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On 20/05/2014 08:40, Joseph Wright wrote:
> Hello Will,
>
> A few questions from me. One 'up front': where does \mathrm fit in to
> all of this?

I think \mathrm is conceptually no different to \mathbf  so whatever so
whatever scheme
is used should apply to both.
> To be clear, the Unicode position is that e.g. bold-B for magnetic field
> should not come from the 'bold' font but from the bold-symbols part of a
> single maths font: correct? That being the case, have the Unicode people
> considered at all multi-letter identifiers or has this simply been
> missed at present? (Anyone on the list sufficiently well-informed about
> this?)

I think that it is a mistake to look at unicode this way. Despite the
appearance of "Unicode fonts"
It's a standard primarily of _input characters_ for _plain text_ So the
fact that there may or may not
be particular characters in the Unicode math alphabet block isn't really
of direct concern any more
than the fact that there isn't an ffi ligature means that we shouldn't
typeset an ffi ligature.
Unicode just doesn't tell you whether f f i should be typeset as one two
or three glyphs, and it
doesn't tell you what font to use for typesetting bold math. (The tables
in the font, once you have
chosen a font,  say something, but that's a different matter).

That said, there are fonts that have useful glyphs in those positions
and so clearly there should be a
latex interface to access those.

>> 3. To get proper bold symbols, including Greek, we'll need a whole new set
>> of commands. These will need sensible names of some sort. Below I've chosen
>> \symbf, etc., which doesn't look too bad to me.
> By 'proper' here I assume you mean 'with attached mathematical meaning'?
> I think it's fair to say that the LaTeX standard \mathbf does produce
> bold symbols, and in the common case of matching text and maths fonts
> the symbols also look 'right'.
> --

Yes it isn't clear to me that any document would ever want both \mathbf
for multi-letter
identifiers and \symbf for single symbols. If the fonts use a matching
design probably you just
need \mathbf, and if the fonts don't use a matching design I think it
would be better for consistency
if you'd just use \mathbf as well.

However sometimes there isn't a matching bold font, but there is (for a
limited character range)
a set of bold glyphs in the base math font in the bold math alphabet
range.  For that use I'd think
a variant declaration which would define \mathbf to flip the mathcodes
into the U+1Dxxx block
using the base font rather than define it as a swutch to new \fam
(\mathgroup)  and  would be useful.

This latter mechanism could probably be a default for things like
blackboard bold and calligraphic where
you can't find default fonts by looking at the text font settings.

But defining \symcal first as a name that always means the unicode block
and then having top level
options that do \let\mathcal\symcal rather than defining \mathcal
directly would also work (and be more
flexible in that it gives top level access to both if both are
available  people really need that.
So I'm happy to run with Will's proposal to see where it leads....

David