From 9ed6c308d96eb36db64abfc3a07e7a4ffae382bb Mon Sep 17 00:00:00 2001
From: Dan Jacques <danjacques@gmail.com>
Date: Thu, 19 Apr 2018 00:04:36 -0400
Subject: [PATCH] more colors, docs

---
 demo/colorphase/app.go | 57 +++++++++++++++++++++++++++---------------
 1 file changed, 37 insertions(+), 20 deletions(-)

diff --git a/demo/colorphase/app.go b/demo/colorphase/app.go
index d6c65ab..3d634e9 100644
--- a/demo/colorphase/app.go
+++ b/demo/colorphase/app.go
@@ -2,6 +2,14 @@
 // Use of this source code is governed under the MIT License
 // that can be found in the LICENSE file.
 
+// Package colorphase defines the logic for the "colorphase" demo app.
+//
+// This app listens for any PixelPusher devices and broadcasts a color cycling
+// animation to each, fading in and out of intensity of various colors.
+//
+// This demonstrates how to listen for connections, register them with a
+// discovery Registry, generate pixel state mutations, and send those mutations
+// to the target device.
 package colorphase
 
 import (
@@ -89,32 +97,41 @@ func cycleColors(d device.D, sleepInterval time.Duration) {
 	}
 }
 
+// 101 110 011 100 010 001
+const cyclerMask = uint(0x2E711)
+
 type cycler struct {
-	r, g, b int
-	offset  int
+	v    int
+	mask uint
 }
 
 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
+	if c.mask == 0 {
+		c.mask = cyclerMask
+	}
+
+	// Select our intensity. >0xFF fades downwards towards 0.
+	v := c.v
+	if v > 0xFF {
+		v = 0xFF - v
+	}
+
+	// Set masked colors.
+	if c.mask&0x01 != 0 {
+		p.Red = byte(v)
+	}
+	if c.mask&0x02 != 0 {
+		p.Green = byte(v)
+	}
+	if c.mask&0x04 != 0 {
+		p.Blue = byte(v)
 	}
 
-	*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)
+	// Cycle.
+	c.v++
+	if c.v > 0x1FF {
+		c.v = 0
+		c.mask >>= 3
 	}
 	return
 }