leapjs/lib/pipeline.js

var Pipeline = module.exports = function (controller) {
  this.steps = [];
  this.controller = controller;
}

Pipeline.prototype.addStep = function (step) {
  this.steps.push(step);
}

Pipeline.prototype.run = function (frame) {
  var stepsLength = this.steps.length;
  for (var i = 0; i != stepsLength; i++) {
    if (!frame) break;
    frame = this.steps[i](frame);
  }
  return frame;
}

Pipeline.prototype.removeStep = function(step){
  var index = this.steps.indexOf(step);
  if (index === -1) throw "Step not found in pipeline";
  this.steps.splice(index, 1);
}

/*
 * Wraps a plugin callback method in method which can be run inside the pipeline.
 * This wrapper method loops the callback over objects within the frame as is appropriate,
 * calling the callback for each in turn.
 *
 * @method createStepFunction
 * @memberOf Leap.Controller.prototype
 * @param {Controller} The controller on which the callback is called.
 * @param {String} type What frame object the callback is run for and receives.
 *       Can be one of 'frame', 'finger', 'hand', 'pointable', 'tool'
 * @param {function} callback The method which will be run inside the pipeline loop.  Receives one argument, such as a hand.
 * @private
 */
Pipeline.prototype.addWrappedStep = function (type, callback) {
  var controller = this.controller,
    step = function (frame) {
      var dependencies, i, len;
      dependencies = (type == 'frame') ? [frame] : (frame[type + 's'] || []);

      for (i = 0, len = dependencies.length; i < len; i++) {
        callback.call(controller, dependencies[i]);
      }

      return frame;
    };

  this.addStep(step);
  return step;
};