ui: Add IsRunnableInBackground / SetRunnableInBackground (#272)

examples/audio/main.go

@@ -58,7 +58,7 @@ type Input struct {
 }
 
 func (i *Input) update() {
-	for _, key := range []ebiten.Key{ebiten.KeyP, ebiten.KeyS, ebiten.KeyX, ebiten.KeyZ} {
+	for _, key := range []ebiten.Key{ebiten.KeyP, ebiten.KeyS, ebiten.KeyX, ebiten.KeyZ, ebiten.KeyB} {
 		if !ebiten.IsKeyPressed(key) {
 			i.keyStates[key] = 0
 		} else {
@@ -170,6 +170,10 @@ func (p *Player) update() error {
 	p.updatePlayPause()
 	p.updateSE()
 	p.updateVolume()
+	if p.input.isKeyTriggered(ebiten.KeyB) {
+		b := ebiten.IsRunnableInBackground()
+		ebiten.SetRunnableInBackground(!b)
+	}
 	if err := p.audioContext.Update(); err != nil {
 		return err
 	}
@@ -262,6 +266,7 @@ func (p *Player) draw(screen *ebiten.Image) {
 Press S to toggle Play/Pause
 Press P to play SE
 Press Z or X to change volume of the music
+Press B to switch the run-in-background state
 %s`, ebiten.CurrentFPS(), currentTimeStr)
 	ebitenutil.DebugPrint(screen, msg)
 }

examples/windowsize/main.go

@@ -21,6 +21,7 @@ import (
 	"image/color"
 	_ "image/jpeg"
 	"log"
+	"math"
 
 	"github.com/hajimehoshi/ebiten"
 	"github.com/hajimehoshi/ebiten/ebitenutil"
@@ -41,7 +42,9 @@ var (
 		ebiten.KeyRight: 0,
 		ebiten.KeyS:     0,
 		ebiten.KeyF:     0,
+		ebiten.KeyB:     0,
 	}
+	count = 0
 )
 
 func update(screen *ebiten.Image) error {
@@ -56,6 +59,7 @@ func update(screen *ebiten.Image) error {
 	d := int(32 / screenScale)
 	screenWidth, screenHeight := screen.Size()
 	fullscreen := ebiten.IsFullscreen()
+	runnableInBackground := ebiten.IsRunnableInBackground()
 
 	if keyStates[ebiten.KeyUp] == 1 {
 		screenHeight += d
@@ -88,9 +92,15 @@ func update(screen *ebiten.Image) error {
 	if keyStates[ebiten.KeyF] == 1 {
 		fullscreen = !fullscreen
 	}
+	if keyStates[ebiten.KeyB] == 1 {
+		runnableInBackground = !runnableInBackground
+	}
 	ebiten.SetScreenSize(screenWidth, screenHeight)
 	ebiten.SetScreenScale(screenScale)
 	ebiten.SetFullscreen(fullscreen)
+	ebiten.SetRunnableInBackground(runnableInBackground)
+
+	count++
 
 	if ebiten.IsRunningSlowly() {
 		return nil
@@ -101,12 +111,16 @@ func update(screen *ebiten.Image) error {
 	w2, h2 := screen.Size()
 	op := &ebiten.DrawImageOptions{}
 	op.GeoM.Translate(float64(-w+w2)/2, float64(-h+h2)/2)
+	dx := math.Cos(2*math.Pi*float64(count)/360) * 10
+	dy := math.Sin(2*math.Pi*float64(count)/360) * 10
+	op.GeoM.Translate(dx, dy)
 	screen.DrawImage(gophersImage, op)
 
 	x, y := ebiten.CursorPosition()
 	msg := fmt.Sprintf(`Press arrow keys to change the window size
 Press S key to change the window scale
 Press F key to change the fullscreen state
+Press B key to change the run-in-background state
 Cursor: (%d, %d)
 FPS: %0.2f`, x, y, ebiten.CurrentFPS())
 	ebitenutil.DebugPrint(screen, msg)

internal/ui/ui_glfw.go

@@ -45,6 +45,7 @@ type userInterface struct {
 	origPosX             int
 	origPosY             int
 	initFullscreen       bool
+	runnableInBackground bool
 	m                    sync.Mutex
 }
 
