Refactor autohide

[wash2]

It doesn't seem to be getting notified of the overlaps even when I add the global to cosmic-comp. I'll have to look more into the cosmic-comp implementation.

[Drakulix]

Looks good, though we probably would want to merge this after the cosmic-comp patches to not temporarily regress the autohide behaviour.

[git-f0x]

Not sure if it's intended, but the panels can no longer draw outside their revealed-state container, so they just get cropped during the autohide animation (most visible with floating and rounded panels).
Also, after opening many apps and then closing them, the center segment applet positions seem to remain at the offset from the center caused by the many app icons (the segment position isn't reset).

Edit: The latter doesn't seem to be a regression, since I can also reproduce it on the current build (not sure if it's related to overflow).

[wash2]

Not sure if it's intended, but the panels can no longer draw outside their revealed-state container, so they just get cropped during the autohide animation (most visible with floating and rounded panels).

I'm not sure I follow. Do you have a screenshot of the issue?

[git-f0x]

Here's a screenshot during the dock hide animation:

Not sure if I'm doing something wrong (using both patched cosmic-comp and cosmic-panel), but the overlap autohide behavior sometimes stops working, and behaves the same as before.
Edit: A reliable way to reproduce it seems to be:

1. Launch the session with a non-autohiding panel (no dock)
2. Enable the dock, place it on the same side as the panel, and enable autohide for the dock
3. Enable autohide for the panel

Afterwards, the panel has the old autohide behavior, even when the dock is disabled, until the session is restarted (restarting the panel by e.g. changing size isn't enough).
Also, the Dock in general has the old autohide behavior when enabled in the current session, regardless of placement, so that might be related.