Support touch scroll gestures in menus.

Depends on http://codereview.chromium.org/8364039/

BUG=None
TEST=None

Review URL: https://chromiumcodereview.appspot.com/8508024

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@118834 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 145 insertions, 0 deletions

diff --git a/ui/views/animation/scroll_animator.cc b/ui/views/animation/scroll_animator.cc
new file mode 100644
index 0000000..1e484a3
--- /dev/null
+++ b/ui/views/animation/scroll_animator.cc
@@ -0,0 +1,82 @@
+// 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 "ui/views/animation/scroll_animator.h"
+
+#include <algorithm>
+#include <cmath>
+
+#include "base/logging.h"
+#include "ui/base/animation/slide_animation.h"
+
+namespace {
+const float kDefaultAcceleration = -1500.0f; // in pixels per second^2
+
+// Assumes that d0 == 0.0f
+float GetPosition(float v0, float a, float t) {
+  float max_t = -v0 / a;
+  if (t > max_t)
+    t = max_t;
+  return t * (v0 + 0.5f * a * t);
+}
+
+float GetDelta(float v0, float a, float t1, float t2) {
+  return GetPosition(v0, a, t2) - GetPosition(v0, a, t1);
+}
+
+}  // namespace
+
+namespace views {
+
+ScrollAnimator::ScrollAnimator(ScrollDelegate* delegate)
+  : delegate_(delegate),
+    velocity_x_(0.0f),
+    velocity_y_(0.0f),
+    last_t_(0.0f),
+    duration_(0.0f),
+    acceleration_(kDefaultAcceleration) {
+  DCHECK(delegate);
+}
+
+ScrollAnimator::~ScrollAnimator() {
+  Stop();
+}
+
+void ScrollAnimator::Start(float velocity_x, float velocity_y) {
+  if (acceleration_ >= 0.0f)
+    acceleration_ = kDefaultAcceleration;
+  float v = std::max(fabs(velocity_x), fabs(velocity_y));
+  last_t_ = 0.0f;
+  velocity_x_ = velocity_x;
+  velocity_y_ = velocity_y;
+  duration_ = -v / acceleration_; // in seconds
+  animation_.reset(new ui::SlideAnimation(this));
+  animation_->SetSlideDuration(static_cast<int>(duration_ * 1000));
+  animation_->Show();
+}
+
+void ScrollAnimator::Stop() {
+  velocity_x_ = velocity_y_ = last_t_ = duration_ = 0.0f;
+  animation_.reset();
+}
+
+void ScrollAnimator::AnimationEnded(const ui::Animation* animation) {
+  Stop();
+}
+
+void ScrollAnimator::AnimationProgressed(const ui::Animation* animation) {
+  float t = static_cast<float>(animation->GetCurrentValue()) * duration_;
+  float a_x = velocity_x_ > 0 ? acceleration_ : -acceleration_;
+  float a_y = velocity_y_ > 0 ? acceleration_ : -acceleration_;
+  float dx = GetDelta(velocity_x_, a_x, last_t_, t);
+  float dy = GetDelta(velocity_y_, a_y, last_t_, t);
+  last_t_ = t;
+  delegate_->OnScroll(dx, dy);
+}
+
+void ScrollAnimator::AnimationCanceled(const ui::Animation* animation) {
+  Stop();
+}
+
+}  // namespace views
diff --git a/ui/views/animation/scroll_animator.h b/ui/views/animation/scroll_animator.h
new file mode 100644
index 0000000..6c3eb6d
--- /dev/null
+++ b/ui/views/animation/scroll_animator.h
@@ -0,0 +1,63 @@
+// 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_ANIMATION_SCROLL_ANIMATOR_H_
+#define UI_VIEWS_ANIMATION_SCROLL_ANIMATOR_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/base/animation/animation_delegate.h"
+#include "ui/views/views_export.h"
+
+namespace ui {
+class SlideAnimation;
+}
+
+namespace views {
+
+class VIEWS_EXPORT ScrollDelegate {
+ public:
+  virtual void OnScroll(float dx, float dy) = 0;
+
+ protected:
+  ~ScrollDelegate() {}
+};
+
+class VIEWS_EXPORT ScrollAnimator : public ui::AnimationDelegate {
+ public:
+  // The ScrollAnimator does not own the delegate. Uses default acceleration.
+  explicit ScrollAnimator(ScrollDelegate* delegate);
+  virtual ~ScrollAnimator();
+
+  // Use this if you would prefer different acceleration than the default.
+  void set_acceleration(float acceleration) { acceleration_ = acceleration; }
+
+  void Start(float velocity_x, float velocity_y);
+  void Stop();
+
+  bool is_scrolling() const { return animation_.get(); }
+
+ private:
+  // Implementation of ui::AnimationDelegate.
+  virtual void AnimationEnded(const ui::Animation* animation) OVERRIDE;
+  virtual void AnimationProgressed(const ui::Animation* animation) OVERRIDE;
+  virtual void AnimationCanceled(const ui::Animation* animation) OVERRIDE;
+
+  ScrollDelegate* delegate_;
+
+  float velocity_x_;
+  float velocity_y_;
+  float last_t_;
+  float duration_;
+  float acceleration_;
+
+  scoped_ptr<ui::SlideAnimation> animation_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScrollAnimator);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_ANIMATION_SCROLL_ANIMATOR_H_