restorable: Reland: Do not record pixels if restoring is not requried

This change also remove the restrictions of operations on
graphicscommand.Image. For example, now DrawTriangles and
ReplacePixels can be mixed on the same image.

Fixes #1022

internal/graphicscommand/image.go

@@ -26,15 +26,6 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/internal/png"
 )
 
-type lastCommand int
-
-const (
-	lastCommandNone lastCommand = iota
-	lastCommandClear
-	lastCommandDrawTriangles
-	lastCommandReplacePixels
-)
-
 // Image represents an image that is implemented with OpenGL.
 type Image struct {
 	image          driver.Image
@@ -51,8 +42,6 @@ type Image struct {
 	id int
 
 	bufferedRP []*driver.ReplacePixelsArgs
-
-	lastCommand lastCommand
 }
 
 var nextID = 1
@@ -151,12 +140,6 @@ func (i *Image) InternalSize() (int, int) {
 // If the source image is not specified, i.e., src is nil and there is no image in the uniform variables, the
 // elements for the source image are not used.
 func (i *Image) DrawTriangles(srcs [graphics.ShaderImageNum]*Image, offsets [graphics.ShaderImageNum - 1][2]float32, vertices []float32, indices []uint16, clr *affine.ColorM, mode driver.CompositeMode, filter driver.Filter, address driver.Address, dstRegion, srcRegion driver.Region, shader *Shader, uniforms []interface{}) {
-	if i.lastCommand == lastCommandNone {
-		if !i.screen && mode != driver.CompositeModeClear {
-			panic("graphicscommand: the image must be cleared first")
-		}
-	}
-
 	if shader == nil {
 		// Fast path for rendering without a shader (#1355).
 		img := srcs[0]
@@ -178,12 +161,6 @@ func (i *Image) DrawTriangles(srcs [graphics.ShaderImageNum]*Image, offsets [gra
 	i.resolveBufferedReplacePixels()
 
 	theCommandQueue.EnqueueDrawTrianglesCommand(i, srcs, offsets, vertices, indices, clr, mode, filter, address, dstRegion, srcRegion, shader, uniforms)
-
-	if i.lastCommand == lastCommandNone && !i.screen {
-		i.lastCommand = lastCommandClear
-	} else {
-		i.lastCommand = lastCommandDrawTriangles
-	}
 }
 
 // Sync syncs the texture data in CPU and GPU so that Pixels can return the texture data immediately.
@@ -218,12 +195,6 @@ func (i *Image) Pixels() ([]byte, error) {
 }
 
 func (i *Image) ReplacePixels(pixels []byte, x, y, width, height int) {
-	// ReplacePixels for a part might invalidate the current image that are drawn by DrawTriangles (#593, #738).
-	if i.lastCommand == lastCommandDrawTriangles {
-		if x != 0 || y != 0 || i.width != width || i.height != height {
-			panic("graphicscommand: ReplacePixels for a part after DrawTriangles is forbidden")
-		}
-	}
 	i.bufferedRP = append(i.bufferedRP, &driver.ReplacePixelsArgs{
 		Pixels: pixels,
 		X:      x,
@@ -231,7 +202,6 @@ func (i *Image) ReplacePixels(pixels []byte, x, y, width, height int) {
 		Width:  width,
 		Height: height,
 	})
-	i.lastCommand = lastCommandReplacePixels
 }
 
