ebiten: add RunOnMainThread(func()) (#1927)

Closes #1926

internal/graphicscommand/command.go

@@ -224,10 +224,11 @@ func (q *commandQueue) Enqueue(command command) {
 }
 
 // Flush flushes the command queue.
-func (q *commandQueue) Flush() error {
-	return runOnMainThread(func() error {
-		return q.flush()
+func (q *commandQueue) Flush() (err error) {
+	RunOnMainThread(func() {
+		err = q.flush()
 	})
+	return
 }
 
 // flush must be called the main thread.
@@ -699,18 +700,19 @@ func (c *newShaderCommand) Exec(indexOffset int) error {
 }
 
 // InitializeGraphicsDriverState initialize the current graphics driver state.
-func InitializeGraphicsDriverState() error {
-	return runOnMainThread(func() error {
-		return theGraphicsDriver.Initialize()
+func InitializeGraphicsDriverState() (err error) {
+	RunOnMainThread(func() {
+		err = theGraphicsDriver.Initialize()
 	})
+	return
 }
 
 // ResetGraphicsDriverState resets the current graphics driver state.
 // If the graphics driver doesn't have an API to reset, ResetGraphicsDriverState does nothing.
-func ResetGraphicsDriverState() error {
+func ResetGraphicsDriverState() (err error) {
 	if r, ok := theGraphicsDriver.(interface{ Reset() error }); ok {
-		return runOnMainThread(func() error {
-			return r.Reset()
+		RunOnMainThread(func() {
+			err = r.Reset()
 		})
 	}
 	return nil
@@ -719,9 +721,8 @@ func ResetGraphicsDriverState() error {
 // MaxImageSize returns the maximum size of an image.
 func MaxImageSize() int {
 	var size int
-	_ = runOnMainThread(func() error {
+	RunOnMainThread(func() {
 		size = theGraphicsDriver.MaxImageSize()
-		return nil
 	})
 	return size
 }

internal/graphicscommand/thread.go

@@ -17,7 +17,7 @@ package graphicscommand
 var theThread Thread
 
 type Thread interface {
-	Call(f func() error) error
+	Call(f func())
 }
 
 // SetMainThread must be called from the main thread (i.e, the goroutine where the thread is created).
@@ -25,12 +25,14 @@ func SetMainThread(thread Thread) {
 	theThread = thread
 }
 
-func runOnMainThread(f func() error) error {
+// RunOnMainThread calls f on the main thread, and returns an error if any.
+func RunOnMainThread(f func()) {
 	// The thread is nil when 1) GOOS=js or 2) using golang.org/x/mobile/gl.
 	// When golang.org/x/mobile/gl is used, all the GL functions are called via Context, which already runs on an
 	// appropriate thread.
 	if theThread == nil {
-		return f()
+		f()
+		return
 	}
-	return theThread.Call(f)
+	theThread.Call(f)
 }

internal/thread/thread.go

@@ -14,20 +14,18 @@
 
 package thread
 
-import (
-	"errors"
-)
-
 // Thread defines threading behavior in Ebiten.
 type Thread interface {
-	Call(func() error) error
+	Call(func())
 	Loop()
+	Stop()
 }
 
 // OSThread represents an OS thread.
 type OSThread struct {
-	funcs   chan func() error
-	results chan error
+	funcs     chan func()
+	done      chan struct{}
+	terminate chan struct{}
 }
 
 // NewOSThread creates a new thread.
@@ -35,38 +33,45 @@ type OSThread struct {
 // 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),
+		funcs:     make(chan func()),
+		done:      make(chan struct{}),
+		terminate: make(chan struct{}),
 	}
 }
 
-// BreakLoop represents an termination of the loop.
-var BreakLoop = errors.New("break loop")
-
-// Loop starts the thread loop until a posted function returns BreakLoop.
+// Loop starts the thread loop until Stop is called.
 //
 // Loop must be called on the thread.
 func (t *OSThread) Loop() {
-	for f := range t.funcs {
-		err := f()
-		if err == BreakLoop {
-			t.results <- nil
+	for {
+		select {
+		case fn := <-t.funcs:
+			func() {
+				defer func() {
+					t.done <- struct{}{}
+				}()
+
+				fn()
+			}()
+		case <-t.terminate:
 			return
 		}
-		t.results <- err
 	}
 }
 
+// Stop stops the thread loop.
+func (t *OSThread) Stop() {
+	close(t.terminate)
+}
+
 // Call calls f on the thread.
 //
 // Do not call this from the same thread. This would block forever.
 //
-// If f returns BreakLoop, Loop returns.
-//
 // Call blocks if Loop is not called.
-func (t *OSThread) Call(f func() error) error {
+func (t *OSThread) Call(f func()) {
 	t.funcs <- f
-	return <-t.results
+	<-t.done
 }
 
