all: specify src-regions correctly

This parameter was not important and actually not used with usual
shaders. However, now this information will be important for the
restorable package optimization later.

There was a performance issue that was caused by srcRegions, but
now this should not happen thanks to FilterUniformVariables.

Updates #1293

image.go

@@ -267,7 +267,32 @@ func (i *Image) DrawImage(img *Image, options *DrawImageOptions) {
 		})
 	}
 
-	i.image.DrawTriangles(srcs, vs, is, blend, i.adjustedBounds(), [graphics.ShaderSrcImageCount]image.Rectangle{img.adjustedBounds()}, shader.shader, i.tmpUniforms, graphicsdriver.FillRuleFillAll, canSkipMipmap(geoM, filter), false, restorable.HintNone)
+	dr := i.adjustedBounds()
+	hint := restorable.HintNone
+	if overwritesDstRegion(options.Blend, dr, geoM, sx0, sy0, sx1, sy1) {
+		hint = restorable.HintOverwriteDstRegion
+	}
+
+	i.image.DrawTriangles(srcs, vs, is, blend, dr, [graphics.ShaderSrcImageCount]image.Rectangle{img.adjustedBounds()}, shader.shader, i.tmpUniforms, graphicsdriver.FillRuleFillAll, canSkipMipmap(geoM, filter), false, hint)
+}
+
+// overwritesDstRegion reports whether the given parameters overwrite the destination region completely.
+func overwritesDstRegion(blend Blend, dstRegion image.Rectangle, geoM GeoM, sx0, sy0, sx1, sy1 int) bool {
+	// TODO: More precisely, BlendFactorDestinationRGB, BlendFactorDestinationAlpha, and operations should be checked.
+	if blend != BlendCopy && blend != BlendClear {
+		return false
+	}
+	// Check the result vertices is not a rotated rectangle.
+	if geoM.b != 0 || geoM.c != 0 {
+		return false
+	}
+	// Check the result vertices completely covers dstRegion.
+	x0, y0 := geoM.Apply(float64(sx0), float64(sy0))
+	x1, y1 := geoM.Apply(float64(sx1), float64(sy1))
+	if float64(dstRegion.Min.X) < x0 || float64(dstRegion.Min.Y) < y0 || float64(dstRegion.Max.X) > x1 || float64(dstRegion.Max.Y) > y1 {
+		return false
+	}
+	return true
 }
 
 // Vertex represents a vertex passed to DrawTriangles.
@@ -856,7 +881,14 @@ func (i *Image) DrawRectShader(width, height int, shader *Shader, options *DrawR
 	i.tmpUniforms = i.tmpUniforms[:0]
 	i.tmpUniforms = shader.appendUniforms(i.tmpUniforms, options.Uniforms)
 
-	i.image.DrawTriangles(imgs, vs, is, blend, i.adjustedBounds(), srcRegions, shader.shader, i.tmpUniforms, graphicsdriver.FillRuleFillAll, true, false, restorable.HintNone)
+	dr := i.adjustedBounds()
+	hint := restorable.HintNone
+	// Do not use srcRegions[0].Dx() and srcRegions[0].Dy() as these might be empty.
+	if overwritesDstRegion(options.Blend, dr, geoM, srcRegions[0].Min.X, srcRegions[0].Min.Y, srcRegions[0].Min.X+width, srcRegions[0].Min.Y+height) {
+		hint = restorable.HintOverwriteDstRegion
+	}
+
+	i.image.DrawTriangles(imgs, vs, is, blend, i.adjustedBounds(), srcRegions, shader.shader, i.tmpUniforms, graphicsdriver.FillRuleFillAll, true, false, hint)
 }
 
 // SubImage returns an image representing the portion of the image p visible through r.

internal/atlas/image.go

@@ -284,8 +284,9 @@ func (i *Image) ensureIsolatedFromSource(backends []*backend) {
 	graphics.QuadVerticesFromDstAndSrc(vs, 0, 0, w, h, 0, 0, w, h, 1, 1, 1, 1)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, i.width, i.height)
+	sr := image.Rect(0, 0, i.width, i.height)
 
-	newI.drawTriangles([graphics.ShaderSrcImageCount]*Image{i}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintOverwriteDstRegion)
+	newI.drawTriangles([graphics.ShaderSrcImageCount]*Image{i}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintOverwriteDstRegion)
 	newI.moveTo(i)
 }
 
@@ -315,7 +316,8 @@ func (i *Image) putOnSourceBackend() {
 	graphics.QuadVerticesFromDstAndSrc(vs, 0, 0, w, h, 0, 0, w, h, 1, 1, 1, 1)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, i.width, i.height)
-	newI.drawTriangles([graphics.ShaderSrcImageCount]*Image{i}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintOverwriteDstRegion)
+	sr := image.Rect(0, 0, i.width, i.height)
+	newI.drawTriangles([graphics.ShaderSrcImageCount]*Image{i}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintOverwriteDstRegion)
 
 	newI.moveTo(i)
 	i.usedAsSourceCount = 0
@@ -433,6 +435,7 @@ func (i *Image) drawTriangles(srcs [graphics.ShaderSrcImageCount]*Image, vertice
 