 func (i *Image) IsInvalidated() bool {

internal/graphicscommand/image_test.go

@@ -69,11 +69,6 @@ func TestClear(t *testing.T) {
 }
 
 func TestReplacePixelsPartAfterDrawTriangles(t *testing.T) {
-	defer func() {
-		if r := recover(); r == nil {
-			t.Errorf("ReplacePixels must panic but not")
-		}
-	}()
 	const w, h = 32, 32
 	clr := NewImage(w, h)
 	src := NewImage(w/2, h/2)
@@ -89,6 +84,8 @@ func TestReplacePixelsPartAfterDrawTriangles(t *testing.T) {
 	dst.DrawTriangles([graphics.ShaderImageNum]*Image{clr}, [graphics.ShaderImageNum - 1][2]float32{}, vs, is, nil, driver.CompositeModeClear, driver.FilterNearest, driver.AddressUnsafe, dr, driver.Region{}, nil, nil)
 	dst.DrawTriangles([graphics.ShaderImageNum]*Image{src}, [graphics.ShaderImageNum - 1][2]float32{}, vs, is, nil, driver.CompositeModeSourceOver, driver.FilterNearest, driver.AddressUnsafe, dr, driver.Region{}, nil, nil)
 	dst.ReplacePixels(make([]byte, 4), 0, 0, 1, 1)
+
+	// TODO: Check the result.
 }
 
 func TestShader(t *testing.T) {

internal/graphicsdriver/opengl/context_desktop.go

@@ -173,6 +173,14 @@ func (c *context) framebufferPixels(f *framebuffer, width, height int) []byte {
 	return pixels
 }
 
+func (c *context) framebufferPixelsToBuffer(f *framebuffer, buffer buffer, width, height int) {
+	gl.Flush()
+	c.bindFramebuffer(f.native)
+	gl.BindBuffer(gl.PIXEL_PACK_BUFFER, uint32(buffer))
+	gl.ReadPixels(0, 0, int32(width), int32(height), gl.RGBA, gl.UNSIGNED_BYTE, nil)
+	gl.BindBuffer(gl.PIXEL_PACK_BUFFER, 0)
+}
+
 func (c *context) activeTexture(idx int) {
 	gl.ActiveTexture(gl.TEXTURE0 + uint32(idx))
 }

internal/graphicsdriver/opengl/context_js.go

@@ -219,6 +219,17 @@ func (c *context) framebufferPixels(f *framebuffer, width, height int) []byte {
 	return jsutil.Uint8ArrayToSlice(p)
 }
 
+func (c *context) framebufferPixelsToBuffer(f *framebuffer, buffer buffer, width, height int) {
+	c.ensureGL()
+	gl := c.gl
+
+	c.bindFramebuffer(f.native)
+	gl.Call("bindBuffer", gles.PIXEL_PACK_BUFFER, js.Value(buffer))
+	// void gl.readPixels(x, y, width, height, format, type, GLintptr offset);
+	gl.Call("readPixels", 0, 0, width, height, gles.RGBA, gles.UNSIGNED_BYTE, 0)
+	gl.Call("bindBuffer", gles.PIXEL_PACK_BUFFER, nil)
+}
+
 func (c *context) activeTexture(idx int) {
 	c.ensureGL()
 	gl := c.gl

internal/graphicsdriver/opengl/context_mobile.go

@@ -160,6 +160,16 @@ func (c *context) framebufferPixels(f *framebuffer, width, height int) []byte {
 	return pixels
 }
 
+func (c *context) framebufferPixelsToBuffer(f *framebuffer, buffer buffer, width, height int) {
+	c.ctx.Flush()
+
+	c.bindFramebuffer(f.native)
+
+	c.ctx.BindBuffer(gles.PIXEL_PACK_BUFFER, uint32(buffer))
+	c.ctx.ReadPixels(nil, 0, 0, int32(width), int32(height), gles.RGBA, gles.UNSIGNED_BYTE)
+	c.ctx.BindBuffer(gles.PIXEL_PACK_BUFFER, 0)
+}
+
 func (c *context) activeTexture(idx int) {
 	c.ctx.ActiveTexture(uint32(gles.TEXTURE0 + idx))
 }

internal/graphicsdriver/opengl/gl/package.go

@@ -21,6 +21,7 @@ const (
 	ELEMENT_ARRAY_BUFFER = 0x8893
 	DYNAMIC_DRAW         = 0x88E8
 	STREAM_DRAW          = 0x88E0
+	PIXEL_PACK_BUFFER    = 0x88EB
 	PIXEL_UNPACK_BUFFER  = 0x88EC
 	SHORT                = 0x1402
 	FLOAT                = 0x1406

