Fix #2525: clamp negative Cyclops power readout with no powercells

[SkiLark1]

Linked Issues / Context

Fixes #2525

Description of Change

Vanilla CyclopsHelmHUDManager.Update computes the displayed power percent as:

int num = Mathf.CeilToInt(subRoot.powerRelay.GetPower() / subRoot.powerRelay.GetMaxPower() * 100f);

With all powercells removed, GetMaxPower() returns 0, so 0f / 0f is NaN and Mathf.CeilToInt(NaN) is int.MinValue. The HUD then reads -2147483648% instead of 0%.

This state is normally unreachable in vanilla Subnautica because the engine auto-shuts when the player exits the helm, but Nitrox intentionally patches that out for MP reasons (see CyclopsMotorMode_SaveEngineStateAndPowerDown_Patch.cs). With auto-shutdown disabled, pulling all powercells at the helm exposes the divide-by-zero path.

The fix transpiles Update to clamp the Mathf.CeilToInt result with Mathf.Max(0, …), so the bad value never gets written and vanilla's own $"{num}%" formatting renders 0%. The clamp is a single insertion right after the uniquely-matchable Mathf.CeilToInt call.

Note: an earlier revision of this PR used a Postfix that overwrote the text after the fact. That approach wrote IntStringCache.GetStringForInt(0) = "0", which dropped the % sign that vanilla's $"{num}%" includes. The transpiler fixes the value at the source and lets vanilla's formatting run, producing the correct "0%". Thanks to the reviewer for pushing for the source-level fix.

The patch is registered in PatchesTranspilerTest so the IL match is covered by the test suite.

This patches a vanilla Subnautica bug (closed-source, can't be upstreamed), but the clamp is a no-op for all legitimate power values (0–100), so it has no effect in normal play.

Validation

Tested locally on Windows, Subnautica build 83031, Nitrox InDev master (bbf5124):

1. Spawn a Cyclops via Developer → Give → Cyclops.
2. Enter the cyclops, walk to the helm.
3. Remove all 6 power cells.
4. HUD power readout shows 0% (was -2147483648% before the fix).
5. Insert a powercell back → shows a normal positive percent. Remove it again → back to 0%.

The transpiler is also covered by PatchesTranspilerTest.AllPatchesTranspilerSanity, which runs it against the real game IL and asserts it matches and inserts exactly 2 instructions.

PR Checklist

• PR rebased on top of master at the time of opening
• Has tests for the changes (registered in PatchesTranspilerTest)
• Has a linked issue (Charge on cyclops is negative after powering up engine without powercells present #2525)
• Has been tested in-game
• Has been tested on Windows/Linux/macOS (Windows only)

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🤖 This code was created with the help of AI.

[dartasen]

What about transpiling patch the actual code, instead of adding a workaround ?

[SkiLark1]

What about transpiling patch the actual code, instead of adding a workaround ?

Pushed the transpiler version. It clamps the Mathf.CeilToInt result with Mathf.Max(0, ...) right after the call, so vanilla's own "{num}%" formatting renders 0% correctly. Added it to PatchesTranspilerTest too, and confirmed in-game the HUD reads 0% now.

Good call on doing it at the source. The old Postfix was dropping the % sign anyway, so this ended up cleaner all around.