 		// A source region can be deliberately empty when this is not needed in order to avoid unexpected
 		// performance issue (#1293).
+		// TODO: This should no longer be needed but is kept just in case. Remove this later.
 		if srcRegions[i].Empty() {
 			continue
 		}

internal/atlas/image_test.go

@@ -103,7 +103,8 @@ func TestEnsureIsolatedFromSourceBackend(t *testing.T) {
 	vs := quadVertices(size/2, size/2, size/4, size/4, 1)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, size, size)
-	img4.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img3}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, size/2, size/2)
+	img4.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img3}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	if got, want := img4.IsOnSourceBackendForTesting(), false; got != want {
 		t.Errorf("got: %v, want: %v", got, want)
 	}
@@ -111,7 +112,8 @@ func TestEnsureIsolatedFromSourceBackend(t *testing.T) {
 	// img5 is not allocated now, but is allocated at DrawTriangles.
 	vs = quadVertices(0, 0, size/2, size/2, 1)
 	dr = image.Rect(0, 0, size/2, size/2)
-	img3.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img5}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr = image.Rect(0, 0, size/2, size/2)
+	img3.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img5}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	if got, want := img3.IsOnSourceBackendForTesting(), false; got != want {
 		t.Errorf("got: %v, want: %v", got, want)
 	}
@@ -145,7 +147,9 @@ func TestEnsureIsolatedFromSourceBackend(t *testing.T) {
 	// Check further drawing doesn't cause panic.
 	// This bug was fixed by 03dcd948.
 	vs = quadVertices(0, 0, size/2, size/2, 1)
-	img4.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img3}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	dr = image.Rect(0, 0, size, size)
+	sr = image.Rect(0, 0, size/2, size/2)
+	img4.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img3}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 }
 
 func TestReputOnSourceBackend(t *testing.T) {
@@ -186,10 +190,11 @@ func TestReputOnSourceBackend(t *testing.T) {
 	// Use img1 as a render target.
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, size, size)
+	sr := image.Rect(0, 0, size, size)
 	// Render onto img1. The count should not matter.
 	for i := 0; i < 5; i++ {
 		vs := quadVertices(size, size, 0, 0, 1)
-		img1.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img2}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		img1.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img2}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 		if got, want := img1.IsOnSourceBackendForTesting(), false; got != want {
 			t.Errorf("got: %v, want: %v", got, want)
 		}
@@ -201,7 +206,7 @@ func TestReputOnSourceBackend(t *testing.T) {
 	for i := 0; i < atlas.BaseCountToPutOnSourceBackend*2; i++ {
 		atlas.PutImagesOnSourceBackendForTesting()
 		vs := quadVertices(size, size, 0, 0, 1)
-		img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 		if got, want := img1.IsOnSourceBackendForTesting(), false; got != want {
 			t.Errorf("got: %v, want: %v", got, want)
 		}
@@ -209,7 +214,7 @@ func TestReputOnSourceBackend(t *testing.T) {
 	// Finally, img1 is on a source backend.
 	atlas.PutImagesOnSourceBackendForTesting()
 	vs := quadVertices(size, size, 0, 0, 1)
-	img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	if got, want := img1.IsOnSourceBackendForTesting(), true; got != want {
 		t.Errorf("got: %v, want: %v", got, want)
 	}
@@ -238,7 +243,7 @@ func TestReputOnSourceBackend(t *testing.T) {
 	}
 
 	vs = quadVertices(size, size, 0, 0, 1)
-	img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	if got, want := img1.IsOnSourceBackendForTesting(), true; got != want {
 		t.Errorf("got: %v, want: %v", got, want)
 	}
@@ -268,7 +273,7 @@ func TestReputOnSourceBackend(t *testing.T) {
 	// Use img1 as a render target again. The count should not matter.
 	for i := 0; i < 5; i++ {
 		vs := quadVertices(size, size, 0, 0, 1)
-		img1.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img2}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		img1.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img2}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 		if got, want := img1.IsOnSourceBackendForTesting(), false; got != want {
 			t.Errorf("got: %v, want: %v", got, want)
 		}
@@ -280,7 +285,7 @@ func TestReputOnSourceBackend(t *testing.T) {
 		atlas.PutImagesOnSourceBackendForTesting()
 		img1.WritePixels(make([]byte, 4*size*size), image.Rect(0, 0, size, size))
 		vs := quadVertices(size, size, 0, 0, 1)
-		img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 		if got, want := img1.IsOnSourceBackendForTesting(), false; got != want {
 			t.Errorf("got: %v, want: %v", got, want)
 		}
@@ -289,7 +294,7 @@ func TestReputOnSourceBackend(t *testing.T) {
 
 	// img1 is not on an atlas due to WritePixels.
 	vs = quadVertices(size, size, 0, 0, 1)
-	img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	if got, want := img1.IsOnSourceBackendForTesting(), false; got != want {
 		t.Errorf("got: %v, want: %v", got, want)
 	}
@@ -298,7 +303,7 @@ func TestReputOnSourceBackend(t *testing.T) {
 	for i := 0; i < atlas.BaseCountToPutOnSourceBackend*2; i++ {
 		atlas.PutImagesOnSourceBackendForTesting()
 		vs := quadVertices(size, size, 0, 0, 1)
-		img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img3}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img3}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 		if got, want := img3.IsOnSourceBackendForTesting(), false; got != want {
 			t.Errorf("got: %v, want: %v", got, want)
 		}
@@ -401,7 +406,8 @@ func TestWritePixelsAfterDrawTriangles(t *testing.T) {
 	vs := quadVertices(w, h, 0, 0, 1)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	dst.WritePixels(pix, image.Rect(0, 0, w, h))
 
