ebiten/run.go

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// Copyright 2014 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 ebiten
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import (
"time"
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"github.com/hajimehoshi/ebiten/internal/ui"
)
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var runContext = &struct {
running bool
fps float64
newScreenWidth int
newScreenHeight int
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newScreenScale int
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isRunningSlowly bool
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}{}
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// FPS represents how many times game updating happens in a second.
const FPS = 60
// CurrentFPS returns the current number of frames per second of rendering.
//
// This value represents how many times rendering happens in 1/60 second and
// NOT how many times logical game updating (a passed function to Run) happens.
// Note that logical game updating is assured to happen 60 times in a second
// as long as the screen is active.
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func CurrentFPS() float64 {
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return runContext.fps
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}
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// IsRunningSlowly returns true if the game is running too slowly to keep 60 FPS of rendering.
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// The game screen is not updated when IsRunningSlowly is true.
// It is recommended to skip heavy processing, especially drawing, when IsRunningSlowly is true.
func IsRunningSlowly() bool {
return runContext.isRunningSlowly
}
// Run runs the game.
// f is a function which is called at every frame.
// The argument (*Image) is the render target that represents the screen.
//
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// This function must be called from the main thread.
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// Note that ebiten bounds the main goroutine to the main OS thread by runtime.LockOSThread.
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//
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// The given function f is guaranteed to be called 60 times a second
// even if a rendering frame is skipped.
// f is not called when the screen is not shown.
func Run(f func(*Image) error, width, height, scale int, title string) error {
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runContext.running = true
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defer func() {
runContext.running = false
}()
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if err := ui.CurrentUI().Start(width, height, scale, title); err != nil {
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return err
}
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defer ui.CurrentUI().Terminate()
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glContext.Check()
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graphicsContext, err := newGraphicsContext(width, height, ui.CurrentUI().ActualScreenScale())
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if err != nil {
return err
}
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frames := 0
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now := ui.Now()
beforeForUpdate := now
beforeForFPS := now
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for {
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// TODO: setSize should be called after swapping buffers?
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if 0 < runContext.newScreenWidth || 0 < runContext.newScreenHeight || 0 < runContext.newScreenScale {
changed := false
if 0 < runContext.newScreenWidth || 0 < runContext.newScreenHeight {
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c := ui.CurrentUI().SetScreenSize(runContext.newScreenWidth, runContext.newScreenHeight)
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changed = changed || c
}
if 0 < runContext.newScreenScale {
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c := ui.CurrentUI().SetScreenScale(runContext.newScreenScale)
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changed = changed || c
}
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if changed {
w, h := runContext.newScreenWidth, runContext.newScreenHeight
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if err := graphicsContext.setSize(w, h, ui.CurrentUI().ActualScreenScale()); err != nil {
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return err
}
}
}
runContext.newScreenWidth = 0
runContext.newScreenHeight = 0
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runContext.newScreenScale = 0
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if err := ui.CurrentUI().DoEvents(); err != nil {
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return err
}
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if ui.CurrentUI().IsClosed() {
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return nil
}
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now := ui.Now()
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// If beforeForUpdate is too old, we assume that screen is not shown.
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runContext.isRunningSlowly = false
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if int64(5*time.Second/FPS) < now-beforeForUpdate {
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beforeForUpdate = now
} else {
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c := float64(now-beforeForUpdate) * FPS / float64(time.Second)
runContext.isRunningSlowly = c >= 2.5
for i := 0; i < int(c); i++ {
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if err := ui.CurrentUI().DoEvents(); err != nil {
return err
}
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if ui.CurrentUI().IsClosed() {
return nil
}
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if err := graphicsContext.update(f); err != nil {
return err
}
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}
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beforeForUpdate += int64(c) * int64(time.Second/FPS)
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ui.CurrentUI().SwapBuffers()
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}
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// Calc the current FPS.
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now = ui.Now()
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frames++
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if time.Second <= time.Duration(now-beforeForFPS) {
runContext.fps = float64(frames) * float64(time.Second) / float64(now-beforeForFPS)
beforeForFPS = now
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frames = 0
}
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}
}
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// SetScreenSize changes the (logical) size of the screen.
// This doesn't affect the current scale of the screen.
func SetScreenSize(width, height int) {
if !runContext.running {
panic("SetScreenSize must be called during Run")
}
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if width <= 0 || height <= 0 {
panic("width and height must be positive")
}
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runContext.newScreenWidth = width
runContext.newScreenHeight = height
}
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// SetScreenSize changes the scale of the screen.
func SetScreenScale(scale int) {
if !runContext.running {
panic("SetScreenScale must be called during Run")
}
if scale <= 0 {
panic("scale must be positive")
}
runContext.newScreenScale = scale
}
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// ScreenScale returns the current screen scale.
func ScreenScale() int {
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return ui.CurrentUI().ScreenScale()
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}