ebiten/internal/clock/clock.go
2022-07-12 13:18:49 +09:00

176 lines
3.7 KiB
Go

// Copyright 2017 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package clock manages game timers.
package clock
import (
"sync"
"time"
)
const (
DefaultTPS = 60
SyncWithFPS = -1
)
var (
// tps represents TPS (ticks per second).
tps = DefaultTPS
lastNow int64
// lastSystemTime is the last system time in the previous UpdateFrame.
// lastSystemTime indicates the logical time in the game, so this can be bigger than the curren time.
lastSystemTime int64
actualFPS float64
actualTPS float64
prevTPS int64
lastUpdated int64
fpsCount = 0
tpsCount = 0
m sync.Mutex
)
func init() {
n := now()
lastNow = n
lastSystemTime = n
lastUpdated = n
}
func ActualFPS() float64 {
m.Lock()
defer m.Unlock()
return actualFPS
}
func ActualTPS() float64 {
m.Lock()
defer m.Unlock()
return actualTPS
}
func max(a, b int64) int64 {
if a < b {
return b
}
return a
}
func calcCountFromTPS(tps int64, now int64) int {
if tps == 0 {
return 0
}
if tps < 0 {
panic("clock: tps must >= 0")
}
diff := now - lastSystemTime
if diff < 0 {
return 0
}
count := 0
syncWithSystemClock := false
// Detect whether the previous time is too old.
// Use either 5 ticks or 5/60 sec in the case when TPS is too big like 300 (#1444).
if diff > max(int64(time.Second)*5/tps, int64(time.Second)*5/60) || prevTPS != tps {
// The previous time is too old.
// Let's force to sync the game time with the system clock.
syncWithSystemClock = true
} else {
count = int(diff * tps / int64(time.Second))
}
prevTPS = tps
// Stabilize the count.
// Without this adjustment, count can be unstable like 0, 2, 0, 2, ...
// TODO: Brush up this logic so that this will work with any FPS. Now this works only when FPS = TPS.
if count == 0 && (int64(time.Second)/tps/2) < diff {
count = 1
}
if count == 2 && (int64(time.Second)/tps*3/2) > diff {
count = 1
}
if syncWithSystemClock {
lastSystemTime = now
} else {
lastSystemTime += int64(count) * int64(time.Second) / tps
}
return count
}
func updateFPSAndTPS(now int64, count int) {
fpsCount++
tpsCount += count
if now < lastUpdated {
panic("clock: lastUpdated must be older than now")
}
if time.Second > time.Duration(now-lastUpdated) {
return
}
actualFPS = float64(fpsCount) * float64(time.Second) / float64(now-lastUpdated)
actualTPS = float64(tpsCount) * float64(time.Second) / float64(now-lastUpdated)
lastUpdated = now
fpsCount = 0
tpsCount = 0
}
// UpdateFrame updates the inner clock state and returns an integer value
// indicating how many times the game should update based on the current tps.
//
// If tps is SyncWithFPS, UpdateFrame always returns 1.
// If tps <= 0 and not SyncWithFPS, UpdateFrame always returns 0.
//
// UpdateFrame is expected to be called once per frame.
func UpdateFrame() int {
m.Lock()
defer m.Unlock()
n := now()
if lastNow > n {
// This ensures that now() must be monotonic (#875).
panic("clock: lastNow must be older than n")
}
lastNow = n
c := 0
if tps == SyncWithFPS {
c = 1
} else if tps > 0 {
c = calcCountFromTPS(int64(tps), n)
}
updateFPSAndTPS(n, c)
return c
}
func SetTPS(newTPS int) {
m.Lock()
defer m.Unlock()
tps = newTPS
}
func TPS() int {
m.Lock()
defer m.Unlock()
return tps
}