ebiten: add RunGameOptions.ScreenTransparent

Closes #2378

examples/windowsize/main.go

@@ -404,7 +404,6 @@ func main() {
 	if x, y, ok := parseWindowPosition(); ok {
 		ebiten.SetWindowPosition(x, y)
 	}
-	ebiten.SetScreenTransparent(*flagTransparent)
 
 	g := &game{
 		width:  initScreenWidth,
@@ -464,6 +463,7 @@ func main() {
 		log.Fatalf("unexpected graphics library: %s", *flagGraphicsLibrary)
 	}
 	op.InitUnfocused = !*flagInitFocused
+	op.ScreenTransparent = *flagTransparent
 
 	const title = "Window Size (Ebitengine Demo)"
 	ww := int(float64(g.width) * initScreenScale)

gameforui.go

@@ -80,11 +80,13 @@ type gameForUI struct {
 	screen       *Image
 	screenShader *Shader
 	imageDumper  imageDumper
+	transparent  bool
 }
 
-func newGameForUI(game Game) *gameForUI {
+func newGameForUI(game Game, transparent bool) *gameForUI {
 	g := &gameForUI{
-		game: game,
+		game:        game,
+		transparent: transparent,
 	}
 
 	s, err := NewShader([]byte(screenShaderSrc))
@@ -157,7 +159,7 @@ func (g *gameForUI) Update() error {
 
 func (g *gameForUI) DrawOffscreen() error {
 	g.game.Draw(g.offscreen)
-	if err := g.imageDumper.dump(g.offscreen); err != nil {
+	if err := g.imageDumper.dump(g.offscreen, g.transparent); err != nil {
 		return err
 	}
 	return nil

imagedumper.go

@@ -31,7 +31,7 @@ func datetimeForFilename() string {
 	return now.Format(datetimeFormat)
 }
 
-func takeScreenshot(screen *Image) error {
+func takeScreenshot(screen *Image, transparent bool) error {
 	name := "screenshot_" + datetimeForFilename() + ".png"
 	// Use the home directory for mobiles as a provisional implementation.
 	if runtime.GOOS == "android" || runtime.GOOS == "ios" {
@@ -41,8 +41,7 @@ func takeScreenshot(screen *Image) error {
 		}
 		name = filepath.Join(home, name)
 	}
-	blackbg := !IsScreenTransparent()
-	dumpedName, err := screen.image.DumpScreenshot(name, blackbg)
+	dumpedName, err := screen.image.DumpScreenshot(name, !transparent)
 	if err != nil {
 		return err
 	}
@@ -155,10 +154,10 @@ func (i *imageDumper) update() error {
 	return nil
 }
 
-func (i *imageDumper) dump(screen *Image) error {
+func (i *imageDumper) dump(screen *Image, transparent bool) error {
 	if i.toTakeScreenshot {
 		i.toTakeScreenshot = false
-		if err := takeScreenshot(screen); err != nil {
+		if err := takeScreenshot(screen, transparent); err != nil {
 			return err
 		}
 	}

internal/ui/ui.go

@@ -97,6 +97,7 @@ func (u *UserInterface) dumpImages(dir string) (string, error) {
 }
 
 type RunOptions struct {
-	GraphicsLibrary GraphicsLibrary
-	InitUnfocused   bool
+	GraphicsLibrary   GraphicsLibrary
+	InitUnfocused     bool
+	ScreenTransparent bool
 }

internal/ui/ui_glfw.go

@@ -92,7 +92,6 @@ type userInterfaceImpl struct {
 	initWindowHeightInDIP    int
 	initWindowFloating       bool
 	initWindowMaximized      bool
-	initScreenTransparent    bool
 
 	origWindowPosX        int
 	origWindowPosY        int
@@ -360,19 +359,6 @@ func (u *userInterfaceImpl) setRunnableOnUnfocused(runnableOnUnfocused bool) {
 	u.m.Unlock()
 }
 
-func (u *userInterfaceImpl) isInitScreenTransparent() bool {
-	u.m.RLock()
-	v := u.initScreenTransparent
-	u.m.RUnlock()
-	return v
-}
-
-func (u *userInterfaceImpl) setInitScreenTransparent(transparent bool) {
-	u.m.Lock()
-	u.initScreenTransparent = transparent
-	u.m.Unlock()
-}
-
 func (u *userInterfaceImpl) getIconImages() []image.Image {
 	u.m.RLock()
 	i := u.iconImages
@@ -874,21 +860,20 @@ func (u *userInterfaceImpl) init(options *RunOptions) error {
 	}
 	glfw.WindowHint(glfw.Decorated, decorated)
 
