shareable: Make images shared when possible

Fixes #864

internal/shareable/shareable.go

@@ -22,10 +22,40 @@ import (
 
 	"github.com/hajimehoshi/ebiten/internal/affine"
 	"github.com/hajimehoshi/ebiten/internal/graphics"
+	"github.com/hajimehoshi/ebiten/internal/hooks"
 	"github.com/hajimehoshi/ebiten/internal/packing"
 	"github.com/hajimehoshi/ebiten/internal/restorable"
 )
 
+func init() {
+	hooks.AppendHookOnBeforeUpdate(func() error {
+		makeImagesShared()
+		return nil
+	})
+}
+
+// MaxCountForShare represents the time duration when the image can become shared.
+//
+// This value is expoted for testing.
+const MaxCountForShare = 10
+
+func makeImagesShared() {
+	backendsM.Lock()
+	defer backendsM.Unlock()
+
+	for i := range imagesToMakeShared {
+		i.nonUpdatedCount++
+		if i.nonUpdatedCount >= MaxCountForShare {
+			i.makeShared()
+		}
+		delete(imagesToMakeShared, i)
+	}
+}
+
+func MakeImagesSharedForTesting() {
+	makeImagesShared()
+}
+
 const (
 	initSize = 1024
 	maxSize  = 4096
@@ -84,6 +114,8 @@ var (
 
 	// theBackends is a set of actually shared images.
 	theBackends = []*backend{}
+
+	imagesToMakeShared = map[*Image]struct{}{}
 )
 
 type Image struct {
@@ -94,7 +126,16 @@ type Image struct {
 	backend *backend
 
 	node *packing.Node
-	countForShare int
+
+	// nonUpdatedCount represents how long the image is kept not modified with DrawTriangles.
+	// In the current implementation, if an image is being modified by DrawTriangles, the image is separated from
+	// a shared (restorable) image by ensureNotShared.
+	//
+	// nonUpdatedCount is increased every frame if the image is not modified, or set to 0 if the image id
+	// modified.
+	//
+	// ReplacePixels doesn't affect this value since ReplacePixels can be done on shared images.
+	nonUpdatedCount int
 
 	neverShared bool
 }
@@ -140,7 +181,7 @@ func (i *Image) ensureNotShared() {
 	}
 }
 
-func (i *Image) forceShared() {
+func (i *Image) makeShared() {
 	if i.backend == nil {
 		i.allocate(true)
 		return
@@ -151,7 +192,7 @@ func (i *Image) forceShared() {
 	}
 
 	if !i.shareable() {
-		panic("shareable: forceShared cannot be called on a non-shareable image")
+		panic("shareable: makeShared cannot be called on a non-shareable image")
 	}
 
 	newI := NewImage(i.width, i.height)
@@ -167,7 +208,7 @@ func (i *Image) forceShared() {
 	}
 	newI.replacePixels(pixels)
 	newI.moveTo(i)
-	i.countForShare = 0
+	i.nonUpdatedCount = 0
 }
 
 func (i *Image) region() (x, y, width, height int) {
@@ -207,8 +248,6 @@ func (i *Image) PutVertex(dest []float32, dx, dy, sx, sy float32, bx0, by0, bx1,
 	i.backend.restorable.PutVertex(dest, dx, dy, sx+oxf, sy+oyf, bx0+oxf, by0+oyf, bx1+oxf, by1+oyf, cr, cg, cb, ca)
 }
 
-const MaxCountForShare = 10
-
 func (i *Image) DrawTriangles(img *Image, vertices []float32, indices []uint16, colorm *affine.ColorM, mode graphics.CompositeMode, filter graphics.Filter, address graphics.Address) {
 	backendsM.Lock()
 	defer backendsM.Unlock()
@@ -233,17 +272,12 @@ func (i *Image) DrawTriangles(img *Image, vertices []float32, indices []uint16,
 
 	i.backend.restorable.DrawTriangles(img.backend.restorable, vertices, indices, colorm, mode, filter, address)
 
-	i.countForShare = 0
+	i.nonUpdatedCount = 0
+	delete(imagesToMakeShared, i)
 
