Smart margins should apply per-display

[edward-jones-tracebit]

Describe the bug
Smart margins are applied based on the number of currently visible tiled windows across all displays. This means that if e.g. there is one (non-fullscreen) window on each of two displays, they will both have margins. Then switching one display to an empty space will cause the window on the other display to resize as its margins are removed.

Applications:
Not application-specific

To Reproduce
Open one window on a display, and at least one window on another.

Expected behavior
A single window on a display should have no margins when smart margins are enabled.

Versions:

• macOS: 15.6.1
• Amethyst: 0.24.0

[ianyh]

Interesting point, yeah. This is probably worth changing.