Request applets to hide when the panel is clicked
This is a more technically complex alternative to !3815 (closed) which creates a new API to ask applets and dialogs to be hidden. Applets can choose to do whatever when requested to be hidden; by default they'll ask dialogs to be hidden. The system tray, which is custom, will do the same. When dialogs are requested to be hidden, they'll hide only if they're not pinned.
This requires MRs:
Edited by Niccolò Venerandi