mirror of
https://github.com/hajimehoshi/ebiten.git
synced 2024-11-10 04:57:26 +01:00
153 lines
3.3 KiB
Go
153 lines
3.3 KiB
Go
// Copyright 2017 The Ebiten Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package clock manages game timers.
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//
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// There are two types of clocks internally:
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//
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// System clock:
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// A clock offered by the OS.
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//
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// Audio clock:
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// An audio clock that is used in the higher priority over the system clock.
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// An audio clock might not exist when the audio is not used.
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package clock
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import (
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"time"
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"github.com/hajimehoshi/ebiten/internal/sync"
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)
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const FPS = 60
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var (
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frames int64
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audioTimeInFrames int64
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lastAudioTimeInFrames int64
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// lastSystemTime is the last system time in the previous Update.
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lastSystemTime int64
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currentFPS float64
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lastFPSUpdated int64
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framesForFPS int64
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ping func()
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m sync.Mutex
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)
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func CurrentFPS() float64 {
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m.Lock()
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v := currentFPS
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m.Unlock()
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return v
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}
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func RegisterPing(pingFunc func()) {
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m.Lock()
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ping = pingFunc
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m.Unlock()
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}
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// ProceedAudioTimer increments the audio time by the given number of frames.
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func ProceedAudioTimer(num int64) {
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m.Lock()
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audioTimeInFrames += num
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m.Unlock()
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}
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func updateFPS(now int64) {
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if lastFPSUpdated == 0 {
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lastFPSUpdated = now
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}
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framesForFPS++
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if time.Second > time.Duration(now-lastFPSUpdated) {
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return
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}
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currentFPS = float64(framesForFPS) * float64(time.Second) / float64(now-lastFPSUpdated)
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lastFPSUpdated = now
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framesForFPS = 0
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}
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// Update updates the inner clock state and returns an integer value
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// indicating how many game frames the game should update.
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func Update() int {
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m.Lock()
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defer m.Unlock()
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n := now()
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if ping != nil {
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ping()
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}
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// Initialize lastSystemTime if needed.
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if lastSystemTime == 0 {
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lastSystemTime = n
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}
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t := n - lastSystemTime
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if t < 0 {
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return 0
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}
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count := 0
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syncWithSystemClock := false
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if audioTimeInFrames > 0 && lastAudioTimeInFrames != audioTimeInFrames {
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// If the audio clock is updated, use this.
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if frames < audioTimeInFrames {
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count = int(audioTimeInFrames - frames)
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}
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lastAudioTimeInFrames = audioTimeInFrames
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// Now the current lastSystemTime value is not meaningful,
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// force to sync lastSystemTime with the system timer.
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syncWithSystemClock = true
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} else {
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// Use system clock when the audio clock is not updated yet.
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// As the audio clock can be updated discountinuously, the system clock is still needed.
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if t > 5*int64(time.Second)/FPS {
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// The previous time is too old.
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// Let's force to sync the game time with the system clock.
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syncWithSystemClock = true
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} else {
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count = int(t * FPS / int64(time.Second))
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}
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}
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// Stabilize FPS.
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if count == 0 && (int64(time.Second)/FPS/2) < t {
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count = 1
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}
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if count == 2 && (int64(time.Second)/FPS*3/2) > t {
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count = 1
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}
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frames += int64(count)
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if syncWithSystemClock {
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lastSystemTime = n
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} else {
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lastSystemTime += int64(count) * int64(time.Second) / FPS
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}
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updateFPS(n)
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return count
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}
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