 	pix = make([]byte, 4*w*h)
@@ -448,7 +454,8 @@ func TestSmallImages(t *testing.T) {
 	vs := quadVertices(w, h, 0, 0, 1)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 
 	pix = make([]byte, 4*w*h)
 	ok, err := dst.ReadPixels(ui.Get().GraphicsDriverForTesting(), pix, image.Rect(0, 0, w, h))
@@ -495,7 +502,8 @@ func TestLongImages(t *testing.T) {
 	vs := quadVertices(w, h, 0, 0, scale)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, dstW, dstH)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 
 	pix = make([]byte, 4*dstW*dstH)
 	ok, err := dst.ReadPixels(ui.Get().GraphicsDriverForTesting(), pix, image.Rect(0, 0, dstW, dstH))
@@ -611,7 +619,8 @@ func TestDeallocatedAndReputOnSourceBackend(t *testing.T) {
 	vs := quadVertices(size, size, 0, 0, 1)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, size, size)
-	src.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src2}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, size, size)
+	src.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src2}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	if got, want := src.IsOnSourceBackendForTesting(), false; got != want {
 		t.Errorf("got: %v, want: %v", got, want)
 	}
@@ -620,7 +629,7 @@ func TestDeallocatedAndReputOnSourceBackend(t *testing.T) {
 	for i := 0; i < atlas.BaseCountToPutOnSourceBackend/2; i++ {
 		atlas.PutImagesOnSourceBackendForTesting()
 		vs := quadVertices(size, size, 0, 0, 1)
-		dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 		if got, want := src.IsOnSourceBackendForTesting(), false; got != want {
 			t.Errorf("got: %v, want: %v", got, want)
 		}
@@ -648,13 +657,14 @@ func TestImageIsNotReputOnSourceBackendWithoutUsingAsSource(t *testing.T) {
 	vs := quadVertices(size, size, 0, 0, 1)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, size, size)
+	sr := image.Rect(0, 0, size, size)
 
 	// Use src2 as a rendering target, and make src2 on a destination backend.
 	//
 	// Call DrawTriangles multiple times.
 	// The number of DrawTriangles doesn't matter as long as these are called in one frame.
 	for i := 0; i < 2; i++ {
-		src2.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		src2.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	}
 	if got, want := src2.IsOnSourceBackendForTesting(), false; got != want {
 		t.Errorf("got: %v, want: %v", got, want)
@@ -673,7 +683,7 @@ func TestImageIsNotReputOnSourceBackendWithoutUsingAsSource(t *testing.T) {
 	for i := 0; i < atlas.BaseCountToPutOnSourceBackend; i++ {
 		atlas.PutImagesOnSourceBackendForTesting()
 		vs := quadVertices(size, size, 0, 0, 1)
-		dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src2}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src2}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 		if got, want := src2.IsOnSourceBackendForTesting(), false; got != want {
 			t.Errorf("got: %v, want: %v", got, want)
 		}
@@ -796,17 +806,18 @@ func TestDestinationCountOverflow(t *testing.T) {
 	vs := quadVertices(w, h, 0, 0, 1)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
+	sr := image.Rect(0, 0, w, h)
 
 	// Use dst0 as a destination for a while.
 	for i := 0; i < 31; i++ {
-		dst0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		dst0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 		atlas.PutImagesOnSourceBackendForTesting()
 	}
 
 	// Use dst0 as a source for a while.
 	// As dst0 is used as a destination too many times (31 is a maximum), dst0's backend should never be a source backend.
 	for i := 0; i < 100; i++ {
-		dst1.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{dst0}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		dst1.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{dst0}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 		atlas.PutImagesOnSourceBackendForTesting()
 		if dst0.IsOnSourceBackendForTesting() {
 			t.Errorf("dst0 cannot be on a source backend: %d", i)
@@ -831,8 +842,9 @@ func TestIteratingImagesToPutOnSourceBackend(t *testing.T) {
 	vs := quadVertices(w, h, 0, 0, 1)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
+	sr := image.Rect(0, 0, w, h)
 	for _, img := range srcs {
-		img.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		img.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	}
 	atlas.PutImagesOnSourceBackendForTesting()
 
@@ -840,7 +852,7 @@ func TestIteratingImagesToPutOnSourceBackend(t *testing.T) {
 	// Check iterating the registered image works correctly.
 	for i := 0; i < 100; i++ {
 		for _, src := range srcs {
-			dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+			dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 		}
 		atlas.PutImagesOnSourceBackendForTesting()
 	}
@@ -888,7 +900,8 @@ func TestDallocateUnmanagedImageBackends(t *testing.T) {
 	vs := quadVertices(w, h, 0, 0, 1)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 
 	// Get the difference of the number of backends before and after the images are deallocated.
 	c := atlas.BackendCountForTesting()

internal/atlas/shader_test.go

@@ -70,11 +70,12 @@ func TestImageDrawTwice(t *testing.T) {
 	vs := quadVertices(w, h, 0, 0, 1)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src0}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src0}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 
 	// Vertices must be recreated (#1755)
 	vs = quadVertices(w, h, 0, 0, 1)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 
 	pix := make([]byte, 4*w*h)
 	ok, err := dst.ReadPixels(ui.Get().GraphicsDriverForTesting(), pix, image.Rect(0, 0, w, h))

internal/buffered/image.go

@@ -310,8 +310,9 @@ func (i *Image) syncPixelsIfNeeded() {
 
 	srcs := [graphics.ShaderSrcImageCount]*atlas.Image{whiteImage.img}
 	dr := image.Rect(0, 0, i.width, i.height)
+	sr := image.Rect(0, 0, whiteImage.width, whiteImage.height)
 	blend := graphicsdriver.BlendCopy
-	i.img.DrawTriangles(srcs, vs, is, blend, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	i.img.DrawTriangles(srcs, vs, is, blend, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 
 	// TODO: Use clear if Go 1.21 is available.
 	for pos := range i.dotsBuffer {

internal/graphicscommand/image_test.go

@@ -56,7 +56,8 @@ func TestClear(t *testing.T) {
 	vs := quadVertices(w/2, h/2)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*graphicscommand.Image{src}, vs, is, graphicsdriver.BlendClear, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, nearestFilterShader, nil, graphicsdriver.FillRuleFillAll)
+	sr := image.Rect(0, 0, w/2, h/2)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*graphicscommand.Image{src}, vs, is, graphicsdriver.BlendClear, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, nearestFilterShader, nil, graphicsdriver.FillRuleFillAll)
 
