app/internal/glimpl: derive version parameter in Functions.Init

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

app/headless/headless_js.go

@@ -17,19 +17,17 @@ type jsContext struct {
 }
 
 func newGLContext() (context, error) {
-	version := 2
 	doc := js.Global().Get("document")
 	cnv := doc.Call("createElement", "canvas")
 	ctx := cnv.Call("getContext", "webgl2")
 	if ctx.IsNull() {
-		version = 1
 		ctx = cnv.Call("getContext", "webgl")
 	}
 	if ctx.IsNull() {
 		return nil, errors.New("headless: webgl is not supported")
 	}
 	f := &glimpl.Functions{Ctx: ctx}
-	if err := f.Init(version); err != nil {
+	if err := f.Init(); err != nil {
 		return nil, err
 	}
 	c := &jsContext{

app/internal/glimpl/gl_js.go

@@ -20,8 +20,10 @@ type Functions struct {
 	int32Buf js.Value
 }
 
-func (f *Functions) Init(version int) error {
-	if version < 2 {
+func (f *Functions) Init() error {
+	webgl2Class := js.Global().Get("WebGL2RenderingContext")
+	iswebgl2 := !webgl2Class.IsNull() && f.Ctx.InstanceOf(webgl2Class)
+	if !iswebgl2 {
 		f.EXT_disjoint_timer_query = f.getExtension("EXT_disjoint_timer_query")
 		if f.getExtension("OES_texture_half_float").IsNull() && f.getExtension("OES_texture_float").IsNull() {
 			return errors.New("gl: no support for neither OES_texture_half_float nor OES_texture_float")

app/internal/window/gl_js.go

@@ -26,17 +26,15 @@ func newContext(w *window) (*context, error) {
 		"desynchronized":        true,
 		"preserveDrawingBuffer": true,
 	}
-	version := 2
 	ctx := w.cnv.Call("getContext", "webgl2", args)
 	if ctx.IsNull() {
-		version = 1
 		ctx = w.cnv.Call("getContext", "webgl", args)
 	}
 	if ctx.IsNull() {
 		return nil, errors.New("app: webgl is not supported")
 	}
 	f := &glimpl.Functions{Ctx: ctx}
-	if err := f.Init(version); err != nil {
+	if err := f.Init(); err != nil {
 		return nil, err
 	}
 	c := &context{