mirror of
https://github.com/hajimehoshi/ebiten.git
synced 2024-12-27 04:08:53 +01:00
148 lines
3.2 KiB
Go
148 lines
3.2 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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package clock
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import (
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"sync"
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"time"
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)
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var (
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lastNow int64
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// lastSystemTime is the last system time in the previous Update.
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// lastSystemTime indicates the logical time in the game, so this can be bigger than the curren time.
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lastSystemTime int64
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currentFPS float64
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currentTPS float64
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lastUpdated int64
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fpsCount = 0
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tpsCount = 0
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m sync.Mutex
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)
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func init() {
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n := now()
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lastNow = n
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lastSystemTime = n
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lastUpdated = n
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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 CurrentTPS() float64 {
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m.Lock()
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v := currentTPS
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m.Unlock()
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return v
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}
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func calcCountFromTPS(tps int64, now int64) int {
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if tps == 0 {
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return 0
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}
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if tps < 0 {
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panic("clock: tps must >= 0")
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}
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diff := now - lastSystemTime
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if diff < 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 diff > int64(time.Second)*5/int64(tps) {
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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(diff * tps / int64(time.Second))
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}
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// Stabilize the count.
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// Without this adjustment, count can be unstable like 0, 2, 0, 2, ...
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if count == 0 && (int64(time.Second)/tps/2) < diff {
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count = 1
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}
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if count == 2 && (int64(time.Second)/tps*3/2) > diff {
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count = 1
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}
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if syncWithSystemClock {
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lastSystemTime = now
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} else {
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lastSystemTime += int64(count) * int64(time.Second) / tps
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}
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return count
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}
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func updateFPSAndTPS(now int64, count int) {
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fpsCount++
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tpsCount += count
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if now < lastUpdated {
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panic("clock: lastUpdated must be older than now")
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}
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if time.Second > time.Duration(now-lastUpdated) {
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return
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}
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currentFPS = float64(fpsCount) * float64(time.Second) / float64(now-lastUpdated)
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currentTPS = float64(tpsCount) * float64(time.Second) / float64(now-lastUpdated)
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lastUpdated = now
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fpsCount = 0
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tpsCount = 0
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}
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const UncappedTPS = -1
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// Update updates the inner clock state and returns an integer value
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// indicating how many times the game should update based on given tps.
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// tps represents TPS (ticks per second).
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// If tps is UncappedTPS, Update always returns 1.
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// If tps <= 0 and not UncappedTPS, Update always returns 0.
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//
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// Update is expected to be called per frame.
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func Update(tps int) 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 lastNow > n {
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// This ensures that now() must be monotonic (#875).
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panic("clock: lastNow must be older than n")
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}
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lastNow = n
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c := 0
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if tps == UncappedTPS {
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c = 1
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} else if tps > 0 {
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c = calcCountFromTPS(int64(tps), n)
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}
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updateFPSAndTPS(n, c)
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return c
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}
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