diff --git a/internal/graphics/opengl/context_mobile.go b/internal/graphics/opengl/context_mobile.go
index 0775c2e35..025e189d4 100644
--- a/internal/graphics/opengl/context_mobile.go
+++ b/internal/graphics/opengl/context_mobile.go
@@ -41,9 +41,11 @@ func (p Program) id() programID {
 }
 
 type context struct {
-	gl          mgl.Context
-	worker      mgl.Worker
-	initialized chan struct{}
+	gl                      mgl.Context
+	worker                  mgl.Worker
+	initialized             chan struct{}
+	screenFramebufferWidth  int
+	screenFramebufferHeight int
 }
 
 func NewContext() (*Context, error) {
@@ -79,11 +81,22 @@ func NewContext() (*Context, error) {
 		c.BlendFunc(CompositeModeSourceOver)
 		f := c.gl.GetInteger(mgl.FRAMEBUFFER_BINDING)
 		c.screenFramebuffer = Framebuffer(mgl.Framebuffer{uint32(f)})
+		// It is invalid to get the size of the deafult framebuffer.
+		if c.screenFramebuffer.Value != 0 {
+			width := c.gl.GetRenderbufferParameteri(mgl.RENDERBUFFER, mgl.RENDERBUFFER_WIDTH)
+			height := c.gl.GetRenderbufferParameteri(mgl.RENDERBUFFER, mgl.RENDERBUFFER_HEIGHT)
+			c.screenFramebufferWidth = width
+			c.screenFramebufferHeight = height
+		}
 		close(c.initialized)
 	}()
 	return c, nil
 }
 
+func (c *Context) ScreenFramebufferSize() (int, int) {
+	return c.screenFramebufferWidth, c.screenFramebufferHeight
+}
+
 func (c *Context) Resume() error {
 	c.locationCache = newLocationCache()
 	c.lastFramebuffer = invalidFramebuffer
@@ -94,12 +107,12 @@ func (c *Context) Resume() error {
 	c.BlendFunc(CompositeModeSourceOver)
 	f := c.gl.GetInteger(mgl.FRAMEBUFFER_BINDING)
 	c.screenFramebuffer = Framebuffer(mgl.Framebuffer{uint32(f)})
+	// TODO: Need to update screenFramebufferWidth/Height?
 	return nil
 }
 
-func (c *Context) WaitUntilInitializingDone() {
-	// TODO: Call this function at an approriate place
-	<-c.initialized
+func (c *Context) InitializedCh() <-chan struct{} {
+	return c.initialized
 }
 
 func (c *Context) Worker() mgl.Worker {
diff --git a/internal/ui/ui_mobile.go b/internal/ui/ui_mobile.go
index 4fb0c01e3..e9d3d0ddf 100644
--- a/internal/ui/ui_mobile.go
+++ b/internal/ui/ui_mobile.go
@@ -36,6 +36,13 @@ func Render(chError <-chan error) error {
 		return errors.New("ui: chError must not be nil")
 	}
 	// TODO: Check this is called on the rendering thread
+	if chGLInitialized != nil {
+		if err := doGLWorks(chError, glContext.InitializedCh()); err != nil {
+			return err
+		}
+		close(chGLInitialized)
+		<-chGLInitializedEnd
+	}
 	select {
 	case chRender <- struct{}{}:
 		return doGLWorks(chError, chRenderEnd)
@@ -67,16 +74,19 @@ loop:
 }
 
 type userInterface struct {
-	width       int
-	height      int
-	scale       int
-	sizeChanged bool
+	width            int
+	height           int
+	scale            int
+	framebufferScale int
+	sizeChanged      bool
 }
 
 var (
-	chRender    = make(chan struct{})
-	chRenderEnd = make(chan struct{})
-	currentUI   = &userInterface{
+	chRender           = make(chan struct{})
+	chRenderEnd        = make(chan struct{})
+	chGLInitialized    = make(chan struct{})
+	chGLInitializedEnd = make(chan struct{})
+	currentUI          = &userInterface{
 		sizeChanged: true,
 	}
 )
@@ -99,6 +109,11 @@ func (u *userInterface) Terminate() error {
 
 func (u *userInterface) Update() (interface{}, error) {
 	// TODO: Need lock?
+	if chGLInitialized != nil {
+		<-chGLInitialized
+		chGLInitialized = nil
+		close(chGLInitializedEnd)
+	}
 	if u.sizeChanged {
 		u.sizeChanged = false
 		e := ScreenSizeEvent{
@@ -132,7 +147,17 @@ func (u *userInterface) ScreenScale() int {
 }
 
 func (u *userInterface) actualScreenScale() int {
-	return u.scale
+	if u.framebufferScale == 0 {
+		width, _ := glContext.ScreenFramebufferSize()
+		if width == 0 {
+			// Android
+			u.framebufferScale = 1
+		} else {
+			// iOS
+			u.framebufferScale = width / u.width
+		}
+	}
+	return u.scale * u.framebufferScale
 }
 
 func UpdateTouches(touches []Touch) {