ebiten/internal/loop/run.go

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// Copyright 2016 Hajime Hoshi
//
// 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.
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package loop
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import (
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"errors"
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"sync"
"time"
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"github.com/hajimehoshi/ebiten/internal/graphics/opengl"
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"github.com/hajimehoshi/ebiten/internal/ui"
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)
func CurrentFPS() float64 {
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return currentRunContext.getCurrentFPS()
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}
func IsRunning() bool {
if currentRunContext == nil {
return false
}
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return currentRunContext.isRunning()
}
type runContext struct {
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running bool
fps int
currentFPS float64
runningSlowly bool
frames int
lastUpdated int64
lastFPSUpdated int64
m sync.RWMutex
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}
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var currentRunContext *runContext
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func (c *runContext) startRunning() {
c.m.Lock()
defer c.m.Unlock()
c.running = true
}
func (c *runContext) isRunning() bool {
c.m.Lock()
defer c.m.Unlock()
return c.running
}
func (c *runContext) endRunning() {
c.m.Lock()
defer c.m.Unlock()
c.running = false
}
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func (c *runContext) getCurrentFPS() float64 {
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c.m.RLock()
defer c.m.RUnlock()
if !c.running {
// TODO: Should panic here?
return 0
}
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return c.currentFPS
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}
func (c *runContext) updateFPS(fps float64) {
c.m.Lock()
defer c.m.Unlock()
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c.currentFPS = fps
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}
type GraphicsContext interface {
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SetSize(width, height int, scale float64) error
UpdateAndDraw(context *opengl.Context, updateCount int) error
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}
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func Run(g GraphicsContext, width, height int, scale float64, title string, fps int) error {
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if currentRunContext != nil {
return errors.New("loop: The game is already running")
}
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currentRunContext = &runContext{
fps: fps,
}
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currentRunContext.startRunning()
defer currentRunContext.endRunning()
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if err := ui.CurrentUI().Start(width, height, scale, title); err != nil {
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return err
}
// TODO: Use the error value
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defer ui.CurrentUI().Terminate()
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n := now()
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currentRunContext.lastUpdated = n
currentRunContext.lastFPSUpdated = n
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for {
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e, err := ui.CurrentUI().Update()
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if err != nil {
return err
}
switch e := e.(type) {
case ui.ScreenSizeEvent:
if err := g.SetSize(e.Width, e.Height, e.ActualScale); err != nil {
return err
}
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case ui.CloseEvent:
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return nil
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case ui.RenderEvent:
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if err := currentRunContext.render(g); err != nil {
return err
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}
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e.Done <- struct{}{}
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default:
panic("not reach")
}
}
}
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func (c *runContext) render(g GraphicsContext) error {
fps := c.fps
n := now()
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defer func() {
// Calc the current FPS.
if time.Second > time.Duration(n-c.lastFPSUpdated) {
return
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}
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currentFPS := float64(c.frames) * float64(time.Second) / float64(n-c.lastFPSUpdated)
c.updateFPS(currentFPS)
c.lastFPSUpdated = n
c.frames = 0
}()
// If lastUpdated is too old, we assume that screen is not shown.
if 5*int64(time.Second)/int64(fps) < n-c.lastUpdated {
c.lastUpdated = n
return nil
}
// Note that generally t is a little different from 1/60[sec].
t := n - c.lastUpdated
tt := int(t * int64(fps) / int64(time.Second))
// As t is not accurate 1/60[sec], errors are accumulated.
// To make the FPS stable, set tt 1 if t is a little less than 1/60[sec].
if tt == 0 && (int64(time.Second)/int64(fps)-int64(5*time.Millisecond)) < t {
tt = 1
}
if err := g.UpdateAndDraw(ui.GLContext(), tt); err != nil {
return err
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}
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if err := ui.CurrentUI().SwapBuffers(); err != nil {
return err
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}
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c.lastUpdated += int64(tt) * int64(time.Second) / int64(fps)
c.frames++
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return nil
}