examples/highdpi: Async loading

examples/highdpi/main.go

@@ -30,6 +30,7 @@ import (
 var (
 	count          int
 	highDPIImage   *ebiten.Image
+	highDPIImageCh = make(chan *ebiten.Image)
 )
 
 func init() {
@@ -37,6 +38,8 @@ func init() {
 	// https://commons.wikimedia.org/wiki/File:As08-16-2593.jpg
 	const url = "https://upload.wikimedia.org/wikipedia/commons/1/1f/As08-16-2593.jpg"
 
+	// Load the image asynchronously.
+	go func() {
 		res, err := http.Get(url)
 		if err != nil {
 			log.Fatal(err)
@@ -48,17 +51,35 @@ func init() {
 			log.Fatal(err)
 		}
 
-	highDPIImage, err = ebiten.NewImageFromImage(img, ebiten.FilterLinear)
+		eimg, err := ebiten.NewImageFromImage(img, ebiten.FilterLinear)
 		if err != nil {
 			log.Fatal(err)
 		}
+
+		highDPIImageCh <- eimg
+		close(highDPIImageCh)
+	}()
 }
 
 func update(screen *ebiten.Image) error {
+	if highDPIImage == nil {
+		// Use select and 'default' clause for non-blocking receiving.
+		select {
+		case img := <-highDPIImageCh:
+			highDPIImage = img
+		default:
+		}
+	}
+
 	if ebiten.IsRunningSlowly() {
 		return nil
 	}
 
+	if highDPIImage == nil {
+		ebitenutil.DebugPrint(screen, "Loading the image...")
+		return nil
+	}
+
 	scale := ebiten.DeviceScaleFactor()
 	sw, sh := screen.Size()