add demo "colorphase" application

cmd/demo/colorphase/main.go

@@ -0,0 +1,13 @@
+// Copyright 2018 Dan Jacques. All rights reserved.
+// Use of this source code is governed under the MIT License
+// that can be found in the LICENSE file.
+
+package main
+
+import (
+	"github.com/danjacques/gopushpixels/demo/colorphase"
+)
+
+func main() {
+	colorphase.Main()
+}

demo/colorphase/app.go

@@ -0,0 +1,120 @@
+// Copyright 2018 Dan Jacques. All rights reserved.
+// Use of this source code is governed under the MIT License
+// that can be found in the LICENSE file.
+
+package colorphase
+
+import (
+	"context"
+	"flag"
+	"log"
+	"time"
+
+	"github.com/danjacques/gopushpixels/device"
+	"github.com/danjacques/gopushpixels/discovery"
+	"github.com/danjacques/gopushpixels/pixel"
+)
+
+var (
+	fps = flag.Int("fps", 30, "FPS that colors will be cycled.")
+)
+
+// Main is the main entry point.
+func Main() {
+	flag.Parse()
+
+	// Calculate sleep interval from FPS.
+	sleepInterval := time.Second / (time.Second * time.Duration(*fps))
+
+	// Start discovery.
+	var l discovery.Listener
+	conn, err := discovery.DefaultListenerConn().ListenMulticastUDP4()
+	if err != nil {
+		log.Fatalf("Couldn't listen for discovery packets: %s", err)
+	}
+	defer conn.Close()
+	if err := l.Start(conn); err != nil {
+		log.Fatalf("Couldn't start discovery listener: %s", err)
+	}
+
+	var reg discovery.Registry
+	c := context.Background()
+	for {
+		dh, err := l.Accept(c)
+		if err != nil {
+			log.Fatalf("Error listening for discovery packets: %s", err)
+		}
+		if d, isNew := reg.Observe(dh); isNew {
+			go cycleColors(d, sleepInterval)
+		}
+	}
+}
+
+func cycleColors(d device.D, sleepInterval time.Duration) {
+	log.Printf("Cycling on device: %s", d.ID())
+
+	sender, err := d.Sender()
+	if err != nil {
+		log.Printf("Could't create sender for device %q: %s", d.ID(), err)
+		return
+	}
+	defer sender.Close()
+
+	// Create a mutable state for the device.
+	var m device.Mutable
+	m.Initialize(d.DiscoveryHeaders())
+
+	var c cycler
+	for {
+		// Cycle colors.
+		//
+		// First, shift all pixels towards the end.
+		next := c.Next()
+		for s := 0; s < m.NumStrips(); s++ {
+			for i := m.PixelsPerStrip() - 1; i > 0; i-- {
+				m.SetPixel(s, i, m.GetPixel(s, i-1))
+			}
+			m.SetPixel(s, 0, next)
+		}
+
+		// Send any update packets.
+		if pkt := m.SyncPacket(); pkt != nil {
+			if err := sender.SendPacket(pkt); err != nil {
+				log.Printf("Couldn't send packet to device %q: %s", d.ID(), err)
+				return
+			}
+		}
+
+		time.Sleep(sleepInterval)
+	}
+}
+
+type cycler struct {
+	r, g, b int
+	offset  int
+}
+
+func (c *cycler) Next() (p pixel.P) {
+	var v *int
+	var pos *byte
+	switch c.offset {
+	case 0:
+		v, pos = &c.r, &p.Red
+	case 1:
+		v, pos = &c.g, &p.Green
+	case 2:
+		v, pos = &c.b, &p.Blue
+	}
+
+	*v++
+	switch {
+	case *v > 0x1FF:
+		*v, *pos = 0, 0
+		c.offset = ((c.offset + 1) % 3)
+	case *v > 0xFF:
+		*pos = 0xFF - byte(*v)
+	default:
+		*pos = byte(*v)
+	}
+	return
+}