ui: Add SetScreenTransparent / IsScreenTransparent

Fixes #1001

examples/windowsize/main.go

@@ -38,6 +38,7 @@ import (
 
 var (
 	flagWindowPosition    = flag.String("windowposition", "", "window position (e.g., 100,200)")
+	flagScreenTransparent = flag.Bool("screentransparent", false, "screen transparent")
 )
 
 func init() {
@@ -86,6 +87,7 @@ func update(screen *ebiten.Image) error {
 	tps := ebiten.MaxTPS()
 	decorated := ebiten.IsWindowDecorated()
 	positionX, positionY := ebiten.WindowPosition()
+	transparent := ebiten.IsScreenTransparent()
 
 	if ebiten.IsKeyPressed(ebiten.KeyShift) {
 		if inpututil.IsKeyJustPressed(ebiten.KeyUp) {
@@ -182,7 +184,9 @@ func update(screen *ebiten.Image) error {
 		return nil
 	}
 
+	if !transparent {
 		screen.Fill(color.RGBA{0x80, 0x80, 0xc0, 0xff})
+	}
 	w, h := gophersImage.Size()
 	w2, h2 := screen.Size()
 	op := &ebiten.DrawImageOptions{}
@@ -261,6 +265,7 @@ func main() {
 	if x, y, ok := parseWindowPosition(); ok {
 		ebiten.SetWindowPosition(x, y)
 	}
+	ebiten.SetScreenTransparent(*flagScreenTransparent)
 
 	if err := ebiten.Run(update, initScreenWidth, initScreenHeight, initScreenScale, "Window Size (Ebiten Demo)"); err != nil {
 		log.Fatal(err)

internal/driver/graphics.go

@@ -26,6 +26,7 @@ type Graphics interface {
 	Begin()
 	End()
 	SetWindow(window unsafe.Pointer)
+	SetTransparent(transparent bool)
 	SetVertices(vertices []float32, indices []uint16)
 	Flush()
 	NewImage(width, height int) (Image, error)

internal/driver/ui.go

@@ -46,6 +46,7 @@ type UI interface {
 	ScreenScale() float64
 	ScreenSizeInFullscreen() (int, int)
 	WindowPosition() (int, int)
+	IsScreenTransparent() bool
 
 	SetCursorVisible(visible bool)
 	SetFullscreen(fullscreen bool)
@@ -58,6 +59,7 @@ type UI interface {
 	SetWindowResizable(resizable bool)
 	SetWindowTitle(title string)
 	SetWindowPosition(x, y int)
+	SetScreenTransparent(transparent bool)
 
 	Input() Input
 }

internal/glfw/const.go

@@ -79,6 +79,7 @@ const (
 	Decorated              = Hint(0x00020005)
 	Focused                = Hint(0x00020001)
 	Resizable              = Hint(0x00020003)
+	TransparentFramebuffer = Hint(0x0002000A)
 	Visible                = Hint(0x00020004)
 )
 

internal/graphicsdriver/metal/ca/ca.go

@@ -78,6 +78,15 @@ func (ml MetalLayer) SetDevice(device mtl.Device) {
 	C.MetalLayer_SetDevice(ml.metalLayer, device.Device())
 }
 
+// SetOpaque a Boolean value indicating whether the layer contains completely opaque content.
+func (ml MetalLayer) SetOpaque(opaque bool) {
+	if opaque {
+		C.MetalLayer_SetOpaque(ml.metalLayer, 1)
+	} else {
+		C.MetalLayer_SetOpaque(ml.metalLayer, 0)
+	}
+}
+
 // SetPixelFormat controls the pixel format of textures for rendering layer content.
 //
 // The pixel format for a Metal layer must be PixelFormatBGRA8UNorm, PixelFormatBGRA8UNormSRGB,

internal/graphicsdriver/metal/ca/ca.h

@@ -16,12 +16,14 @@
 
 #include <stdint.h>
 
+typedef signed char BOOL;
 typedef unsigned long uint_t;
 
 void *MakeMetalLayer();
 
 uint16_t MetalLayer_PixelFormat(void *metalLayer);
 void MetalLayer_SetDevice(void *metalLayer, void *device);
+void MetalLayer_SetOpaque(void *metalLayer, BOOL opaque);
 const char *MetalLayer_SetPixelFormat(void *metalLayer, uint16_t pixelFormat);
 const char *MetalLayer_SetMaximumDrawableCount(void *metalLayer,
                                                uint_t maximumDrawableCount);

internal/graphicsdriver/metal/ca/ca.m

@@ -38,6 +38,10 @@ void MetalLayer_SetDevice(void *metalLayer, void *device) {
   ((CAMetalLayer *)metalLayer).device = (id<MTLDevice>)device;
 }
 
