code: function _runEventCallback($canvas, layer, eventType, callbacks, arg) {
  	// Prevent callback from firing recursively
  	if (callbacks[eventType] && layer._running && !layer._running[eventType]) {
  		// Signify the start of callback execution for this event
  		layer._running[eventType] = true;
  		// Run event callback with the given arguments
  		callbacks[eventType].call($canvas[0], layer, arg);
  		// Signify the end of callback execution for this event
  		layer._running[eventType] = false;
  	}
  }
docs: Run the given event callback with the given arguments