 // NoopThread is used to disable threading.
@@ -81,6 +86,7 @@ func NewNoopThread() *NoopThread {
 func (t *NoopThread) Loop() {}
 
 // Call executes the func immediately
-func (t *NoopThread) Call(f func() error) error {
-	return f()
-}
+func (t *NoopThread) Call(f func()) { f() }
+
+// Stop does nothing
+func (t *NoopThread) Stop() {}

internal/uidriver/glfw/run_notsinglethread.go

@@ -32,16 +32,13 @@ func (u *UserInterface) Run(uicontext driver.UIContext) error {
 
 	ch := make(chan error, 1)
 	go func() {
-		defer func() {
-			_ = u.t.Call(func() error {
-				return thread.BreakLoop
-			})
-		}()
+		defer u.t.Stop()
 
 		defer close(ch)
 
-		if err := u.t.Call(func() error {
-			return u.init()
+		var err error
+		if u.t.Call(func() {
+			err = u.init()
 		}); err != nil {
 			ch <- err
 			return
@@ -77,11 +74,7 @@ func (u *UserInterface) runOnAnotherThreadFromMainThread(f func() error) error {
 
 	var err error
 	go func() {
-		defer func() {
-			_ = u.t.Call(func() error {
-				return thread.BreakLoop
-			})
-		}()
+		defer u.t.Stop()
 		err = f()
 	}()
 	u.t.Loop()

internal/uidriver/glfw/ui.go

@@ -484,12 +484,11 @@ func (u *UserInterface) ScreenSizeInFullscreen() (int, int) {
 	}
 
 	var w, h int
-	_ = u.t.Call(func() error {
+	u.t.Call(func() {
 		m := u.currentMonitor()
 		v := m.GetVideoMode()
 		w = int(u.dipFromGLFWMonitorPixel(float64(v.Width), m))
 		h = int(u.dipFromGLFWMonitorPixel(float64(v.Height), m))
-		return nil
 	})
 	return w, h
 }
@@ -507,9 +506,8 @@ func (u *UserInterface) IsFullscreen() bool {
 		return u.isInitFullscreen()
 	}
 	b := false
-	_ = u.t.Call(func() error {
+	u.t.Call(func() {
 		b = u.isFullscreen()
-		return nil
 	})
 	return b
 }
@@ -521,18 +519,16 @@ func (u *UserInterface) SetFullscreen(fullscreen bool) {
 	}
 
 	var update bool
-	_ = u.t.Call(func() error {
+	u.t.Call(func() {
 		update = u.isFullscreen() != fullscreen
-		return nil
 	})
 	if !update {
 		return
 	}
 
-	_ = u.t.Call(func() error {
+	u.t.Call(func() {
 		w, h := u.windowWidthInDIP, u.windowHeightInDIP
 		u.setWindowSizeInDIP(w, h, fullscreen)
-		return nil
 	})
 }
 
@@ -542,9 +538,8 @@ func (u *UserInterface) IsFocused() bool {
 	}
 
 	var focused bool
-	_ = u.t.Call(func() error {
+	u.t.Call(func() {
 		focused = u.window.GetAttrib(glfw.Focused) == glfw.True
-		return nil
 	})
 	return focused
 }
@@ -564,14 +559,13 @@ func (u *UserInterface) SetFPSMode(mode driver.FPSMode) {
 		u.m.Unlock()
 		return
 	}
-	_ = u.t.Call(func() error {
+	u.t.Call(func() {
 		if !u.fpsModeInited {
 			u.fpsMode = mode
-			return nil
+			return
 		}
 		u.setFPSMode(mode)
 		u.updateVsync()
-		return nil
 	})
 }
 
