ebiten/examples/contextlost/main.go

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// Copyright 2018 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.
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//go:build example
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// +build example
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package main
import (
"bytes"
"image"
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_ "image/jpeg"
"log"
"math"
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"github.com/hajimehoshi/ebiten/v2"
"github.com/hajimehoshi/ebiten/v2/ebitenutil"
"github.com/hajimehoshi/ebiten/v2/examples/resources/images"
"github.com/hajimehoshi/ebiten/v2/inpututil"
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)
const (
screenWidth = 640
screenHeight = 480
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)
var (
gophersImage *ebiten.Image
extraImages []*ebiten.Image
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)
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type Game struct {
count int
lost bool
}
func (g *Game) Update() error {
if inpututil.IsKeyJustPressed(ebiten.KeySpace) {
g.loseAndRestoreContext()
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return nil
}
if inpututil.IsKeyJustPressed(ebiten.KeyS) {
ebiten.SetScreenClearedEveryFrame(!ebiten.IsScreenClearedEveryFrame())
}
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g.count++
return nil
}
func (g *Game) Draw(screen *ebiten.Image) {
if g.lost {
// When the context is lost, skip rendering. Usually this logic should not be required, but when the
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// context lost happens by the API explicitly, Draw can be called even after the data in GPU
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// disappeared.
return
}
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w, h := gophersImage.Size()
op := &ebiten.DrawImageOptions{}
// For the details, see examples/rotate.
op.GeoM.Translate(-float64(w)/2, -float64(h)/2)
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op.GeoM.Rotate(float64(g.count%360) * 2 * math.Pi / 360)
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op.GeoM.Translate(screenWidth/2, screenHeight/2)
screen.DrawImage(gophersImage, op)
msg := `Press Space to force to lose/restore the GL context!
(Browser only)
Press S to switch clearing the screen
at the beginning of each frame.`
ebitenutil.DebugPrint(screen, msg)
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}
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func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
return screenWidth, screenHeight
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}
func main() {
// Decode an image from the image file's byte slice.
// Now the byte slice is generated with //go:generate for Go 1.15 or older.
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// If you use Go 1.16 or newer, it is strongly recommended to use //go:embed to embed the image file.
// See https://pkg.go.dev/embed for more details.
img, _, err := image.Decode(bytes.NewReader(images.Gophers_jpg))
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if err != nil {
log.Fatal(err)
}
gophersImage = ebiten.NewImageFromImage(img)
// Extend the shared backend GL texture on purpose.
for i := 0; i < 20; i++ {
eimg := ebiten.NewImageFromImage(img)
extraImages = append(extraImages, eimg)
}
ebiten.SetWindowSize(screenWidth, screenHeight)
ebiten.SetWindowTitle("Context Lost (Ebitengine Demo)")
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if err := ebiten.RunGame(&Game{}); err != nil {
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log.Fatal(err)
}
}