[Fontconfig] Detecting whether a font is a fallback

[Lawrence D'Oliveiro]

On Thu, 20 Apr 2023 11:22:36 +0200, Jean Abou Samra wrote:

> If we were starting the LilyPond project today, that might make
> sense. However, there are plenty of existing LilyPond files that use
> font family names like “times new roman” that are substituted with
> “Times New Roman”, and I think we'd rather not start making those
> emit warnings.

I think you could make an exception for some simple things like case
differences (as in your example above).