Gis major key signature; Lily's key signature algorithm

[Richard M]

Hello, list,

how does LilyPond create the key signature for Gis major?

I've attached a file to compile the key signature, which results in: C#, 
G#, D#, A#, E#, B#, and Fx. It is interesting to me that the key 
signature begins with C#, and the Fx is placed at the end.

I'm wondering if there's a resource the developers used (perhaps a 
notation manual) that gave a rule for how key signatures with double 
accidentals should be formatted. We all know how 'normal' key signatures 
are formed, but I can not find a resource that mentions key signatures 
with double accidentals. It seems more likely that LilyPond uses an 
algorithm to create the key signature (especially since, for example, 
inputting `\key fisis \major` gives an output).

Regarding Gis major, other possibilities are: Fx, C#, G#, D#, A#, E#, 
and B# (with Fx at the beginning). Or even: F#, C#, G#, D#, A#, E#, B#, 
and Fx (with F# at the beginning and Fx at the end). There may be others.

So I'm looking for how LilyPond forms these key signatures, and why Gis 
major results in one particular key signature and not one of the other 
two. There must be a rule somewhere that makes that determination.

Thank you,

Richard

gis_major.ly
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