From 6d898d752ef6b212d1087a04b815297bdad380d4 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Mon, 12 Feb 2024 15:03:07 +0900
Subject: [PATCH] ebiten: add (*Monitor).DeviceScaleFactor()

This replaces ebiten.DeviceScaleFactor().

Updates #2795
---
 examples/fullscreen/main.go       |  8 +++---
 examples/highdpi/main.go          |  4 +--
 examples/windowsize/main.go       |  4 +--
 internal/ui/context.go            |  2 +-
 internal/ui/input_glfw.go         |  2 +-
 internal/ui/input_js.go           |  2 +-
 internal/ui/input_mobile.go       |  2 +-
 internal/ui/input_nintendosdk.go  |  2 +-
 internal/ui/monitor_glfw.go       |  3 ++-
 internal/ui/ui_glfw.go            | 29 +++-------------------
 internal/ui/ui_js.go              | 41 ++++++++++++++++---------------
 internal/ui/ui_linbsd.go          |  4 +--
 internal/ui/ui_mobile.go          | 38 ++++++++++++++++++----------
 internal/ui/ui_nintendosdk.go     | 12 ++++-----
 internal/ui/ui_playstation5.go    | 15 ++++++-----
 internal/ui/ui_windows.go         |  4 +--
 mobile/ebitenmobileview/mobile.go |  2 +-
 monitor.go                        | 14 +++++++++++
 run.go                            |  6 ++---
 19 files changed, 98 insertions(+), 96 deletions(-)

diff --git a/examples/fullscreen/main.go b/examples/fullscreen/main.go
index 187aecd2b..b8de6df2e 100644
--- a/examples/fullscreen/main.go
+++ b/examples/fullscreen/main.go
@@ -72,7 +72,7 @@ func (g *Game) Update() error {
 }
 
 func (g *Game) Draw(screen *ebiten.Image) {
-	scale := ebiten.DeviceScaleFactor()
+	scale := ebiten.Monitor().DeviceScaleFactor()
 
 	w, h := gophersImage.Bounds().Dx(), gophersImage.Bounds().Dy()
 	op := &ebiten.DrawImageOptions{}
@@ -99,15 +99,15 @@ func (g *Game) Draw(screen *ebiten.Image) {
 	textOp := &text.DrawOptions{}
 	textOp.GeoM.Translate(50*scale, 50*scale)
 	textOp.ColorScale.ScaleWithColor(color.White)
-	textOp.LineSpacing = 12 * ebiten.DeviceScaleFactor() * 1.5
+	textOp.LineSpacing = 12 * ebiten.Monitor().DeviceScaleFactor() * 1.5
 	text.Draw(screen, msg, &text.GoTextFace{
 		Source: mplusFaceSource,
-		Size:   12 * ebiten.DeviceScaleFactor(),
+		Size:   12 * ebiten.Monitor().DeviceScaleFactor(),
 	}, textOp)
 }
 
 func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
-	s := ebiten.DeviceScaleFactor()
+	s := ebiten.Monitor().DeviceScaleFactor()
 	return int(float64(outsideWidth) * s), int(float64(outsideHeight) * s)
 }
 
diff --git a/examples/highdpi/main.go b/examples/highdpi/main.go
index 240197429..23f653593 100644
--- a/examples/highdpi/main.go
+++ b/examples/highdpi/main.go
@@ -84,7 +84,7 @@ func (g *Game) Draw(screen *ebiten.Image) {
 
 	// Scale the image by the device ratio so that the rendering result can be same
 	// on various (different-DPI) environments.
-	scale := ebiten.DeviceScaleFactor()
+	scale := ebiten.Monitor().DeviceScaleFactor()
 	op.GeoM.Scale(scale, scale)
 
