Re: ligature usage - WAS: How do we find out what assigned code points aren't normally used in text?

From: Kent Karlsson <>
Date: Sun, 11 Sep 2011 23:14:04 +0200

Den 2011-09-11 18:53, skrev "Peter Constable" <>:

> There's no requirement that the width of glyphs in a monospaced font be 1 em.
> I would agree, though, that if a monospaced font forms a ligature of a pair
> like <0066, 0069>, then it should be twice the width (not necessarily 2em) of
> single-character glyphs.

That's fine (assuming the ligature is well designed, in the case of a
monospace font connecting the bar of the f to the top serif of the i and
only that).

> In a monospace font, nothing prevents the glyph for FB01 being a ligature, and
> some monospaced fonts do have a ligature glyph for that character.

Fine too. But see below.

> Of course, in a monospaced font, the glyph for that character should be the
> same width as all other glyphs. So if it's not a ligature, then the "f" and
> "i" elements still need to be narrower than the glyphs for 0066 and 0069.
> Hence, in a monospaced font, FB01 certainly should look different from <0066,
> 0069>, regardless of whether ligature glyphs are used in either case.

If "monospace" is interpreted that rigidly, then it is much better *not* to
have any glyph at all for FB01 (and other characters like it) in a
"monospace" font.

    /Kent K

> Peter
> -----Original Message-----
> From: [] On Behalf
> Of Philippe Verdy
> Sent: Saturday, September 10, 2011 10:33 PM
> To: Michael Everson
> Cc: unicode Unicode Discussion
> Subject: Re: ligature usage - WAS: How do we find out what assigned code
> points aren't normally used in text?
> 2011/9/11 Michael Everson <>:
>> On 11 Sep 2011, at 00:23, Richard Wordingham wrote:
>>> A font need not support such ligation, but a glyph for U+FB01 must
>>> ligate the letters - otherwise it's not U+FB01!
>> Not in monowidth, it doesn't.
> I also agree, a monospaced font can perfectly show the dot and ligate the
> letters, using a "double-width" (2em) ligature without any problem, or simply
> not map it at all, or choose to just map a composite glyph made of the
> 1em-width glyphs assigned to the two letters f and (dotted) i without showing
> any visible ligation between those glyphs (this being consistant with
> monospaced fonts that remove all ligations, variable advances and kernings
> between letters).
> You could as well have a font design in which all pairs or Latin letters are
> joined, including in a monospaced font, in which case you should not see any
> difference between FB01 and the pair or Basic Latin letters. Joining letters
> is fully independant of the fact that the upper part of letter f may or may
> not interact graphically with the presence of a dot. If the style of letter
> glyphs does not cause any interaction, there's no reason to remove the dot
> over i or j in the "ligature" or joining letters.
> You should not be limited by the common style used in modern Times-like fonts
> (notably in italic styles, where the letter f is overhanging over the nearby
> letters). Other font styles also exist that do not require adjustment to
> remove the dot, or merge it with a graphic feature of the preceding letter f
> which is specific to some fonts.
> As the pair of letters f and (dotted) i is perfectly valid in Turkish, there's
> absolutely no reason why the fi ligature would be invalid in Turkish. But
> given that this character is just provided for compatibility with legacy
> encodings, I would still not recommand it for Turkish or for any other
> language, including English. This FB01 character is not necessary to any
> orthography and if possible, should be replaced by the pair of Basic Latin
> letters (and in fact I don't see any reason why a font would not choose to do
> this everywhere)
> -- Philippe.
Received on Sun Sep 11 2011 - 16:17:45 CDT

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