API: Add PrototypeFilter for type="signal"

[kryojenik]

TL;DR; Desire to filter / limit the signals presented by the "choose-elem-button" LuaGuiElement type.

Specifically in the case of implementing an extension to a constant combinator (e.g. https://mods.factorio.com/mod/LTN_Combinator_Modernized) the special signals (signal-each, signal-anything, signal-everything) don't make sense. The in game constant combinator has these signals filtered out in its "choose-elem-button" panel. In fact, if they are selected in a mod an applied to the underlying constant combinator entity it crashes the game. I'm working to trap for these selections in the mod, but ideally it would be best to not present invalid selections to begin with.

Crash report
Constant combinator: invalid signal in parameters: signal-anything

Vanilla Constant Combinator

const.png (346.9 KiB) Viewed 2600 times

LTN Combinator using a choose-elem-button type=signal

ltn.png (316.09 KiB) Viewed 2600 times

These signals were added to the "choose-elem-button" panel after a bug report in 0.18.24. via viewtopic.php?f=11&t=84877.

[curiosity]

Potentially related: viewtopic.php?f=28&t=97127

[meifray]

and this is why Improved Combinator just faked the signal selection screen himself.

guimeme.png (447.3 KiB) Viewed 2532 times

[BinarySpike]

+1 because it seems train fluid conditions already have something like this implemented and it would make my mod look much nicer: