restorable: Better calculation to clear restorable.Image

graphicscontext.go

@@ -55,8 +55,8 @@ func (c *graphicsContext) SetSize(screenWidth, screenHeight int, screenScale flo
 
 	w := int(float64(screenWidth) * screenScale)
 	h := int(float64(screenHeight) * screenScale)
-	ox, oy := ui.ScreenOffset()
-	c.screen = newImageWithScreenFramebuffer(w, h, ox, oy)
+	px0, py0, px1, py1 := ui.ScreenPadding()
+	c.screen = newImageWithScreenFramebuffer(w, h, px0, py0, px1, py1)
 	_ = c.screen.Clear()
 
 	c.offscreen = offscreen

image.go

@@ -382,9 +382,9 @@ func NewImageFromImage(source image.Image, filter Filter) (*Image, error) {
 	return i, nil
 }
 
-func newImageWithScreenFramebuffer(width, height int, offsetX, offsetY float64) *Image {
+func newImageWithScreenFramebuffer(width, height int, paddingX0, paddingY0, paddingX1, paddingY1 float64) *Image {
 	checkSize(width, height)
-	r := restorable.NewScreenFramebufferImage(width, height, offsetX, offsetY)
+	r := restorable.NewScreenFramebufferImage(width, height, paddingX0, paddingY0, paddingX1, paddingY1)
 	i := &Image{r, FilterDefault}
 	runtime.SetFinalizer(i, (*Image).Dispose)
 	return i

internal/restorable/image.go

@@ -80,8 +80,10 @@ type Image struct {
 	// screen indicates whether the image is used as an actual screen.
 	screen bool
 
-	offsetX float64
-	offsetY float64
+	paddingX0 float64
+	paddingY0 float64
+	paddingX1 float64
+	paddingY1 float64
 }
 
 // NewImage creates an empty image with the given size.
@@ -115,13 +117,15 @@ func NewImageFromImage(source image.Image) *Image {
 }
 
 // NewScreenFramebufferImage creates a special image that framebuffer is one for the screen.
-func NewScreenFramebufferImage(width, height int, offsetX, offsetY float64) *Image {
+func NewScreenFramebufferImage(width, height int, paddingX0, paddingY0, paddingX1, paddingY1 float64) *Image {
 	i := &Image{
-		image:    graphics.NewScreenFramebufferImage(width, height, offsetX, offsetY),
-		volatile: true,
-		screen:   true,
-		offsetX:  offsetX,
-		offsetY:  offsetY,
+		image:     graphics.NewScreenFramebufferImage(width, height, paddingX0, paddingY0),
+		volatile:  true,
+		screen:    true,
+		paddingX0: paddingX0,
+		paddingY0: paddingY0,
+		paddingX1: paddingX1,
+		paddingY1: paddingY1,
 	}
 	theImages.add(i)
 	runtime.SetFinalizer(i, (*Image).Dispose)
@@ -167,12 +171,10 @@ func (i *Image) clearIfVolatile() {
 	}
 
 	w, h := i.image.Size()
-	x0 := -float32(i.offsetX)
-	y0 := -float32(i.offsetY)
-	// TODO: This is an ad-hoc way to fix the problem #513.
-	// Fix this for better calculation.
-	x1 := float32(w) + float32(i.offsetX)
-	y1 := float32(h) + float32(i.offsetY)
+	x0 := -float32(i.paddingX0)
+	y0 := -float32(i.paddingY0)
+	x1 := float32(w) + float32(i.paddingX1)
+	y1 := float32(h) + float32(i.paddingY1)
 	// For the rule of values, see vertices.go.
 	clearVertices := []float32{
 		x0, y0, 0, 0, 1, 1,
@@ -320,7 +322,7 @@ func (i *Image) restore() error {
 	if i.screen {
 		// The screen image should also be recreated because framebuffer might
 		// be changed.
-		i.image = graphics.NewScreenFramebufferImage(w, h, i.offsetX, i.offsetY)
+		i.image = graphics.NewScreenFramebufferImage(w, h, i.paddingX0, i.paddingY0)
 		i.basePixels = nil
 		i.drawImageHistory = nil
 		i.stale = false

internal/ui/ui_glfw.go

@@ -300,17 +300,18 @@ func SetWindowIcon(iconImages []image.Image) {
 	})
 }
 
-func ScreenOffset() (float64, float64) {
+func ScreenPadding() (x0, y0, x1, y1 float64) {
 	u := currentUI
 	if !u.isRunning() {
-		return 0, 0
+		return 0, 0, 0, 0
 	}
 	if !IsFullscreen() {
 		if u.width == u.windowWidth {
-			return 0, 0
+			return 0, 0, 0, 0
 		}
 		// The window width can be bigger than the game screen width (#444).
-		return (float64(u.windowWidth)*u.actualScreenScale() - float64(u.width)*u.actualScreenScale()) / 2, 0
+		ox := (float64(u.windowWidth)*u.actualScreenScale() - float64(u.width)*u.actualScreenScale()) / 2
+		return ox, 0, ox, 0
 	}
 	ox := 0.0
 	oy := 0.0
@@ -322,7 +323,7 @@ func ScreenOffset() (float64, float64) {
 		oy = (float64(v.Height)*d/glfwScale() - float64(u.height)*u.actualScreenScale()) / 2
 		return nil
 	})
-	return ox, oy
+	return ox, oy, ox, oy
 }
 
 func adjustCursorPosition(x, y int) (int, int) {
@@ -330,7 +331,7 @@ func adjustCursorPosition(x, y int) (int, int) {
 	if !u.isRunning() {
 		return x, y
 	}
-	ox, oy := ScreenOffset()
+	ox, oy, _, _ := ScreenPadding()
 	s := 0.0
 	_ = currentUI.runOnMainThread(func() error {
 		s = currentUI.actualScreenScale()

internal/ui/ui_js.go

@@ -73,8 +73,8 @@ func IsRunnableInBackground() bool {
 	return currentUI.runnableInBackground
 }
 
-func ScreenOffset() (float64, float64) {
-	return 0, 0
+func ScreenPadding() (x0, y0, x1, y1 float64) {
+	return 0, 0, 0, 0
 }
 
 func adjustCursorPosition(x, y int) (int, int) {

internal/ui/ui_mobile.go

@@ -156,8 +156,8 @@ func ScreenScale() float64 {
 	return s
 }
 
-func ScreenOffset() (float64, float64) {
-	return 0, 0
+func ScreenPadding() (x0, y0, x1, y1 float64) {
+	return 0, 0, 0, 0
 }
 
 func adjustCursorPosition(x, y int) (int, int) {