-	transparent := u.isInitScreenTransparent()
 	glfwTransparent := glfw.False
-	if transparent {
+	if options.ScreenTransparent {
 		glfwTransparent = glfw.True
 	}
 	glfw.WindowHint(glfw.TransparentFramebuffer, glfwTransparent)
 
 	g, err := newGraphicsDriver(&graphicsDriverCreatorImpl{
-		transparent: transparent,
+		transparent: options.ScreenTransparent,
 	}, options.GraphicsLibrary)
 	if err != nil {
 		return err
 	}
 	u.graphicsDriver = g
-	u.graphicsDriver.SetTransparent(u.isInitScreenTransparent())
+	u.graphicsDriver.SetTransparent(options.ScreenTransparent)
 
 	if u.graphicsDriver.IsGL() {
 		u.graphicsDriver.(interface{ SetGLFWClientAPI() }).SetGLFWClientAPI()
@@ -1417,25 +1402,6 @@ func monitorFromWindow(window *glfw.Window) *glfw.Monitor {
 	return nil
 }
 
-func (u *userInterfaceImpl) SetScreenTransparent(transparent bool) {
-	if !u.isRunning() {
-		u.setInitScreenTransparent(transparent)
-		return
-	}
-	panic("ui: SetScreenTransparent can't be called after the main loop starts")
-}
-
-func (u *userInterfaceImpl) IsScreenTransparent() bool {
-	if !u.isRunning() {
-		return u.isInitScreenTransparent()
-	}
-	val := false
-	u.t.Call(func() {
-		val = u.window.GetAttrib(glfw.TransparentFramebuffer) == glfw.True
-	})
-	return val
-}
-
 func (u *userInterfaceImpl) resetForTick() {
 	u.input.resetForTick()
 
@@ -1617,3 +1583,7 @@ func (u *userInterfaceImpl) setOrigWindowPos(x, y int) {
 	u.origWindowPosX = x
 	u.origWindowPosY = y
 }
+
+func IsScreenTransparentAvailable() bool {
+	return true
+}

internal/ui/ui_js.go

@@ -652,6 +652,13 @@ func (u *userInterfaceImpl) Run(game Game, options *RunOptions) error {
 		return err
 	}
 	u.graphicsDriver = g
+
+	if bodyStyle := document.Get("body").Get("style"); options.ScreenTransparent {
+		bodyStyle.Set("backgroundColor", "transparent")
+	} else {
+		bodyStyle.Set("backgroundColor", "#000")
+	}
+
 	return <-u.loop(game)
 }
 
@@ -670,17 +677,6 @@ func (u *userInterfaceImpl) SetScreenTransparent(transparent bool) {
 		panic("ui: SetScreenTransparent can't be called after the main loop starts")
 	}
 
-	bodyStyle := document.Get("body").Get("style")
-	if transparent {
-		bodyStyle.Set("backgroundColor", "transparent")
-	} else {
-		bodyStyle.Set("backgroundColor", "#000")
-	}
-}
-
-func (u *userInterfaceImpl) IsScreenTransparent() bool {
-	bodyStyle := document.Get("body").Get("style")
-	return bodyStyle.Get("backgroundColor").Equal(stringTransparent)
 }
 
 func (u *userInterfaceImpl) resetForTick() {
@@ -700,3 +696,7 @@ func (u *userInterfaceImpl) beginFrame() {
 
 func (u *userInterfaceImpl) endFrame() {
 }
+
+func IsScreenTransparentAvailable() bool {
+	return true
+}

internal/ui/ui_mobile.go

@@ -421,14 +421,6 @@ func (u *userInterfaceImpl) DeviceScaleFactor() float64 {
 	return deviceScale()
 }
 
-func (u *userInterfaceImpl) SetScreenTransparent(transparent bool) {
-	// Do nothing
-}
-
-func (u *userInterfaceImpl) IsScreenTransparent() bool {
-	return false
-}
-
 func (u *userInterfaceImpl) resetForTick() {
 	u.input.resetForTick()
 }
@@ -475,3 +467,7 @@ func (u *userInterfaceImpl) beginFrame() {
 
 func (u *userInterfaceImpl) endFrame() {
 }
+
+func IsScreenTransparentAvailable() bool {
+	return false
+}

internal/ui/ui_nintendosdk.go

@@ -126,13 +126,6 @@ func (*userInterfaceImpl) SetFPSMode(mode FPSModeType) {
 func (*userInterfaceImpl) ScheduleFrame() {
 }
 