internal/graphicsdriver/opengl/gles/const.go

@@ -22,6 +22,7 @@ const (
 	ELEMENT_ARRAY_BUFFER = 0x8893
 	DYNAMIC_DRAW         = 0x88E8
 	STREAM_DRAW          = 0x88E0
+	PIXEL_PACK_BUFFER    = 0x88EB
 	PIXEL_UNPACK_BUFFER  = 0x88EC
 	SHORT                = 0x1402
 	FLOAT                = 0x1406

internal/graphicsdriver/opengl/image.go

@@ -135,6 +135,12 @@ func (i *Image) ReplacePixels(args []*driver.ReplacePixelsArgs) {
 
 	if i.pbo.equal(*new(buffer)) {
 		i.pbo = i.graphics.context.newPixelBufferObject(w, h)
+		if i.pbo.equal(*new(buffer)) {
+			panic("opengl: newPixelBufferObject failed")
+		}
+		if i.framebuffer != nil {
+			i.graphics.context.framebufferPixelsToBuffer(i.framebuffer, i.pbo, i.width, i.height)
+		}
 	}
 	if i.pbo.equal(*new(buffer)) {
 		panic("opengl: newPixelBufferObject failed")

internal/restorable/image.go

@@ -170,19 +170,29 @@ func (i *Image) Extend(width, height int) *Image {
 		panic(fmt.Sprintf("restorable: the original size (%d, %d) cannot be extended to (%d, %d)", i.width, i.height, width, height))
 	}
 
-	if i.stale {
-		panic("restorable: Extend at a stale image is forbidden")
-	}
-
-	if len(i.drawTrianglesHistory) > 0 {
-		panic("restorable: Extend after DrawTriangles is forbidden")
-	}
-
 	newImg := NewImage(width, height)
 	newImg.SetVolatile(i.volatile)
-	i.basePixels.Apply(newImg.image)
 
+	// Use DrawTriangles instead of ReplacePixels because the image i might be stale and not have its pixels
+	// information.
+	srcs := [graphics.ShaderImageNum]*Image{i}
+	var offsets [graphics.ShaderImageNum - 1][2]float32
+	sw, sh := i.image.InternalSize()
+	vs := quadVertices(0, 0, float32(sw), float32(sh), 0, 0, float32(sw), float32(sh), 1, 1, 1, 1)
+	is := graphics.QuadIndices()
+	dr := driver.Region{
+		X:      0,
+		Y:      0,
+		Width:  float32(sw),
+		Height: float32(sh),
+	}
+	newImg.DrawTriangles(srcs, offsets, vs, is, nil, driver.CompositeModeCopy, driver.FilterNearest, driver.AddressUnsafe, dr, driver.Region{}, nil, nil)
+
+	// Overwrite the history as if the image newImg is created only by ReplacePixels. Now drawTrianglesHistory
+	// and basePixels cannot be mixed.
+	newImg.drawTrianglesHistory = nil
 	newImg.basePixels = i.basePixels
+	newImg.stale = i.stale
 
 	i.Dispose()
 
@@ -287,6 +297,11 @@ func (i *Image) ReplacePixels(pixels []byte, x, y, width, height int) {
 		i.image.ReplacePixels(make([]byte, 4*width*height), x, y, width, height)
 	}
 
+	if !needsRestoring() || i.screen || i.volatile {
+		i.makeStale()
+		return
+	}
+
 	if x == 0 && y == 0 && width == w && height == h {
 		if pixels != nil {
 			i.basePixels.AddOrReplace(pixels, 0, 0, w, h)
@@ -298,9 +313,7 @@ func (i *Image) ReplacePixels(pixels []byte, x, y, width, height int) {
 		return
 	}
 
-	// It looked like ReplacePixels on a part of image deletes other region that are rendered by DrawTriangles
+	// drawTrianglesHistory and basePixels cannot be mixed.
-	// (#593, #758).
-
 	if len(i.drawTrianglesHistory) > 0 {
 		panic("restorable: ReplacePixels for a part after DrawTriangles is forbidden")
 	}