gpu: specify target Texture Backend.NewFramebuffer

OpenGL doesn't care if the texture to a framebuffer changes, but
Direct3D does. Change Backend to better match both APIs.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/backend.go

@@ -20,7 +20,7 @@ type Backend interface {
 	IsTimeContinuous() bool
 	NewTexture(format TextureFormat, width, height int, minFilter, magFilter TextureFilter, bindings BufferBinding) Texture
 	DefaultFramebuffer() Framebuffer
-	NewFramebuffer() Framebuffer
+	NewFramebuffer(tex Texture) Framebuffer
 	NewImmutableBuffer(typ BufferBinding, data []byte) Buffer
 	NewBuffer(typ BufferBinding, size int) Buffer
 	NewProgram(vertexShader, fragmentShader ShaderSources) (Program, error)
@@ -125,7 +125,6 @@ type Buffer interface {
 
 type Framebuffer interface {
 	Bind()
-	BindTexture(t Texture)
 	Invalidate()
 	Release()
 	IsComplete() error

gpu/gl/backend.go

@@ -162,9 +162,13 @@ func (b *Backend) IsTimeContinuous() bool {
 	return b.funcs.GetInteger(GPU_DISJOINT_EXT) == FALSE
 }
 
-func (b *Backend) NewFramebuffer() gpu.Framebuffer {
+func (b *Backend) NewFramebuffer(tex gpu.Texture) gpu.Framebuffer {
+	gltex := tex.(*gpuTexture)
 	fb := b.funcs.CreateFramebuffer()
-	return &gpuFramebuffer{funcs: b.funcs, obj: fb}
+	fbo := &gpuFramebuffer{funcs: b.funcs, obj: fb}
+	fbo.Bind()
+	b.funcs.FramebufferTexture2D(FRAMEBUFFER, COLOR_ATTACHMENT0, TEXTURE_2D, gltex.obj, 0)
+	return fbo
 }
 
 func (b *Backend) DefaultFramebuffer() gpu.Framebuffer {
@@ -552,12 +556,6 @@ func (f *gpuFramebuffer) Release() {
 	f.funcs.DeleteFramebuffer(f.obj)
 }
 
-func (f *gpuFramebuffer) BindTexture(t gpu.Texture) {
-	gltex := t.(*gpuTexture)
-	f.Bind()
-	f.funcs.FramebufferTexture2D(FRAMEBUFFER, COLOR_ATTACHMENT0, TEXTURE_2D, gltex.obj, 0)
-}
-
 func toTexFilter(f gpu.TextureFilter) int {
 	switch f {
 	case gpu.FilterNearest:

gpu/path.go

@@ -193,9 +193,7 @@ func newStenciler(ctx Backend) *stenciler {
 func (s *fboSet) resize(ctx Backend, sizes []image.Point) {
 	// Add fbos.
 	for i := len(s.fbos); i < len(sizes); i++ {
-		s.fbos = append(s.fbos, stencilFBO{
-			fbo: ctx.NewFramebuffer(),
-		})
+		s.fbos = append(s.fbos, stencilFBO{})
 	}
 	// Resize fbos.
 	for i, sz := range sizes {
@@ -206,13 +204,14 @@ func (s *fboSet) resize(ctx Backend, sizes []image.Point) {
 		waste := float32(sz.X*sz.Y) / float32(f.size.X*f.size.Y)
 		resize = resize || waste > 1.2
 		if resize {
-			if f.tex != nil {
+			if f.fbo != nil {
+				f.fbo.Release()
 				f.tex.Release()
 			}
 			f.size = sz
 			f.tex = ctx.NewTexture(TextureFormatFloat, sz.X, sz.Y, FilterNearest, FilterNearest,
 				BufferBindingTexture|BufferBindingFramebuffer)
-			f.fbo.BindTexture(f.tex)
+			f.fbo = ctx.NewFramebuffer(f.tex)
 		}
 	}
 	// Delete extra fbos.