+void MetalLayer_SetOpaque(void *metalLayer, BOOL opaque) {
+  ((CAMetalLayer *)metalLayer).opaque = opaque;
+}
+
 const char *MetalLayer_SetPixelFormat(void *metalLayer, uint16_t pixelFormat) {
   @try {
     ((CAMetalLayer *)metalLayer).pixelFormat = (MTLPixelFormat)pixelFormat;

internal/graphicsdriver/metal/driver.go

@@ -295,13 +295,12 @@ type Driver struct {
 
 	vb  mtl.Buffer
 	ib  mtl.Buffer
-
 	src *Image
 	dst *Image
 
-	drawCalled bool
-
+	transparent  bool
 	maxImageSize int
+	drawCalled   bool
 
 	t *thread.Thread
 
@@ -440,6 +439,10 @@ func (d *Driver) NewScreenFramebufferImage(width, height int) (driver.Image, err
 	}, nil
 }
 
+func (d *Driver) SetTransparent(transparent bool) {
+	d.transparent = transparent
+}
+
 func (d *Driver) Reset() error {
 	if err := d.t.Call(func() error {
 		if d.cq != (mtl.CommandQueue{}) {
@@ -455,6 +458,9 @@ func (d *Driver) Reset() error {
 		if err := d.view.reset(); err != nil {
 			return err
 		}
+		if d.transparent {
+			d.view.ml.SetOpaque(false)
+		}
 
 		replaces := map[string]string{
 			"{{.FilterNearest}}":      fmt.Sprintf("%d", driver.FilterNearest),

internal/graphicsdriver/opengl/driver.go

@@ -54,6 +54,10 @@ func (d *Driver) SetWindow(window unsafe.Pointer) {
 	// Do nothing.
 }
 
+func (d *Driver) SetTransparent(transparent bool) {
+	// Do nothings.
+}
+
 func (d *Driver) checkSize(width, height int) {
 	if width < 1 {
 		panic(fmt.Sprintf("opengl: width (%d) must be equal or more than %d", width, 1))

internal/uidriver/glfw/ui.go

@@ -62,6 +62,7 @@ type UserInterface struct {
 	initWindowResizable   bool
 	initWindowPositionX   int
 	initWindowPositionY   int
+	initScreenTransparent bool
 	initIconImages        []image.Image
 
 	reqWidth  int
@@ -260,6 +261,19 @@ func (u *UserInterface) setInitWindowResizable(resizable bool) {
 	u.m.Unlock()
 }
 
+func (u *UserInterface) isInitScreenTransparent() bool {
+	u.m.RLock()
+	v := u.initScreenTransparent
+	u.m.RUnlock()
+	return v
+}
+
+func (u *UserInterface) setInitScreenTransparent(transparent bool) {
+	u.m.RLock()
+	u.initScreenTransparent = transparent
+	u.m.RUnlock()
+}
+
 func (u *UserInterface) getInitIconImages() []image.Image {
 	u.m.RLock()
 	i := u.initIconImages
@@ -617,13 +631,19 @@ func (u *UserInterface) run(width, height int, scale float64, title string, cont
 			glfw.WindowHint(glfw.ClientAPI, glfw.NoAPI)
 		}
 
-		// 'decorated' must be solved before creating a window (#556).
 		decorated := glfw.False
 		if u.isInitWindowDecorated() {
 			decorated = glfw.True
 		}
 		glfw.WindowHint(glfw.Decorated, decorated)
 
