diff --git a/image.go b/image.go
index 717bc924e..f0ee6c6e1 100644
--- a/image.go
+++ b/image.go
@@ -23,6 +23,7 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/internal/graphics"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
 	"github.com/hajimehoshi/ebiten/v2/internal/mipmap"
+	"github.com/hajimehoshi/ebiten/v2/internal/ui"
 )
 
 // panicOnErrorAtImageAt indicates whether (*Image).At panics on an error or not.
@@ -718,7 +719,7 @@ func (i *Image) at(x, y int) (r, g, b, a uint8) {
 		if panicOnErrorAtImageAt {
 			panic(err)
 		}
-		theUIContext.setError(err)
+		ui.SetError(err)
 		return 0, 0, 0, 0
 	}
 	return pix[0], pix[1], pix[2], pix[3]
@@ -746,7 +747,7 @@ func (i *Image) Set(x, y int, clr color.Color) {
 	r, g, b, a := clr.RGBA()
 	pix := []byte{byte(r >> 8), byte(g >> 8), byte(b >> 8), byte(a >> 8)}
 	if err := i.mipmap.ReplacePixels(pix, x, y, 1, 1); err != nil {
-		theUIContext.setError(err)
+		ui.SetError(err)
 	}
 }
 
@@ -794,7 +795,7 @@ func (i *Image) ReplacePixels(pixels []byte) {
 	// * In internal/mipmap, pixels are copied when necessary.
 	// * In internal/shareable, pixels are copied to make its paddings.
 	if err := i.mipmap.ReplacePixels(pixels, r.Min.X, r.Min.Y, r.Dx(), r.Dy()); err != nil {
-		theUIContext.setError(err)
+		ui.SetError(err)
 	}
 }
 
diff --git a/internal/ui/context.go b/internal/ui/context.go
new file mode 100644
index 000000000..ed04cad7f
--- /dev/null
+++ b/internal/ui/context.go
@@ -0,0 +1,70 @@
+// Copyright 2022 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ui
+
+import (
+	"sync/atomic"
+)
+
+type Context interface {
+	UpdateFrame() error
+	ForceUpdateFrame() error
+	Layout(outsideWidth, outsideHeight float64)
+
+	// AdjustPosition can be called from a different goroutine from Update's or Layout's.
+	AdjustPosition(x, y float64, deviceScaleFactor float64) (float64, float64)
+}
+
+type contextImpl struct {
+	context Context
+
+	err atomic.Value
+}
+
+func (c *contextImpl) updateFrame() error {
+	if err, ok := c.err.Load().(error); ok && err != nil {
+		return err
+	}
+	return c.context.UpdateFrame()
+}
+
+func (c *contextImpl) forceUpdateFrame() error {
+	if err, ok := c.err.Load().(error); ok && err != nil {
+		return err
+	}
+	return c.context.ForceUpdateFrame()
+}
+
+func (c *contextImpl) layout(outsideWidth, outsideHeight float64) {
+	// The given outside size can be 0 e.g. just after restoring from the fullscreen mode on Windows (#1589)
+	// Just ignore such cases. Otherwise, creating a zero-sized framebuffer causes a panic.
+	if outsideWidth == 0 || outsideHeight == 0 {
+		return
+	}
+
+	c.context.Layout(outsideWidth, outsideHeight)
+}
+
+func (c *contextImpl) adjustPosition(x, y float64, deviceScaleFactor float64) (float64, float64) {
+	return c.context.AdjustPosition(x, y, deviceScaleFactor)
+}
+
+func (c *contextImpl) setError(err error) {
+	c.err.Store(err)
+}
+
+func SetError(err error) {
+	Get().context.setError(err)
+}
diff --git a/internal/ui/input_cbackend.go b/internal/ui/input_cbackend.go
index 7a90d0777..56a10793d 100644
--- a/internal/ui/input_cbackend.go
+++ b/internal/ui/input_cbackend.go
@@ -31,7 +31,7 @@ type Input struct {
 	m sync.Mutex
 }
 
-func (i *Input) update(context Context) {
+func (i *Input) update(context *contextImpl) {
 	i.m.Lock()
 	defer i.m.Unlock()
 
