I realise that 'font-feature-settings' is still not officially in CSS3, so it is unlikely to be supported in ePUB or even any device, but I'm somewhat confused about the layout tags.
There is a registry of various tags such as 'liga', 'dlig', 'hist' maintained
here, but MS seem to be shy about defining what each tag must contain, only supplying examples fo what is typical. I appreciate they will vary depending on the script, but surely something called standard ligatures should contain a certain set for latin, and another set for other say greek, yadda yadda.
The only way I can figure out what ligatures and other layout features are supported is by digging through the font info in FontForge, which is not entirely straight forward.
For instance, the "IM FELL Great Primer PRO" font available
here has 'liga','dlig' but no 'hist' to get the long s directly, it can only be had via 'ss01' style set, only then will the long s ligatures 'liga' in work.
I did find a funky web tool that lets you turn on/off certain of the tags
here, but it only supports certain of the most common tags. Even so , the drag and drop bit works very well.
So my question is how does one find out
quickly and easily what layout tags are available and what they contain for a given font?