@@ -583,9 +577,8 @@ func (u *UserInterface) FPSMode() driver.FPSMode {
 		return m
 	}
 	var v driver.FPSMode
-	_ = u.t.Call(func() error {
+	u.t.Call(func() {
 		v = u.fpsMode
-		return nil
 	})
 	return v
 }
@@ -603,21 +596,23 @@ func (u *UserInterface) CursorMode() driver.CursorMode {
 	if !u.isRunning() {
 		return u.getInitCursorMode()
 	}
-	var v driver.CursorMode
-	_ = u.t.Call(func() error {
-		mode := u.window.GetInputMode(glfw.CursorMode)
-		switch mode {
-		case glfw.CursorNormal:
-			v = driver.CursorModeVisible
-		case glfw.CursorHidden:
-			v = driver.CursorModeHidden
-		case glfw.CursorDisabled:
-			v = driver.CursorModeCaptured
-		default:
-			panic(fmt.Sprintf("glfw: invalid GLFW cursor mode: %d", mode))
-		}
-		return nil
+
+	var mode int
+	u.t.Call(func() {
+		mode = u.window.GetInputMode(glfw.CursorMode)
 	})
+
+	var v driver.CursorMode
+	switch mode {
+	case glfw.CursorNormal:
+		v = driver.CursorModeVisible
+	case glfw.CursorHidden:
+		v = driver.CursorModeHidden
+	case glfw.CursorDisabled:
+		v = driver.CursorModeCaptured
+	default:
+		panic(fmt.Sprintf("glfw: invalid GLFW cursor mode: %d", mode))
+	}
 	return v
 }
 
@@ -626,9 +621,8 @@ func (u *UserInterface) SetCursorMode(mode driver.CursorMode) {
 		u.setInitCursorMode(mode)
 		return
 	}
-	_ = u.t.Call(func() error {
+	u.t.Call(func() {
 		u.window.SetInputMode(glfw.CursorMode, driverCursorModeToGLFWCursorMode(mode))
-		return nil
 	})
 }
 
@@ -644,9 +638,8 @@ func (u *UserInterface) SetCursorShape(shape driver.CursorShape) {
 	if !u.isRunning() {
 		return
 	}
-	_ = u.t.Call(func() error {
+	u.t.Call(func() {
 		u.setNativeCursor(shape)
-		return nil
 	})
 }
 
@@ -657,9 +650,8 @@ func (u *UserInterface) DeviceScaleFactor() float64 {
 	}
 
 	f := 0.0
-	_ = u.t.Call(func() error {
+	u.t.Call(func() {
 		f = u.deviceScaleFactor(u.currentMonitor())
-		return nil
 	})
 	return f
 }
@@ -745,7 +737,7 @@ func (u *UserInterface) registerWindowSetSizeCallback() {
 
 				var outsideWidth, outsideHeight float64
 
-				_ = u.t.Call(func() error {
+				u.t.Call(func() {
 					if width != 0 || height != 0 {
 						w := int(u.dipFromGLFWPixel(float64(width), u.currentMonitor()))
 						h := int(u.dipFromGLFWPixel(float64(height), u.currentMonitor()))
@@ -753,16 +745,14 @@ func (u *UserInterface) registerWindowSetSizeCallback() {
 					}
 
 					outsideWidth, outsideHeight = u.updateSize()
-					return nil
 				})
 				u.context.Layout(outsideWidth, outsideHeight)
 				if err := u.context.ForceUpdateFrame(); err != nil {
 					return err
 				}
 				if u.Graphics().IsGL() {
-					_ = u.t.Call(func() error {
+					u.t.Call(func() {
 						u.swapBuffers()
-						return nil
 					})
 				}
 				return nil
@@ -1023,12 +1013,7 @@ func (u *UserInterface) update() (float64, float64, error) {
 }
 
 func (u *UserInterface) loop() error {
-	defer func() {
-		_ = u.t.Call(func() error {
-			glfw.Terminate()
-			return nil
-		})
-	}()
+	defer u.t.Call(glfw.Terminate)
 
 	for {
 		var unfocused bool
@@ -1047,10 +1032,9 @@ func (u *UserInterface) loop() error {
 		}
 
 		var outsideWidth, outsideHeight float64
-		if err := u.t.Call(func() error {
-			var err error
+		var err error
+		if u.t.Call(func() {
 			outsideWidth, outsideHeight, err = u.update()
-			return err
 		}); err != nil {
 			return err
 		}
@@ -1084,14 +1068,13 @@ func (u *UserInterface) loop() error {
 					newImgs[i] = rgba
 				}
 
-				_ = u.t.Call(func() error {
+				u.t.Call(func() {
 					// In the fullscreen mode, reset the icon images and try again later.
 					if u.isFullscreen() {
 						u.setIconImages(imgs)
-						return nil
+						return
 					}
 					u.window.SetIcon(newImgs)
-					return nil
 				})
 			}()
 		}
@@ -1100,10 +1083,7 @@ func (u *UserInterface) loop() error {
 		// However, (*thread).Call is not good for performance due to channels.
 		// Let's avoid this whenever possible (#1367).
 		if u.Graphics().IsGL() {
-			_ = u.t.Call(func() error {
-				u.swapBuffers()
-				return nil
-			})
+			u.t.Call(u.swapBuffers)
 		}
 