 	// Move the image's center to the screen's center.
@@ -99,7 +99,7 @@ func (g *Game) Draw(screen *ebiten.Image) {
 func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
 	// The unit of outsideWidth/Height is device-independent pixels.
 	// By multiplying them by the device scale factor, we can get a hi-DPI screen size.
-	s := ebiten.DeviceScaleFactor()
+	s := ebiten.Monitor().DeviceScaleFactor()
 	return int(float64(outsideWidth) * s), int(float64(outsideHeight) * s)
 }
 
diff --git a/examples/windowsize/main.go b/examples/windowsize/main.go
index be130f4d7..4d352c150 100644
--- a/examples/windowsize/main.go
+++ b/examples/windowsize/main.go
@@ -376,7 +376,7 @@ Window size limitation: (%d, %d) - (%d, %d)
 Cursor: (%d, %d)
 TPS: Current: %0.2f / Max: %s
 FPS: %0.2f
-Device Scale Factor: %0.2f`, msgM, msgR, fg, wx, wy, ww, wh, minw, minh, maxw, maxh, cx, cy, ebiten.ActualTPS(), tpsStr, ebiten.ActualFPS(), ebiten.DeviceScaleFactor())
+Device Scale Factor: %0.2f`, msgM, msgR, fg, wx, wy, ww, wh, minw, minh, maxw, maxh, cx, cy, ebiten.ActualTPS(), tpsStr, ebiten.ActualFPS(), ebiten.Monitor().DeviceScaleFactor())
 	ebitenutil.DebugPrint(screen, msg)
 }
 
@@ -400,7 +400,7 @@ func parseWindowPosition() (int, int, bool) {
 }
 
 func main() {
-	fmt.Printf("Device scale factor: %0.2f\n", ebiten.DeviceScaleFactor())
+	fmt.Printf("Device scale factor: %0.2f\n", ebiten.Monitor().DeviceScaleFactor())
 	w, h := ebiten.ScreenSizeInFullscreen()
 	fmt.Printf("Screen size in fullscreen: %d, %d\n", w, h)
 
diff --git a/internal/ui/context.go b/internal/ui/context.go
index 7abcf395a..d045e3b5e 100644
--- a/internal/ui/context.go
+++ b/internal/ui/context.go
@@ -286,5 +286,5 @@ func (c *context) screenScaleAndOffsets() (scale, offsetX, offsetY float64) {
 }
 
 func (u *UserInterface) LogicalPositionToClientPosition(x, y float64) (float64, float64) {
-	return u.context.logicalPositionToClientPosition(x, y, u.DeviceScaleFactor())
+	return u.context.logicalPositionToClientPosition(x, y, u.Monitor().DeviceScaleFactor())
 }
diff --git a/internal/ui/input_glfw.go b/internal/ui/input_glfw.go
index feee4a7eb..cff97e880 100644
--- a/internal/ui/input_glfw.go
+++ b/internal/ui/input_glfw.go
@@ -86,7 +86,7 @@ func (u *UserInterface) updateInputStateImpl() error {
 	if err != nil {
 		return err
 	}
-	s := m.deviceScaleFactor()
+	s := m.DeviceScaleFactor()
 
 	cx, cy := u.savedCursorX, u.savedCursorY
 	defer func() {
diff --git a/internal/ui/input_js.go b/internal/ui/input_js.go
index 0d8ce47c6..4f5ff6c41 100644
--- a/internal/ui/input_js.go
+++ b/internal/ui/input_js.go
@@ -305,7 +305,7 @@ func (u *UserInterface) updateInputState() error {
 		u.keyDurationsByKeyProperty[key]++
 	}
 
-	s := u.DeviceScaleFactor()
+	s := theMonitor.DeviceScaleFactor()
 
 	if !math.IsNaN(u.savedCursorX) && !math.IsNaN(u.savedCursorY) {
 		// If savedCursorX and savedCursorY are valid values, the cursor is saved just before entering or exiting from fullscreen.
diff --git a/internal/ui/input_mobile.go b/internal/ui/input_mobile.go
index 582cd3a18..e2fb5ca52 100644
--- a/internal/ui/input_mobile.go
+++ b/internal/ui/input_mobile.go
@@ -47,7 +47,7 @@ func (u *UserInterface) updateInputState() error {
 	u.m.Lock()
 	defer u.m.Unlock()
 
