Crash: IndexOutOfRangeException in SystemRenderPlayerEffects.onBeforeRender when maxDynamicLights = 0 and a dynamic light appears

[Petyok]

Optimum version: 0.3.14 (built from source via install-linux.sh)
Game version: 1.22.7 (Stable), Linux x64 (Arch, kernel 7.1.9), Mesa 26.2.1, Intel HD 6000

Summary

Client crashes with IndexOutOfRangeException in SystemRenderPlayerEffects.onBeforeRender the moment any dynamic light source appears (e.g. lighting a torch), when the vanilla setting maxDynamicLights is 0 (as set by the low-end graphics presets).

Crash

System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at Vintagestory.Client.NoObf.SystemRenderPlayerEffects.onBeforeRender(Single dt)
   at Vintagestory.Client.NoObf.ClientMain.MainRenderLoop(Single dt)
   ...

Root cause

In patches/VintagestoryLib/Vintagestory.Client.NoObf/SystemRenderPlayerEffects.cs.patch, the alloc-free K-nearest selection (B3) does not handle maxDynLights == 0:

if (array.Length > maxDynLights)            // 1 > 0 → true
{
    if (_lightScratch == null || _lightScratch.Length < maxDynLights)
    {
        _lightScratch = new Entity[maxDynLights];       // new Entity[0]
        _lightScratchDistSq = new double[maxDynLights]; // new double[0]
    }
    _lightScratchCount = 0;
    for (int i = 0; i < array.Length; i++)
    {
        ...
        if (_lightScratchCount < maxDynLights)  // 0 < 0 → false
        { ... }
        else
        {
            int farthest = 0;
            double farthestDist = _lightScratchDistSq[0];  // ← throws: zero-length array

With maxDynLights = 0 the first entity that passes HasLight goes straight to the eviction branch and reads _lightScratchDistSq[0] from a zero-length array.

Repro: set maxDynamicLights: 0 in clientsettings.json, join any world, light a torch (or approach any glowing entity) → instant crash to desktop. 100% reproducible.

Suggested fix

Guard the selection branch, preserving vanilla semantics for 0 (no dynamic lights rendered):

if (maxDynLights > 0 && array.Length > maxDynLights)
{
    ...
}
else if (maxDynLights == 0)
{
    array = Array.Empty<Entity>();
}

Workaround for affected users until then: set maxDynamicLights to ≥ 1.

Thanks for Optimum — on a 15W Broadwell laptop with HD 6000 it took the package temperature from thermal-throttle city (100°C+) down to a stable ~80°C with FSR at 0.67. Great work.