Update builtinShader to not use mutex when single thread build tag is…

… set

shader.go

@@ -16,7 +16,6 @@ package ebiten
 
 import (
 	"fmt"
-	"sync"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/builtinshader"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphics"
@@ -82,14 +81,10 @@ func (s *Shader) appendUniforms(dst []uint32, uniforms map[string]any) []uint32
 }
 
 var (
-	builtinShaders  [builtinshader.FilterCount][builtinshader.AddressCount][2]*Shader
-	builtinShadersM sync.Mutex
+	builtinShaders [builtinshader.FilterCount][builtinshader.AddressCount][2]*Shader
 )
 
-func builtinShader(filter builtinshader.Filter, address builtinshader.Address, useColorM bool) *Shader {
-	builtinShadersM.Lock()
-	defer builtinShadersM.Unlock()
-
+func getBuiltinShader(filter builtinshader.Filter, address builtinshader.Address, useColorM bool) *Shader {
 	var c int
 	if useColorM {
 		c = 1

shader_multithread.go

@@ -0,0 +1,32 @@
+// 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.
+
+//go:build !ebitenginesinglethread && !ebitensinglethread
+
+package ebiten
+
+import (
+	"sync"
+
+	"github.com/hajimehoshi/ebiten/v2/internal/builtinshader"
+)
+
+var shaderMu sync.Mutex
+
+func builtinShader(filter builtinshader.Filter, address builtinshader.Address, useColorM bool) *Shader {
+	shaderMu.Lock()
+	defer shaderMu.Unlock()
+
+	return getBuiltinShader(filter, address, useColorM)
+}

shader_singlethread.go

@@ -0,0 +1,23 @@
+// 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.
+
+//go:build ebitenginesinglethread || ebitensinglethread
+
+package ebiten
+
+import "github.com/hajimehoshi/ebiten/v2/internal/builtinshader"
+
+func builtinShader(filter builtinshader.Filter, address builtinshader.Address, useColorM bool) *Shader {
+	return getBuiltinShader(filter, address, useColorM)
+}