graphics: Bug fix: Flush after filling (#419)

image_test.go

@@ -490,7 +490,7 @@ func TestImageFill(t *testing.T) {
 	}
 }
 
-// Issue 317
+// Issue #317
 func TestImageEdge(t *testing.T) {
 	const (
 		img0Width  = 16
@@ -561,6 +561,28 @@ func TestImageEdge(t *testing.T) {
 	}
 }
 
+// Issue #419
+func TestImageTooManyFill(t *testing.T) {
+	const width = 256
+
+	src, _ := NewImage(1, 1, FilterNearest)
+	dst, _ := NewImage(width, 1, FilterNearest)
+	for i := 0; i < width; i++ {
+		src.Fill(color.RGBA{uint8(i), uint8(i), uint8(i), 0xff})
+		op := &DrawImageOptions{}
+		op.GeoM.Translate(float64(i), 0)
+		dst.DrawImage(src, op)
+	}
+
+	for i := 0; i < width; i++ {
+		got := color.RGBAModel.Convert(dst.At(i, 0))
+		want := color.RGBA{uint8(i), uint8(i), uint8(i), 0xff}
+		if got != want {
+			t.Errorf("src At(%d, %d): got %#v, want: %#v", i, 0, got, want)
+		}
+	}
+}
+
 func BenchmarkDrawImage(b *testing.B) {
 	img0, _ := NewImage(16, 16, FilterNearest)
 	img1, _ := NewImage(16, 16, FilterNearest)

internal/graphics/command.go

@@ -181,7 +181,13 @@ func (c *fillCommand) Exec(indexOffsetInBytes int) error {
 	g := float64(cg) / max
 	b := float64(cb) / max
 	a := float64(ca) / max
-	return opengl.GetContext().FillFramebuffer(r, g, b, a)
+	if err := opengl.GetContext().FillFramebuffer(r, g, b, a); err != nil {
+		return err
+	}
+
+	// Flush is needed after filling (#419)
+	opengl.GetContext().Flush()
+	return nil
 }
 
 type drawImageCommand struct {