diff --git a/internal/ui/ui_glfw.go b/internal/ui/ui_glfw.go
index d5db026ce..f867a10cb 100644
--- a/internal/ui/ui_glfw.go
+++ b/internal/ui/ui_glfw.go
@@ -68,7 +68,7 @@ func Init() *opengl.Context {
 	return u.context
 }
 
-func Start(width, height, scale int, title string) (framebufferScale int, err error) {
+func Start(width, height, scale int, title string) error {
 	return currentUI.start(width, height, scale, title)
 }
 
@@ -88,14 +88,16 @@ func SwapBuffers() {
 	currentUI.swapBuffers()
 }
 
-func SetScreenSize(width, height int) (bool, int) {
-	result := currentUI.setScreenSize(width, height, currentUI.scale)
-	return result, currentUI.framebufferScale()
+func SetScreenSize(width, height int) bool {
+	return currentUI.setScreenSize(width, height, currentUI.scale)
 }
 
-func SetScreenScale(scale int) (bool, int) {
-	result := currentUI.setScreenSize(currentUI.width, currentUI.height, scale)
-	return result, currentUI.framebufferScale()
+func SetScreenScale(scale int) bool {
+	return currentUI.setScreenSize(currentUI.width, currentUI.height, scale)
+}
+
+func ActualScale() int {
+	return currentUI.actualScale()
 }
 
 type userInterface struct {
@@ -104,16 +106,16 @@ type userInterface struct {
 	height            int
 	scale             int
 	deviceScaleFactor float64
-	framebufferScale_ int
+	framebufferScale  int
 	context           *opengl.Context
 }
 
-func (u *userInterface) start(width, height, scale int, title string) (framebufferScale int, err error) {
+func (u *userInterface) start(width, height, scale int, title string) error {
 	m := glfw.GetPrimaryMonitor()
 	v := m.GetVideoMode()
 	mw, _ := m.GetPhysicalSize()
 	u.deviceScaleFactor = 1
-	u.framebufferScale_ = 1
+	u.framebufferScale = 1
 	// mw can be 0 on some environment like Linux VM
 	if 0 < mw {
 		dpi := float64(v.Width) * 25.4 / float64(mw)
@@ -128,15 +130,15 @@ func (u *userInterface) start(width, height, scale int, title string) (framebuff
 	y := (v.Height - height*u.windowScale()) / 3
 	u.window.SetPos(x, y)
 
-	return u.framebufferScale(), nil
+	return nil
 }
 
 func (u *userInterface) windowScale() int {
 	return int(float64(u.scale) * u.deviceScaleFactor)
 }
 
-func (u *userInterface) framebufferScale() int {
-	return u.windowScale() * u.framebufferScale_
+func (u *userInterface) actualScale() int {
+	return u.windowScale() * u.framebufferScale
 }
 
 func (u *userInterface) pollEvents() error {
@@ -207,6 +209,6 @@ event:
 	}
 	// This is usually 1, but sometimes more than 1 (e.g. Retina Mac)
 	fw, _ := window.GetFramebufferSize()
-	u.framebufferScale_ = fw / width / u.windowScale()
+	u.framebufferScale = fw / width / u.windowScale()
 	return true
 }
diff --git a/internal/ui/ui_js.go b/internal/ui/ui_js.go
index 25257267a..b3fa0e7f6 100644
--- a/internal/ui/ui_js.go
+++ b/internal/ui/ui_js.go
@@ -29,7 +29,7 @@ func Now() int64 {
 	return int64(js.Global.Get("performance").Call("now").Float() * float64(time.Millisecond))
 }
 
-func Start(width, height, scale int, title string) (actualScale int, err error) {
+func Start(width, height, scale int, title string) error {
 	return currentUI.start(width, height, scale, title)
 }
 
@@ -49,18 +49,18 @@ func SwapBuffers() {
 	currentUI.swapBuffers()
 }
 
-func SetScreenSize(width, height int) (bool, int) {
+func SetScreenSize(width, height int) bool {
 	scale := canvas.Get("dataset").Get("ebitenScale").Int()
-	result := currentUI.setScreenSize(width, height, scale)
-	actualScale := canvas.Get("dataset").Get("ebitenActualScale").Int()
-	return result, actualScale
+	return currentUI.setScreenSize(width, height, scale)
 }
 
-func SetScreenScale(scale int) (bool, int) {
+func SetScreenScale(scale int) bool {
 	width, height := currentUI.size()
-	result := currentUI.setScreenSize(width, height, scale)
-	actualScale := canvas.Get("dataset").Get("ebitenActualScale").Int()
-	return result, actualScale
+	return currentUI.setScreenSize(width, height, scale)
+}
+
+func ActualScale() int {
+	return canvas.Get("dataset").Get("ebitenActualScale").Int()
 }
 
 var canvas *js.Object
@@ -240,14 +240,12 @@ func devicePixelRatio() int {
 	return ratio
 }
 
-func (u *userInterface) start(width, height, scale int, title string) (actualScale int, err error) {
+func (u *userInterface) start(width, height, scale int, title string) error {
 	doc := js.Global.Get("document")
 	doc.Set("title", title)
 	u.setScreenSize(width, height, scale)
 	canvas.Call("focus")
-
-	actualScale = canvas.Get("dataset").Get("ebitenActualScale").Int()
-	return actualScale, nil
+	return nil
 }
 
 func (*userInterface) size() (width, height int) {
diff --git a/run.go b/run.go
index c6f7c44c0..f0cb46e64 100644
--- a/run.go
+++ b/run.go
@@ -48,14 +48,13 @@ func Run(f func(*Image) error, width, height, scale int, title string) error {
 		runContext.running = false
 	}()
 
-	actualScale, err := ui.Start(width, height, scale, title)
-	if err != nil {
+	if err := ui.Start(width, height, scale, title); err != nil {
 		return err
 	}
 	defer ui.Terminate()
 
 	glContext.Check()
-	graphicsContext, err := newGraphicsContext(width, height, actualScale)
+	graphicsContext, err := newGraphicsContext(width, height, ui.ActualScale())
 	if err != nil {
 		return err
 	}
@@ -67,21 +66,17 @@ func Run(f func(*Image) error, width, height, scale int, title string) error {
 		// TODO: setSize should be called after swapping buffers?
 		if 0 < runContext.newScreenWidth || 0 < runContext.newScreenHeight || 0 < runContext.newScreenScale {
 			changed := false
-			actualScale := 0
 			if 0 < runContext.newScreenWidth || 0 < runContext.newScreenHeight {
-				c, a := ui.SetScreenSize(runContext.newScreenWidth, runContext.newScreenHeight)
+				c := ui.SetScreenSize(runContext.newScreenWidth, runContext.newScreenHeight)
 				changed = changed || c
-				actualScale = a
 			}
 			if 0 < runContext.newScreenScale {
-				c, a := ui.SetScreenScale(runContext.newScreenScale)
+				c := ui.SetScreenScale(runContext.newScreenScale)
 				changed = changed || c
-				// actualScale of SetScreenState is more reliable than one of SetScreenSize
-				actualScale = a
 			}
 			if changed {
 				w, h := runContext.newScreenWidth, runContext.newScreenHeight
-				if err := graphicsContext.setSize(w, h, actualScale); err != nil {
+				if err := graphicsContext.setSize(w, h, ui.ActualScale()); err != nil {
 					return err
 				}
 			}