-	s := u.DeviceScaleFactor()
+	s := theMonitor.DeviceScaleFactor()
 
 	u.inputState.Touches = u.inputState.Touches[:0]
 	for _, t := range u.touches {
diff --git a/internal/ui/input_nintendosdk.go b/internal/ui/input_nintendosdk.go
index 281bf2cb0..f800f3947 100644
--- a/internal/ui/input_nintendosdk.go
+++ b/internal/ui/input_nintendosdk.go
@@ -60,7 +60,7 @@ func (u *UserInterface) updateInputStateImpl() error {
 
 	u.inputState.Touches = u.inputState.Touches[:0]
 	for _, t := range u.nativeTouches {
-		x, y := u.context.clientPositionToLogicalPosition(float64(t.x), float64(t.y), deviceScaleFactor)
+		x, y := u.context.clientPositionToLogicalPosition(float64(t.x), float64(t.y), theMonitor.DeviceScaleFactor())
 		u.inputState.Touches = append(u.inputState.Touches, Touch{
 			ID: TouchID(t.id),
 			X:  int(x),
diff --git a/internal/ui/monitor_glfw.go b/internal/ui/monitor_glfw.go
index 6509d3d89..fa9496db5 100644
--- a/internal/ui/monitor_glfw.go
+++ b/internal/ui/monitor_glfw.go
@@ -40,7 +40,8 @@ func (m *Monitor) Name() string {
 	return m.name
 }
 
-func (m *Monitor) deviceScaleFactor() float64 {
+// DeviceScaleFactor is concurrent-safe as contentScale is immutable.
+func (m *Monitor) DeviceScaleFactor() float64 {
 	// It is rare, but monitor can be nil when glfw.GetPrimaryMonitor returns nil.
 	// In this case, return 1 as a tentative scale (#1878).
 	if m == nil {
diff --git a/internal/ui/ui_glfw.go b/internal/ui/ui_glfw.go
index 96ea90d75..90e863eb0 100644
--- a/internal/ui/ui_glfw.go
+++ b/internal/ui/ui_glfw.go
@@ -833,29 +833,6 @@ func (u *UserInterface) SetCursorShape(shape CursorShape) {
 	})
 }
 
-func (u *UserInterface) DeviceScaleFactor() float64 {
-	if u.isTerminated() {
-		return 0
-	}
-	if !u.isRunning() {
-		return u.getInitMonitor().deviceScaleFactor()
-	}
-
-	var f float64
-	u.mainThread.Call(func() {
-		if u.isTerminated() {
-			return
-		}
-		m, err := u.currentMonitor()
-		if err != nil {
-			u.setError(err)
-			return
-		}
-		f = m.deviceScaleFactor()
-	})
-	return f
-}
-
 // createWindow creates a GLFW window.
 //
 // createWindow must be called from the main thread.
@@ -988,7 +965,7 @@ func (u *UserInterface) registerWindowFramebufferSizeCallback() error {
 				u.setError(err)
 				return
 			}
-			s := m.deviceScaleFactor()
+			s := m.DeviceScaleFactor()
 			ww := int(float64(w) / s)
 			wh := int(float64(h) / s)
 			if err := u.setWindowSizeInDIP(ww, wh, false); err != nil {
@@ -1460,7 +1437,7 @@ func (u *UserInterface) updateGame() error {
 		if err != nil {
 			return
 		}
-		deviceScaleFactor = m.deviceScaleFactor()
+		deviceScaleFactor = m.DeviceScaleFactor()
 	}); err != nil {
 		return err
 	}
@@ -1639,7 +1616,7 @@ func (u *UserInterface) setWindowSizeInDIP(width, height int, callSetSize bool)
 	if err != nil {
 		return err
 	}
-	scale := mon.deviceScaleFactor()
+	scale := mon.DeviceScaleFactor()
 	if u.origWindowWidthInDIP == width && u.origWindowHeightInDIP == height && u.lastDeviceScaleFactor == scale {
 		return nil
 	}
diff --git a/internal/ui/ui_js.go b/internal/ui/ui_js.go
index ce1d956ca..fc16e05db 100644
--- a/internal/ui/ui_js.go
+++ b/internal/ui/ui_js.go
@@ -97,8 +97,6 @@ type userInterfaceImpl struct {
 	onceUpdateCalled    bool
 	lastCaptureExitTime time.Time
 
-	deviceScaleFactor float64
-
 	context                   *context
 	inputState                InputState
 	keyDurationsByKeyProperty map[Key]int
@@ -271,19 +269,6 @@ func (u *UserInterface) SetCursorShape(shape CursorShape) {
 	}
 }
 
