/* * 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 "include/core/SkScalar.h" #include "include/core/SkTime.h" #ifndef AnimTimer_DEFINED #define AnimTimer_DEFINED /** * Class to track a "timer". It supports 3 states: stopped, paused, and running. * Playback speed is variable. * * 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 AnimTimer { public: /** * Class begins in the "stopped" state. */ AnimTimer() {} enum State { kStopped_State, kPaused_State, kRunning_State }; State state() const { return fState; } double nanos() const { return fElapsedNanos; } /** * Control the rate at which time advances. */ float getSpeed() const { return fSpeed; } void setSpeed(float speed) { fSpeed = speed; } /** * If the timer is paused or stopped, it will resume (or start if it was stopped). */ void run() { switch (this->state()) { case kStopped_State: fPreviousNanos = SkTime::GetNSecs(); fElapsedNanos = 0; break; case kPaused_State: // they want "resume" fPreviousNanos = SkTime::GetNSecs(); break; case kRunning_State: break; } fState = kRunning_State; } void pause() { if (kRunning_State == this->state()) { fState = kPaused_State; } // else stay stopped or paused } /** * If the timer is stopped, start running, else it toggles between paused and running. */ void togglePauseResume() { if (kRunning_State == this->state()) { this->pause(); } else { this->run(); } } /** * 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 == this->state()) { double now = SkTime::GetNSecs(); fElapsedNanos += (now - fPreviousNanos) * fSpeed; fPreviousNanos = now; } } private: double fPreviousNanos = 0; double fElapsedNanos = 0; float fSpeed = 1; State fState = kStopped_State; }; #endif