Add IsVsyncEnabled / SetVsyncEnabled

This enables the game to work more efficiently (but consume much
more CPU).

Fixes #405.

examples/windowsize/main.go

@@ -86,6 +86,7 @@ func update(screen *ebiten.Image) error {
 	fullscreen := ebiten.IsFullscreen()
 	runnableInBackground := ebiten.IsRunnableInBackground()
 	cursorVisible := ebiten.IsCursorVisible()
+	vsyncEnabled := ebiten.IsVsyncEnabled()
 
 	if inpututil.IsKeyJustPressed(ebiten.KeyUp) {
 		screenHeight += d
@@ -126,11 +127,16 @@ func update(screen *ebiten.Image) error {
 	if inpututil.IsKeyJustPressed(ebiten.KeyC) {
 		cursorVisible = !cursorVisible
 	}
+	if inpututil.IsKeyJustPressed(ebiten.KeyV) {
+		vsyncEnabled = !vsyncEnabled
+	}
+
 	ebiten.SetScreenSize(screenWidth, screenHeight)
 	ebiten.SetScreenScale(screenScale)
 	ebiten.SetFullscreen(fullscreen)
 	ebiten.SetRunnableInBackground(runnableInBackground)
 	ebiten.SetCursorVisible(cursorVisible)
+	ebiten.SetVsyncEnabled(vsyncEnabled)
 
 	if inpututil.IsKeyJustPressed(ebiten.KeyI) {
 		ebiten.SetWindowIcon([]image.Image{createRandomIconImage()})
@@ -159,6 +165,7 @@ Press F key to switch the fullscreen state
 Press B key to switch the run-in-background state
 Press C key to switch the cursor visibility
 Press I key to change the window icon
+Press V key to switch vsync
 Press Q key to quit
 Cursor: (%d, %d)
 FPS: %0.2f`, x, y, ebiten.CurrentFPS())

internal/ui/ui_glfw.go

@@ -49,6 +49,7 @@ type userInterface struct {
 	origPosX             int
 	origPosY             int
 	runnableInBackground bool
+	vsync                bool
 
 	initFullscreen      bool
 	initCursorVisible   bool
@@ -66,6 +67,7 @@ var (
 		origPosY:            -1,
 		initCursorVisible:   true,
 		initWindowDecorated: true,
+		vsync:               true,
 	}
 )
 
@@ -241,7 +243,7 @@ func SetScreenSize(width, height int) bool {
 	}
 	r := false
 	_ = u.runOnMainThread(func() error {
-		r = u.setScreenSize(width, height, u.scale, u.fullscreen())
+		r = u.setScreenSize(width, height, u.scale, u.fullscreen(), u.vsync)
 		return nil
 	})
 	return r
@@ -254,7 +256,7 @@ func SetScreenScale(scale float64) bool {
 	}
 	r := false
 	_ = u.runOnMainThread(func() error {
-		r = u.setScreenSize(u.width, u.height, scale, u.fullscreen())
+		r = u.setScreenSize(u.width, u.height, scale, u.fullscreen(), u.vsync)
 		return nil
 	})
 	return r
@@ -302,7 +304,7 @@ func SetFullscreen(fullscreen bool) {
 	}
 	_ = u.runOnMainThread(func() error {
 		u := currentUI
-		u.setScreenSize(u.width, u.height, u.scale, fullscreen)
+		u.setScreenSize(u.width, u.height, u.scale, fullscreen, u.vsync)
 		return nil
 	})
 }
@@ -315,6 +317,32 @@ func IsRunnableInBackground() bool {
 	return currentUI.isRunnableInBackground()
 }
 
+func SetVsyncEnabled(enabled bool) {
+	u := currentUI
+	if !u.isRunning() {
+		_ = u.runOnMainThread(func() error {
+			u.vsync = enabled
+			return nil
+		})
+		return
+	}
+	_ = u.runOnMainThread(func() error {
+		u := currentUI
+		u.setScreenSize(u.width, u.height, u.scale, u.fullscreen(), enabled)
+		return nil
+	})
+}
+
+func IsVsyncEnabled() bool {
+	r := false
+	u := currentUI
+	_ = u.runOnMainThread(func() error {
+		r = currentUI.vsync
+		return nil
+	})
+	return r
+}
+
 func SetWindowTitle(title string) {
 	if !currentUI.isRunning() {
 		return
@@ -459,7 +487,7 @@ func Run(width, height int, scale float64, title string, g GraphicsContext, main
 
 		// The game is in window mode (not fullscreen mode) at the first state.
 		// Don't refer u.initFullscreen here to avoid some GLFW problems.
-		u.setScreenSize(width, height, scale, false)
+		u.setScreenSize(width, height, scale, false, u.vsync)
 		u.title = title
 		u.window.SetTitle(title)
 		u.window.Show()
@@ -542,7 +570,7 @@ func (u *userInterface) update(g GraphicsContext) error {
 	_ = u.runOnMainThread(func() error {
 		if u.isInitFullscreen() {
 			u := currentUI
-			u.setScreenSize(u.width, u.height, u.scale, true)
+			u.setScreenSize(u.width, u.height, u.scale, true, u.vsync)
 			u.setInitFullscreen(false)
 		}
 		return nil
@@ -603,8 +631,8 @@ func (u *userInterface) swapBuffers() {
 }
 
