> For the complete documentation index, see [llms.txt](https://stylizededge-devs.gitbook.io/aqs-doc/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://stylizededge-devs.gitbook.io/aqs-doc/advanced/single-field-apply.md).

# Single-Field Apply

This is internal plumbing you'll likely never call directly — documented here because understanding *why* it exists explains a real bug it prevents, and helps if you're extending the plugin yourself.

## The Problem It Solves

Early in development, every row change in the Auto Panel re-applied the **entire** preset struct — all 23 fields, every time, on every single slider drag. This caused a genuinely strange symptom: set Resolution Scale to 50%, then toggle Bloom on, and Resolution Scale would silently jump back to 100%.

The root cause: writing **any** `sg.*` CVar makes Unreal's own scalability system think "the quality level changed," and it responds by reloading that entire group's CVars straight from `Scalability.ini` — dozens of values, none of which the player actually touched, all overwriting whatever had been individually tweaked.

## The Fix

`UAQSPresetApplier::ApplySingleField(FieldName, Settings)` sets **only** the one CVar tied to the field that actually changed — using the same field-to-CVar mapping as the full apply path, just isolated to a single branch. Every row's change handler in the Auto Panel calls this instead of a full re-apply when live-editing.

```
Player drags Resolution Scale slider
  → ApplySingleField("ResolutionScale", ...)
  → only r.ScreenPercentage is touched

Player toggles Bloom
  → ApplySingleField("bBloom", ...)
  → only r.BloomQuality is touched
  → Resolution Scale's CVar is never touched, so it never resets
```

## When the Full Apply Still Happens

Clicking an actual preset button, or pressing an explicit Apply button (when `bAutoApplyOnChange = false`), still goes through the full `ApplyLive`/`ApplyPreset` path — re-applying everything is correct and intended there, since that's a deliberate "commit this whole preset" moment, not a per-keystroke live preview.


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