ebiten/examples/contextlost/context_js.go

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// Copyright 2020 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.
// +build example
package main
import (
"fmt"
"syscall/js"
"time"
)
func (g *Game) loseAndRestoreContext() {
doc := js.Global().Get("document")
canvas := doc.Call("getElementsByTagName", "canvas").Index(0)
context := canvas.Call("getContext", "webgl2")
if !context.Truthy() {
context = canvas.Call("getContext", "webgl")
if !context.Truthy() {
context = canvas.Call("getContext", "experimental-webgl")
}
}
if g.lost {
return
}
// Edge might not support the extension. See
// https://developer.mozilla.org/en-US/docs/Web/API/WEBGL_lose_context
ext := context.Call("getExtension", "WEBGL_lose_context")
if !ext.Truthy() {
fmt.Println("Fail to force context lost. Edge might not support the extension yet.")
return
}
ext.Call("loseContext")
fmt.Println("Lost the context!")
fmt.Println("The context is automatically restored after 3 seconds.")
g.lost = true
// If and only if the context is lost by loseContext, you need to call restoreContext. Note that in usual
// case of context lost, you cannot call restoreContext but the context should be restored automatically.
//
// After the context is lost, update will not be called. Instead, fire the goroutine to restore the context.
go func() {
time.Sleep(3 * time.Second)
ext.Call("restoreContext")
fmt.Println("Restored the context!")
g.lost = false
}()
}