ebiten: Add ebitensinglethread build tag (#1396)

Updates #1367

doc.go

@@ -70,4 +70,7 @@
 // number of graphics commands affects the performance of your game.
 //
 // `ebitengl` forces to use OpenGL in any environments.
+//
+// `ebitensinglethread` disables Ebiten's thread safety to unlock maximum performance. If you use this you will have
+// to manage threads yourself. Functions like IsKeyPressed will no longer be concurrent-safe with this build tag.
 package ebiten

internal/thread/thread.go

@@ -18,17 +18,23 @@ import (
 	"errors"
 )
 
-// Thread represents an OS thread.
-type Thread struct {
+// Thread defines threading behavior in ebiten.
+type Thread interface {
+	Call(func() error) error
+	Loop()
+}
+
+// OSThread represents an OS thread.
+type OSThread struct {
 	funcs   chan func() error
 	results chan error
 }
 
-// New creates a new thread.
+// NewOSThread creates a new thread.
 //
-// It is assumed that the OS thread is fixed by runtime.LockOSThread when New is called.
-func New() *Thread {
-	return &Thread{
+// It is assumed that the OS thread is fixed by runtime.LockOSThread when NewOSThread is called.
+func NewOSThread() *OSThread {
+	return &OSThread{
 		funcs:   make(chan func() error),
 		results: make(chan error),
 	}
@@ -40,7 +46,7 @@ var BreakLoop = errors.New("break loop")
 // Loop starts the thread loop until a posted function returns BreakLoop.
 //
 // Loop must be called on the thread.
-func (t *Thread) Loop() {
+func (t *OSThread) Loop() {
 	for f := range t.funcs {
 		err := f()
 		if err == BreakLoop {
@@ -58,7 +64,23 @@ func (t *Thread) Loop() {
 // If f returns BreakLoop, Loop returns.
 //
 // Call blocks if Loop is not called.
-func (t *Thread) Call(f func() error) error {
+func (t *OSThread) Call(f func() error) error {
 	t.funcs <- f
 	return <-t.results
 }
+
+// NoopThread is used to disable threading.
+type NoopThread struct{}
+
+// NewNoopThread creates a new thread that does no threading.
+func NewNoopThread() Thread {
+	return &NoopThread{}
+}
+
+// Loop does nothing
+func (t *NoopThread) Loop() {}
+
+// Call executes the func immediately
+func (t *NoopThread) Call(f func() error) error {
+	return f()
+}

internal/uidriver/glfw/run_notsinglethread.go

@@ -0,0 +1,61 @@
+// 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 !ebitensinglethread
+// +build darwin freebsd linux windows
+// +build !android
+// +build !ios
+
+package glfw
+
+import (
+	"github.com/hajimehoshi/ebiten/v2/internal/driver"
+	"github.com/hajimehoshi/ebiten/v2/internal/graphicscommand"
+	"github.com/hajimehoshi/ebiten/v2/internal/thread"
+)
+
+func (u *UserInterface) Run(uicontext driver.UIContext) error {
+	u.context = uicontext
+
+	// Initialize the main thread first so the thread is available at u.run (#809).
+	u.t = thread.NewOSThread()
+	graphicscommand.SetMainThread(u.t)
+
+	ch := make(chan error, 1)
+	go func() {
+		defer func() {
+			_ = u.t.Call(func() error {
+				return thread.BreakLoop
+			})
+		}()
+
+		defer close(ch)
+
+		_ = u.t.Call(func() error {
+			if err := u.init(); err != nil {
+				ch <- err
+			}
+			return nil
+		})
+
+		if err := u.loop(); err != nil {
+			ch <- err
+		}
+	}()
+
+	u.setRunning(true)
+	u.t.Loop()
+	u.setRunning(false)
+	return <-ch
+}

internal/uidriver/glfw/run_singlethread.go

@@ -0,0 +1,47 @@
+// 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 ebitensinglethread
+// +build darwin freebsd linux windows
+// +build !android
+// +build !ios
+
+package glfw
+
+import (
+	"github.com/hajimehoshi/ebiten/v2/internal/driver"
+	"github.com/hajimehoshi/ebiten/v2/internal/graphicscommand"
+	"github.com/hajimehoshi/ebiten/v2/internal/thread"
+)
+
+func (u *UserInterface) Run(uicontext driver.UIContext) error {
+	u.context = uicontext
+
+	// Initialize the main thread first so the thread is available at u.run (#809).
+	u.t = thread.NewNoopThread()
+	graphicscommand.SetMainThread(u.t)
+
+	u.setRunning(true)
+
+	if err := u.init(); err != nil {
+		return err
+	}
+
+	if err := u.loop(); err != nil {
+		return err
+	}
+
+	u.setRunning(false)
+	return nil
+}

internal/uidriver/glfw/ui.go

@@ -29,7 +29,6 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/internal/devicescale"
 	"github.com/hajimehoshi/ebiten/v2/internal/driver"
 	"github.com/hajimehoshi/ebiten/v2/internal/glfw"
-	"github.com/hajimehoshi/ebiten/v2/internal/graphicscommand"
 	"github.com/hajimehoshi/ebiten/v2/internal/hooks"
 	"github.com/hajimehoshi/ebiten/v2/internal/thread"
 )
@@ -80,7 +79,7 @@ type UserInterface struct {
 	input   Input
 	iwindow window
 
-	t *thread.Thread
+	t thread.Thread
 	m sync.RWMutex
 }
 
@@ -583,41 +582,6 @@ func init() {
 	runtime.LockOSThread()
 }
 
-func (u *UserInterface) Run(uicontext driver.UIContext) error {
-	u.context = uicontext
-
-	// Initialize the main thread first so the thread is available at u.run (#809).
-	u.t = thread.New()
-	graphicscommand.SetMainThread(u.t)
-
-	ch := make(chan error, 1)
-	go func() {
-		defer func() {
-			_ = u.t.Call(func() error {
-				return thread.BreakLoop
-			})
-		}()
-
-		defer close(ch)
-
-		_ = u.t.Call(func() error {
-			if err := u.init(); err != nil {
-				ch <- err
-			}
-			return nil
-		})
-
-		if err := u.loop(); err != nil {
-			ch <- err
-		}
-	}()
-
-	u.setRunning(true)
-	u.t.Loop()
-	u.setRunning(false)
-	return <-ch
-}
-
 func (u *UserInterface) RunWithoutMainLoop(context driver.UIContext) {
 	panic("glfw: RunWithoutMainLoop is not implemented")
 }

internal/uidriver/mobile/ui.go

@@ -111,7 +111,7 @@ type UserInterface struct {
 
 	input Input
 
-	t *thread.Thread
+	t *thread.OSThread
 
 	m sync.RWMutex
 }
@@ -271,7 +271,7 @@ func (u *UserInterface) run(context driver.UIContext, mainloop bool) (err error)
 		ctx := <-glContextCh
 		u.Graphics().(*opengl.Graphics).SetGomobileGLContext(ctx)
 	} else {
-		u.t = thread.New()
+		u.t = thread.NewOSThread()
 		graphicscommand.SetMainThread(u.t)
 	}