Improve Structure of Callback for focussing in Video.js module
Steps to reproduce
As indicated by Markus Ruepp in the review of PR817:
"This is callback is really long. Should be grouped in functions, that have a explaining title."
Engage.on(plugin.events.focusVideo.getName(), function (display)) in modules/matterhorn-engage-theodul-plugin-video-videojs/src/main/resources/static/main.js
This needs to be improved.