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

ash/common/shelf/shelf_background_animator.cc

Index: ash/common/shelf/shelf_background_animator.cc
diff --git a/ash/common/shelf/shelf_background_animator.cc b/ash/common/shelf/shelf_background_animator.cc
new file mode 100644
index 0000000000000000000000000000000000000000..7cbc31a02a0a2dbb8c96dee82d8d27e6896bcee1
--- /dev/null
+++ b/ash/common/shelf/shelf_background_animator.cc
@@ -0,0 +1,206 @@
+// 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.
+
+#include "ash/common/shelf/shelf_background_animator.h"
+
+#include <algorithm>
+
+#include "ash/common/material_design/material_design_controller.h"
+#include "ash/common/shelf/shelf_background_animator_observer.h"
+#include "ash/common/shelf/shelf_constants.h"
+#include "ash/common/shelf/wm_shelf.h"
+
+namespace ash {
+
+namespace {
+// The total number of animators that will call BackgroundAnimationEnded().
+const int kNumAnimators = 3;
+
+const int kMaxAlpha = 255;
+}  // namespace
+
+ShelfBackgroundAnimator::ShelfBackgroundAnimator(
+    ShelfBackgroundType background_type,
+    WmShelf* wm_shelf)
+    : wm_shelf_(wm_shelf) {
+  if (wm_shelf_)
+    wm_shelf_->AddObserver(this);
+  // Initialize animators so that adding observers get notified with consistent
+  // values.
+  AnimateBackground(background_type, BACKGROUND_CHANGE_IMMEDIATE);
+}
+
+ShelfBackgroundAnimator::~ShelfBackgroundAnimator() {
+  if (wm_shelf_)
+    wm_shelf_->RemoveObserver(this);
+}
+
+void ShelfBackgroundAnimator::AddObserver(
+    ShelfBackgroundAnimatorObserver* observer) {
+  observers_.AddObserver(observer);
+  Initialize(observer);
+}
+
+void ShelfBackgroundAnimator::RemoveObserver(
+    ShelfBackgroundAnimatorObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+void ShelfBackgroundAnimator::Initialize(
+    ShelfBackgroundAnimatorObserver* observer) const {
+  observer->UpdateShelfOpaqueBackground(opaque_background_animator_->alpha());
+  observer->UpdateShelfAssetBackground(asset_background_animator_->alpha());
+  observer->UpdateShelfItemBackground(item_background_animator_->alpha());
+}
+
+void ShelfBackgroundAnimator::PaintBackground(
+    ShelfBackgroundType background_type,
+    BackgroundAnimatorChangeType change_type) {
+  if (target_background_type_ == background_type &&
+      change_type == BACKGROUND_CHANGE_ANIMATE) {
+    return;
+  }
+
+  AnimateBackground(background_type, change_type);
+}
+
+void ShelfBackgroundAnimator::OnBackgroundTypeChanged(
+    ShelfBackgroundType background_type,
+    BackgroundAnimatorChangeType change_type) {
+  PaintBackground(background_type, change_type);
+}
+
+void ShelfBackgroundAnimator::UpdateBackground(BackgroundAnimator* animator,
+                                               int alpha) {
+  OnAlphaChanged(animator, alpha);
+}
+
+void ShelfBackgroundAnimator::BackgroundAnimationEnded(
+    BackgroundAnimator* animator) {
+  ++successful_animator_count_;
+  DCHECK_LE(successful_animator_count_, kNumAnimators);
+  // UpdateBackground() is only called when alpha values change, this ensures
+  // observers are always notified for every background change.
+  OnAlphaChanged(animator, animator->alpha());
+}
+
+void ShelfBackgroundAnimator::OnAlphaChanged(BackgroundAnimator* animator,
+                                             int alpha) {
+  if (animator == opaque_background_animator_.get()) {
+    FOR_EACH_OBSERVER(ShelfBackgroundAnimatorObserver, observers_,
+                      UpdateShelfOpaqueBackground(alpha));
+  } else if (animator == asset_background_animator_.get()) {
+    FOR_EACH_OBSERVER(ShelfBackgroundAnimatorObserver, observers_,
+                      UpdateShelfAssetBackground(alpha));
+  } else if (animator == item_background_animator_.get()) {
+    FOR_EACH_OBSERVER(ShelfBackgroundAnimatorObserver, observers_,
+                      UpdateShelfItemBackground(alpha));
+  } else {
+    NOTREACHED();
+  }
+}
+
+void ShelfBackgroundAnimator::AnimateBackground(
+    ShelfBackgroundType background_type,
+    BackgroundAnimatorChangeType change_type) {
+  // Ensure BackgroundAnimationEnded() has been called for all the
+  // BackgroundAnimators owned by this so that |successful_animator_count_|
+  // is stable and doesn't get updated as a side effect of destroying/animating
+  // the animators.
