The #delay_body{} element allows you to quickly render the page and leave a placeholder for content that might be slower to load. This is particularly useful for content that is either slow to process such as querying some external API, or for greater content that might be cached, but you want user-specific content to show within the cache.

This will require a delay_body_event(Tag) function to be defined in your page module (or the delegate module if so specified) and it must handle the tag specified with the #delay_body element.

The return value of this function will be placed into the content's page.

All these delay_body_event calls are performed in serial, and retrieved via postback. If the content to retrieve is expected to be very slow, or you simply need to ensure all results are retrieved or processed in parallel then the content is recommended to be loaded with Continuations, as each continuation will update when the content is available, rather than being handled in serial.