clock.go

// Copyright 2014 Joseph Hager. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package engi

import (
	"math"
	"time"
)

type Clock struct {
	elapsed     float64
	elapsedStep float64
	step        float64
	numStep     uint32
	delta       float64
	fps         float64
	frames      uint64
	start       time.Time
	frame       time.Time
}

func NewClock(step float64) *Clock {
	clock := new(Clock)
	clock.start = time.Now()
	clock.step = step
	clock.Tick()
	return clock
}

func (c *Clock) Tick() {
	now := time.Now()
	c.frames += 1
	c.delta = now.Sub(c.frame).Seconds()
	c.elapsed += c.delta
	c.frame = now

	if c.elapsed >= 1 {
		c.fps = float64(c.frames)
		c.elapsed = math.Mod(c.elapsed, 1)
		c.frames = 0
		c.numStep = 0.0
	}
	if (c.elapsed / c.step) >= float64(c.numStep) {
		c.numStep++
		responder.Step(c.step, c.numStep)
	}
}

func (c *Clock) Delta() float32 {
	return float32(c.delta)
}

func (c *Clock) Fps() float32 {
	return float32(c.fps)
}

func (c *Clock) Time() float32 {
	return float32(time.Now().Sub(c.start).Seconds())
}