@@ -41,7 +41,7 @@ func (i *Input) update(context Context) {
 	i.touches = cbackend.AppendTouches(i.touches)
 
 	for idx, t := range i.touches {
-		x, y := context.AdjustPosition(float64(t.X), float64(t.Y), deviceScaleFactor)
+		x, y := context.adjustPosition(float64(t.X), float64(t.Y), deviceScaleFactor)
 		i.touches[idx].X = int(x)
 		i.touches[idx].Y = int(y)
 	}
diff --git a/internal/ui/input_glfw.go b/internal/ui/input_glfw.go
index 12822d6bc..8d8c053f3 100644
--- a/internal/ui/input_glfw.go
+++ b/internal/ui/input_glfw.go
@@ -155,7 +155,7 @@ var glfwMouseButtonToMouseButton = map[glfw.MouseButton]MouseButton{
 }
 
 // update must be called from the main thread.
-func (i *Input) update(window *glfw.Window, context Context) error {
+func (i *Input) update(window *glfw.Window, context *contextImpl) error {
 	i.ui.m.Lock()
 	defer i.ui.m.Unlock()
 
@@ -196,7 +196,7 @@ func (i *Input) update(window *glfw.Window, context Context) error {
 	s := i.ui.deviceScaleFactor(m)
 	cx = i.ui.dipFromGLFWPixel(cx, m)
 	cy = i.ui.dipFromGLFWPixel(cy, m)
-	cx, cy = context.AdjustPosition(cx, cy, s)
+	cx, cy = context.adjustPosition(cx, cy, s)
 
 	// AdjustPosition can return NaN at the initialization.
 	if !math.IsNaN(cx) && !math.IsNaN(cy) {
diff --git a/internal/ui/input_js.go b/internal/ui/input_js.go
index 61efe72b9..bda10d445 100644
--- a/internal/ui/input_js.go
+++ b/internal/ui/input_js.go
@@ -75,7 +75,7 @@ func (i *Input) CursorPosition() (x, y int) {
 	if i.ui.context == nil {
 		return 0, 0
 	}
-	xf, yf := i.ui.context.AdjustPosition(float64(i.cursorX), float64(i.cursorY), i.ui.DeviceScaleFactor())
+	xf, yf := i.ui.context.adjustPosition(float64(i.cursorX), float64(i.cursorY), i.ui.DeviceScaleFactor())
 	return int(xf), int(yf)
 }
 
@@ -90,7 +90,7 @@ func (i *Input) TouchPosition(id TouchID) (x, y int) {
 	d := i.ui.DeviceScaleFactor()
 	for tid, pos := range i.touches {
 		if id == tid {
-			x, y := i.ui.context.AdjustPosition(float64(pos.X), float64(pos.Y), d)
+			x, y := i.ui.context.adjustPosition(float64(pos.X), float64(pos.Y), d)
 			return int(x), int(y)
 		}
 	}
diff --git a/internal/ui/run_notsinglethread.go b/internal/ui/run_notsinglethread.go
index 3dd0aa2d2..3f83ba2fe 100644
--- a/internal/ui/run_notsinglethread.go
+++ b/internal/ui/run_notsinglethread.go
@@ -23,7 +23,9 @@ import (
 )
 
 func (u *UserInterface) Run(uicontext Context) error {
-	u.context = uicontext
+	u.context = &contextImpl{
+		context: uicontext,
+	}
 
 	// Initialize the main thread first so the thread is available at u.run (#809).
 	u.t = thread.NewOSThread()
diff --git a/internal/ui/run_singlethread.go b/internal/ui/run_singlethread.go
index 649048e8f..8b77ea5a6 100644
--- a/internal/ui/run_singlethread.go
+++ b/internal/ui/run_singlethread.go
@@ -23,7 +23,9 @@ import (
 )
 
 func (u *UserInterface) Run(uicontext Context) error {
-	u.context = uicontext
+	u.context = &contextImpl{
+		context: uicontext,
+	}
 
 	// Initialize the main thread first so the thread is available at u.run (#809).
 	u.t = thread.NewNoopThread()
diff --git a/internal/ui/ui.go b/internal/ui/ui.go
index 335a21297..8053315a8 100644
--- a/internal/ui/ui.go
+++ b/internal/ui/ui.go
@@ -20,15 +20,6 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
 )
 
