[MPEG-OTSPEC] Is it valid to use a GSUB sequence with a leading ZWJ character please?

[David Lemon]

PBS had a ten-minute (or so) segment in yesterday's News Hour program about glasses emoji and moving beyond the "nerd" stigma, so I'm not surprised there's chatter on the Unicode list.

William, I'm curious: Why are you leading with a ZWNJ instead of placing it between the to-be-ligated characters?
thanks,
David Lemon

-----Original Message-----
From: William_J_G Overington <wjgo_10009 at btinternet.com>
Sent: Oct 14, 2022 2:46 AM
To: 'MPEG OT Spec list' <mpeg-otspec at lists.aau.at>, Vladimir Levantovsky <vladimir.levantovsky at gmail.com>
Subject: [MPEG-OTSPEC] Is it valid to use a GSUB sequence with a leading ZWJ character please?

An interesting discussion about glasses emoji is taking place in the Unicode public mailing list.

https://corp.unicode.org/pipermail/unicode/2022-October/date.html

Thinking about this, earlier this morning here in England I adapted one of my own fonts to add some additional glyphs to run a test, and it worked. I used the High-Logic FontCreator program to make the font and Serif Affinity Publisher to run the test.

The font that I adapted is the Mariposa.otf font that is available from the following web page, though in fact I started with a copy of the unpublished High-Logic project file for the font.

http://www.users.globalnet.co.uk/~ngo/mariposa_novel.htm

To the font I added glyphs for three Unicode characters and for one unmapped glyph.

U+200D ZERO WIDTH JOINER though I used a wide visible glyph design

U+1F453 EYEGLASSES

U+1F469 WOMAN

unmapped ceyeglasses, a copy of the glyph used for eyeglasses, moved 2048 font units to the left and the glyph having zero advance width.

Within the liga table I added the following line.

sub uni200D u1F453 -> ceyeglasses;

that is, for "combining eyeglasses".

Please note that the substitution starts with a ZERO WIDTH JOINER

In the test in Affinity Publisher I used the Glyph Browser to enter the three characters

U+1F469 U+200D U+1F4F3

and the result displayed was of a woman wearing the eyeglasses as the display was of the glyph for WOMAN with the glyph for ceyeglasses superimposed upon it.

So if it is valid to use a glyph substitution with a leading ZWJ in this way then the issue appears to be solved.

Is it valid to use a glyph substitution with a leading ZWJ in this way please?

One could go further with a sequence also involving a pink square and a large circle to produce stylish large round pink rimmed glasses for the lady to be wearing.

Indeed the technique could be adapted so that the lady is also wearing a U+1F452 WOMANS HAT in a stylish purple colour.

William Overington

Friday 14 October 2022






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