1 files changed, 57 insertions, 0 deletions
diff --git a/ash/shelf/background_animator.cc b/ash/shelf/background_animator.cc
new file mode 100644
index 0000000..7b968c8
--- /dev/null
+++ b/ash/shelf/background_animator.cc
@@ -0,0 +1,57 @@
+// 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.
+
+#include "ash/shelf/background_animator.h"
+
+
+namespace ash {
+namespace internal {
+
+namespace {
+
+// Duration of the background animation.
+const int kBackgroundDurationMS = 1000;
+
+}
+
+BackgroundAnimator::BackgroundAnimator(BackgroundAnimatorDelegate* delegate,
+                                       int min_alpha,
+                                       int max_alpha)
+    : delegate_(delegate),
+      min_alpha_(min_alpha),
+      max_alpha_(max_alpha),
+      ALLOW_THIS_IN_INITIALIZER_LIST(animation_(this)),
+      paints_background_(false),
+      alpha_(min_alpha) {
+  animation_.SetSlideDuration(kBackgroundDurationMS);
+}
+
+BackgroundAnimator::~BackgroundAnimator() {
+}
+
+void BackgroundAnimator::SetPaintsBackground(bool value, ChangeType type) {
+  if (paints_background_ == value)
+    return;
+  paints_background_ = value;
+  if (type == CHANGE_IMMEDIATE && !animation_.is_animating()) {
+    animation_.Reset(value ? 1.0f : 0.0f);
+    AnimationProgressed(&animation_);
+    return;
+  }
+  if (paints_background_)
+    animation_.Show();
+  else
+    animation_.Hide();
+}
+
+void BackgroundAnimator::AnimationProgressed(const ui::Animation* animation) {
+  int alpha = animation->CurrentValueBetween(min_alpha_, max_alpha_);
+  if (alpha_ == alpha)
+    return;
+  alpha_ = alpha;
+  delegate_->UpdateBackground(alpha_);
+}
+
+}  // namespace internal
+}  // namespace ash