-type Context interface {
-	UpdateFrame() error
-	ForceUpdateFrame() error
-	Layout(outsideWidth, outsideHeight float64)
-
-	// AdjustPosition can be called from a different goroutine from Update's or Layout's.
-	AdjustPosition(x, y float64, deviceScaleFactor float64) (float64, float64)
-}
-
 type MouseButton int
 
 const (
diff --git a/internal/ui/ui_cbackend.go b/internal/ui/ui_cbackend.go
index f4cf2e29d..fe7264216 100644
--- a/internal/ui/ui_cbackend.go
+++ b/internal/ui/ui_cbackend.go
@@ -30,7 +30,8 @@ func init() {
 }
 
 type UserInterface struct {
-	input Input
+	context *contextImpl
+	input   Input
 }
 
 var theUserInterface UserInterface
@@ -40,15 +41,18 @@ func Get() *UserInterface {
 }
 
 func (u *UserInterface) Run(context Context) error {
+	u.context = &contextImpl{
+		context: context,
+	}
 	cbackend.InitializeGame()
 	for {
 		w, h := cbackend.ScreenSize()
-		context.Layout(float64(w), float64(h))
+		u.context.layout(float64(w), float64(h))
 
 		cbackend.BeginFrame()
-		u.input.update(context)
+		u.input.update(u.context)
 
-		if err := context.UpdateFrame(); err != nil {
+		if err := u.context.updateFrame(); err != nil {
 			return err
 		}
 
diff --git a/internal/ui/ui_glfw.go b/internal/ui/ui_glfw.go
index dbcc66eb1..96c1858d4 100644
--- a/internal/ui/ui_glfw.go
+++ b/internal/ui/ui_glfw.go
@@ -46,7 +46,7 @@ func driverCursorModeToGLFWCursorMode(mode CursorMode) int {
 }
 
 type UserInterface struct {
-	context Context
+	context *contextImpl
 	title   string
 	window  *glfw.Window
 
@@ -731,8 +731,8 @@ func (u *UserInterface) registerWindowSetSizeCallback() {
 
 					outsideWidth, outsideHeight = u.updateSize()
 				})
-				u.context.Layout(outsideWidth, outsideHeight)
-				if err := u.context.ForceUpdateFrame(); err != nil {
+				u.context.layout(outsideWidth, outsideHeight)
+				if err := u.context.forceUpdateFrame(); err != nil {
 					return err
 				}
 				if graphics().IsGL() {
@@ -1042,9 +1042,9 @@ func (u *UserInterface) loop() error {
 		}); err != nil {
 			return err
 		}
-		u.context.Layout(outsideWidth, outsideHeight)
+		u.context.layout(outsideWidth, outsideHeight)
 
-		if err := u.context.UpdateFrame(); err != nil {
+		if err := u.context.updateFrame(); err != nil {
 			return err
 		}
 
@@ -1365,7 +1365,7 @@ func (u *UserInterface) ResetForFrame() {
 	u.t.Call(func() {
 		w, h = u.updateSize()
 	})
-	u.context.Layout(w, h)
+	u.context.layout(w, h)
 	u.input.resetForFrame()
 
 	u.m.Lock()
diff --git a/internal/ui/ui_js.go b/internal/ui/ui_js.go
index 7704d2804..958ffaa59 100644
--- a/internal/ui/ui_js.go
+++ b/internal/ui/ui_js.go
@@ -61,7 +61,7 @@ type UserInterface struct {
 
 	lastDeviceScaleFactor float64
 
-	context Context
+	context *contextImpl
 	input   Input
 }
 
@@ -240,14 +240,14 @@ func (u *UserInterface) updateSize() {
 			body := document.Get("body")
 			bw := body.Get("clientWidth").Float()
 			bh := body.Get("clientHeight").Float()
-			u.context.Layout(bw, bh)
+			u.context.layout(bw, bh)
 		case go2cpp.Truthy():
 			w := go2cpp.Get("screenWidth").Float()
 			h := go2cpp.Get("screenHeight").Float()
-			u.context.Layout(w, h)
+			u.context.layout(w, h)
 		default:
 			// Node.js
-			u.context.Layout(640, 480)
+			u.context.layout(640, 480)
 		}
 	}
 }
@@ -293,11 +293,11 @@ func (u *UserInterface) updateImpl(force bool) error {
 	u.input.updateForGo2Cpp()
 	u.updateSize()
 	if force {
-		if err := u.context.ForceUpdateFrame(); err != nil {
+		if err := u.context.forceUpdateFrame(); err != nil {
 			return err
 		}
 	} else {
-		if err := u.context.UpdateFrame(); err != nil {
+		if err := u.context.updateFrame(); err != nil {
 			return err
 		}
 	}
@@ -319,7 +319,9 @@ func (u *UserInterface) needsUpdate() bool {
 }
 