 	pix := make([]byte, 4*w*h)
 	if err := dst.ReadPixels(ui.Get().GraphicsDriverForTesting(), []graphicsdriver.PixelsArgs{
@@ -87,8 +88,10 @@ func TestWritePixelsPartAfterDrawTriangles(t *testing.T) {
 	vs := quadVertices(w/2, h/2)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*graphicscommand.Image{clr}, vs, is, graphicsdriver.BlendClear, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, nearestFilterShader, nil, graphicsdriver.FillRuleFillAll)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*graphicscommand.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, nearestFilterShader, nil, graphicsdriver.FillRuleFillAll)
+	sr0 := image.Rect(0, 0, w, h)
+	sr1 := image.Rect(0, 0, w/2, h/2)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*graphicscommand.Image{clr}, vs, is, graphicsdriver.BlendClear, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr0}, nearestFilterShader, nil, graphicsdriver.FillRuleFillAll)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*graphicscommand.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr1}, nearestFilterShader, nil, graphicsdriver.FillRuleFillAll)
 	bs := graphics.NewManagedBytes(4, func(bs []byte) {
 		for i := range bs {
 			bs[i] = 0
@@ -106,7 +109,8 @@ func TestShader(t *testing.T) {
 	vs := quadVertices(w, h)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*graphicscommand.Image{clr}, vs, is, graphicsdriver.BlendClear, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, nearestFilterShader, nil, graphicsdriver.FillRuleFillAll)
+	sr := image.Rect(0, 0, w, h)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*graphicscommand.Image{clr}, vs, is, graphicsdriver.BlendClear, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, nearestFilterShader, nil, graphicsdriver.FillRuleFillAll)
 
 	g := ui.Get().GraphicsDriverForTesting()
 	s := graphicscommand.NewShader(etesting.ShaderProgramFill(0xff, 0, 0, 0xff), "")

internal/mipmap/mipmap.go

@@ -185,7 +185,10 @@ func (m *Mipmap) level(level int) *buffered.Image {
 	s := buffered.NewImage(w2, h2, m.imageType)
 
 	dstRegion := image.Rect(0, 0, w2, h2)
-	s.DrawTriangles([graphics.ShaderSrcImageCount]*buffered.Image{src}, vs, is, graphicsdriver.BlendCopy, dstRegion, [graphics.ShaderSrcImageCount]image.Rectangle{}, atlas.LinearFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintOverwriteDstRegion)
+	w := sizeForLevel(m.width, level-1)
+	h := sizeForLevel(m.height, level-1)
+	srcRegion := image.Rect(0, 0, w, h)
+	s.DrawTriangles([graphics.ShaderSrcImageCount]*buffered.Image{src}, vs, is, graphicsdriver.BlendCopy, dstRegion, [graphics.ShaderSrcImageCount]image.Rectangle{srcRegion}, atlas.LinearFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintOverwriteDstRegion)
 	m.setImg(level, s)
 
 	return m.imgs[level]

internal/restorable/image.go

@@ -80,7 +80,7 @@ func (p *Pixels) Dispose() {
 
 // drawTrianglesHistoryItem is an item for history of draw-image commands.
 type drawTrianglesHistoryItem struct {
-	images     [graphics.ShaderSrcImageCount]*Image
+	srcImages  [graphics.ShaderSrcImageCount]*Image
 	vertices   []float32
 	indices    []uint32
 	blend      graphicsdriver.Blend
@@ -233,6 +233,10 @@ func (i *Image) makeStale(rect image.Rectangle) {
 		return
 	}
 
+	if !i.needsRestoration() {
+		return
+	}
+
 	origSize := len(i.staleRegions)
 	i.staleRegions = i.appendRegionsForDrawTriangles(i.staleRegions)
 	if !rect.Empty() {
@@ -283,8 +287,7 @@ func (i *Image) WritePixels(pixels *graphics.ManagedBytes, region image.Rectangl
 		clearImage(i.image, region)
 	}
 
-	// Even if the image is already stale, call makeStale to extend the stale region.
-	if !needsRestoration() || !i.needsRestoration() || i.stale {
+	if !needsRestoration() || !i.needsRestoration() {
 		i.makeStale(region)
 		return
 	}
@@ -292,9 +295,9 @@ func (i *Image) WritePixels(pixels *graphics.ManagedBytes, region image.Rectangl
 	if region.Eq(image.Rect(0, 0, w, h)) {
 		if pixels != nil {
 			// Clone a ManagedBytes as the package graphicscommand has a different lifetime management.
-			i.basePixels.AddOrReplace(pixels.Clone(), image.Rect(0, 0, w, h))
+			i.basePixels.AddOrReplace(pixels.Clone(), region)
 		} else {
-			i.basePixels.Clear(image.Rect(0, 0, w, h))
+			i.basePixels.Clear(region)
 		}
 		i.clearDrawTrianglesHistory()
 		i.stale = false
@@ -302,6 +305,14 @@ func (i *Image) WritePixels(pixels *graphics.ManagedBytes, region image.Rectangl
 		return
 	}
 
+	if i.stale {
+		// Even if the image is already stale, call makeStale to extend the stale region.
+		i.makeStale(region)
+		return
+	}
+
+	i.removeDrawTrianglesHistoryItems(region)
+
 	// Records for DrawTriangles cannot come before records for WritePixels.
 	if len(i.drawTrianglesHistory) > 0 {
 		i.makeStale(region)
@@ -347,10 +358,25 @@ func (i *Image) DrawTriangles(srcs [graphics.ShaderSrcImageCount]*Image, vertice
 	}
 
