1 // Copyright 2013 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "cc/animation/scroll_offset_animation_curve.h"
6
7 #include <algorithm>
8 #include <cmath>
9
10 #include "base/logging.h"
11 #include "cc/animation/timing_function.h"
12 #include "ui/gfx/animation/tween.h"
13
14 const double kDurationDivisor = 60.0;
15
16 namespace cc {
17
18 namespace {
19
MaximumDimension(gfx::Vector2dF delta)20 static float MaximumDimension(gfx::Vector2dF delta) {
21 return std::max(std::abs(delta.x()), std::abs(delta.y()));
22 }
23
DurationFromDelta(gfx::Vector2dF delta)24 static base::TimeDelta DurationFromDelta(gfx::Vector2dF delta) {
25 // The duration of a scroll animation depends on the size of the scroll.
26 // The exact relationship between the size and the duration isn't specified
27 // by the CSSOM View smooth scroll spec and is instead left up to user agents
28 // to decide. The calculation performed here will very likely be further
29 // tweaked before the smooth scroll API ships.
30 return base::TimeDelta::FromMicroseconds(
31 (std::sqrt(MaximumDimension(delta)) / kDurationDivisor) *
32 base::Time::kMicrosecondsPerSecond);
33 }
34
EaseOutWithInitialVelocity(double velocity)35 static scoped_ptr<TimingFunction> EaseOutWithInitialVelocity(double velocity) {
36 // Based on EaseInOutTimingFunction::Create with first control point rotated.
37 const double r2 = 0.42 * 0.42;
38 const double v2 = velocity * velocity;
39 const double x1 = std::sqrt(r2 / (v2 + 1));
40 const double y1 = std::sqrt(r2 * v2 / (v2 + 1));
41 return CubicBezierTimingFunction::Create(x1, y1, 0.58, 1)
42 .PassAs<TimingFunction>();
43 }
44
45 } // namespace
46
Create(const gfx::Vector2dF & target_value,scoped_ptr<TimingFunction> timing_function)47 scoped_ptr<ScrollOffsetAnimationCurve> ScrollOffsetAnimationCurve::Create(
48 const gfx::Vector2dF& target_value,
49 scoped_ptr<TimingFunction> timing_function) {
50 return make_scoped_ptr(
51 new ScrollOffsetAnimationCurve(target_value, timing_function.Pass()));
52 }
53
ScrollOffsetAnimationCurve(const gfx::Vector2dF & target_value,scoped_ptr<TimingFunction> timing_function)54 ScrollOffsetAnimationCurve::ScrollOffsetAnimationCurve(
55 const gfx::Vector2dF& target_value,
56 scoped_ptr<TimingFunction> timing_function)
57 : target_value_(target_value), timing_function_(timing_function.Pass()) {
58 }
59
~ScrollOffsetAnimationCurve()60 ScrollOffsetAnimationCurve::~ScrollOffsetAnimationCurve() {}
61
SetInitialValue(const gfx::Vector2dF & initial_value)62 void ScrollOffsetAnimationCurve::SetInitialValue(
63 const gfx::Vector2dF& initial_value) {
64 initial_value_ = initial_value;
65 total_animation_duration_ = DurationFromDelta(target_value_ - initial_value_);
66 }
67
GetValue(double t) const68 gfx::Vector2dF ScrollOffsetAnimationCurve::GetValue(double t) const {
69 double duration = (total_animation_duration_ - last_retarget_).InSecondsF();
70 t -= last_retarget_.InSecondsF();
71
72 if (t <= 0)
73 return initial_value_;
74
75 if (t >= duration)
76 return target_value_;
77
78 double progress = (timing_function_->GetValue(t / duration));
79 return gfx::Vector2dF(gfx::Tween::FloatValueBetween(
80 progress, initial_value_.x(), target_value_.x()),
81 gfx::Tween::FloatValueBetween(
82 progress, initial_value_.y(), target_value_.y()));
83 }
84
Duration() const85 double ScrollOffsetAnimationCurve::Duration() const {
86 return total_animation_duration_.InSecondsF();
87 }
88
Type() const89 AnimationCurve::CurveType ScrollOffsetAnimationCurve::Type() const {
90 return ScrollOffset;
91 }
92
Clone() const93 scoped_ptr<AnimationCurve> ScrollOffsetAnimationCurve::Clone() const {
94 scoped_ptr<TimingFunction> timing_function(
95 static_cast<TimingFunction*>(timing_function_->Clone().release()));
96 scoped_ptr<ScrollOffsetAnimationCurve> curve_clone =
97 Create(target_value_, timing_function.Pass());
98 curve_clone->initial_value_ = initial_value_;
99 curve_clone->total_animation_duration_ = total_animation_duration_;
100 curve_clone->last_retarget_ = last_retarget_;
101 return curve_clone.PassAs<AnimationCurve>();
102 }
103
UpdateTarget(double t,const gfx::Vector2dF & new_target)104 void ScrollOffsetAnimationCurve::UpdateTarget(
105 double t,
106 const gfx::Vector2dF& new_target) {
107 gfx::Vector2dF current_position = GetValue(t);
108 gfx::Vector2dF old_delta = target_value_ - initial_value_;
109 gfx::Vector2dF new_delta = new_target - current_position;
110
111 double old_duration =
112 (total_animation_duration_ - last_retarget_).InSecondsF();
113 double new_duration = DurationFromDelta(new_delta).InSecondsF();
114
115 double old_velocity = timing_function_->Velocity(
116 (t - last_retarget_.InSecondsF()) / old_duration);
117
118 // TimingFunction::Velocity gives the slope of the curve from 0 to 1.
119 // To match the "true" velocity in px/sec we must adjust this slope for
120 // differences in duration and scroll delta between old and new curves.
121 double new_velocity =
122 old_velocity * (new_duration / old_duration) *
123 (MaximumDimension(old_delta) / MaximumDimension(new_delta));
124
125 initial_value_ = current_position;
126 target_value_ = new_target;
127 total_animation_duration_ = base::TimeDelta::FromSecondsD(t + new_duration);
128 last_retarget_ = base::TimeDelta::FromSecondsD(t);
129 timing_function_ = EaseOutWithInitialVelocity(new_velocity);
130 }
131
132 } // namespace cc
133