language tags, HTML lang attributes and locl features

Kazunari Tsuboi

I'm working on switching the glyph of Eng (U+014A) with the locl feature.

However, I couldn't find a suitable language system tags for Dagbani.

How can I find the right tag?

The information I referred to is:

https://docs.microsoft.com/en-us/typography/opentype/spec/languagetags

https://github.com/davelab6/dancingshoes/blob/master/dancingshoes/opentypenames.py

https://github.com/jclark/lang-ietf-opentype/blob/master/lib/map.json

I plan to use the font I created as a webfont.

For example, in Luganda, HTML lang is "lg". In this case, the OpenType lanugage system tag can use the locl function by specifying "LUG".

However, in Dagbani, HTML lang is "dag". Since the OpenType language system tag in this case is unknown, the locl function cannot be used.

I would be grateful if you could give me some good information.

Peter Constable

Look again at https://docs.microsoft.com/en-us/typography/opentype/spec/languagetags: Dagbani has been added.

Kazunari Tsuboi

Thank you so much! I have confirmed that the Dagbani language has been added.

I was able to create an OTF with the Dabgani word added as "DAG".

The ideal display is displayed on Windows10 Chrome 88.0.4324.150.

On the other hand, all browsers on iOS, such as iOS 14.4 Safari, do not allow the locl function in Dagbani.

Apple iOS display results are a serious issue for me. I'm Japanese so I sent feedback from here.

https://www.apple.com/jp/feedback/safari.html

Looking at the harfbuzz source code, it seems to work if the three-letter HTML lang tag and the OTF language tag are the same.

https://github.com/harfbuzz/harfbuzz/blob/master/src/hb-ot-tag-table.hh

https://github.com/harfbuzz/harfbuzz/blob/master/src/gen-tag-table.py

For me, the relationship between OpenType Layout and browsers is very mysterious. However, it was also a good learning opportunity for language system tangs.

Thomas Phinney

It will take at least weeks, maybe even months for all the browsers to catch up and support the new language tag.