-func (u *UserInterface) DeviceScaleFactor() float64 {
-	if u.deviceScaleFactor != 0 {
-		return u.deviceScaleFactor
-	}
-
-	ratio := window.Get("devicePixelRatio").Float()
-	if ratio == 0 {
-		ratio = 1
-	}
-	u.deviceScaleFactor = ratio
-	return u.deviceScaleFactor
-}
-
 func (u *UserInterface) outsideSize() (float64, float64) {
 	if document.Truthy() {
 		body := document.Get("body")
@@ -365,11 +350,11 @@ func (u *UserInterface) updateImpl(force bool) error {
 
 	w, h := u.outsideSize()
 	if force {
-		if err := u.context.forceUpdateFrame(u.graphicsDriver, w, h, u.DeviceScaleFactor(), u); err != nil {
+		if err := u.context.forceUpdateFrame(u.graphicsDriver, w, h, theMonitor.DeviceScaleFactor(), u); err != nil {
 			return err
 		}
 	} else {
-		if err := u.context.updateFrame(u.graphicsDriver, w, h, u.DeviceScaleFactor(), u); err != nil {
+		if err := u.context.updateFrame(u.graphicsDriver, w, h, theMonitor.DeviceScaleFactor(), u); err != nil {
 			return err
 		}
 	}
@@ -771,8 +756,9 @@ func (u *UserInterface) initOnMainThread(options *RunOptions) error {
 func (u *UserInterface) updateScreenSize() {
 	if document.Truthy() {
 		body := document.Get("body")
-		bw := int(body.Get("clientWidth").Float() * u.DeviceScaleFactor())
-		bh := int(body.Get("clientHeight").Float() * u.DeviceScaleFactor())
+		f := theMonitor.DeviceScaleFactor()
+		bw := int(body.Get("clientWidth").Float() * f)
+		bh := int(body.Get("clientHeight").Float() * f)
 		canvas.Set("width", bw)
 		canvas.Set("height", bh)
 	}
@@ -787,7 +773,9 @@ func (u *UserInterface) Window() Window {
 	return &nullWindow{}
 }
 
-type Monitor struct{}
+type Monitor struct {
+	deviceScaleFactor float64
+}
 
 var theMonitor = &Monitor{}
 
@@ -795,6 +783,19 @@ func (m *Monitor) Name() string {
 	return ""
 }
 
+func (m *Monitor) DeviceScaleFactor() float64 {
+	if m.deviceScaleFactor != 0 {
+		return m.deviceScaleFactor
+	}
+
+	ratio := window.Get("devicePixelRatio").Float()
+	if ratio == 0 {
+		ratio = 1
+	}
+	m.deviceScaleFactor = ratio
+	return m.deviceScaleFactor
+}
+
 func (u *UserInterface) AppendMonitors(mons []*Monitor) []*Monitor {
 	return append(mons, theMonitor)
 }
diff --git a/internal/ui/ui_linbsd.go b/internal/ui/ui_linbsd.go
index bd07899d7..c94dddac2 100644
--- a/internal/ui/ui_linbsd.go
+++ b/internal/ui/ui_linbsd.go
@@ -123,11 +123,11 @@ func glfwMonitorSizeInGLFWPixels(m *glfw.Monitor) (int, int, error) {
 }
 
 func dipFromGLFWPixel(x float64, monitor *Monitor) float64 {
-	return x / monitor.deviceScaleFactor()
+	return x / monitor.DeviceScaleFactor()
 }
 
 func dipToGLFWPixel(x float64, monitor *Monitor) float64 {
-	return x * monitor.deviceScaleFactor()
+	return x * monitor.DeviceScaleFactor()
 }
 
 func (u *UserInterface) adjustWindowPosition(x, y int, monitor *Monitor) (int, int) {
diff --git a/internal/ui/ui_mobile.go b/internal/ui/ui_mobile.go
index ff4633d11..c23dbd924 100644
--- a/internal/ui/ui_mobile.go
+++ b/internal/ui/ui_mobile.go
@@ -89,9 +89,6 @@ type userInterfaceImpl struct {
 	outsideWidth  float64
 	outsideHeight float64
 
-	deviceScaleFactorOnce sync.Once
-	deviceScaleFactor     float64
-
 	foreground int32
 	errCh      chan error
 
@@ -179,8 +176,11 @@ func (u *UserInterface) update() error {
 		renderEndCh <- struct{}{}
 	}()
 
