Pass delay to Loop

examples/example.go

@@ -16,8 +16,7 @@ func main() {
 		log.Fatal(err)
 	}
 	defer f.Close()
-	lastFrame := time.Now()
+	for f.Loop(time.Second / 60) {
-	for f.Loop() {
 		// If escape is pressed - exit
 		if f.Key(27) {
 			break
@@ -28,11 +27,5 @@ func main() {
 				f.Set(j, i, fenster.RGB(rand.Uint32()))
 			}
 		}
-		// Wait for FPS rate
-		sleep := 16*time.Millisecond - time.Since(lastFrame)
-		if sleep > 0 {
-			time.Sleep(sleep)
-		}
-		lastFrame = time.Now()
 	}
 }

examples/testimage.go

@@ -29,7 +29,6 @@ func main() {
 		log.Fatal(err)
 	}
 	defer f.Close()
-	lastFrame := time.Now()
 
 	img, err := openImage("testdata/Testbild.png")
 	if err != nil {
@@ -40,7 +39,7 @@ func main() {
 	pimg := image.NewPaletted(img.Bounds(), palette.Plan9)
 	draw.Draw(pimg, pimg.Bounds(), img, image.Point{}, draw.Src)
 
-	for f.Loop() {
+	for f.Loop(time.Second / 24) {
 		// If escape is pressed - exit
 		if f.Key(27) {
 			break
@@ -49,12 +48,5 @@ func main() {
 		// rotate palette
 		pimg.Palette = append(pimg.Palette[1:], pimg.Palette[0])
 		draw.Draw(f, f.Bounds(), pimg, image.Point{}, draw.Src)
-
-		// Wait for FPS rate
-		sleep := 16*time.Millisecond - time.Since(lastFrame)
-		if sleep > 0 {
-			time.Sleep(sleep)
-		}
-		lastFrame = time.Now()
 	}
 }

fenster.go

@@ -13,6 +13,7 @@ import (
 	"image/color"
 	"image/draw"
 	"runtime"
+	"time"
 	"unsafe"
 )
 
@@ -22,7 +23,7 @@ func init() {
 }
 
 type Fenster interface {
-	Loop() bool
+	Loop(d time.Duration) bool
 	Close()
 	Key(byte) bool
 	Mod() Mods
@@ -58,6 +59,7 @@ type Mods int
 type fenster struct {
 	f         C.struct_fenster
 	buf       []uint32
+	lastFrame time.Time
 }
 
 func (f *fenster) ColorModel() color.Model { return RGBModel }
@@ -72,14 +74,22 @@ func New(w, h int, title string) (Fenster, error) {
 	f.f.height = C.int(h)
 	f.f.buf = (*C.uint32_t)(C.malloc(C.size_t(w * h * 4)))
 	f.buf = unsafe.Slice((*uint32)(f.f.buf), w*h)
+	f.lastFrame = time.Now()
 	res := C.fenster_open(&f.f)
 	if res != 0 {
 		return nil, fmt.Errorf("failed to open window: %d", res)
 	}
 	return f, nil
 }
-func (f *fenster) Loop() bool { return C.fenster_loop(&f.f) == 0 }
+
 func (f *fenster) Close() { C.fenster_close(&f.f) }
+func (f *fenster) Loop(d time.Duration) bool {
+	if sleep := d - time.Since(f.lastFrame); sleep > 0 {
+		time.Sleep(sleep)
+	}
+	f.lastFrame = time.Now()
+	return C.fenster_loop(&f.f) == 0
+}
 
 func (f *fenster) Key(code byte) bool { return f.f.keys[code] != 0 }
 func (f *fenster) Mod() Mods          { return Mods(f.f.mod) }