelfBackgroundAnimatorObserver* observer);
+
+  // Updates |observer| with current values.
+  void Initialize(ShelfBackgroundAnimatorObserver* observer) const;
+
+  // Conditionally animates the background to the specified |background_type|
+  // and notifies observers of the new background parameters (e.g. alpha).
+  // If |change_type| is BACKGROUND_CHANGE_IMMEDIATE then the
+  // observers will only receive one notification with the final background
+  // state, otherwise the observers will be notified multiple times in order to
+  // animate the changes to the backgrounds.
+  //
+  // NOTE: If a second request to paint the same |background_type| using the
+  // BACKGROUND_CHANGE_ANIMATE change type is received it will be ignored and
+  // observers will NOT be notified.
+  void PaintBackground(ShelfBackgroundType background_type,
+                       BackgroundAnimatorChangeType change_type);
+
+ protected:
+  // WmShelfObserver:
+  void OnBackgroundTypeChanged(
+      ShelfBackgroundType background_type,
+      BackgroundAnimatorChangeType change_type) override;
+
+  // BackgroundAnimatorDelegate:
+  void UpdateBackground(BackgroundAnimator* animator, int alpha) override;
+  void BackgroundAnimationEnded(BackgroundAnimator* animator) override;
+
+ private:
+  friend class ShelfBackgroundAnimatorTestApi;
+
+  // Helper function used by PaintBackground() to animate the background.
+  void AnimateBackground(ShelfBackgroundType background_type,
+                         BackgroundAnimatorChangeType change_type);
+
+  // Creates new BackgroundAnimators configured with the correct durations and
+  // initial/target alpha values. If any BackgroundAnimators are currently
+  // animating they will be stopped.
+  void CreateAnimators(ShelfBackgroundType background_type,
+                       BackgroundAnimatorChangeType change_type);
+
+  // Stops all existing animators owned by this.
+  void StopAnimators();
+
+  // Called when an alpha value changes and observers need to be notified.
+  void OnAlphaChanged(BackgroundAnimator* animator, int alpha);
+
+  // The background type that this is animating towards or has reached.
+  ShelfBackgroundType target_background_type_ = SHELF_BACKGROUND_DEFAULT;
+
+  // The last background type this is animating away from.
+  ShelfBackgroundType previous_background_type_ = SHELF_BACKGROUND_MAXIMIZED;
+
+  // Animates the solid color background of the Shelf.
+  // TODO(bruthig): Replace all BackgroundAnimators with a single
+  // gfx::SlideAnimation.
+  std::unique_ptr<BackgroundAnimator> opaque_background_animator_;
+
+  // Animates the asset/image based background of the Shelf.
+  // TODO(bruthig): Remove when non-md is no longer needed (crbug.com/614453).
+  std::unique_ptr<BackgroundAnimator> asset_background_animator_;
+
+  // Animates the backgrounds of Shelf child Views.
+  std::unique_ptr<BackgroundAnimator> item_background_animator_;
+
+  base::ObserverList<ShelfBackgroundAnimatorObserver> observers_;
+
+  // True if the existing BackgroundAnimators can be re-used to animate to the
+  // |previous_background_type_|. This allows for pre-empted animations to take
+  // the same amount of time to reverse to the |previous_background_type_|.
+  bool can_reuse_animators_ = false;
+
+  // Tracks how many animators completed successfully since the last
+  // CreateAnimators() call. Used to properly set |can_reuse_animators_|.
+  int successful_animator_count_ = 0;
+
+  // The shelf to observe for changes to the shelf background type, can be null.
+  WmShelf* wm_shelf_;
+
+  DISALLOW_COPY_AND_ASSIGN(ShelfBackgroundAnimator);
+};
+
+}  // namespace ash
+
+#endif  // ASH_COMMON_SHELF_SHELF_BACKGROUND_ANIMATOR_H_