+	// The device scale factor can be obtained after the main function starts, especially on Android.
+	theMonitor.initDeviceScaleFactorIfNeeded()
+
 	w, h := u.outsideSize()
-	if err := u.context.updateFrame(u.graphicsDriver, w, h, u.DeviceScaleFactor(), u); err != nil {
+	if err := u.context.updateFrame(u.graphicsDriver, w, h, theMonitor.DeviceScaleFactor(), u); err != nil {
 		return err
 	}
 	return nil
@@ -256,14 +256,6 @@ func (u *UserInterface) updateExplicitRenderingModeIfNeeded(fpsMode FPSModeType)
 	u.renderRequester.SetExplicitRenderingMode(fpsMode == FPSModeVsyncOffMinimum)
 }
 
-func (u *UserInterface) DeviceScaleFactor() float64 {
-	// Assume that the device scale factor never changes on mobiles.
-	u.deviceScaleFactorOnce.Do(func() {
-		u.deviceScaleFactor = deviceScaleFactorImpl()
-	})
-	return u.deviceScaleFactor
-}
-
 func (u *UserInterface) readInputState(inputState *InputState) {
 	u.m.Lock()
 	defer u.m.Unlock()
@@ -274,7 +266,11 @@ func (u *UserInterface) Window() Window {
 	return &nullWindow{}
 }
 
-type Monitor struct{}
+type Monitor struct {
+	deviceScaleFactor float64
+
+	m sync.Mutex
+}
 
 var theMonitor = &Monitor{}
 
@@ -282,6 +278,22 @@ func (m *Monitor) Name() string {
 	return ""
 }
 
+func (m *Monitor) initDeviceScaleFactorIfNeeded() {
+	// Assume that the device scale factor never changes on mobiles.
+	m.m.Lock()
+	defer m.m.Unlock()
+	if m.deviceScaleFactor != 0 {
+		return
+	}
+	m.deviceScaleFactor = deviceScaleFactorImpl()
+}
+
+func (m *Monitor) DeviceScaleFactor() float64 {
+	m.m.Lock()
+	defer m.m.Unlock()
+	return m.deviceScaleFactor
+}
+
 func (u *UserInterface) AppendMonitors(mons []*Monitor) []*Monitor {
 	return append(mons, theMonitor)
 }
diff --git a/internal/ui/ui_nintendosdk.go b/internal/ui/ui_nintendosdk.go
index a2f445dee..914703dd9 100644
--- a/internal/ui/ui_nintendosdk.go
+++ b/internal/ui/ui_nintendosdk.go
@@ -54,8 +54,6 @@ func (*graphicsDriverCreatorImpl) newPlayStation5() (graphicsdriver.Graphics, er
 	return nil, errors.New("ui: PlayStation 5 is not supported in this environment")
 }
 
-const deviceScaleFactor = 1
-
 func init() {
 	runtime.LockOSThread()
 }
@@ -94,16 +92,12 @@ func (u *UserInterface) loopGame() error {
 	for {
 		recordProfilerHeartbeat()
 
-		if err := u.context.updateFrame(u.graphicsDriver, float64(C.kScreenWidth), float64(C.kScreenHeight), deviceScaleFactor, u); err != nil {
+		if err := u.context.updateFrame(u.graphicsDriver, float64(C.kScreenWidth), float64(C.kScreenHeight), theMonitor.DeviceScaleFactor(), u); err != nil {
 			return err
 		}
 	}
 }
 
-func (*UserInterface) DeviceScaleFactor() float64 {
-	return deviceScaleFactor
-}
-
 func (*UserInterface) IsFocused() bool {
 	return true
 }
@@ -172,6 +166,10 @@ func (m *Monitor) Name() string {
 	return ""
 }
 
+func (m *Monitor) DeviceScaleFactor() float64 {
+	return 1
+}
+
 func (u *UserInterface) AppendMonitors(mons []*Monitor) []*Monitor {
 	return append(mons, theMonitor)
 }
diff --git a/internal/ui/ui_playstation5.go b/internal/ui/ui_playstation5.go
index 0a95e50d9..faadc296e 100644
--- a/internal/ui/ui_playstation5.go
+++ b/internal/ui/ui_playstation5.go
@@ -50,9 +50,8 @@ func (*graphicsDriverCreatorImpl) newPlayStation5() (graphicsdriver.Graphics, er
 
 const (
 	// TODO: Get this value from the SDK.
-	screenWidth       = 3840
-	screenHeight      = 2160
-	deviceScaleFactor = 1
+	screenWidth  = 3840
+	screenHeight = 2160
 )
 
 func init() {
@@ -82,17 +81,13 @@ func (u *UserInterface) initOnMainThread(options *RunOptions) error {
 
 func (u *UserInterface) loopGame() error {
 	for {
-		if err := u.context.updateFrame(u.graphicsDriver, screenWidth, screenHeight, deviceScaleFactor, u); err != nil {
+		if err := u.context.updateFrame(u.graphicsDriver, screenWidth, screenHeight, theMonitor.DeviceScaleFactor(), u); err != nil {
 			return err
 		}
 	}
 	return nil
 }
 
