In options, support functions wherever selectors can be used

It would be great if Widget had a helper function like this (but better named):

_selectorOrFunction: function(arg) {
  return $.isFunction(arg) ? arg.call(this.element) : $(arg);
}

This function, when used to process an option, would allow a user to pass in a value that's a:

• CSS selector string
• DOM element
• Array of DOM elements
• jQuery object
• Function that returns a jQuery object.

I used this code in a recent project, and it really helped. I'd even go so far as to say that anywhere a selector string (or any of the other preceding bullet point items) can currently be used, this processing could automatically be applied.

Of course, if a selector string is used, it doesn't do a relative find by default, but the tradeoff is that it offers a lot more flexibility. If that were a problem:

_selectorOrFunction: function(arg) {
  return $.isFunction(arg) ? arg.call(this.element) : this.element.find(arg);
}

Maybe this would be the most consistent / backwards compatible with jQuery UI:

_selectorOrFunction: function(arg) {
  return $.isFunction(arg) ? arg.call(this) : this.element.find(arg);
}

Either way, those are my 2¢. Thanks.