 func (u *UserInterface) loop(context Context) <-chan error {
-	u.context = context
+	u.context = &contextImpl{
+		context: context,
+	}
 
 	errCh := make(chan error, 1)
 	reqStopAudioCh := make(chan struct{})
diff --git a/internal/ui/ui_mobile.go b/internal/ui/ui_mobile.go
index d0cda231e..21a566490 100644
--- a/internal/ui/ui_mobile.go
+++ b/internal/ui/ui_mobile.go
@@ -109,7 +109,7 @@ type UserInterface struct {
 	setGBuildSizeCh chan struct{}
 	once            sync.Once
 
-	context Context
+	context *contextImpl
 
 	input Input
 
@@ -273,7 +273,9 @@ func (u *UserInterface) run(context Context, mainloop bool) (err error) {
 	u.sizeChanged = true
 	u.m.Unlock()
 
-	u.context = context
+	u.context = &contextImpl{
+		context: context,
+	}
 
 	if mainloop {
 		// When mainloop is true, gomobile-build is used. In this case, GL functions must be called via
@@ -320,7 +322,7 @@ func (u *UserInterface) layoutIfNeeded() {
 	u.m.RUnlock()
 
 	if sizeChanged {
-		u.context.Layout(outsideWidth, outsideHeight)
+		u.context.layout(outsideWidth, outsideHeight)
 	}
 }
 
@@ -330,7 +332,7 @@ func (u *UserInterface) update() error {
 		renderEndCh <- struct{}{}
 	}()
 
-	if err := u.context.UpdateFrame(); err != nil {
+	if err := u.context.updateFrame(); err != nil {
 		return err
 	}
 	return nil
@@ -368,7 +370,7 @@ func (u *UserInterface) setGBuildSize(widthPx, heightPx int) {
 }
 
 func (u *UserInterface) adjustPosition(x, y int) (int, int) {
-	xf, yf := u.context.AdjustPosition(float64(x), float64(y), deviceScale())
+	xf, yf := u.context.adjustPosition(float64(x), float64(y), deviceScale())
 	return int(xf), int(yf)
 }
 
diff --git a/uicontext.go b/uicontext.go
index 86afb4861..167bbf8bc 100644
--- a/uicontext.go
+++ b/uicontext.go
@@ -18,7 +18,6 @@ import (
 	"fmt"
 	"math"
 	"sync"
-	"sync/atomic"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/buffered"
 	"github.com/hajimehoshi/ebiten/v2/internal/clock"
@@ -39,8 +38,6 @@ type uiContext struct {
 	outsideWidth  float64
 	outsideHeight float64
 
-	err atomic.Value
-
 	m sync.Mutex
 }
 
@@ -52,16 +49,7 @@ func (c *uiContext) set(game Game) {
 	c.game = game
 }
 
-func (c *uiContext) setError(err error) {
-	c.err.Store(err)
-}
-
 func (c *uiContext) Layout(outsideWidth, outsideHeight float64) {
-	// The given outside size can be 0 e.g. just after restoring from the fullscreen mode on Windows (#1589)
-	// Just ignore such cases. Otherwise, creating a zero-sized framebuffer causes a panic.
-	if outsideWidth == 0 || outsideHeight == 0 {
-		return
-	}
 	c.outsideWidth = outsideWidth
 	c.outsideHeight = outsideHeight
 }
@@ -149,10 +137,6 @@ func (c *uiContext) ForceUpdateFrame() error {
 }
 
 func (c *uiContext) updateFrame(updateCount int) error {
-	if err, ok := c.err.Load().(error); ok && err != nil {
-		return err
-	}
-
 	debug.Logf("----\n")
 
 	if err := buffered.BeginFrame(); err != nil {