internal/buffer: bug fix: shader manipulations must be buffered

Closes #2162

internal/buffered/image.go

@@ -229,12 +229,32 @@ type Shader struct {
 }
 
 func NewShader(ir *shaderir.Program) *Shader {
-	return &Shader{
-		shader: atlas.NewShader(ir),
+	s := &Shader{}
+	s.initialize(ir)
+	return s
+}
+
+func (s *Shader) initialize(ir *shaderir.Program) {
+	if maybeCanAddDelayedCommand() {
+		if tryAddDelayedCommand(func() error {
+			s.initialize(ir)
+			return nil
+		}) {
+			return
+		}
 	}
+	s.shader = atlas.NewShader(ir)
 }
 
 func (s *Shader) MarkDisposed() {
+	if maybeCanAddDelayedCommand() {
+		if tryAddDelayedCommand(func() error {
+			s.MarkDisposed()
+			return nil
+		}) {
+			return
+		}
+	}
 	s.shader.MarkDisposed()
 	s.shader = nil
 }

internal/processtest/testdata/issue2162.go

@@ -0,0 +1,65 @@
+// Copyright 2022 The Ebitengine 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.
+
+//go:build ignore
+// +build ignore
+
+package main
+
+import (
+	"errors"
+
+	"github.com/hajimehoshi/ebiten/v2"
+)
+
+func init() {
+	s, err := ebiten.NewShader([]byte(`
+package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	return vec4(1)
+}`))
+	if err != nil {
+		panic(err)
+	}
+	s.Dispose()
+}
+
+var regularTermination = errors.New("regular termination")
+
+type Game struct {
+	counter int
+}
+
+func (g *Game) Update() error {
+	g.counter++
+	if g.counter > 1 {
+		return regularTermination
+	}
+	return nil
+}
+
+func (g *Game) Draw(screen *ebiten.Image) {
+}
+
+func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
+	return outsideWidth, outsideHeight
+}
+
+func main() {
+	// Run a game loop at least for one frame to ensure the shader disposed.
+	if err := ebiten.RunGame(&Game{}); err != nil && err != regularTermination {
+		panic(err)
+	}
+}