+  StopAnimators();
+
+  bool show_background = true;
+  if (can_reuse_animators_ && previous_background_type_ == background_type) {
+    DCHECK_EQ(opaque_background_animator_->paints_background(),
+              asset_background_animator_->paints_background());
+    DCHECK_EQ(asset_background_animator_->paints_background(),
+              item_background_animator_->paints_background());
+
+    show_background = !opaque_background_animator_->paints_background();
+  } else {
+    CreateAnimators(background_type, change_type);
+
+    // If all the previous animators completed successfully and the animation
+    // was between 2 distinct states, then the last alpha values are valid
+    // end state values.
+    can_reuse_animators_ = target_background_type_ != background_type &&
+                           successful_animator_count_ == kNumAnimators;
+  }
+
+  successful_animator_count_ = 0;
+
+  opaque_background_animator_->SetPaintsBackground(show_background,
+                                                   change_type);
+  asset_background_animator_->SetPaintsBackground(show_background, change_type);
+  item_background_animator_->SetPaintsBackground(show_background, change_type);
+
+  if (target_background_type_ != background_type) {
+    previous_background_type_ = target_background_type_;
+    target_background_type_ = background_type;
+  }
+}
+
+void ShelfBackgroundAnimator::CreateAnimators(
+    ShelfBackgroundType background_type,
+    BackgroundAnimatorChangeType change_type) {
+  const int opaque_background_alpha =
+      opaque_background_animator_ ? opaque_background_animator_->alpha() : 0;
+  const int asset_background_alpha =
+      asset_background_animator_ ? asset_background_animator_->alpha() : 0;
+  const int item_background_alpha =
+      item_background_animator_ ? item_background_animator_->alpha() : 0;
+
+  const bool is_material = MaterialDesignController::IsShelfMaterial();
+  int duration_ms = 0;
+
+  switch (background_type) {
+    case SHELF_BACKGROUND_DEFAULT:
+      duration_ms = is_material ? 500 : 1000;
+      opaque_background_animator_.reset(
+          new BackgroundAnimator(this, opaque_background_alpha, 0));
+      asset_background_animator_.reset(
+          new BackgroundAnimator(this, asset_background_alpha, 0));
+      item_background_animator_.reset(
+          new BackgroundAnimator(this, item_background_alpha,
+                                 GetShelfConstant(SHELF_BACKGROUND_ALPHA)));
+      break;
+    case SHELF_BACKGROUND_OVERLAP:
+      duration_ms = is_material ? 500 : 1000;
+      opaque_background_animator_.reset(new BackgroundAnimator(
+          this, opaque_background_alpha,
+          is_material ? GetShelfConstant(SHELF_BACKGROUND_ALPHA) : 0));
+      asset_background_animator_.reset(new BackgroundAnimator(
+          this, asset_background_alpha,
+          is_material ? 0 : GetShelfConstant(SHELF_BACKGROUND_ALPHA)));
+      item_background_animator_.reset(new BackgroundAnimator(
+          this, item_background_alpha,
+          is_material ? 0 : GetShelfConstant(SHELF_BACKGROUND_ALPHA)));
+      break;
+    case SHELF_BACKGROUND_MAXIMIZED:
+      duration_ms = is_material ? 250 : 1000;
+      opaque_background_animator_.reset(
+          new BackgroundAnimator(this, opaque_background_alpha, kMaxAlpha));
+      asset_background_animator_.reset(new BackgroundAnimator(
+          this, asset_background_alpha,
+          is_material ? 0 : GetShelfConstant(SHELF_BACKGROUND_ALPHA)));
+      item_background_animator_.reset(new BackgroundAnimator(
+          this, item_background_alpha, is_material ? 0 : kMaxAlpha));
+      break;
+  }
+
+  opaque_background_animator_->SetDuration(duration_ms);
+  asset_background_animator_->SetDuration(duration_ms);
+  item_background_animator_->SetDuration(duration_ms);
+}
+
+void ShelfBackgroundAnimator::StopAnimators() {
+  if (opaque_background_animator_)
+    opaque_background_animator_->Stop();
+  if (asset_background_animator_)
+    asset_background_animator_->Stop();
+  if (item_background_animator_)
+    item_background_animator_->Stop();
+}
+
+}  // namespace ash