examples: Refactoring

examples/additive/main.go

@@ -40,16 +40,19 @@ func update(screen *ebiten.Image) error {
 	}
 
 	const (
+		// The offset point to render the image.
 		ox = 10
 		oy = 10
 	)
 
 	screen.Fill(color.NRGBA{0x00, 0x40, 0x80, 0xff})
 
+	// Draw the image with 'Source Alpha' composite mode (default).
 	op := &ebiten.DrawImageOptions{}
 	op.GeoM.Translate(ox, oy)
 	screen.DrawImage(ebitenImage, op)
 
+	// Draw the image with 'Lighter (a.k.a Additive)' composite mode.
 	op = &ebiten.DrawImageOptions{}
 	w, _ := ebitenImage.Size()
 	op.GeoM.Translate(ox+float64(w), oy)

examples/alphablending/main.go

@@ -45,10 +45,14 @@ func update(screen *ebiten.Image) error {
 	case 240 < count:
 		diff = float64(480-count) * 0.2
 	}
+
 	if ebiten.IsRunningSlowly() {
 		return nil
 	}
+
 	screen.Fill(color.NRGBA{0x00, 0x00, 0x80, 0xff})
+
+	// Draw 100 Ebitens
 	op := &ebiten.DrawImageOptions{}
 	op.ColorM.Scale(1.0, 1.0, 1.0, 0.5)
 	for i := 0; i < 10*10; i++ {

examples/audioinfiniteloop/main.go

@@ -47,22 +47,30 @@ var player *audio.Player
 
 func update(screen *ebiten.Image) error {
 	if player == nil {
+		// Open a wav file.
+		// wavF is *os.File, which is an io.ReadCloser and io.Seeker.
 		wavF, err := ebitenutil.OpenFile(filepath.Join("_resources", "audio", "jab.wav"))
 		if err != nil {
 			return err
 		}
 
+		// Decode the wav file.
+		// wavS is a decoded io.ReadCloser and io.Seeker.
 		wavS, err := wav.Decode(audioContext, wavF)
 		if err != nil {
 			return err
 		}
 
+		// Create an infinite loop stream from the decoded bytes.
+		// s is still an io.ReadCloser and io.Seeker.
 		s := audio.NewInfiniteLoop(wavS, wavS.Length())
 
 		player, err = audio.NewPlayer(audioContext, s)
 		if err != nil {
 			return err
 		}
+
+		// Play the infinite-length stream. This never ends.
 		player.Play()
 	}