internal/builtinshader: add shader constants for shaderlister

Updates #3157

gameforui.go

@@ -144,7 +144,7 @@ var (
 // in your implementation of [FinalScreenDrawer], for example.
 func DefaultDrawFinalScreen(screen FinalScreen, offscreen *Image, geoM GeoM) {
 	theScreenShaderOnce.Do(func() {
-		s, err := newShader(builtinshader.ScreenShaderSource, "screen")
+		s, err := newShader([]byte(builtinshader.ScreenShaderSource), "screen")
 		if err != nil {
 			panic(fmt.Sprintf("ebiten: compiling the screen shader failed: %v", err))
 		}

internal/builtinshader/gen.go

@@ -0,0 +1,84 @@
+// Copyright 2024 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
+
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+
+	"github.com/hajimehoshi/ebiten/v2/internal/builtinshader"
+)
+
+func main() {
+	if err := xmain(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+const license = `// Copyright 2024 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.
+`
+
+func xmain() error {
+	f, err := os.Create("defs.go")
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	w := bufio.NewWriter(f)
+
+	if _, err := w.WriteString("// Code generated by gen.go using 'go generate'. DO NOT EDIT.\n\n"); err != nil {
+		return err
+	}
+	if _, err := w.WriteString(license); err != nil {
+		return err
+	}
+	if _, err := w.WriteString("\npackage builtinshader\n"); err != nil {
+		return err
+	}
+
+	for _, s := range builtinshader.AppendShaderSources(nil) {
+		if _, err := w.WriteString("\n"); err != nil {
+			return err
+		}
+		if _, err := w.WriteString("//ebitengine:shader\n"); err != nil {
+			return err
+		}
+		if _, err := fmt.Fprintf(w, "const _ = %q\n", s); err != nil {
+			return err
+		}
+	}
+
+	if err := w.Flush(); err != nil {
+		return err
+	}
+	return nil
+}

internal/builtinshader/shader.go

@@ -12,6 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:generate go run gen.go
+//go:generate gofmt -s -w .
+
 package builtinshader
 
 import (
@@ -166,7 +169,8 @@ func ShaderSource(filter Filter, address Address, useColorM bool) []byte {
 	return b
 }
 
-var ScreenShaderSource = []byte(`//kage:unit pixels
+//ebitengine:shader
+const ScreenShaderSource = `//kage:unit pixels
 
 package main
 
@@ -185,23 +189,23 @@ func Fragment(dstPos vec4, srcPos vec2) vec4 {
 	rate := clamp(fract(p1)*scale, 0, 1)
 	return mix(mix(c0, c1, rate.x), mix(c2, c3, rate.x), rate.y)
 }
-`)
+`
 
-var ClearShaderSource = []byte(`//kage:unit pixels
+//ebitengine:shader
+const ClearShaderSource = `//kage:unit pixels
 
 package main
 
 func Fragment() vec4 {
 	return vec4(0)
 }
-`)
+`
 
 func AppendShaderSources(sources [][]byte) [][]byte {
 	for filter := Filter(0); filter < FilterCount; filter++ {
 		for address := Address(0); address < AddressCount; address++ {
 			sources = append(sources, ShaderSource(filter, address, false), ShaderSource(filter, address, true))
 		}
 	}
-	sources = append(sources, ScreenShaderSource, ClearShaderSource)
 	return sources
 }