-	// TODO: Reusing shared images is temporarily suspended for performance. See #661.
-	//
-	// if !img.isShared() && img.shareable() {
-	//	img.countForShare++
-	//	if img.countForShare >= MaxCountForShare {
-	//		img.forceShared()
-	//		img.countForShare = 0
-	//	}
-	// }
+	if !img.isShared() && img.shareable() {
+		imagesToMakeShared[img] = struct{}{}
+	}
 }
 
 // Fill fills the image with a color. This affects not only the (0, 0)-(width, height) region but also the whole

internal/shareable/shareable_test.go

@@ -112,7 +112,7 @@ func TestEnsureNotShared(t *testing.T) {
 	img4.DrawTriangles(img3, vs, is, nil, graphics.CompositeModeCopy, graphics.FilterNearest, graphics.AddressClampToZero)
 }
 
-func Disabled_TestReshared(t *testing.T) {
+func TestReshared(t *testing.T) {
 	const size = 16
 
 	img0 := NewImage(size, size)
@@ -122,8 +122,7 @@ func Disabled_TestReshared(t *testing.T) {
 	img1 := NewImage(size, size)
 	defer img1.Dispose()
 	img1.ReplacePixels(make([]byte, 4*size*size))
-	want := true
-	if got := img1.IsSharedForTesting(); got != want {
+	if got, want := img1.IsSharedForTesting(), true; got != want {
 		t.Errorf("got: %v, want: %v", got, want)
 	}
 
@@ -144,8 +143,7 @@ func Disabled_TestReshared(t *testing.T) {
 	img3.MakeVolatile()
 	defer img3.Dispose()
 	img1.ReplacePixels(make([]byte, 4*size*size))
-	want = false
-	if got := img3.IsSharedForTesting(); got != want {
+	if got, want := img3.IsSharedForTesting(), false; got != want {
 		t.Errorf("got: %v, want: %v", got, want)
 	}
 
@@ -153,19 +151,19 @@ func Disabled_TestReshared(t *testing.T) {
 	vs := img2.QuadVertices(0, 0, size, size, 1, 0, 0, 1, 0, 0, 1, 1, 1, 1)
 	is := graphics.QuadIndices()
 	img1.DrawTriangles(img2, vs, is, nil, graphics.CompositeModeCopy, graphics.FilterNearest, graphics.AddressClampToZero)
-	want = false
-	if got := img1.IsSharedForTesting(); got != want {
+	if got, want := img1.IsSharedForTesting(), false; got != want {
 		t.Errorf("got: %v, want: %v", got, want)
 	}
 
 	// Use img1 as a render source.
-	for i := 0; i < MaxCountForShare-1; i++ {
+	for i := 0; i < MaxCountForShare; i++ {
+		MakeImagesSharedForTesting()
 		img0.DrawTriangles(img1, vs, is, nil, graphics.CompositeModeCopy, graphics.FilterNearest, graphics.AddressClampToZero)
-		want := false
-		if got := img1.IsSharedForTesting(); got != want {
+		if got, want := img1.IsSharedForTesting(), false; got != want {
 			t.Errorf("got: %v, want: %v", got, want)
 		}
 	}
+	MakeImagesSharedForTesting()
 
 	for j := 0; j < size; j++ {
 		for i := 0; i < size; i++ {
@@ -179,8 +177,7 @@ func Disabled_TestReshared(t *testing.T) {
 	}
 
 	img0.DrawTriangles(img1, vs, is, nil, graphics.CompositeModeCopy, graphics.FilterNearest, graphics.AddressClampToZero)
-	want = true
-	if got := img1.IsSharedForTesting(); got != want {
+	if got, want := img1.IsSharedForTesting(), true; got != want {
 		t.Errorf("got: %v, want: %v", got, want)
 	}
 
@@ -197,9 +194,9 @@ func Disabled_TestReshared(t *testing.T) {
 
 	// Use img3 as a render source. img3 never uses a shared texture.
 	for i := 0; i < MaxCountForShare*2; i++ {
+		MakeImagesSharedForTesting()
 		img0.DrawTriangles(img3, vs, is, nil, graphics.CompositeModeCopy, graphics.FilterNearest, graphics.AddressClampToZero)
-		want := false
-		if got := img3.IsSharedForTesting(); got != want {
+		if got, want := img3.IsSharedForTesting(), false; got != want {
 			t.Errorf("got: %v, want: %v", got, want)
 		}
 	}