 	// Even if the image is already stale, call makeStale to extend the stale region.
-	if srcstale || !needsRestoration() || !i.needsRestoration() || i.stale {
+	if srcstale || !needsRestoration() || !i.needsRestoration() {
 		i.makeStale(dstRegion)
-	} else {
-		// TODO: Consider overwritten.
+	} else if i.stale {
+		var overwrite bool
+		if hint == HintOverwriteDstRegion {
+			overwrite = i.areStaleRegionsIncludedIn(dstRegion)
+		}
+		if overwrite {
+			i.basePixels.Clear(dstRegion)
+			i.clearDrawTrianglesHistory()
+			i.stale = false
+			i.staleRegions = i.staleRegions[:0]
+		} else {
+			// Even if the image is already stale, call makeStale to extend the stale region.
+			i.makeStale(dstRegion)
+		}
+	}
+
+	if !i.stale {
 		i.appendDrawTrianglesHistory(srcs, vertices, indices, blend, dstRegion, srcRegions, shader, uniforms, fillRule, hint)
 	}
 
@@ -364,6 +390,37 @@ func (i *Image) DrawTriangles(srcs [graphics.ShaderSrcImageCount]*Image, vertice
 	i.image.DrawTriangles(imgs, vertices, indices, blend, dstRegion, srcRegions, shader.shader, uniforms, fillRule)
 }
 
+func (i *Image) areStaleRegionsIncludedIn(r image.Rectangle) bool {
+	if !i.stale {
+		return false
+	}
+	for _, sr := range i.staleRegions {
+		if !sr.In(r) {
+			return false
+		}
+	}
+	return true
+}
+
+// removeDrawTrianglesHistoryItems removes draw-image history items whose destination regions are in the given region.
+// This is useful when the destination region is overwritten soon later.
+func (i *Image) removeDrawTrianglesHistoryItems(region image.Rectangle) {
+	for idx, c := range i.drawTrianglesHistory {
+		if c.dstRegion.In(region) {
+			i.drawTrianglesHistory[idx] = nil
+		}
+	}
+	var n int
+	for _, c := range i.drawTrianglesHistory {
+		if c == nil {
+			continue
+		}
+		i.drawTrianglesHistory[n] = c
+		n++
+	}
+	i.drawTrianglesHistory = i.drawTrianglesHistory[:n]
+}
+
 // appendDrawTrianglesHistory appends a draw-image history item to the image.
 func (i *Image) appendDrawTrianglesHistory(srcs [graphics.ShaderSrcImageCount]*Image, vertices []float32, indices []uint32, blend graphicsdriver.Blend, dstRegion image.Rectangle, srcRegions [graphics.ShaderSrcImageCount]image.Rectangle, shader *Shader, uniforms []uint32, fillRule graphicsdriver.FillRule, hint Hint) {
 	if i.stale || !i.needsRestoration() {
@@ -375,20 +432,7 @@ func (i *Image) appendDrawTrianglesHistory(srcs [graphics.ShaderSrcImageCount]*I
 
 	// If the command overwrites the destination region, remove the history items that are in the region.
 	if hint == HintOverwriteDstRegion {
-		for idx, c := range i.drawTrianglesHistory {
-			if c.dstRegion.In(dstRegion) {
-				i.drawTrianglesHistory[idx] = nil
-			}
-		}
-		var n int
-		for _, c := range i.drawTrianglesHistory {
-			if c == nil {
-				continue
-			}
-			i.drawTrianglesHistory[n] = c
-			n++
-		}
-		i.drawTrianglesHistory = i.drawTrianglesHistory[:n]
+		i.removeDrawTrianglesHistoryItems(dstRegion)
 	}
 
 	// TODO: Would it be possible to merge draw image history items?
@@ -410,7 +454,7 @@ func (i *Image) appendDrawTrianglesHistory(srcs [graphics.ShaderSrcImageCount]*I
 	copy(us, uniforms)
 
 	item := &drawTrianglesHistoryItem{
-		images:     srcs,
+		srcImages:  srcs,
 		vertices:   vs,
 		indices:    is,
 		blend:      blend,
@@ -433,7 +477,7 @@ func (i *Image) readPixelsFromGPUIfNeeded(graphicsDriver graphicsdriver.Graphics
 }
 
 func (i *Image) ReadPixels(graphicsDriver graphicsdriver.Graphics, pixels []byte, region image.Rectangle) error {
-	if AlwaysReadPixelsFromGPU() {
+	if AlwaysReadPixelsFromGPU() || !i.needsRestoration() {
 		if err := i.image.ReadPixels(graphicsDriver, []graphicsdriver.PixelsArgs{
 			{
 				Pixels: pixels,
@@ -455,12 +499,12 @@ func (i *Image) ReadPixels(graphicsDriver graphicsdriver.Graphics, pixels []byte
 	return nil
 }
 
-// makeStaleIfDependingOn makes the image stale if the image depends on target.
-func (i *Image) makeStaleIfDependingOn(target *Image) {
+// makeStaleIfDependingOn makes the image stale if the image depends on src.
+func (i *Image) makeStaleIfDependingOn(src *Image) {
 	if i.stale {
 		return
 	}
-	if i.dependsOn(target) {
+	if i.dependsOn(src) {
 		// There is no new region to make stale.
 		i.makeStale(image.Rectangle{})
 	}
@@ -546,16 +590,14 @@ func (i *Image) resolveStale(graphicsDriver graphicsdriver.Graphics) error {
 	return i.readPixelsFromGPU(graphicsDriver)
 }
 