+		transparent := glfw.False
+		if u.isInitScreenTransparent() {
+			transparent = glfw.True
+		}
+		glfw.WindowHint(glfw.TransparentFramebuffer, transparent)
+		u.graphics.SetTransparent(u.isInitScreenTransparent())
+
 		resizable := glfw.False
 		if u.isInitWindowResizable() {
 			resizable = glfw.True
@@ -1050,6 +1070,26 @@ func (u *UserInterface) WindowPosition() (int, int) {
 	return x, y
 }
 
+func (u *UserInterface) SetScreenTransparent(transparent bool) {
+	if !u.isRunning() {
+		u.setInitScreenTransparent(transparent)
+		return
+	}
+	panic("ui: SetScreenTransparent can't be called after Run.")
+}
+
+func (u *UserInterface) IsScreenTransparent() bool {
+	if !u.isRunning() {
+		return u.isInitScreenTransparent()
+	}
+	val := false
+	_ = u.t.Call(func() error {
+		val = u.window.GetAttrib(glfw.TransparentFramebuffer) == glfw.True
+		return nil
+	})
+	return val
+}
+
 func (u *UserInterface) Input() driver.Input {
 	return &u.input
 }

internal/uidriver/js/ui.go

@@ -34,6 +34,7 @@ type UserInterface struct {
 	scale                float64
 	runnableInBackground bool
 	vsync                bool
+	running              bool
 
 	sizeChanged bool
 	contextLost bool
@@ -156,6 +157,9 @@ func (u *UserInterface) IsWindowResizable() bool {
 
 func (u *UserInterface) SetWindowResizable(decorated bool) {
 	// Do nothing
+	if u.running {
+		panic("js: SetWindowResizable can't be called after the main loop starts")
+	}
 }
 
 func (u *UserInterface) DeviceScaleFactor() float64 {
@@ -426,6 +430,7 @@ func (u *UserInterface) Run(width, height int, scale float64, title string, cont
 	u.setScreenSize(width, height)
 	u.pseudoScale = scale
 	canvas.Call("focus")
+	u.running = true
 	ch := u.loop(context)
 	if runtime.GOARCH == "wasm" {
 		return <-ch
@@ -434,6 +439,9 @@ func (u *UserInterface) Run(width, height int, scale float64, title string, cont
 	// On GopherJS, the main goroutine cannot be blocked due to the bug (gopherjs/gopherjs#826).
 	// Return immediately.
 	go func() {
+		defer func() {
+			u.running = false
+		}()
 		if err := <-ch; err != nil {
 			log.Fatal(err)
 		}
@@ -484,9 +492,30 @@ func (u *UserInterface) SetWindowPosition(x, y int) {
 }
 
 func (u *UserInterface) WindowPosition() (int, int) {
+	if !u.running {
+		panic("js: WindowPosition can't be called before the main loop starts")
+	}
 	return 0, 0
 }
 
+func (u *UserInterface) SetScreenTransparent(transparent bool) {
+	if u.running {
+		panic("js: 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 *UserInterface) IsScreenTransparent() bool {
+	bodyStyle := document.Get("body").Get("style")
+	return bodyStyle.Get("backgroundColor").String() == "transparent"
+}
+
 func (u *UserInterface) Input() driver.Input {
 	return &u.input
 }

internal/uidriver/mobile/ui.go

@@ -451,6 +451,14 @@ func (u *UserInterface) WindowPosition() (int, int) {
 	return 0, 0
 }
 
+func (u *UserInterface) SetScreenTransparent(transparent bool) {
+	// Do nothing
+}
+
+func (u *UserInterface) IsScreenTransparent() bool {
+	return false
+}
+
 func (u *UserInterface) Input() driver.Input {
 	return &u.input
 }

run.go

@@ -411,3 +411,17 @@ func SetMaxTPS(tps int) {
 	}
 	atomic.StoreInt32(&currentMaxTPS, int32(tps))
 }
+
+// IsScreenTransparent reports whether the window is transparent.
+func IsScreenTransparent() bool {
+	return uiDriver().IsScreenTransparent()
+}
+
+// SetScreenTransparent sets the state if the window is transparent.
+//
+// SetScreenTransparent panics if SetScreenTransparent is called after Run.
+//
+// SetScreenTransparent does nothing on mobiles.
+func SetScreenTransparent(transparent bool) {
+	uiDriver().SetScreenTransparent(transparent)
+}