graphicscommand: Simplify Image

First I thought Metal requried an initialization process by
replacing pixels, but now this is not needed. Initialize images by
the dummy texture.

internal/graphicscommand/image.go

@@ -20,44 +20,20 @@ import (
 	"github.com/hajimehoshi/ebiten/internal/graphicsdriver"
 )
 
-var (
-	// maxImageSize is the maximum texture size
-	//
-	// maxImageSize also represents the default size (width or height) of viewport.
-	maxImageSize = 0
-)
-
-// imageState is a state of an image.
-type imageState int
-
-const (
-	// imageStateInit represents that the image is just allocated and not ready for DrawImages.
-	imageStateInit imageState = iota
-
-	// imageStateReplacePixelsOnly represents that only ReplacePixels is acceptable.
-	imageStateReplacePixelsOnly
-
-	// imageStateDrawable represents that the image is ready to draw with any commands.
-	imageStateDrawable
-
-	// imageStateScreen is the special state for screen framebuffer.
-	// Only copying image on the screen image is allowed.
-	imageStateScreen
-)
-
 // Image represents an image that is implemented with OpenGL.
 type Image struct {
 	image  graphicsdriver.Image
 	width  int
 	height int
-	state  imageState
 }
 
+// NewImage returns a new image.
+//
+// Note that the image is not initialized yet.
 func NewImage(width, height int) *Image {
 	i := &Image{
 		width:  width,
 		height: height,
-		state:  imageStateInit, // The screen image must be inited with ReplacePixels first.
 	}
 	c := &newImageCommand{
 		result: i,
@@ -72,7 +48,6 @@ func NewScreenFramebufferImage(width, height int) *Image {
 	i := &Image{
 		width:  width,
 		height: height,
-		state:  imageStateScreen,
 	}
 	c := &newScreenFramebufferImageCommand{
 		result: i,
@@ -83,26 +58,6 @@ func NewScreenFramebufferImage(width, height int) *Image {
 	return i
 }
 
-// clearByReplacingPixels clears the image by replacing pixels.
-//
-// The implementation must use replacing-pixels way instead of drawing polygons, since
-// some environments (e.g. Metal) require replacing-pixels way as initialization.
-func (i *Image) clearByReplacingPixels() {
-	if i.state != imageStateInit {
-		panic("not reached")
-	}
-	c := &replacePixelsCommand{
-		dst:    i,
-		pixels: make([]byte, 4*i.width*i.height),
-		x:      0,
-		y:      0,
-		width:  i.width,
-		height: i.height,
-	}
-	theCommandQueue.Enqueue(c)
-	i.state = imageStateDrawable
-}
-
 func (i *Image) Dispose() {
 	c := &disposeCommand{
 		target: i,
@@ -116,56 +71,12 @@ func (i *Image) Size() (int, int) {
 }
 
 func (i *Image) DrawImage(src *Image, vertices []float32, indices []uint16, clr *affine.ColorM, mode graphics.CompositeMode, filter graphics.Filter) {
-	switch i.state {
-	case imageStateInit:
-		// Before DrawImage, the image must be initialized with ReplacePixels.
-		// Especially on Metal, the image might be broken when drawing without initializing.
-		i.clearByReplacingPixels()
-	case imageStateReplacePixelsOnly:
-		panic("not reached")
-	case imageStateDrawable:
-		// Do nothing
-	case imageStateScreen:
-		if mode != graphics.CompositeModeCopy {
-			panic("not reached")
-		}
-	default:
-		panic("not reached")
-	}
-
-	switch src.state {
-	case imageStateInit:
-		src.clearByReplacingPixels()
-	case imageStateReplacePixelsOnly:
-		// Do nothing
-		// TODO: Check the region.
-	case imageStateDrawable:
-		// Do nothing
-	case imageStateScreen:
-		panic("not reached")
-	default:
-		panic("not reached")
-	}
-
 	theCommandQueue.EnqueueDrawImageCommand(i, src, vertices, indices, clr, mode, filter)
 }
 
 // Pixels returns the image's pixels.
 // Pixels might return nil when OpenGL error happens.
 func (i *Image) Pixels() []byte {
-	switch i.state {
-	case imageStateInit:
-		i.clearByReplacingPixels()
-	case imageStateReplacePixelsOnly:
-		// Do nothing
-		// TODO: Check the region?
-	case imageStateDrawable:
-		// Do nothing
-	case imageStateScreen:
-		panic("not reached")
-	default:
-		panic("not reached")
-	}
 	c := &pixelsCommand{
 		result: nil,
 		img:    i,
@@ -176,22 +87,6 @@ func (i *Image) Pixels() []byte {
 }
 
 func (i *Image) ReplacePixels(p []byte, x, y, width, height int) {
-	switch i.state {
-	case imageStateInit:
-		if x == 0 && y == 0 && width == i.width && height == i.height {
-			i.state = imageStateDrawable
-		} else {
-			i.state = imageStateReplacePixelsOnly
-		}
-	case imageStateReplacePixelsOnly:
-		// Do nothing
-	case imageStateDrawable:
-		// Do nothing
-	case imageStateScreen:
-		panic("not reached")
-	default:
-		panic("not reached")
-	}
 	pixels := make([]byte, len(p))
 	copy(pixels, p)
 	c := &replacePixelsCommand{

internal/restorable/image.go

@@ -57,7 +57,14 @@ type Image struct {
 	h2 int
 }
 
-var emptyImage = NewImage(16, 16, false)
+var dummyImage *Image
+
+func init() {
+	dummyImage = &Image{
+		image:    graphicscommand.NewImage(16, 16),
+		volatile: false,
+	}
+}
 
 // NewImage creates an empty image with the given size.
 //
@@ -69,6 +76,7 @@ func NewImage(width, height int, volatile bool) *Image {
 		image:    graphicscommand.NewImage(width, height),
 		volatile: volatile,
 	}
+	i.ReplacePixels(nil, 0, 0, width, height)
 	theImages.add(i)
 	return i
 }
@@ -143,13 +151,13 @@ func (i *Image) ReplacePixels(pixels []byte, x, y, width, height int) {
 	if pixels != nil {
 		i.image.ReplacePixels(pixels, x, y, width, height)
 	} else {
-		// There are not 'drawImageHistoryItem's for this image and emptyImage.
+		// There are not 'drawImageHistoryItem's for this image and dummyImage.
-		// This means emptyImage might not be restored yet when this image is restored.
+		// This means dummyImage might not be restored yet when this image is restored.
 		// However, that's ok since this image will be stale or have its updated pixel data soon,
-		// and this image can be restored without emptyImage.
+		// and this image can be restored without dummyImage.
 		//
-		// emptyImage should be restored later anyway.
+		// dummyImage should be restored later anyway.
-		dw, dh := emptyImage.Size()
+		dw, dh := dummyImage.Size()
 		w2 := graphics.NextPowerOf2Int(w)
 		h2 := graphics.NextPowerOf2Int(h)
 		vs := graphics.QuadVertices(w2, h2, 0, 0, dw, dh,
@@ -157,7 +165,7 @@ func (i *Image) ReplacePixels(pixels []byte, x, y, width, height int) {
 			float32(x), float32(y),
 			1, 1, 1, 1)
 		is := graphics.QuadIndices()
-		i.image.DrawImage(emptyImage.image, vs, is, nil, graphics.CompositeModeCopy, graphics.FilterNearest)
+		i.image.DrawImage(dummyImage.image, vs, is, nil, graphics.CompositeModeClear, graphics.FilterNearest)
 	}
 
 	if x == 0 && y == 0 && width == w && height == h {