2017-07-13 17:28:28 +02:00
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// 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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2018-01-07 08:43:01 +01:00
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// Package clock manages game timers.
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2017-07-13 17:28:28 +02:00
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package clock
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import (
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2018-05-09 16:41:06 +02:00
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"sync"
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2017-08-05 17:18:38 +02:00
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"time"
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2017-07-13 17:28:28 +02:00
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)
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var (
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2018-05-26 17:30:08 +02:00
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frames int64
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2018-01-07 08:43:01 +01:00
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2018-01-07 12:19:18 +01:00
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// lastSystemTime is the last system time in the previous Update.
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lastSystemTime int64
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2017-08-05 19:09:33 +02:00
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currentFPS float64
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lastFPSUpdated int64
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framesForFPS int64
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2018-05-26 11:04:20 +02:00
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started bool
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onStart func()
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2017-08-05 19:09:33 +02:00
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m sync.Mutex
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)
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2017-08-05 19:09:33 +02:00
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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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2018-05-26 11:04:20 +02:00
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func OnStart(f func()) {
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m.Lock()
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onStart = f
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m.Unlock()
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}
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2017-08-05 19:09:33 +02:00
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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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2017-08-05 18:43:09 +02:00
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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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2018-07-15 15:43:14 +02:00
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func Update(logicFPS int) int {
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m.Lock()
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defer m.Unlock()
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2018-05-26 11:04:20 +02:00
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if !started {
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if onStart != nil {
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onStart()
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}
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started = true
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}
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2018-05-26 11:04:20 +02:00
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n := now()
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2018-01-07 12:19:18 +01:00
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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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2017-08-05 17:52:12 +02:00
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}
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2018-01-07 12:32:18 +01:00
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diff := n - lastSystemTime
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if diff < 0 {
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return 0
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}
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2017-08-05 17:18:38 +02:00
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count := 0
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2018-01-07 08:43:01 +01:00
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syncWithSystemClock := false
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2018-07-15 15:43:14 +02:00
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if diff > 5*int64(time.Second)/int64(logicFPS) {
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2018-05-26 17:30:08 +02:00
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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 * int64(logicFPS) / int64(time.Second))
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}
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// Stabilize FPS.
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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)/int64(logicFPS)/2) < diff {
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count = 1
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}
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2018-07-15 15:43:14 +02:00
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if count == 2 && (int64(time.Second)/int64(logicFPS)*3/2) > diff {
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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) / int64(logicFPS)
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}
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2017-08-05 19:09:33 +02:00
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2017-08-05 19:12:23 +02:00
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updateFPS(n)
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2017-08-05 17:52:12 +02:00
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return count
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2017-07-13 17:28:28 +02:00
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}
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