Quote:
Originally Posted by lensmann
Thanks - this is useful. Could I ask which fonts failed for you? I'd like to take a closer look at their structure.
Basically, OpenType fonts include a glyph positioning table (GPOS). One of the actions this table supports is contextual positioning. Contextual positioning tells the renderer where exactly to put combining diacritics - for example, that a pasekh combined with an alef should display at the very bottom of the character, whereas a pasekh combined with a kuf should come under the curve and not at the bottom, and a pasekh combined with tsvey yudn should come in the middle of the space for the glyph centred under the yudn and not at the bottom. Likewise for other nikkudim, e.g. the difference in the positioning of a khoylam when over a vov (centred on top) as opposed to over an alef (top right corner).
Your screenshots seem to confirm my theory that contextual positioning isn't working for some Hebrew fonts, so looking into how the fonts are set up might help figure out precisely what's failing. Giving Kobo those details may help speed up their release of a fix. I have a holiday coming up and this seems like a nice project to take on then.
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I think you might be right, since:
1. All the rendering problems are in such cases (that I can see, anyway).
2. If the source of the problem is with hinting, wouldn't increasing text size hide the problem? I tried that and the problems persists.
The font is FrankRe:
https://alefalefalef.co.il/en/font/frank-re/
I'm not sure if it's a good idea to share it. Probably not.