Circuit-Controlled Quality Filters

This mod allows you to set generic quality filters (no specific item selected) on inserters, splitters, and loaders using circuits.

TLDR how to use:

Open an inserter, splitter, or compatible loader
Enable "Set filters with quality signals"
Send quality + (optional) comparator + (optional) item signals on the connected circuit network.

longer boring description:

When you open a filterable inserter, splitter, or loader, you’ll see a new option: "Set filters with quality signals".

Setting this option will allow the entity to read quality signals from connected circuit networks and set its filters to match. This mod adds quality signals to the Signals tab for convenience, but you can also use the ones found in the Unsorted tab.

Comparator signals are also supported (>, <, =, ≥, ≤, ≠). For example, if you want to set the filter for qualities greater than rare, you can send both the "Rare" and "Greater than" signals. If no comparator signal is present the filter will default to "=". If multiple comparator signals are present, the highest-value one wins.

You can also set filters for specific items (instead of generic quality-only filters). If multiple quality and/or item signals are sent, the mod creates a filter for each quality × item combination, ordered by highest quality signal value and highest item signal value (limited by available filter slots).

Other Notes

This mod should automatically support qualities added by other mods.
Inserters, splitters, and loaders with circuit connections and filter slots are supported, including those added by other mods.
Loaders with per-lane filtering use the two highest-priority quality filters, one for each lane. If only one quality filter is available, it is applied to both lanes.

Known Issues/Limitations:

The vanilla circuit-controlled "Set filters" option doesn't support generic quality filters, so it is disabled while this mod's setting is active. When "Set filters with quality signals" is enabled, this mod takes control of the filter settings ("Use filters" ON, "Whitelist", "Set filters" OFF).
Removing an entity with "Set filters with quality signals" enabled then restoring it with the Undo action does not keep its setting.