-// dependsOn reports whether the image depends on target.
-func (i *Image) dependsOn(target *Image) bool {
+// dependsOn reports whether the image depends on src.
+func (i *Image) dependsOn(src *Image) bool {
 	for _, c := range i.drawTrianglesHistory {
-		for _, img := range c.images {
-			if img == nil {
+		for _, img := range c.srcImages {
+			if img != src {
 				continue
 			}
-			if img == target {
-				return true
-			}
+			return true
 		}
 	}
 	return false
@@ -575,7 +617,7 @@ func (i *Image) dependsOnShader(shader *Shader) bool {
 func (i *Image) dependingImages() map[*Image]struct{} {
 	r := map[*Image]struct{}{}
 	for _, c := range i.drawTrianglesHistory {
-		for _, img := range c.images {
+		for _, img := range c.srcImages {
 			if img == nil {
 				continue
 			}
@@ -629,7 +671,7 @@ func (i *Image) restore(graphicsDriver graphicsdriver.Graphics) error {
 
 	for _, c := range i.drawTrianglesHistory {
 		var imgs [graphics.ShaderSrcImageCount]*graphicscommand.Image
-		for i, img := range c.images {
+		for i, img := range c.srcImages {
 			if img == nil {
 				continue
 			}

internal/restorable/images.go

@@ -62,7 +62,6 @@ func AlwaysReadPixelsFromGPU() bool {
 type images struct {
 	images      map[*Image]struct{}
 	shaders     map[*Shader]struct{}
-	lastTarget  *Image
 	contextLost atomic.Bool
 }
 
@@ -91,7 +90,7 @@ func resolveStaleImages(graphicsDriver graphicsdriver.Graphics, endFrame bool) e
 	if disabled.Load() {
 		disabledOnce.Do(func() {
 			for img := range theImages.images {
-				img.makeStale(image.Rectangle{})
+				img.makeStale(image.Rect(0, 0, img.width, img.height))
 			}
 		})
 	}
@@ -157,7 +156,6 @@ func (i *images) removeShader(shader *Shader) {
 
 // resolveStaleImages resolves stale images.
 func (i *images) resolveStaleImages(graphicsDriver graphicsdriver.Graphics) error {
-	i.lastTarget = nil
 	for img := range i.images {
 		if err := img.resolveStale(graphicsDriver); err != nil {
 			return err
@@ -166,20 +164,16 @@ func (i *images) resolveStaleImages(graphicsDriver graphicsdriver.Graphics) erro
 	return nil
 }
 
-// makeStaleIfDependingOn makes all the images stale that depend on target.
+// makeStaleIfDependingOn makes all the images stale that depend on src.
 //
-// When target is modified, all images depending on target can't be restored with target.
+// When src is modified, all images depending on src can't be restored with src.
 // makeStaleIfDependingOn is called in such situation.
-func (i *images) makeStaleIfDependingOn(target *Image) {
-	if target == nil {
-		panic("restorable: target must not be nil at makeStaleIfDependingOn")
+func (i *images) makeStaleIfDependingOn(src *Image) {
+	if src == nil {
+		panic("restorable: src must not be nil at makeStaleIfDependingOn")
 	}
-	if i.lastTarget == target {
-		return
-	}
-	i.lastTarget = target
 	for img := range i.images {
-		img.makeStaleIfDependingOn(target)
+		img.makeStaleIfDependingOn(src)
 	}
 }
 
@@ -242,9 +236,7 @@ func (i *images) restore(graphicsDriver graphicsdriver.Graphics) error {
 			current[i] = struct{}{}
 		}
 		for e := range edges {
-			if _, ok := current[e.target]; ok {
-				delete(current, e.target)
-			}
+			delete(current, e.target)
 		}
 		for i := range current {
 			delete(images, i)

internal/restorable/images_test.go

@@ -140,7 +140,8 @@ func TestRestoreChain(t *testing.T) {
 		vs := quadVertices(1, 1, 0, 0)
 		is := graphics.QuadIndices()
 		dr := image.Rect(0, 0, 1, 1)
-		imgs[i+1].DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{imgs[i]}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		sr := image.Rect(0, 0, 1, 1)
+		imgs[i+1].DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{imgs[i]}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	}
 	if err := restorable.ResolveStaleImages(ui.Get().GraphicsDriverForTesting()); err != nil {
 		t.Fatal(err)
@@ -183,10 +184,11 @@ func TestRestoreChain2(t *testing.T) {
 
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	imgs[8].DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{imgs[7]}, quadVertices(w, h, 0, 0), is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
-	imgs[9].DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{imgs[8]}, quadVertices(w, h, 0, 0), is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	imgs[8].DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{imgs[7]}, quadVertices(w, h, 0, 0), is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	imgs[9].DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{imgs[8]}, quadVertices(w, h, 0, 0), is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	for i := 0; i < 7; i++ {
-		imgs[i+1].DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{imgs[i]}, quadVertices(w, h, 0, 0), is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		imgs[i+1].DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{imgs[i]}, quadVertices(w, h, 0, 0), is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	}
 
