| // 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/gfx/animation/slide_animation.h" |
| |
| namespace { |
| constexpr 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_ = std::make_unique<gfx::SlideAnimation>(this); |
| animation_->SetSlideDuration(base::TimeDelta::FromSecondsD(duration_)); |
| animation_->Show(); |
| } |
| |
| void ScrollAnimator::Stop() { |
| velocity_x_ = velocity_y_ = last_t_ = duration_ = 0.0f; |
| animation_.reset(); |
| } |
| |
| void ScrollAnimator::AnimationEnded(const gfx::Animation* animation) { |
| Stop(); |
| } |
| |
| void ScrollAnimator::AnimationProgressed(const gfx::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 gfx::Animation* animation) { |
| Stop(); |
| } |
| |
| } // namespace views |