added an activate function and an exported TextureID so that other GL code can also use the canvas

backend/gogl/gogl.go

@@ -257,6 +257,8 @@ func New(x, y, w, h int, ctx *GLContext) (*GoGLBackend, error) {
 type GoGLBackendOffscreen struct {
 	GoGLBackend
 
+	TextureID uint32
+
 	offscrBuf offscreenBuffer
 	offscrImg Image
 }
@@ -281,6 +283,7 @@ func NewOffscreen(w, h int, alpha bool, ctx *GLContext) (*GoGLBackendOffscreen,
 		bo.offscrImg.w = bo.offscrBuf.w
 		bo.offscrImg.h = bo.offscrBuf.h
 		bo.offscrImg.tex = bo.offscrBuf.tex
+		bo.TextureID = bo.offscrBuf.tex
 	}
 	b.disableTextureRenderTarget = func() {
 		b.enableTextureRenderTarget(&bo.offscrBuf)
@@ -326,6 +329,13 @@ func glError() error {
 	return nil
 }
 
+// Activate only needs to be called if there is other
+// code also using the GL state
+func (b *GoGLBackend) Activate() {
+	activeContext = nil
+	b.activate()
+}
+
 var activeContext *GoGLBackend
 
 func (b *GoGLBackend) activate() {

backend/xmobile/gen/gen.go

@@ -258,6 +258,7 @@ func rewriteMain(src string) string {
 		"type XMobileBackend struct {\n", 1)
 	src = strings.Replace(src, "func NewGLContext() (*GLContext, error) {",
 		"func NewGLContext(glctx gl.Context) (*GLContext, error) {", 1)
+	src = strings.Replace(src, "TextureID uint32", "TextureID gl.Texture", 1)
 
 	src = strings.Replace(src,
 		`	err := gl.Init()

backend/xmobile/xmobile.go

@@ -252,6 +252,8 @@ func New(x, y, w, h int, ctx *GLContext) (*XMobileBackend, error) {
 type XMobileBackendOffscreen struct {
 	XMobileBackend
 
+	TextureID gl.Texture
+
 	offscrBuf offscreenBuffer
 	offscrImg Image
 }
@@ -274,6 +276,7 @@ func NewOffscreen(w, h int, alpha bool, ctx *GLContext) (*XMobileBackendOffscree
 		bo.offscrImg.w = bo.offscrBuf.w
 		bo.offscrImg.h = bo.offscrBuf.h
 		bo.offscrImg.tex = bo.offscrBuf.tex
+		bo.TextureID = bo.offscrBuf.tex
 	}
 	b.disableTextureRenderTarget = func() {
 		b.enableTextureRenderTarget(&bo.offscrBuf)
@@ -319,6 +322,13 @@ func glError(b *XMobileBackend) error {
 	return nil
 }
 
+// Activate only needs to be called if there is other
+// code also using the GL state
+func (b *XMobileBackend) Activate() {
+	activeContext = nil
+	b.activate()
+}
+
 var activeContext *XMobileBackend
 
 func (b *XMobileBackend) activate() {