set-icon.js

var x11 = require('x11');
var PNG = require('png-js');
var bl = require('bl');

require('child_process').exec('locate png | grep 48').stdout.pipe(bl(function(err, files) {

  var pngNames = files.toString().split('\n');
  var pngIndex = 0;

  x11.createClient(function(err, display) {
    var X = display.client;
    var root = display.screen[0].root;
    var wid = X.AllocID();
    X.CreateWindow(wid, root, 10, 10, 300, 300);
    X.MapWindow(wid);
 
    function nextPng() {
      pngIndex++;
      if (pngIndex >= pngNames.length)
        pngIndex = 0;
      var pngData = require('fs').readFileSync(pngNames[pngIndex]);
      var png = new PNG(pngData);
      png.decode(function(pixels) {
        var icon = new Buffer(pixels.length + 8);
        icon.writeUInt32LE(png.width, 0);
        icon.writeUInt32LE(png.height, 4);
        for (var i = 0; i < pixels.length; i+= 4) {
          // pixels in BGRA, icon needs to be ARGB (prefixed with 2 bytes w,h)
          icon[i + 8] = pixels[i + 2];
          icon[i + 9] = pixels[i + 1];
          icon[i + 10] = pixels[i + 0];
          icon[i + 11] = pixels[i + 3];
        }
        X.InternAtom(false, '_NET_WM_ICON', function(err, wmIconAtom) {
          X.InternAtom(false, '_NET_WM_WINDOW_TYPE_NORMAL', function(err, wmTypeNormal) {
            X.InternAtom(false, '_NET_WM_WINDOW_TYPE', function(err, wmType) {
               X.ChangeProperty(0, wid, wmIconAtom, X.atoms.CARDINAL, 32, icon);
               var prop = new Buffer(4);
               prop.writeUInt32LE(wmTypeNormal, 0);
               X.ChangeProperty(0, wid, wmType, X.atoms.ATOM, 32, prop);
            });
          });
        });
      });
    }
    setInterval(nextPng, 2000);
  });
})); // end of pipe(bl(function() {}));