 // setScreenSize must be called from the main thread.
-func (u *userInterface) setScreenSize(width, height int, scale float64, fullscreen bool) bool {
-	if u.width == width && u.height == height && u.scale == scale && u.fullscreen() == fullscreen {
+func (u *userInterface) setScreenSize(width, height int, scale float64, fullscreen bool, vsync bool) bool {
+	if u.width == width && u.height == height && u.scale == scale && u.fullscreen() == fullscreen && u.vsync == vsync {
 		return false
 	}
 
@@ -622,6 +650,7 @@ func (u *userInterface) setScreenSize(width, height int, scale float64, fullscre
 	u.height = height
 	u.scale = scale
 	u.fullscreenScale = 0
+	u.vsync = vsync
 
 	// To make sure the current existing framebuffers are rendered,
 	// swap buffers here before SetSize is called.
@@ -665,6 +694,7 @@ func (u *userInterface) setScreenSize(width, height int, scale float64, fullscre
 		// Window title might be lost on macOS after coming back from fullscreen.
 		u.window.SetTitle(u.title)
 	}
+
 	// SwapInterval is affected by the current monitor of the window.
 	// This needs to be called at least after SetMonitor.
 	// Without SwapInterval after SetMonitor, vsynch doesn't work (#375).
@@ -672,7 +702,11 @@ func (u *userInterface) setScreenSize(width, height int, scale float64, fullscre
 	// TODO: (#405) If triple buffering is needed, SwapInterval(0) should be called,
 	// but is this correct? If glfw.SwapInterval(0) and the driver doesn't support triple
 	// buffering, what will happen?
+	if u.vsync {
 		glfw.SwapInterval(1)
+	} else {
+		glfw.SwapInterval(0)
+	}
 
 	u.toChangeSize = true
 	return true

internal/ui/ui_js.go

@@ -36,6 +36,7 @@ type userInterface struct {
 	scale                float64
 	fullscreen           bool
 	runnableInBackground bool
+	vsync                bool
 
 	sizeChanged bool
 	windowFocus bool
@@ -46,12 +47,14 @@ var currentUI = &userInterface{
 	sizeChanged: true,
 	windowFocus: true,
 	pageVisible: true,
+	vsync:       true,
 }
 
 var (
 	window                = js.Global().Get("window")
 	document              = js.Global().Get("document")
 	requestAnimationFrame = window.Get("requestAnimationFrame")
+	setTimeoutForLoop     = js.Global().Call("eval", "((f) => { setTimeout(f, 0); })")
 )
 
 func MonitorSize() (int, int) {
@@ -86,6 +89,14 @@ func IsRunnableInBackground() bool {
 	return currentUI.runnableInBackground
 }
 
+func SetVsyncEnabled(enabled bool) {
+	currentUI.vsync = enabled
+}
+
+func IsVsyncEnabled() bool {
+	return currentUI.vsync
+}
+
 func ScreenPadding() (x0, y0, x1, y1 float64) {
 	return 0, 0, 0, 0
 }
@@ -215,7 +226,11 @@ func (u *userInterface) loop(g GraphicsContext) error {
 			close(ch)
 			return
 		}
+		if u.vsync {
 			requestAnimationFrame.Invoke(cf)
+		} else {
+			setTimeoutForLoop.Invoke(cf)
+		}
 	}
 	cf = js.NewCallback(f)
 	// Call f asyncly to be async since ch is used in f.

internal/ui/ui_mobile.go

@@ -394,6 +394,14 @@ func SetWindowDecorated(decorated bool) {
 	// Do nothing
 }
 
+func IsVsyncEnabled() bool {
+	return true
+}
+
+func SetVsyncEnabled(enabled bool) {
+	// Do nothing
+}
+
 func UpdateTouches(touches []*input.Touch) {
 	input.Get().UpdateTouches(touches)
 }

run.go

@@ -520,3 +520,28 @@ func SetWindowIcon(iconImages []image.Image) {
 func DeviceScaleFactor() float64 {
 	return devicescale.DeviceScale()
 }
+
+// IsVsyncEnabled returns a boolean value indicating whether
+// the game uses the display's vsync.
+//
+// IsVsyncEnabled is concurrent-safe.
+func IsVsyncEnabled() bool {
+	return ui.IsVsyncEnabled()
+}
+
+// SetVsyncEnabled sets a boolean value indicating whether
+// the game uses the display's vsync.
+//
+// If the given value is true, the game tries to sync the display's refresh rate.
+// If false, the game ignores the display's refresh rate.
+// The initial value is true.
+// By disabling vsync, the game works more efficiently but consumes more CPU.
+//
+// Note that the state doesn't affect how many the run funciton is updated per second.
+//
+// SetVsyncEnabled doesn't work on mobiles so far.
+//
+// SetVsyncEnabled is concurrent-safe.
+func SetVsyncEnabled(enabled bool) {
+	ui.SetVsyncEnabled(enabled)
+}