 	if err := restorable.ResolveStaleImages(ui.Get().GraphicsDriverForTesting()); err != nil {
@@ -227,10 +229,11 @@ func TestRestoreOverrideSource(t *testing.T) {
 	img1.WritePixels(bytesToManagedBytes([]byte{clr0.R, clr0.G, clr0.B, clr0.A}), image.Rect(0, 0, w, h))
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	img2.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img1}, quadVertices(w, h, 0, 0), is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
-	img3.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img2}, quadVertices(w, h, 0, 0), is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	img2.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img1}, quadVertices(w, h, 0, 0), is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img3.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img2}, quadVertices(w, h, 0, 0), is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	img0.WritePixels(bytesToManagedBytes([]byte{clr1.R, clr1.G, clr1.B, clr1.A}), image.Rect(0, 0, w, h))
-	img1.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img0}, quadVertices(w, h, 0, 0), is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img1.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img0}, quadVertices(w, h, 0, 0), is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	if err := restorable.ResolveStaleImages(ui.Get().GraphicsDriverForTesting()); err != nil {
 		t.Fatal(err)
 	}
@@ -309,24 +312,25 @@ func TestRestoreComplexGraph(t *testing.T) {
 	}()
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
+	sr := image.Rect(0, 0, w, h)
 	vs := quadVertices(w, h, 0, 0)
-	img3.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img0}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img3.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img0}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	vs = quadVertices(w, h, 1, 0)
-	img3.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img1}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img3.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img1}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	vs = quadVertices(w, h, 1, 0)
-	img4.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img1}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img4.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img1}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	vs = quadVertices(w, h, 2, 0)
-	img4.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img2}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img4.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img2}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	vs = quadVertices(w, h, 0, 0)
-	img5.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img3}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img5.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img3}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	vs = quadVertices(w, h, 0, 0)
-	img6.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img3}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img6.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img3}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	vs = quadVertices(w, h, 1, 0)
-	img6.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img4}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img6.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img4}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	vs = quadVertices(w, h, 0, 0)
-	img7.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img2}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img7.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img2}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	vs = quadVertices(w, h, 2, 0)
-	img7.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img3}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img7.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img3}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	if err := restorable.ResolveStaleImages(ui.Get().GraphicsDriverForTesting()); err != nil {
 		t.Fatal(err)
 	}
@@ -419,8 +423,9 @@ func TestRestoreRecursive(t *testing.T) {
 	}()
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	img1.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img0}, quadVertices(w, h, 1, 0), is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
-	img0.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img1}, quadVertices(w, h, 1, 0), is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	img1.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img0}, quadVertices(w, h, 1, 0), is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img0.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img1}, quadVertices(w, h, 1, 0), is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	if err := restorable.ResolveStaleImages(ui.Get().GraphicsDriverForTesting()); err != nil {
 		t.Fatal(err)
 	}
@@ -519,7 +524,8 @@ func TestDrawTrianglesAndWritePixels(t *testing.T) {
 	vs := quadVertices(1, 1, 0, 0)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, 2, 1)
-	img1.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img0}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, 1, 1)
+	img1.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img0}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	img1.WritePixels(bytesToManagedBytes([]byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff}), image.Rect(0, 0, 2, 1))
 
 	if err := restorable.ResolveStaleImages(ui.Get().GraphicsDriverForTesting()); err != nil {
@@ -557,8 +563,9 @@ func TestDispose(t *testing.T) {
 
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, 1, 1)
-	img1.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img2}, quadVertices(1, 1, 0, 0), is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
-	img0.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img1}, quadVertices(1, 1, 0, 0), is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, 1, 1)
+	img1.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img2}, quadVertices(1, 1, 0, 0), is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	img0.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img1}, quadVertices(1, 1, 0, 0), is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	img1.Dispose()
 
 	if err := restorable.ResolveStaleImages(ui.Get().GraphicsDriverForTesting()); err != nil {
@@ -667,7 +674,8 @@ func TestWritePixelsOnly(t *testing.T) {
 	vs := quadVertices(1, 1, 0, 0)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, 1, 1)
-	img1.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img0}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	img1.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{img0}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	img0.WritePixels(bytesToManagedBytes([]byte{5, 6, 7, 8}), image.Rect(0, 0, 1, 1))
 
 	// BasePixelsForTesting is available without GPU accessing.
@@ -721,7 +729,8 @@ func TestReadPixelsFromVolatileImage(t *testing.T) {
 	vs := quadVertices(1, 1, 0, 0)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 
 	// Read the pixels. If the implementation is correct, dst tries to read its pixels from GPU due to being
 	// stale.
@@ -745,7 +754,8 @@ func TestAllowWritePixelsAfterDrawTriangles(t *testing.T) {
 	vs := quadVertices(w, h, 0, 0)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	dst.WritePixels(bytesToManagedBytes(make([]byte, 4*w*h)), image.Rect(0, 0, w, h))
 	// WritePixels for a whole image doesn't panic.
 }
@@ -764,7 +774,8 @@ func TestAllowWritePixelsForPartAfterDrawTriangles(t *testing.T) {
 	vs := quadVertices(w, h, 0, 0)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	dst.WritePixels(bytesToManagedBytes(make([]byte, 4*2*2)), image.Rect(0, 0, 2, 2))
 	// WritePixels for a part of image doesn't panic.
 
@@ -858,7 +869,8 @@ func TestDrawTrianglesAndExtend(t *testing.T) {
 	vs := quadVertices(w, h, 0, 0)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	orig.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	orig.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	extended := orig.Extend(w*2, h*2) // After this, orig is already disposed.
 
 	result := make([]byte, 4*(w*2)*(h*2))
@@ -908,7 +920,8 @@ func TestMutateSlices(t *testing.T) {
 	is := make([]uint32, len(graphics.QuadIndices()))
 	copy(is, graphics.QuadIndices())
 	dr := image.Rect(0, 0, w, h)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	for i := range vs {
 		vs[i] = 0
 	}
@@ -1100,7 +1113,8 @@ func TestDrawTrianglesAndReadPixels(t *testing.T) {
 	vs := quadVertices(w, h, 0, 0)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 
 	pix := make([]byte, 4*w*h)
 	if err := dst.ReadPixels(ui.Get().GraphicsDriverForTesting(), pix, image.Rect(0, 0, w, h)); err != nil {
@@ -1124,7 +1138,8 @@ func TestWritePixelsAndDrawTriangles(t *testing.T) {
 	vs := quadVertices(1, 1, 1, 0)
 	is := graphics.QuadIndices()
 	dr := image.Rect(1, 0, 2, 1)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, 1, 1)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 
 	// Get the pixels.
 	pix := make([]byte, 4*2*1)
@@ -1151,10 +1166,11 @@ func TestOverwriteDstRegion(t *testing.T) {
 	vs := quadVertices(w, h, 0, 0)
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src0}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, w, h)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src0}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	// This tests that HintOverwriteDstRegion removes the previous DrawTriangles.
 	// In practice, BlendCopy should be used instead of BlendSourceOver in this case.
-	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src1}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintOverwriteDstRegion)
+	dst.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{src1}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintOverwriteDstRegion)
 