 		if unfocused {
@@ -1399,9 +1379,8 @@ func (u *UserInterface) IsScreenTransparent() bool {
 		return u.isInitScreenTransparent()
 	}
 	val := false
-	_ = u.t.Call(func() error {
+	u.t.Call(func() {
 		val = u.window.GetAttrib(glfw.TransparentFramebuffer) == glfw.True
-		return nil
 	})
 	return val
 }
@@ -1409,9 +1388,8 @@ func (u *UserInterface) IsScreenTransparent() bool {
 func (u *UserInterface) ResetForFrame() {
 	// The offscreens must be updated every frame (#490).
 	var w, h float64
-	_ = u.t.Call(func() error {
+	u.t.Call(func() {
 		w, h = u.updateSize()
-		return nil
 	})
 	u.context.Layout(w, h)
 	u.input.resetForFrame()

internal/uidriver/glfw/window.go

@@ -32,9 +32,8 @@ func (w *window) IsDecorated() bool {
 		return w.ui.isInitWindowDecorated()
 	}
 	v := false
-	_ = w.ui.t.Call(func() error {
+	w.ui.t.Call(func() {
 		v = w.ui.window.GetAttrib(glfw.Decorated) == glfw.True
-		return nil
 	})
 	return v
 }
@@ -45,13 +44,12 @@ func (w *window) SetDecorated(decorated bool) {
 		return
 	}
 
-	_ = w.ui.t.Call(func() error {
+	w.ui.t.Call(func() {
 		if w.ui.isNativeFullscreen() {
-			return nil
+			return
 		}
 
 		w.ui.setWindowDecorated(decorated)
-		return nil
 	})
 }
 
@@ -60,9 +58,8 @@ func (w *window) IsResizable() bool {
 		return w.ui.isInitWindowResizable()
 	}
 	v := false
-	_ = w.ui.t.Call(func() error {
+	w.ui.t.Call(func() {
 		v = w.ui.window.GetAttrib(glfw.Resizable) == glfw.True
-		return nil
 	})
 	return v
 }
@@ -72,12 +69,11 @@ func (w *window) SetResizable(resizable bool) {
 		w.ui.setInitWindowResizable(resizable)
 		return
 	}
-	_ = w.ui.t.Call(func() error {
+	w.ui.t.Call(func() {
 		if w.ui.isNativeFullscreen() {
-			return nil
+			return
 		}
 		w.ui.setWindowResizable(resizable)
-		return nil
 	})
 }
 
@@ -86,9 +82,8 @@ func (w *window) IsFloating() bool {
 		return w.ui.isInitWindowFloating()
 	}
 	var v bool
-	_ = w.ui.t.Call(func() error {
+	w.ui.t.Call(func() {
 		v = w.ui.window.GetAttrib(glfw.Floating) == glfw.True
-		return nil
 	})
 	return v
 }
@@ -98,12 +93,11 @@ func (w *window) SetFloating(floating bool) {
 		w.ui.setInitWindowFloating(floating)
 		return
 	}
-	_ = w.ui.t.Call(func() error {
+	w.ui.t.Call(func() {
 		if w.ui.isNativeFullscreen() {
-			return nil
+			return
 		}
 		w.ui.setWindowFloating(floating)
-		return nil
 	})
 }
 
@@ -112,9 +106,8 @@ func (w *window) IsMaximized() bool {
 		return w.ui.isInitWindowMaximized()
 	}
 	var v bool
-	_ = w.ui.t.Call(func() error {
+	w.ui.t.Call(func() {
 		v = w.ui.window.GetAttrib(glfw.Maximized) == glfw.True
-		return nil
 	})
 	return v
 }
@@ -127,10 +120,7 @@ func (w *window) Maximize() {
 		w.ui.setInitWindowMaximized(true)
 		return
 	}
-	_ = w.ui.t.Call(func() error {
-		w.ui.maximizeWindow()
-		return nil
-	})
+	w.ui.t.Call(w.ui.maximizeWindow)
 }
 
 func (w *window) IsMinimized() bool {
@@ -138,9 +128,8 @@ func (w *window) IsMinimized() bool {
 		return false
 	}
 	var v bool
-	_ = w.ui.t.Call(func() error {
+	w.ui.t.Call(func() {
 		v = w.ui.window.GetAttrib(glfw.Iconified) == glfw.True
-		return nil
 	})
 	return v
 }
@@ -150,10 +139,7 @@ func (w *window) Minimize() {
 		// Do nothing
 		return
 	}
-	_ = w.ui.t.Call(func() error {
-		w.ui.iconifyWindow()
-		return nil
-	})
+	w.ui.t.Call(w.ui.iconifyWindow)
 }
 
