Proposal: per-display inner gaps in General settings

[1Pio]

Why this feels missing

OmniWM already lets outer margins follow each display, while inner gaps remain global. That makes the General spacing model feel incomplete on mixed-display setups. A gap that feels balanced on a large external display can feel oversized on a built-in panel, even though both belong to the same workspace configuration.

Proposed interaction

Extend the existing Configuration Scope control in General so it governs both Layout > Inner Gaps and Outer Margins:

• Global Defaults keeps the current behavior.
• Selecting a display exposes an overridable inner gap alongside its existing outer-margin overrides.
• A missing display value inherits the global value.
• 0 remains a valid explicit override.
• Resetting the final value removes the empty monitor override record.

This reuses the existing monitorGapOverrides model instead of adding another settings path.

Layout behavior

• Niri resolves the effective inner gap from the display assigned to the workspace being laid out.
• Dwindle uses that same effective General gap when Use Global Gaps is enabled.
• A Dwindle-specific gap keeps its existing precedence when Use Global Gaps is disabled.

Compatibility and IPC

The persisted innerGap value would be optional, so existing configurations need no migration and continue inheriting the current global gap. The display IPC query could expose the resolved value through an optional inner-gap field. Gap changes would also emit the existing display-changed event so subscribers can refresh resolved display values.

Implementation status

I have a clean, standalone implementation against current main (v0.5.6) ready to submit. It passes the full local test suite and has been validated with distinct gaps on two physical displays in both Niri and Dwindle. I have opened the working implementation as draft PR #477 so it is available for inspection while the direction is discussed. I am also happy to adjust the interaction or IPC scope before marking it ready for review.

Questions

1. Does one shared General scope selector feel like the right interaction for inner gaps and outer margins?
2. Should the optional inner-gap display query field ship with the settings change, or would you prefer it separately?
3. Now that “global” can mean either the global default or the General settings family, should the Dwindle label eventually become Use General Gaps? The proposed implementation keeps the current wording.

[BarutSRB]

I'll take a look tomorrow and answer your questions as it's my free day but thank you for the PR ♥️♥️♥️