Another jjs demo - use javafx libraries to display a line graph of values read from stdin

plotstdin.js

/*
  stdinplot.js

  demo of jss usage - reads numbers from stdin and displays a dynamically
  scaling line graph. ignores non-numerical values.

  example:

    $ jjs -fx stdinplot.js < sin_values.txt
*/

var Application = javafx.application.Application;
var Group = javafx.scene.Group;
var Scene = javafx.scene.Scene;
var Canvas = javafx.scene.canvas.Canvas;
var GraphicsContext = javafx.scene.canvas.GraphicsContext;
var PixelWriter = javafx.scene.image.PixelWriter;
var Color = javafx.scene.paint.Color;
var AbstractAnimationTimer = javafx.animation.AnimationTimer;
var AnimationTimer = Java.extend(AbstractAnimationTimer);
var LinkedList = java.util.LinkedList;

function CircularBuffer(size) {
    this.size = size;
    this.queue = new LinkedList();
}

CircularBuffer.prototype.add = function(e) {
    if (this.size == this.queue.size()) {
	this.queue.remove();
    }

    this.queue.add(e);
}

CircularBuffer.prototype.any = function() {
    return this.queue.size() > 0;
}

CircularBuffer.prototype.toArray = function() {
    return this.queue.toArray();
}

function plot(gc, height, values) {
    var pixelWriter = gc.getPixelWriter();

    var max = Math.max.apply(null, values);
    var min = Math.min.apply(null, values);
    var range = Math.abs(max) + Math.abs(min);
    
    for (var x = 0; x < values.length; x++) {
	var y_pre = values[x];

	if (min < 0) {
	    y_pre -= min;
	}
	
	var y = ((y_pre / range) * height);

	pixelWriter.setColor(x, y, Color.BLACK);
    }
}

function start(primaryStage) {
    primaryStage.title = "stdinplot";

    var width = 300;
    var height = 100;
    
    var root = new Group();
    var canvas = new Canvas(width, height);
    var graphicsContext = canvas.getGraphicsContext2D();

    root.getChildren().add(canvas);
    primaryStage.scene = new Scene(root, width, height);
    primaryStage.show();

    var graphData = new CircularBuffer(width);
    
    var stdinReader =  new java.io.BufferedReader(
	new java.io.InputStreamReader(java.lang.System.in)
    );

    new AnimationTimer() {
	handle: function handle(now) {
	    var l = stdinReader.readLine();
	    var n = parseFloat(l);

	    if (! isNaN(n)) {
		graphData.add(n);
		
	    }
	    
	    graphicsContext.clearRect(0, 0, width, height);	    

	    plot(graphicsContext, height, graphData.toArray());
	}
    }.start();
}

sin_values.txt

generated by the following python:

import math

def dumpsin(lim):
    for r in [ math.radians(x) for x in range(lim) ]:
        print math.sin(r)

dumpsin(1000)

0.0
0.0174524064373
0.0348994967025
0.0523359562429
0.0697564737441
0.0871557427477
0.104528463268
0.121869343405
0.13917310096
0.15643446504
0.173648177667
0.190808995377
0.207911690818
0.224951054344
0.2419218956
0.258819045103
0.275637355817
0.292371704723
0.309016994375
0.325568154457
0.342020143326
0.358367949545
0.374606593416
0.390731128489
0.406736643076
0.422618261741
0.438371146789
0.45399049974
0.469471562786
0.484809620246
0.5
0.51503807491
0.529919264233
0.544639035015
0.559192903471
0.573576436351
0.587785252292
0.601815023152
0.615661475326
0.62932039105
0.642787609687
0.656059028991
0.669130606359
0.681998360062
0.694658370459
0.707106781187
0.719339800339
0.731353701619
0.743144825477
0.754709580223
0.766044443119
0.777145961457
0.788010753607
0.798635510047
0.809016994375
0.819152044289
0.829037572555
0.838670567945
0.848048096156
0.857167300702
0.866025403784
0.874619707139
0.882947592859
0.891006524188
0.898794046299
0.906307787037
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