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/*
* Copyright 2015 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkTime.h"
#ifndef SkAnimTimer_DEFINED
#define SkAnimTimer_DEFINED
/**
* Class to track a "timer". It supports 3 states: stopped, paused, running.
*
* The caller must call updateTime() to resync with the clock (typically just before
* using the timer). Forcing the caller to do this ensures that the timer's return values
* are consistent if called repeatedly, as they only reflect the time since the last
* calle to updateTimer().
*/
class SkAnimTimer {
public:
enum State {
kStopped_State,
kPaused_State,
kRunning_State
};
/**
* Class begins in the "stopped" state.
*/
SkAnimTimer() : fBaseTimeNanos(0), fCurrTimeNanos(0), fState(kStopped_State) {}
bool isStopped() const { return kStopped_State == fState; }
bool isRunning() const { return kRunning_State == fState; }
bool isPaused() const { return kPaused_State == fState; }
/**
* Stops the timer, and resets it, such that the next call to run or togglePauseResume
* will begin at time 0.
*/
void stop() {
this->setState(kStopped_State);
}
/**
* If the timer is paused or stopped, it will resume (or start if it was stopped).
*/
void run() {
this->setState(kRunning_State);
}
/**
* If the timer is stopped, this has no effect, else it toggles between paused and running.
*/
void togglePauseResume() {
if (kRunning_State == fState) {
this->setState(kPaused_State);
} else {
this->setState(kRunning_State);
}
}
/**
* Call this each time you want to sample the clock for the timer. This is NOT done
* automatically, so that repeated calls to msec() or secs() will always return the
* same value.
*
* This may safely be called with the timer in any state.
*/
void updateTime() {
if (kRunning_State == fState) {
fCurrTimeNanos = SkTime::GetNSecs();
}
}
/**
* Return the time in milliseconds the timer has been in the running state.
* Returns 0 if the timer is stopped. Behavior is undefined if the timer
* has been running longer than SK_MSecMax.
*/
SkMSec msec() const {
const double msec = (fCurrTimeNanos - fBaseTimeNanos) * 1e-6;
SkASSERT(SK_MSecMax >= msec);
return static_cast<SkMSec>(msec);
}
/**
* Return the time in seconds the timer has been in the running state.
* Returns 0 if the timer is stopped.
*/
double secs() const { return (fCurrTimeNanos - fBaseTimeNanos) * 1e-9; }
/**
* Return the time in seconds the timer has been in the running state,
* scaled by "speed" and (if not zero) mod by period.
* Returns 0 if the timer is stopped.
*/
SkScalar scaled(SkScalar speed, SkScalar period = 0) const {
double value = this->secs() * speed;
if (period) {
value = ::fmod(value, SkScalarToDouble(period));
}
return SkDoubleToScalar(value);
}
/**
* Transitions from ends->mid->ends linearly over period seconds. The phase specifies a phase
* shift in seconds.
*/
SkScalar pingPong(SkScalar period, SkScalar phase, SkScalar ends, SkScalar mid) const {
return PingPong(this->secs(), period, phase, ends, mid);
}
/** Helper for computing a ping-pong value without a SkAnimTimer object. */
static SkScalar PingPong(double t, SkScalar period, SkScalar phase, SkScalar ends,
SkScalar mid) {
double value = ::fmod(t + phase, period);
double half = period / 2.0;
double diff = ::fabs(value - half);
return SkDoubleToScalar(ends + (1.0 - diff / half) * (mid - ends));
}
private:
double fBaseTimeNanos;
double fCurrTimeNanos;
State fState;
void setState(State newState) {
switch (newState) {
case kStopped_State:
fBaseTimeNanos = fCurrTimeNanos = 0;
fState = kStopped_State;
break;
case kPaused_State:
if (kRunning_State == fState) {
fState = kPaused_State;
} // else stay stopped or paused
break;
case kRunning_State:
switch (fState) {
case kStopped_State:
fBaseTimeNanos = fCurrTimeNanos = SkTime::GetNSecs();
break;
case kPaused_State: {// they want "resume"
double now = SkTime::GetNSecs();
fBaseTimeNanos += now - fCurrTimeNanos;
fCurrTimeNanos = now;
} break;
case kRunning_State:
break;
}
fState = kRunning_State;
break;
}
}
};
#endif
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