Quick knock-up of scrolling chevron effect

bfr_chevron.go

package main
import "fmt"
import "time"
import "github.com/mgutz/ansi"

const ledsAcross = 12                  // rows of display
const ledsDown = 16                // columns of display (was 8)
const ledTotal = 12*16

type Colour struct {
    r, g, b int
}
var LEDs[ledTotal] Colour

// define a few colour shortcuts:
var black = Colour{0,0,0}
var red = Colour{255,0,0}
var blue = Colour{0,0,255}
var green = Colour{0,255,0}
var yellow = Colour{200,200,0}




func main() {
    fmt.Println("total LEDs:", ledTotal)
    blankLEDs()
    setLED(0, 0, red)
    setLED(ledsAcross-1, 0, green)
    setLED(0, ledsDown-1, blue)
    setLED(ledsAcross-1, ledsDown-1, yellow)
    printLEDs()
    time.Sleep(1000 * time.Millisecond)

    chevronDemo(1)
    chevronDemo(-1)
}

// Note that this clips coordinates to allowed region
func setLED(x,y int, c Colour) {
    if x >= 0 && x < ledsAcross && y >= 0 && y < ledsDown {
        LEDs[x + y*ledsAcross] = c
    }
}

func blankLEDs() {
    for i := range LEDs {
        LEDs[i] = black
    }
}

func chevronDemo(dir int) {
    var ystart, yend int
    if (dir > 0) {
        ystart = ledsDown+10
        yend = -10
    } else {
        ystart = 1
        yend = ledsDown+14
    }

    for i:=ystart; i != yend; i+=-1*dir {
        time.Sleep(150 * time.Millisecond)
        blankLEDs()
        chevron(i, dir, red)
        chevron(i - 3, dir, yellow)
        chevron(i - 4, dir, yellow)
        chevron(i - 7, dir, green)
        printLEDs()
    }
}

// direction should be -1 or 1
func chevron(y, direction int, c Colour) {
    var middleX int = ledsAcross/2
    offset := 0
    for y >= -5 && y < ledsDown+5 && offset < middleX {
        setLED(middleX-offset, y, c)
        setLED(middleX+offset, y, c)
        y += direction
        offset ++
    }
}


// A hacky way to display output to terminal while testing:
var ansiMap = map[Colour]string {
    red:    ansi.ColorCode("red+h:red+h"),
    green:  ansi.ColorCode("green+h:green+h"),
    blue:   ansi.ColorCode("blue+h:blue+h"),
    yellow: ansi.ColorCode("yellow+h:yellow+h"),
    black:  ansi.ColorCode("gray:black"),
}

var ansiReset = ansi.ColorCode("reset")

func printLEDs() {
    // clear screen:
    fmt.Print("\033[2J")

    for y := 0; y < ledsDown; y++ {
        for x := 0; x < ledsAcross; x++ {
            idx := x + y*ledsAcross
            fmt.Print(" ")
            fmt.Print(ansiMap[LEDs[idx]], "*", ansiReset)
        }
        fmt.Println()
    }

}