Bug: Contextual Alternate implementation with OpenType font

[ctrayne]

Hello! I am a type designer, and I am testing an in-development typeface in Affinity Designer 1.10 (both Windows 10 and macOS Big Sur). I noticed that, despite selecting the correct typographical options, there were issues with the way Designer was implementing the typeface's contextual alternates, as shown in the photo below.

In the example shown, the font is programmed to use an alternate 'E' when it is followed by two lowercase 's' glyphs. The reason for this is so that it can properly connect to the 'ss' ligature. In this case, the alternate 'E' used before 'ss' is from stylistic set 01, and I made sure no stylistic sets were enabled so it wouldn't interfere with the contextual alternate code.

However, in Affinity Designer, the program puts the alternate 'E' in front of just a single 's', rather than only in front of 'ss'. This causes a strange collision because those glyphs aren't meant to be used together. It's like Designer sees the OpenType code is asking for an alternate 's' after 'E' and stops reading any further.

So the app is acting like this:

sub E' s by E.ss01;

when the font is actually programmed as:

sub E' s s by E.ss01;

The bug has been confirmed by another user who wasn't using my typeface, and the typeface works correctly in other apps – so as far as I can tell, this is a bug with Designer's typography system (and probably the other Affinity apps).

[Sean P]

Hi ctrayne,

Would it be possible for you to attach a copy of your font to our internal Dropbox account please? I'll then be able to get it passed on to development to investigate properly.
https://www.dropbox.com/request/VGD8QGbuvJtYth75nPfU

Thanks,