add generic waybar auto hide/reveal via IPC

[wegel]

Summary

Adds generic edge-based Waybar auto hide/reveal, driven by compositor IPC state.

It includes:

• pointer reveal state in IPC (state.pointer.reveal_hover, state.pointer.reveal_edge)
• compositor-side pointer edge tracking (top/bottom/left/right)
• a reusable contrib helper script at contrib/waybar/vwl-reveal
• docs updates for IPC and Waybar integration

Motivation

I got a new laptop with an OLED screen that's potentially prone to burn in damage. In order to mitigate this, it seems like a good idea to auto hide/reveal waybar on mouse hover where waybar /should/ be.

What Changed

• Added IPC snapshot fields:
  • state.pointer.output
  • state.pointer.reveal_hover
  • state.pointer.reveal_edge (top|bottom|left|right|null)
• Added compositor logic to compute reveal edge from pointer position with hysteresis.
• Added contrib/waybar/vwl-reveal:
  • subscribes to vwlctl subscribe
  • supports all Waybar positions (top|bottom|left|right)
  • toggles Waybar visibility via SIGUSR1
• Added contrib/docs guidance for setup.

Known Bug

On empty workspaces, hide/show can fail to repaint immediately (bar ghosting/stale pixels may remain until later damage). Will try to fix later.

[wilriker]

I have no vote on this one as that is a feature I am not going to use.

But maybe I will at least try it tonight to see if it works on my machine if that is of help to you in this case.

[wegel]

I have no vote on this one as that is a feature I am not going to use.

But maybe I will at least try it tonight to see if it works on my machine if that is of help to you in this case.

Would be helpful, but no pressure at all, only if you have the time and feel like it. Thanks.

[wilriker]

I guess tonight I can have look at it.

Just a heads-up: I will be away for the next couple of days so I might not respond a lot/delayed/at all. ;-)

[wilriker]

I won't make it tonight. Don't expect anything meaningful from me before early next week. ;-)