LIGA and RLIG

[kleinpoe]

Hi,

I am sorry to bother, this is not an issue with the Material Symbols Font but I have researched for quite some time now and I am kindly asking for a help or a small lead, I would be so thankful... :-)

I used Material Icons in a private C# WPF Application and it works fine.
I now tried to upgrade to the Material Symbols. Unfortunately the ligatures do not work anymore.

I have analyzed the fonts and I think I have found the issue: it seems that the Material Icons use the "Liga" Ligatures and the new Material Symbols use the "RLIG" Ligatures. The latter is not supported by WPF. I am no font expert and this seems to be a kind of nieche topic which I was not able to find good resources. Is there a way to get the Material Symbols with "Liga" ligatures. Is this an easy conversion or is this a larger format change?

Thank you for reading <3

[tphinney]

Hi! Well, that does sound frustrating.

So, 'liga' ligatures are supposed to be on by default in supporting apps, but can be turned off and are not “reguired.” 'rlig' ligatures are supposed to be always on and are supported in many environments where 'liga' is not, because they are “required ligatures.” We moved to 'rlig' specifically because I knew it ought to work in more environments, even some that would not bother supporting 'liga'. (Yes, I understand this is small consolation to you at the moment, as it does not help your use case!)

So I am a bit surprised that these are not working in your application. That would seem to be an app bug, and if you have a private app, you/they ought to fix it.

That said, in principle, I am not instantly thinking of any good reason we could not support the same ligatures in both 'liga' and 'rlig' features. If coded correctly, it would be a lookup (or set of lookups) referenced by both features and not add very much to the file size. (The liga code is quite large, so literally duplicating the code would be “bad.”)

[tphinney]

So, although we COULD do that change to the font, and in THEORY it ought not to break anything or make the font much larger, some folks have suggested it seems a bit excessive to do this for one specific custom app.

If this is indeed a custom app, can it not... be modified to do this properly? Once an app supports one OpenType layout feature, supporting others that work the exact same way, especially if they need no interface additions, it pretty trivial.

(At other times we might actually have free time, but right now we are doing some major build process changes that are sucking up available time like you wouldn’t believe.)

[kleinpoe]

Hi tphinney,

thank you very much for going into discussions with my request I really appreciate it! :-) Of course I can understand that this is not a priority.

I am using the microsoft c# WPF framework and its built in controls (like TextBox, Label, ...). Unfortunately it only supports
StandardLigatures, ContextualLigatures, DiscretionaryLigatures and HistoricalLigatures (see https://learn.microsoft.com/en-us/dotnet/desktop/wpf/advanced/opentype-font-features?view=netframeworkdesktop-4.8 chapter Ligatures ). I am not sure whether it is easily possible to extend this. I could maybe use the codepoints and substitute the strings myself, I will try this then :-)

Again thank you very much for your kind responses

[tphinney]

So yes, one alternative for you would be to just use the correct Unicode value for each icon instead of going the ligature route at all.

I was surprised to learn that WPF does not support 'rlig' (required ligatures). But looking through the documentation it certainly appears that this is indeed so. Darn!