Extensibility via Events or "hooks"/callbacks

Goal

To let other modules do actions before/after RefreshLess replaces regions.

Example

• Animation: Animates a region (old content fades out, new content fades in). Or even do "shared-element animations". Similar effects was showcased in this Drupalcon talk.
• Progress bar
• Other Drupal behaviours that needs to be re-attached. (Already exists, but could be generalised into one system)

Proposal

• Add two custom events RefreshLessBeforeRegionUpdate and RefreshLessAfterRegionUpdate.

Things that aren't clear

• Blocking vs. non-blocking. In the case of animation we what to work in a blocking way (let animation finish before replacing content). That's probably not going to work with events.

See also

http://youtube.github.io/spfjs/documentation/events/
https://vuejs.org/guide/transitions.html#Transition-Flow-Details