Loading indicator with ability to ACTUALLY indicate when load of EL has finished

[csuwldcat]

Many plugins exist for displaying a preloading gif for element contents that haven't fully finished loading on the page. There is one for Prototype lib that is pretty weaksauce in that it is statically set to a predefined ms timer length. If there existed a simple one-line instantiation to add a REAL dynamic preloader for elements that devs could call (with ref to a gif image of choosing of course) for such elements it would really step up the presentation layer of applications and be one more awesome addition to the plugin set :)