-func (*userInterfaceImpl) IsScreenTransparent() bool {
-	return false
-}
-
-func (*userInterfaceImpl) SetScreenTransparent(transparent bool) {
-}
-
 func (*userInterfaceImpl) Input() *Input {
 	return &theUI.input
 }
@@ -146,3 +139,7 @@ func (u *userInterfaceImpl) beginFrame() {
 
 func (u *userInterfaceImpl) endFrame() {
 }
+
+func IsScreenTransparentAvailable() bool {
+	return false
+}

run.go

@@ -241,6 +241,12 @@ type RunGameOptions struct {
 	//
 	// The default (zero) value is false, which means that the window is focused.
 	InitUnfocused bool
+
+	// ScreenTransparent represents whether the window is transparent or not.
+	// ScreenTransparent is valid on desktops and browsers.
+	//
+	// The default (zero) value is false, which means that the window is not transparent.
+	ScreenTransparent bool
 }
 
 // RunGameWithOptions starts the main loop and runs the game with the specified options.
@@ -280,8 +286,17 @@ func RunGameWithOptions(game Game, options *RunGameOptions) error {
 	defer atomic.StoreInt32(&isRunGameEnded_, 1)
 
 	initializeWindowPositionIfNeeded(WindowSize())
-	g := newGameForUI(game)
-	if err := ui.Get().Run(g, toUIRunOptions(options)); err != nil {
+
+	op := toUIRunOptions(options)
+	// This is necessary to change the result of IsScreenTransparent.
+	if op.ScreenTransparent {
+		atomic.StoreInt32(&screenTransparent, 1)
+	} else {
+		atomic.StoreInt32(&screenTransparent, 0)
+	}
+	g := newGameForUI(game, op.ScreenTransparent)
+
+	if err := ui.Get().Run(g, op); err != nil {
 		if errors.Is(err, Termination) {
 			return nil
 		}
@@ -582,8 +597,13 @@ func SetMaxTPS(tps int) {
 // IsScreenTransparent reports whether the window is transparent.
 //
 // IsScreenTransparent is concurrent-safe.
+//
+// Deprecated: as of v2.5.
 func IsScreenTransparent() bool {
-	return ui.Get().IsScreenTransparent()
+	if !ui.IsScreenTransparentAvailable() {
+		return false
+	}
+	return atomic.LoadInt32(&screenTransparent) != 0
 }
 
 // SetScreenTransparent sets the state if the window is transparent.
@@ -593,10 +613,18 @@ func IsScreenTransparent() bool {
 // SetScreenTransparent does nothing on mobiles.
 //
 // SetScreenTransparent is concurrent-safe.
+//
+// Deprecated: as of v2.5. Use RunGameWithOptions instead.
 func SetScreenTransparent(transparent bool) {
-	ui.Get().SetScreenTransparent(transparent)
+	if transparent {
+		atomic.StoreInt32(&screenTransparent, 1)
+	} else {
+		atomic.StoreInt32(&screenTransparent, 0)
+	}
 }
 
+var screenTransparent int32 = 0
+
 // SetInitFocused sets whether the application is focused on show.
 // The default value is true, i.e., the application is focused.
 //
@@ -620,11 +648,13 @@ var initUnfocused int32 = 0
 func toUIRunOptions(options *RunGameOptions) *ui.RunOptions {
 	if options == nil {
 		return &ui.RunOptions{
-			InitUnfocused: atomic.LoadInt32(&initUnfocused) != 0,
+			InitUnfocused:     atomic.LoadInt32(&initUnfocused) != 0,
+			ScreenTransparent: atomic.LoadInt32(&screenTransparent) != 0,
 		}
 	}
 	return &ui.RunOptions{
-		GraphicsLibrary: ui.GraphicsLibrary(options.GraphicsLibrary),
-		InitUnfocused:   options.InitUnfocused,
+		GraphicsLibrary:   ui.GraphicsLibrary(options.GraphicsLibrary),
+		InitUnfocused:     options.InitUnfocused,
+		ScreenTransparent: options.ScreenTransparent,
 	}
 }

run_mobile.go

@@ -28,5 +28,6 @@ import (
 //
 // TODO: Remove this. In order to remove this, the gameForUI should be in another package.
 func RunGameWithoutMainLoop(game Game, options *RunGameOptions) {
-	ui.RunWithoutMainLoop(newGameForUI(game), toUIRunOptions(options))
+	op := toUIRunOptions(options)
+	ui.RunWithoutMainLoop(newGameForUI(game, op.ScreenTransparent), op)
 }