 	if err := restorable.ResolveStaleImages(ui.Get().GraphicsDriverForTesting()); err != nil {
 		t.Fatal(err)

internal/restorable/shader_test.go

@@ -46,7 +46,8 @@ func clearImage(img *restorable.Image, w, h int) {
 	}
 	is := graphics.QuadIndices()
 	dr := image.Rect(0, 0, w, h)
-	img.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{emptyImage}, vs, is, graphicsdriver.BlendClear, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	sr := image.Rect(0, 0, 3, 3)
+	img.DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{emptyImage}, vs, is, graphicsdriver.BlendClear, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, restorable.NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 }
 
 func TestShader(t *testing.T) {
@@ -85,7 +86,8 @@ func TestShaderChain(t *testing.T) {
 	s := restorable.NewShader(etesting.ShaderProgramImages(1), "")
 	for i := 0; i < num-1; i++ {
 		dr := image.Rect(0, 0, 1, 1)
-		imgs[i+1].DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{imgs[i]}, quadVertices(1, 1, 0, 0), graphics.QuadIndices(), graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, s, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+		sr := image.Rect(0, 0, 1, 1)
+		imgs[i+1].DrawTriangles([graphics.ShaderSrcImageCount]*restorable.Image{imgs[i]}, quadVertices(1, 1, 0, 0), graphics.QuadIndices(), graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, s, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 	}
 
 	if err := restorable.ResolveStaleImages(ui.Get().GraphicsDriverForTesting()); err != nil {
@@ -117,7 +119,12 @@ func TestShaderMultipleSources(t *testing.T) {
 
 	s := restorable.NewShader(etesting.ShaderProgramImages(3), "")
 	dr := image.Rect(0, 0, 1, 1)
-	dst.DrawTriangles(srcs, quadVertices(1, 1, 0, 0), graphics.QuadIndices(), graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{}, s, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
+	srs := [graphics.ShaderSrcImageCount]image.Rectangle{
+		image.Rect(0, 0, 1, 1),
+		image.Rect(0, 0, 1, 1),
+		image.Rect(0, 0, 1, 1),
+	}
+	dst.DrawTriangles(srcs, quadVertices(1, 1, 0, 0), graphics.QuadIndices(), graphicsdriver.BlendCopy, dr, srs, s, nil, graphicsdriver.FillRuleFillAll, restorable.HintNone)
 
 	// Clear one of the sources after DrawTriangles. dst should not be affected.
 	clearImage(srcs[0], 1, 1)

internal/ui/image.go

@@ -183,8 +183,9 @@ func (i *Image) Fill(r, g, b, a float32, region image.Rectangle) {
 	if a == 1 && i.lastBlend == graphicsdriver.BlendSourceOver {
 		blend = graphicsdriver.BlendSourceOver
 	}
+	sr := image.Rect(0, 0, i.ui.whiteImage.width, i.ui.whiteImage.height)
 	// i.lastBlend is updated in DrawTriangles.
-	i.DrawTriangles(srcs, i.tmpVerticesForFill, is, blend, region, [graphics.ShaderSrcImageCount]image.Rectangle{}, NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, true, false, restorable.HintOverwriteDstRegion)
+	i.DrawTriangles(srcs, i.tmpVerticesForFill, is, blend, region, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, true, false, restorable.HintOverwriteDstRegion)
 }
 
 type bigOffscreenImage struct {
@@ -253,7 +254,8 @@ func (i *bigOffscreenImage) drawTriangles(srcs [graphics.ShaderSrcImageCount]*Im
 			1, 1, 1, 1)
 		is := graphics.QuadIndices()
 		dstRegion := image.Rect(0, 0, i.region.Dx()*bigOffscreenScale, i.region.Dy()*bigOffscreenScale)
-		i.image.DrawTriangles(srcs, i.tmpVerticesForCopying, is, graphicsdriver.BlendCopy, dstRegion, [graphics.ShaderSrcImageCount]image.Rectangle{}, NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, true, false, restorable.HintOverwriteDstRegion)
+		srcRegion := i.region
+		i.image.DrawTriangles(srcs, i.tmpVerticesForCopying, is, graphicsdriver.BlendCopy, dstRegion, [graphics.ShaderSrcImageCount]image.Rectangle{srcRegion}, NearestFilterShader, nil, graphicsdriver.FillRuleFillAll, true, false, restorable.HintOverwriteDstRegion)
 	}
 
 	for idx := 0; idx < len(vertices); idx += graphics.VertexFloatCount {
@@ -297,13 +299,14 @@ func (i *bigOffscreenImage) flush() {
 		1, 1, 1, 1)
 	is := graphics.QuadIndices()
 	dstRegion := i.region
+	srcRegion := image.Rect(0, 0, i.region.Dx()*bigOffscreenScale, i.region.Dy()*bigOffscreenScale)
 	blend := graphicsdriver.BlendSourceOver
 	hint := restorable.HintNone
 	if i.blend != graphicsdriver.BlendSourceOver {
 		blend = graphicsdriver.BlendCopy
 		hint = restorable.HintOverwriteDstRegion
 	}
-	i.orig.DrawTriangles(srcs, i.tmpVerticesForFlushing, is, blend, dstRegion, [graphics.ShaderSrcImageCount]image.Rectangle{}, LinearFilterShader, nil, graphicsdriver.FillRuleFillAll, true, false, hint)
+	i.orig.DrawTriangles(srcs, i.tmpVerticesForFlushing, is, blend, dstRegion, [graphics.ShaderSrcImageCount]image.Rectangle{srcRegion}, LinearFilterShader, nil, graphicsdriver.FillRuleFillAll, true, false, hint)
 
 	i.image.clear()
 	i.dirty = false