 func (w *window) Restore() {
@@ -161,10 +147,7 @@ func (w *window) Restore() {
 		// Do nothing
 		return
 	}
-	_ = w.ui.t.Call(func() error {
-		w.ui.restoreWindow()
-		return nil
-	})
+	w.ui.t.Call(w.ui.restoreWindow)
 }
 
 func (w *window) Position() (int, int) {
@@ -172,7 +155,7 @@ func (w *window) Position() (int, int) {
 		panic("glfw: WindowPosition can't be called before the main loop starts")
 	}
 	x, y := 0, 0
-	_ = w.ui.t.Call(func() error {
+	w.ui.t.Call(func() {
 		var wx, wy int
 		if w.ui.isFullscreen() && !w.ui.isNativeFullscreenAvailable() {
 			wx, wy = w.ui.origPos()
@@ -186,7 +169,6 @@ func (w *window) Position() (int, int) {
 		xf := w.ui.dipFromGLFWPixel(float64(wx), m)
 		yf := w.ui.dipFromGLFWPixel(float64(wy), m)
 		x, y = int(xf), int(yf)
-		return nil
 	})
 	return x, y
 }
@@ -196,9 +178,8 @@ func (w *window) SetPosition(x, y int) {
 		w.ui.setInitWindowPositionInDIP(x, y)
 		return
 	}
-	_ = w.ui.t.Call(func() error {
+	w.ui.t.Call(func() {
 		w.ui.setWindowPositionInDIP(x, y, w.ui.currentMonitor())
-		return nil
 	})
 }
 
@@ -208,10 +189,9 @@ func (w *window) Size() (int, int) {
 		return w.ui.adjustWindowSizeBasedOnSizeLimitsInDIP(ww, wh)
 	}
 	ww, wh := 0, 0
-	_ = w.ui.t.Call(func() error {
+	w.ui.t.Call(func() {
 		ww = w.ui.windowWidthInDIP
 		wh = w.ui.windowHeightInDIP
-		return nil
 	})
 	return ww, wh
 }
@@ -221,15 +201,14 @@ func (w *window) SetSize(width, height int) {
 		w.ui.setInitWindowSizeInDIP(width, height)
 		return
 	}
-	_ = w.ui.t.Call(func() error {
+	w.ui.t.Call(func() {
 		// When a window is a native fullscreen, forcing to resize the window might leave unexpected image lags.
 		// Forbid this.
 		if w.ui.isNativeFullscreen() {
-			return nil
+			return
 		}
 
 		w.ui.setWindowSizeInDIP(width, height, w.ui.isFullscreen())
-		return nil
 	})
 }
 
@@ -245,10 +224,7 @@ func (w *window) SetSizeLimits(minw, minh, maxw, maxh int) {
 		return
 	}
 
-	_ = w.ui.t.Call(func() error {
-		w.ui.updateWindowSizeLimits()
-		return nil
-	})
+	w.ui.t.Call(w.ui.updateWindowSizeLimits)
 }
 
 func (w *window) SetIcon(iconImages []image.Image) {
@@ -264,9 +240,8 @@ func (w *window) SetTitle(title string) {
 		return
 	}
 	w.ui.title = title
-	_ = w.ui.t.Call(func() error {
+	w.ui.t.Call(func() {
 		w.ui.setWindowTitle(title)
-		return nil
 	})
 }
 

internal/uidriver/mobile/ui.go

@@ -88,9 +88,7 @@ func (u *UserInterface) Update() error {
 	renderCh <- struct{}{}
 	go func() {
 		<-renderEndCh
-		u.t.Call(func() error {
-			return thread.BreakLoop
-		})
+		u.t.Stop()
 	}()
 	u.t.Loop()
 	return nil

run.go

@@ -19,6 +19,7 @@ import (
 
 	"github.com/hajimehoshi/ebiten/v2/internal/clock"
 	"github.com/hajimehoshi/ebiten/v2/internal/driver"
+	"github.com/hajimehoshi/ebiten/v2/internal/graphicscommand"
 )
 
 // Game defines necessary functions for a game.
@@ -168,6 +169,11 @@ func RunGame(game Game) error {
 	return nil
 }
 
+// RunOnMainThread calls the given f on the main thread, and blocks until f returns.
+func RunOnMainThread(f func()) {
+	graphicscommand.RunOnMainThread(f)
+}
+
 func isRunGameEnded() bool {
 	return atomic.LoadInt32(&isRunGameEnded_) != 0
 }