99 lines
2.6 KiB
C
99 lines
2.6 KiB
C
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/*
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* Copyright 2015 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#include "include/core/SkScalar.h"
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#include "include/core/SkTime.h"
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#ifndef AnimTimer_DEFINED
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#define AnimTimer_DEFINED
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/**
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* Class to track a "timer". It supports 3 states: stopped, paused, and running.
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* Playback speed is variable.
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*
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* The caller must call updateTime() to resync with the clock (typically just before
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* using the timer). Forcing the caller to do this ensures that the timer's return values
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* are consistent if called repeatedly, as they only reflect the time since the last
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* calle to updateTimer().
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*/
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class AnimTimer {
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public:
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/**
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* Class begins in the "stopped" state.
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*/
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AnimTimer() {}
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enum State { kStopped_State, kPaused_State, kRunning_State };
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State state() const { return fState; }
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double nanos() const { return fElapsedNanos; }
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/**
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* Control the rate at which time advances.
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*/
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float getSpeed() const { return fSpeed; }
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void setSpeed(float speed) { fSpeed = speed; }
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/**
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* If the timer is paused or stopped, it will resume (or start if it was stopped).
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*/
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void run() {
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switch (this->state()) {
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case kStopped_State:
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fPreviousNanos = SkTime::GetNSecs();
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fElapsedNanos = 0;
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break;
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case kPaused_State: // they want "resume"
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fPreviousNanos = SkTime::GetNSecs();
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break;
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case kRunning_State: break;
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}
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fState = kRunning_State;
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}
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void pause() {
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if (kRunning_State == this->state()) {
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fState = kPaused_State;
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} // else stay stopped or paused
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}
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/**
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* If the timer is stopped, start running, else it toggles between paused and running.
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*/
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void togglePauseResume() {
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if (kRunning_State == this->state()) {
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this->pause();
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} else {
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this->run();
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}
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}
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/**
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* Call this each time you want to sample the clock for the timer. This is NOT done
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* automatically, so that repeated calls to msec() or secs() will always return the
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* same value.
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*
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* This may safely be called with the timer in any state.
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*/
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void updateTime() {
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if (kRunning_State == this->state()) {
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double now = SkTime::GetNSecs();
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fElapsedNanos += (now - fPreviousNanos) * fSpeed;
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fPreviousNanos = now;
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}
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}
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private:
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double fPreviousNanos = 0;
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double fElapsedNanos = 0;
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float fSpeed = 1;
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State fState = kStopped_State;
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};
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#endif
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