shader: Fix the case when the source image is nil for shaders

internal/buffered/image.go

@@ -288,9 +288,21 @@ func (i *Image) drawImage(src *Image, bounds image.Rectangle, g mipmap.GeoM, col
 //
 // Copying vertices and indices is the caller's responsibility.
 func (i *Image) DrawTriangles(src *Image, vertices []float32, indices []uint16, colorm *affine.ColorM, mode driver.CompositeMode, filter driver.Filter, address driver.Address, shader *Shader, uniforms []interface{}) {
+	var srcs []*Image
+	if src != nil {
+		srcs = append(srcs, src)
+	}
+	for _, u := range uniforms {
+		if src, ok := u.(*Image); ok {
+			srcs = append(srcs, src)
+		}
+	}
+
+	for _, src := range srcs {
 		if i == src {
 			panic("buffered: Image.DrawTriangles: src must be different from the receiver")
 		}
+	}
 
 	delayedCommandsM.Lock()
 	defer delayedCommandsM.Unlock()
@@ -304,7 +316,9 @@ func (i *Image) DrawTriangles(src *Image, vertices []float32, indices []uint16,
 		return
 	}
 
+	for _, src := range srcs {
 		src.resolvePendingPixels(true)
+	}
 	i.resolvePendingPixels(false)
 
 	var s *mipmap.Shader
@@ -322,7 +336,11 @@ func (i *Image) DrawTriangles(src *Image, vertices []float32, indices []uint16,
 		}
 	}
 
-	i.img.DrawTriangles(src.img, vertices, indices, colorm, mode, filter, address, s, us)
+	var srcImg *mipmap.Mipmap
+	if src != nil {
+		srcImg = src.img
+	}
+	i.img.DrawTriangles(srcImg, vertices, indices, colorm, mode, filter, address, s, us)
 }
 
 type Shader struct {

internal/graphicscommand/image.go

@@ -152,9 +152,21 @@ 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(src *Image, vertices []float32, indices []uint16, clr *affine.ColorM, mode driver.CompositeMode, filter driver.Filter, address driver.Address, shader *Shader, uniforms []interface{}) {
-	if src != nil && src.screen {
+	var srcs []*Image
+	if src != nil {
+		srcs = append(srcs, src)
+	}
+	for _, u := range uniforms {
+		if src, ok := u.(*Image); ok {
+			srcs = append(srcs, src)
+		}
+	}
+
+	for _, src := range srcs {
+		if src.screen {
 			panic("graphicscommand: the screen image cannot be the rendering source")
 		}
+	}
 
 	if i.lastCommand == lastCommandNone {
 		if !i.screen && mode != driver.CompositeModeClear {
@@ -162,14 +174,9 @@ func (i *Image) DrawTriangles(src *Image, vertices []float32, indices []uint16,
 		}
 	}
 
-	if src != nil {
+	for _, src := range srcs {
 		src.resolveBufferedReplacePixels()
 	}
-	for _, v := range uniforms {
-		if img, ok := v.(*Image); ok {
-			img.resolveBufferedReplacePixels()
-		}
-	}
 	i.resolveBufferedReplacePixels()
 
 	theCommandQueue.EnqueueDrawTrianglesCommand(i, src, vertices, indices, clr, mode, filter, address, shader, uniforms)

internal/mipmap/mipmap.go

@@ -200,7 +200,12 @@ func (m *Mipmap) DrawTriangles(src *Mipmap, vertices []float32, indices []uint16
 		}
 	}
 
-	m.orig.DrawTriangles(src.orig, vertices, indices, colorm, mode, filter, address, s, us)
+	var srcOrig *shareable.Image
+	if src != nil {
+		srcOrig = src.orig
+	}
+
+	m.orig.DrawTriangles(srcOrig, vertices, indices, colorm, mode, filter, address, s, us)
 	m.disposeMipmaps()
 }
 

internal/restorable/image.go

@@ -384,7 +384,26 @@ func (i *Image) DrawTriangles(img *Image, vertices []float32, indices []uint16,
 	}
 	theImages.makeStaleIfDependingOn(i)
 
