PDF builds ignoring some kerning

[JeremyTankard]

I have noticed that several kerns are ignored when exporting to PDF from Affinity apps (Publisher, though I suspect this will also be the same for Designer and Photo). Exporting the same from InDesign to PDF is OK. I think there was previous issue with OpenType styled superiors in past versions of Publisher.

An example is superior lowercase glyphs following a lowercase f

This screengrab shows a string of glyphs in Publisher,

 

This image shows the same glyphs in a PDF made from Publisher,
the positive kerning values have been ignored.

 

This image shows the string set in a PDF exported from InDesign,
here the positive kern values have been retained.

 

[JeremyTankard]

Further to this I have found that if I export a small document (1 page or 3 pages) then all the kerns are respected. If I exprt a large docuemnt (70 pages) then the issue occurs.

Is there a limit to size, processing size, cache? that Publisher uses/needs in order to build a PDF?

Is there a seeting in Prefs that I can increase if the PDF is a large document?

[JeremyTankard]

I had this info back from a couple of colleagues:

 

"I believe kerning is not preserved in a PDF. It depends entirely on the app that puts the glyphs on the page."

"All glyph positions are calculated when the PDF is created; usually kerned text is placed line-by-line using the TJ operator, which takes a sequence of strings and kerning adjustments between them. So the kerning is still implicitly there within the text, but the original GPOS code is not."

[kenmcd]

What font are you using?

You mention "OpenType styled superiors" so I assume you are using OpenType Superscripts applied from the Typography Panel, and that the font supports this OpenType feature, and the font has the proper glyphs, and actual kerning pairs for those substitute glyphs.

Not a lot of fonts have full OpenType superscript lowercase support (with substitute glyphs).
And even fewer have the full actual Unicode superscript lowercase characters.

All of these could be interacting with what Affinity is doing with the superscripts.

And if you have used the Transform panel instead, or mixed that in...

It would be helpful to see an actual document, and the resultant PDF.

[Callum]

Hi Jeremy Tankard,

If you could provide the info kenmcd has requested I should be able to look into this further with you.

Thanks
C

[JeremyTankard]

Thanks both for your replies.

I'm a type designer (been designing type since 1993) and the font in question is under development. It is an extend typeface principally for typographic use rather than branding and general graphic design. All my types have extended character sets and it is normal for me to add many figure sets and extended typographic functionality delivered through OpenType feature code.

As the type and associated masterial is sensitive, where can I email the requested files so they are not public?