Add open-sticky window rule for sticky floating windows across workspaces

[AtefR]

Summary

• Add open-sticky window rule to keep a window visible across all workspaces on the current output
• Add toggle-window-sticky action to toggle stickiness via keybinds
• Add match is-sticky=true rule for matching sticky windows
• Expose is_sticky in IPC window info
• Treat sticky windows as floating for sizing/positioning rules
• Update docs and hotkey overlay

Testing

• cargo test -p niri
• Manual test: open a PiP window with open-sticky true, toggle stickiness via keybind, and verify it stays visible across workspace switches

Notes

• open-sticky implies open-floating
• Developed/implemented with assistance from OpenAI Codex; all changes reviewed and tested by me

[HigherOrderLogic]

From a quick skim, this looks like a less-featureful PR compared to #3205, which even supports pinning non-floating window.

[AtefR]

From a quick skim, this looks like a less-featureful PR compared to #3205, which even supports pinning non-floating window

the PR actually also allows non picture on picture or non-floating windows to be sticky too, my main objective was to be able to make a picture on picture window or a terminal sticky, I tested both and they're working flawlessly.

I also added the action toggle-window-sticky to allow binding it and is-sticky window matcher

[claymorwan]

quick question, can sticky windows go above fullscreen windows ?

[Sempyos]

nothing can go above fullscreen windows

[claymorwan]

nothing can go above fullscreen windows

dam really ? iS there no way at all to have an additional layer above fullscreen window for that ? I do know that wayland layers can do it but ik that it's not exactly the same thing
It'd be really useful to watch videos while playing games for example

[Sempyos]

You can have windows above full width columns, maximized-to-edges, but not fullscreen windows

[YaLTeR]

A proper sticky impl will go above fullscreen windows. The sticky impl on top of the regular floating layer can't do that

[AtefR]

I updated the pull request to show the sticky windows above the fullscreen windows/video players, unsticking a window will make it go back to it's original workspace/position if the position is unavailable it'll go to the nearest position in same workspace.

• Sticky windows now render above fullscreen windows and receive input correctly in that z-order.
• window_under/resize hit-testing prioritizes sticky windows consistently.
• On toggle-window-sticky off, windows restore to their original context:
  • tiling windows return to tiling (original column/position when possible),
  • floating windows return to floating.
• Restore targets the original workspace, with safe fallback when exact placement is unavailable.
• Added regression tests for sticky-over-fullscreen hit behavior and sticky restore behavior (column + workspace).