.go

package main

import (
	"math"
	"time"

	"github.com/faiface/pixel"
	"github.com/faiface/pixel/audio"
	"github.com/faiface/pixel/audio/speaker"
	"github.com/faiface/pixel/pixelgl"
)

func sin(freq, volume float64) audio.Streamer {
	t := 0.0
	dt := 1.0 / audio.SampleRate
	return audio.StreamerFunc(func(samples [][2]float64) (n int, ok bool) {
		for i := range samples {
			val := math.Sin(math.Pi*freq*t) * volume
			samples[i][0] = val
			samples[i][1] = val
			t += dt
		}
		return len(samples), true
	})
}

func run() {
	speaker.Init(time.Second / 25)

	cfg := pixelgl.WindowConfig{
		Title:  "Piano",
		Bounds: pixel.R(0, 0, 800, 600),
		VSync:  true,
	}
	win, err := pixelgl.NewWindow(cfg)
	if err != nil {
		panic(err)
	}

	keysCtrl := map[pixelgl.Button]*audio.Ctrl{
		pixelgl.KeyA: &audio.Ctrl{Streamer: sin(523.25, 0.3)},
		pixelgl.KeyS: &audio.Ctrl{Streamer: sin(554.37, 0.3)},
		pixelgl.KeyD: &audio.Ctrl{Streamer: sin(587.33, 0.3)},
		pixelgl.KeyF: &audio.Ctrl{Streamer: sin(622.25, 0.3)},
		pixelgl.KeyG: &audio.Ctrl{Streamer: sin(659.25, 0.3)},
		pixelgl.KeyH: &audio.Ctrl{Streamer: sin(698.46, 0.3)},
		pixelgl.KeyJ: &audio.Ctrl{Streamer: sin(739.99, 0.3)},
		pixelgl.KeyK: &audio.Ctrl{Streamer: sin(783.99, 0.3)},
		pixelgl.KeyL: &audio.Ctrl{Streamer: sin(830.61, 0.3)},
	}

	for _, ctrl := range keysCtrl {
		speaker.Play(ctrl)
	}

	for !win.Closed() {
		for key, ctrl := range keysCtrl {
			speaker.Lock()
			ctrl.Paused = !win.Pressed(key)
			speaker.Unlock()
		}
		win.Update()
	}
}

func main() {
	pixelgl.Run(run)
}