Asynchronous Widgets allows you to have any registered widget on your WordPress.org-powered site be loaded asynchronously via an AJAX call.
The plugin replaces the callback a widget has registered with the WordPress.org engine
with one of its own. When that callback is invoked, instead of outputting the widget content,
it outputs a customized chunk of HTML. That chunk contains information that will be parsed
injects on the page. This will result in an AJAX call to the server delivering the actual
widget content (one call for each widget).
The HTML also contains a
shouldn't be enabled.
This mechanism is set to run on the
wp_head action hook, at priority 2^17.
Good question. I don't know. It seemed like a froody idea.
I'm anxious to see whether it can have any other uses, though. I am also aware that the purpose stated above isn't entirely uncontroversial.
In terms of performance, this plugin will most definitely increase your pages' delivery speed (in proportion to how many and how "heavy" widgets you have), and probably not increase your server's load average significantly.
Yet another good question. I'm not sure, but I'm trusting you to help me find out.
I've tested it successfully with a very few custom widgets. But there might be problems, due to one significant change this plugin introduces. Namely, the fact that it detaches the widget display callback from the rest of the WordPress loop (the widget callback is invoked asynchronously, thus outside of the loop). If a custom widget makes some non-persistent changes somewhere in the loop AND relies on those changes in its display callback, there MAY be compatibility problems.
One specific instance I've encountered was with the WP Widget Cache plugin (http://wordpress.org/extend/plugins/wp-widget-cache/) (which doesn't work with WordPress 2.9, anyway). I had to integrate a little hack (essentially, making the changes WidgetCache performs persistent) to ensure compatibility with it.
Other such conficts might arise. If you encounter one, please provide some feedback.
This plugin has been developped with PHP version 5.3.1.
Each of these take one argument: the "widget settings" array as would normally be passed to the widget display callback (they'll be invoked once for each widget).
If using the filter, you MUST return that value, lest you want to supress the widget's output.
No. Go buy yourself something nice.