-	if (img != nil && (img.stale || img.volatile)) || i.screen || !needsRestoring() || i.volatile {
+	var srcs []*Image
+	if img != nil {
+		srcs = append(srcs, img)
+	}
+	for _, u := range uniforms {
+		if src, ok := u.(*Image); ok {
+			srcs = append(srcs, src)
+		}
+	}
+
+	// TODO: Add tests to confirm this logic.
+	var srcstale bool
+	for _, src := range srcs {
+		if src.stale || src.volatile {
+			srcstale = true
+			break
+		}
+	}
+
+	if srcstale || i.screen || !needsRestoring() || i.volatile {
 		i.makeStale()
 	} else {
 		i.appendDrawTrianglesHistory(img, vertices, indices, colorm, mode, filter, address, shader, uniforms)

internal/shareable/image.go

@@ -286,26 +286,45 @@ func (i *Image) DrawTriangles(img *Image, vertices []float32, indices []uint16,
 	backendsM.Lock()
 	// Do not use defer for performance.
 
-	if img.disposed {
+	var srcs []*Image
+	if img != nil {
+		srcs = append(srcs, img)
+	}
+	for _, u := range uniforms {
+		if src, ok := u.(*Image); ok {
+			srcs = append(srcs, src)
+		}
+	}
+
+	for _, src := range srcs {
+		if src.disposed {
 			panic("shareable: the drawing source image must not be disposed (DrawTriangles)")
 		}
+	}
 	if i.disposed {
 		panic("shareable: the drawing target image must not be disposed (DrawTriangles)")
 	}
-	if img.backend == nil {
-		img.allocate(true)
+
+	for _, src := range srcs {
+		if src.backend == nil {
+			src.allocate(true)
+		}
 	}
 
 	i.ensureNotShared()
 
-	// Compare i and img after ensuring i is not shared, or
-	// i and img might share the same texture even though i != img.
-	if i.backend.restorable == img.backend.restorable {
-		panic("shareable: Image.DrawTriangles: img must be different from the receiver")
+	// Compare i and source images after ensuring i is not shared, or
+	// i and a source image might share the same texture even though i != src.
+	for _, src := range srcs {
+		if i.backend.restorable == src.backend.restorable {
+			panic("shareable: Image.DrawTriangles: source must be different from the receiver")
+		}
 	}
 
-	ox, oy, _, _ := img.region()
-	oxf, oyf := float32(ox), float32(oy)
+	var oxf, oyf float32
+	if len(srcs) > 0 {
+		ox, oy, _, _ := srcs[0].region()
+		oxf, oyf = float32(ox), float32(oy)
 		n := len(vertices) / graphics.VertexFloatNum
 		for i := 0; i < n; i++ {
 			vertices[i*graphics.VertexFloatNum+2] += oxf
@@ -315,6 +334,7 @@ func (i *Image) DrawTriangles(img *Image, vertices []float32, indices []uint16,
 			vertices[i*graphics.VertexFloatNum+6] += oxf
 			vertices[i*graphics.VertexFloatNum+7] += oyf
 		}
+	}
 
 	var s *restorable.Shader
 	if shader != nil {
@@ -343,13 +363,19 @@ func (i *Image) DrawTriangles(img *Image, vertices []float32, indices []uint16,
 		}
 	}
 
-	i.backend.restorable.DrawTriangles(img.backend.restorable, vertices, indices, colorm, mode, filter, address, s, us)
+	var r *restorable.Image
+	if img != nil {
+		r = img.backend.restorable
+	}
+	i.backend.restorable.DrawTriangles(r, vertices, indices, colorm, mode, filter, address, s, us)
 
 	i.nonUpdatedCount = 0
 	delete(imagesToMakeShared, i)
 
-	if !img.isShared() && img.shareable() {
-		imagesToMakeShared[img] = struct{}{}
+	for _, src := range srcs {
+		if !src.isShared() && src.shareable() {
+			imagesToMakeShared[src] = struct{}{}
+		}
 	}
 
 	backendsM.Unlock()