Re-using glyphs: yes or no

Theunis de Jong23 Mar 2012

If you create an all-uppercase font, it's possible to assign two Unicode values to each glyph: one for the uppercase and one for the lowercase. In both cases the same glyph can be used. (It seems nothing in the specification prohibits assigning yet even more UC code points to the same glyph.)

Some software doesn't appear to notice this: both Windows and Mac OSX show a 'full' character repertoire in their default preview field. OS X's Font Book only reveals the hidden truth when you select "Full repertoire"; Adobe InDesign, on the other hand, only shows capitals in its Glyphs panel (although typing in lowercase still works).

Are there any significant advantages for re-using glyphs this way? File size is one. It also makes Opentype feature programming a bit easier, or so I imagine, as you don't have to worry about all combinations of F-I, F-i, f-I and f-i ligatures ... (Imagine a six-letter ligature).

Are there known disadvantages? If you copy text out of a PDF, do you get the original uppercase/lowercase you entered, or is it All Uppercase by then?

riccard023 Mar 2012#

If I remember correctly, Craig Eliason faced this dilemma with his Ambicase Modern, but I don’t remember which solution he has chosen in the end.

brianskywalker23 Mar 2012#

[follow]

eliason23 Mar 2012#

Riccard0 is right, and here's the thread about it:
http://typophile.com/node/67092

The potential issue of retaining case in reconstituting texts from PDFs is the only concern I heard voiced, and I decided for a unicase display font that was an ignorable issue.
(As I mentioned in that thread, I had all sorts of system trouble during development when I double-encoded the font and generated it with the same name as a previously-installed single-encoded version. But since my caches were cleared, it has worked like a charm.)

Theunis de Jong24 Mar 2012#

Craig, thanks for being the guinea pig! That thread contained exactly everything I was cont'mplating.

So I guess it's Okay with doubling uppercase to lowercase for an all-caps font; your Unicase is indeed another style where the "actual" case of characters is irrelevant.

So, what about the Unicodes that get stored in a PDF? Hold on while I make a test file ... Result of copying text out of a PDF:
"THIS IS CAPS
THIS IS CAPS-lC
THIS IS All lC"

That returns all as capitals except for that lowercase L. Hmm. Let me add a disclaimer then: I used OS X's Preview, which may not have been the best choice.

John Hudson24 Mar 2012#

Much depends on how the PDF is created. If it is exported from a program such as InDesign then the original Unicode text strings should be written to the PDF. If it is distilled from a print stream, then Acrobat uses the glyph names to try to recreate the text strings. The latter situation is where having single glyphs named e.g. /A/ /B/ /C/ etc. representing both upper- and lowercase characters is problematic. Whether this is a problem for you or your users depends on whether they care about the case of the original text source.

I recently made a monocase font in which we double-encoded for upper- and lowercase, but in this instance the recommendation to users is to always set all-caps text, and the lowercase encodings are only provided for compatibility purposes.

Theunis de Jong24 Mar 2012#

Thanks, John. Interesting:

If it is exported from a program such as InDesign then the original Unicode text strings should be written to the PDF.

because that's exactly what I did. That's why I added the "disclaimer" about using Preview ;-) If I hover above my font in InDesign's Glyphs panel all capitals are identified as "Uppercase". It's expected as well, as the CFF part of my font only contains the uppercase, as lowercase is added with the Encoding trick.

Whether this is a problem for you or your users depends on whether they care about the case of the original text source.

I don't think that's a problem. If one sees all-caps in a PDF, it's reasonable to expect that copying the text would also result in all-caps.

Theunis de Jong26 Mar 2012#

Apple's Preview is a funny thing (*). Copying text in such an All-Caps font out of Acrobat Pro indeed returns the original case.

(*) That is, it's funny right until you get clients complaining "your PDF is no good" and after a lot of e-mailing to and fro it dawns on you they were using it to preview your immaculate PDF with.

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