examples: Add comments

examples/typewriter/main.go

@@ -31,14 +31,23 @@ var (
 )
 
 func update(screen *ebiten.Image) error {
+	// Add a string from InputChars, that returns string input by users.
+	// Note that InputChars result changes every frame, so you need to call this
+	// every frame.
 	text += string(ebiten.InputChars())
+
+	// Adjust the string to be at most 10 lines.
 	ss := strings.Split(text, "\n")
 	if len(ss) > 10 {
 		text = strings.Join(ss[len(ss)-10:], "\n")
 	}
+
+	// If the enter key is pressed, add a line break.
 	if ebiten.IsKeyPressed(ebiten.KeyEnter) && !strings.HasSuffix(text, "\n") {
 		text += "\n"
 	}
+
+	// If the backspace key is pressed, remove one character.
 	bsPressed := ebiten.IsKeyPressed(ebiten.KeyBackspace)
 	if !bsPrevPressed && bsPressed {
 		if len(text) >= 1 {
@@ -53,6 +62,7 @@ func update(screen *ebiten.Image) error {
 		return nil
 	}
 
+	// Blink the cursor.
 	t := text
 	if counter%60 < 30 {
 		t += "_"

examples/wav/main.go

@@ -38,21 +38,27 @@ var (
 
 func init() {
 	var err error
+	// Initialize audio context.
 	audioContext, err = audio.NewContext(sampleRate)
 	if err != nil {
 		log.Fatal(err)
 	}
 
+	// Open a wav file.
+	// Note that f.Close() should not be closed in this init function
+	// since audio.Player manages stream state.
 	f, err := ebitenutil.OpenFile("_resources/audio/jab.wav")
 	if err != nil {
 		log.Fatal(err)
 	}
 
+	// Decode wav-formatted data and retrieve decoded PCM stream.
 	d, err := wav.Decode(audioContext, f)
 	if err != nil {
 		log.Fatal(err)
 	}
 
+	// Create an audio.Player that has one stream.
 	audioPlayer, err = audio.NewPlayer(audioContext, d)
 	if err != nil {
 		log.Fatal(err)
@@ -61,6 +67,8 @@ func init() {
 
 func update(screen *ebiten.Image) error {
 	if ebiten.IsKeyPressed(ebiten.KeyP) && !audioPlayer.IsPlaying() {
+		// As audioPlayer has one stream and remembers the playing position,
+		// rewinding is needed before playing when reusing audioPlayer.
 		audioPlayer.Rewind()
 		audioPlayer.Play()
 	}