app/headless,internal/rendertest: report errors from headless renders

Updates gio#144

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

app/headless/headless.go

@@ -106,8 +106,8 @@ func (w *Window) Release() {
 
 // Frame replace the window content and state with the
 // operation list.
-func (w *Window) Frame(frame *op.Ops) {
+func (w *Window) Frame(frame *op.Ops) error {
-	contextDo(w.ctx, func() error {
+	return contextDo(w.ctx, func() error {
 		w.gpu.Collect(w.size, frame)
 		w.gpu.BeginFrame()
 		w.gpu.EndFrame()

app/headless/headless_test.go

@@ -26,7 +26,9 @@ func TestHeadless(t *testing.T) {
 		X: float32(sz.X) - 100,
 		Y: float32(sz.Y) - 100,
 	}}}.Add(&ops)
-	w.Frame(&ops)
+	if err := w.Frame(&ops); err != nil {
+		t.Fatal(err)
+	}
 
 	img, err := w.Screenshot()
 	if err != nil {
@@ -70,7 +72,9 @@ func TestClipping(t *testing.T) {
 		NW: 75,
 	}.Op(&ops).Add(&ops)
 	pop.Add(&ops)
-	w.Frame(&ops)
+	if err := w.Frame(&ops); err != nil {
+		t.Fatal(err)
+	}
 
 	img, err := w.Screenshot()
 	if err != nil {
@@ -113,7 +117,9 @@ func TestDepth(t *testing.T) {
 	paint.PaintOp{Rect: f32.Rectangle{
 		Max: f32.Point{X: 100, Y: 50},
 	}}.Add(&ops)
-	w.Frame(&ops)
+	if err := w.Frame(&ops); err != nil {
+		t.Fatal(err)
+	}
 
 	img, err := w.Screenshot()
 	if err != nil {

internal/rendertest/util_test.go

@@ -44,7 +44,9 @@ func drawImage(t *testing.T, size int, ops *op.Ops, draw func(o *op.Ops)) (im *i
 	sz := image.Point{X: size, Y: size}
 	w := newWindow(t, sz.X, sz.Y)
 	draw(ops)
-	w.Frame(ops)
+	if err := w.Frame(ops); err != nil {
+		return nil, err
+	}
 	return w.Screenshot()
 }
 
@@ -100,13 +102,16 @@ func multiRun(t *testing.T, frames ...frameT) {
 	for i := range frames {
 		ops.Reset()
 		frames[i].f(ops)
-		w.Frame(ops)
+		if err := w.Frame(ops); err != nil {
+			t.Errorf("rendering failed: %v", err)
+			continue
+		}
 		img, err = w.Screenshot()
 		if err != nil {
-			t.Error("error rendering:", err)
+			t.Errorf("screenshot failed: %v", err)
-			return
+			continue
 		}
-		// check for a reference image and make sure we are identical.
+		// Check for a reference image and make sure they are identical.
 		ok := verifyRef(t, img, i)
 		if frames[i].c != nil {
 			frames[i].c(result{t: t, img: img})