@@ -133,6 +134,19 @@ func (u *userInterface) setInitFullscreen(initFullscreen bool) {
 	u.m.Unlock()
 }
 
+func (u *userInterface) isRunnableInBackground() bool {
+	u.m.Lock()
+	v := u.runnableInBackground
+	u.m.Unlock()
+	return v
+}
+
+func (u *userInterface) setRunnableInBackground(runnableInBackground bool) {
+	u.m.Lock()
+	u.runnableInBackground = runnableInBackground
+	u.m.Unlock()
+}
+
 func (u *userInterface) runOnMainThread(f func() error) error {
 	if u.funcs == nil {
 		// already closed
@@ -213,6 +227,14 @@ func SetFullscreen(fullscreen bool) {
 	})
 }
 
+func SetRunnableInBackground(runnableInBackground bool) {
+	currentUI.setRunnableInBackground(runnableInBackground)
+}
+
+func IsRunnableInBackground() bool {
+	return currentUI.isRunnableInBackground()
+}
+
 func ScreenOffset() (float64, float64) {
 	u := currentUI
 	if !u.isRunning() {
@@ -372,7 +394,7 @@ func (u *userInterface) update(g GraphicsContext) error {
 
 	_ = u.runOnMainThread(func() error {
 		u.pollEvents()
-		for u.window.GetAttrib(glfw.Focused) == 0 {
+		for !u.isRunnableInBackground() && u.window.GetAttrib(glfw.Focused) == 0 {
 			// Wait for an arbitrary period to avoid busy loop.
 			time.Sleep(time.Second / 60)
 			u.pollEvents()

internal/ui/ui_js.go

@@ -31,6 +31,7 @@ type userInterface struct {
 	height               int
 	scale                float64
 	fullscreen           bool
+	runnableInBackground bool
 
 	deviceScale float64
 	sizeChanged bool
@@ -67,6 +68,14 @@ func IsFullscreen() bool {
 	return currentUI.fullscreen
 }
 
+func SetRunnableInBackground(runnableInBackground bool) {
+	currentUI.runnableInBackground = runnableInBackground
+}
+
+func IsRunnableInBackground() bool {
+	return currentUI.runnableInBackground
+}
+
 func ScreenOffset() (float64, float64) {
 	return 0, 0
 }
@@ -104,7 +113,7 @@ func (u *userInterface) actualScreenScale() float64 {
 }
 
 func (u *userInterface) update(g GraphicsContext) error {
-	if !u.windowFocus {
+	if !u.runnableInBackground && !u.windowFocus {
 		return nil
 	}
 	if opengl.GetContext().IsContextLost() {

internal/ui/ui_mobile.go

@@ -118,12 +118,20 @@ func SetCursorVisibility(visibility bool) {
 	// Do nothing
 }
 
-func SetFullscreen(fullscreen bool) bool {
+func SetFullscreen(fullscreen bool) {
+	// Do nothing
+}
+
+func IsFullscreen() bool {
 	// Do nothing
 	return false
 }
 
-func IsFullscreen() bool {
+func SetRunnableInBackground(runnableInBackground bool) {
+	// Do nothing
+}
+
+func IsRunnableInBackground() bool {
 	// Do nothing
 	return false
 }

run.go

@@ -178,3 +178,25 @@ func IsFullscreen() bool {
 func SetFullscreen(fullscreen bool) {
 	ui.SetFullscreen(fullscreen)
 }
+
+// IsRunnableInBackground returns a boolean value indicating whether the game runs even in background.
+//
+// This function is concurrent-safe.
+func IsRunnableInBackground() bool {
+	return ui.IsRunnableInBackground()
+}
+
+// SetRunnableInBackground sets the state if the game runs even in background.
+//
+// If the given value is true, the game runs in background e.g. when losing focus.
+// The initial state is false.
+//
+// Known issue: On browsers, even if the state is on, the game doesn't run in background tabs.
+// This is because browsers throttles background tabs not to often update.
+//
+// SetRunnableInBackground doesn't work on mobiles so far.
+//
+// This function is concurrent-safe.
+func SetRunnableInBackground(runnableInBackground bool) {
+	ui.SetRunnableInBackground(runnableInBackground)
+}