Conditional per-corner rounding (square inner corners when windows touch)

[Valognolo09]

Summary

Currently, Hyprland applies a single uniform corner radius per window (decoration:rounding or via windowrulev2 rounding). This means all four corners of a window are always rounded or square.

It would be very useful to support conditional per-corner rounding, so that only the outer corners of tiled windows are rounded, while the inner corners (where two windows touch) remain square.

Motivation / Use Case

• In tiling layouts, when two windows touch, their rounded corners create a visual "hole" that makes the desktop visible. This creates a seam that many users find aesthetically unpleasant.

• Users often want rounded outer edges (for floating windows, outer borders of tiled layouts, etc.), while keeping clean square inner corners where windows meet.

• This is a common request in other compositors / DEs with rounded corner support (GNOME extensions, kwin scripts, etc.), and it improves visual consistency.

Proposed Solution

Add support for per-corner rounding (e.g. rounding_top-left, rounding_top-right, etc.) at the window decoration level.

Optionally, add a config option like:

decoration {
    rounding_outer = 12   # applied to outer corners
    rounding_inner = 0    # applied to touching corners
}

The compositor could detect when two windows are adjacent (within a tiling layout) and automatically apply rounding_inner.

Alternatively, expose per-corner properties (via setprop or windowrulev2) so that scripts or plugins can set them based on adjacency logic.

Alternatives Considered

Scripting via IPC + setprop rounding=0 works today, but only at the whole-window level. It is not possible to disable rounding on only the touching corners while keeping outer corners rounded.

Increasing gaps_in hides the problem somewhat, but gaps change the layout and don’t truly solve the inner-corner rounding issue.

### Benefits

• Cleaner look in tiled layouts with rounded corners.

• More customization / theming flexibility.

• Matches user expectations from other compositors and DEs.

[matdave]

I like the idea of having different rules for "inner" and "outer" corners, but I think the title is a bit confusing. I actually want north, east, south, and west type rounding options as well. E.g. top two corners are round and bottom corners are straight, or vice versa.