-func (*UserInterface) DeviceScaleFactor() float64 {
-	return deviceScaleFactor
-}
-
 func (*UserInterface) IsFocused() bool {
 	return true
 }
@@ -164,6 +159,10 @@ func (m *Monitor) Name() string {
 	return ""
 }
 
+func (m *Monitor) DeviceScaleFactor() float64 {
+	return 1
+}
+
 func (u *UserInterface) AppendMonitors(mons []*Monitor) []*Monitor {
 	return append(mons, theMonitor)
 }
diff --git a/internal/ui/ui_windows.go b/internal/ui/ui_windows.go
index a6c423d66..ffe4830d8 100644
--- a/internal/ui/ui_windows.go
+++ b/internal/ui/ui_windows.go
@@ -102,11 +102,11 @@ func glfwMonitorSizeInGLFWPixels(m *glfw.Monitor) (int, int, error) {
 }
 
 func dipFromGLFWPixel(x float64, monitor *Monitor) float64 {
-	return x / monitor.deviceScaleFactor()
+	return x / monitor.DeviceScaleFactor()
 }
 
 func dipToGLFWPixel(x float64, monitor *Monitor) float64 {
-	return x * monitor.deviceScaleFactor()
+	return x * monitor.DeviceScaleFactor()
 }
 
 func (u *UserInterface) adjustWindowPosition(x, y int, monitor *Monitor) (int, int) {
diff --git a/mobile/ebitenmobileview/mobile.go b/mobile/ebitenmobileview/mobile.go
index 7f5193564..d83e0090c 100644
--- a/mobile/ebitenmobileview/mobile.go
+++ b/mobile/ebitenmobileview/mobile.go
@@ -113,7 +113,7 @@ func Resume() error {
 }
 
 func DeviceScale() float64 {
-	return ui.Get().DeviceScaleFactor()
+	return ui.Get().Monitor().DeviceScaleFactor()
 }
 
 type RenderRequester interface {
diff --git a/monitor.go b/monitor.go
index 31a45a8a7..f5c7691f5 100644
--- a/monitor.go
+++ b/monitor.go
@@ -27,6 +27,20 @@ func (m *MonitorType) Name() string {
 	return (*ui.Monitor)(m).Name()
 }
 
+// DeviceScaleFactor returns the device scale factor of the monitor.
+//
+// DeviceScaleFactor returns a meaningful value on high-DPI display environment,
+// otherwise DeviceScaleFactor returns 1.
+//
+// DeviceScaleFactor might panic on init function on some devices like Android.
+// Then, it is not recommended to call DeviceScaleFactor from init functions.
+//
+// DeviceScaleFactor must be called on the main thread before the main loop,
+// and is concurrent-safe after the main loop.
+func (m *MonitorType) DeviceScaleFactor() float64 {
+	return (*ui.Monitor)(m).DeviceScaleFactor()
+}
+
 // Monitor returns the current monitor.
 func Monitor() *MonitorType {
 	m := ui.Get().Monitor()
diff --git a/run.go b/run.go
index 813d174fd..668cfee31 100644
--- a/run.go
+++ b/run.go
@@ -480,11 +480,11 @@ func SetRunnableOnUnfocused(runnableOnUnfocused bool) {
 // DeviceScaleFactor must be called on the main thread before the main loop, and is concurrent-safe after the main
 // loop.
 //
-// DeviceScaleFactor is concurrent-safe.
-//
 // BUG: DeviceScaleFactor value is not affected by SetWindowPosition before RunGame (#1575).
+//
+// Deprecated: as of v2.6. Use Monitor().DeviceScaleFactor() instead.
 func DeviceScaleFactor() float64 {
-	return ui.Get().DeviceScaleFactor()
+	return Monitor().DeviceScaleFactor()
 }
 
 // IsVsyncEnabled returns a boolean value indicating whether