ui: Add WindowPosition()

Fixes #936

examples/windowsize/main.go

@@ -167,7 +167,8 @@ func update(screen *ebiten.Image) error {
 	op.GeoM.Translate(dx, dy)
 	screen.DrawImage(gophersImage, op)
 
-	x, y := ebiten.CursorPosition()
+	wx, wy := ebiten.WindowPosition()
+	cx, cy := ebiten.CursorPosition()
 	tpsStr := "Uncapped"
 	if t := ebiten.MaxTPS(); t != ebiten.UncappedTPS {
 		tpsStr = fmt.Sprintf("%d", t)
@@ -181,10 +182,11 @@ Press I key to change the window icon (only for desktops)
 Press V key to switch vsync
 Press T key to switch TPS (ticks per second)
 Press D key to switch the window decoration
+Windows Position: (%d, %d)
 Cursor: (%d, %d)
 TPS: Current: %0.2f / Max: %s
 FPS: %0.2f
-Device Scale Factor: %0.2f`, x, y, ebiten.CurrentTPS(), tpsStr, ebiten.CurrentFPS(), ebiten.DeviceScaleFactor())
+Device Scale Factor: %0.2f`, wx, wy, cx, cy, ebiten.CurrentTPS(), tpsStr, ebiten.CurrentFPS(), ebiten.DeviceScaleFactor())
 	ebitenutil.DebugPrint(screen, msg)
 	return nil
 }

internal/driver/ui.go

@@ -32,6 +32,9 @@ type UIContext interface {
 var RegularTermination = errors.New("regular termination")
 
 type UI interface {
+	Run(width, height int, scale float64, title string, context UIContext, graphics Graphics) error
+	RunWithoutMainLoop(width, height int, scale float64, title string, context UIContext, graphics Graphics) <-chan error
+
 	DeviceScaleFactor() float64
 	IsCursorVisible() bool
 	IsFullscreen() bool
@@ -39,11 +42,11 @@ type UI interface {
 	IsVsyncEnabled() bool
 	IsWindowDecorated() bool
 	IsWindowResizable() bool
-	Run(width, height int, scale float64, title string, context UIContext, graphics Graphics) error
-	RunWithoutMainLoop(width, height int, scale float64, title string, context UIContext, graphics Graphics) <-chan error
 	ScreenPadding() (x0, y0, x1, y1 float64)
 	ScreenScale() float64
 	ScreenSizeInFullscreen() (int, int)
+	WindowPosition() (int, int)
+
 	SetCursorVisible(visible bool)
 	SetFullscreen(fullscreen bool)
 	SetRunnableInBackground(runnableInBackground bool)
@@ -54,5 +57,6 @@ type UI interface {
 	SetWindowIcon(iconImages []image.Image)
 	SetWindowResizable(resizable bool)
 	SetWindowTitle(title string)
+
 	Input() Input
 }

internal/uidriver/glfw/ui.go

@@ -997,6 +997,18 @@ func (u *UserInterface) currentMonitor() *glfw.Monitor {
 	return u.currentMonitorFromPosition()
 }
 
+func (u *UserInterface) WindowPosition() (int, int) {
+	if !u.isRunning() {
+		panic("ui: Run is not called yet")
+	}
+	x, y := 0, 0
+	_ = u.t.Call(func() error {
+		x, y = u.window.GetPos()
+		return nil
+	})
+	return x, y
+}
+
 func (u *UserInterface) Input() driver.Input {
 	return &u.input
 }

internal/uidriver/js/ui.go

@@ -479,6 +479,10 @@ func (u *UserInterface) updateScreenSize() {
 	u.sizeChanged = true
 }
 
+func (u *UserInterface) WindowPosition() (int, int) {
+	return 0, 0
+}
+
 func (u *UserInterface) Input() driver.Input {
 	return &u.input
 }

internal/uidriver/mobile/ui.go

@@ -443,6 +443,10 @@ func (u *UserInterface) DeviceScaleFactor() float64 {
 	return deviceScale()
 }
 
+func (u *UserInterface) WindowPosition() (int, int) {
+	return 0, 0
+}
+
 func (u *UserInterface) Input() driver.Input {
 	return &u.input
 }

window.go

@@ -94,3 +94,12 @@ func SetWindowTitle(title string) {
 func SetWindowIcon(iconImages []image.Image) {
 	uiDriver().SetWindowIcon(iconImages)
 }
+
+// WindowPosition returns the window position.
+//
+// WindowPosition panics before Run is called.
+//
+// WindowPosition returns (0, 0) on browsers and mobiles.
+func WindowPosition() (int, int) {
+	return uiDriver().WindowPosition()
+}