Re: XS: needed features? -- underline position

Subject: Re: XS: needed features? -- underline position
From: lee@xxxxxx
Date: Sat, 24 May 97 18:43:38 EDT
> It's exactly because you may need to underscore text in multiple fonts
> [...] that you need the font characteristics to be applicable to score.
> Otherwise, if you're underscoring text in multiple fonts, how is the
> formatter supposed to know which font it should use to control
> the position of the underscore?

At least as important as the position is the thickness.  This makes a
bigger difference today for paper than for the screen, but as screen
resolution improves (_very_ slowly!) and as anti-aliasing is used
more and more, this will change.

The font metrics also give a suggested underline thickness, and this
generally ought to be comparable to the thickness of an HStem (e.g.
the middle arm of an E).  The space between the top of the underline
and the basline probably ought to be comparable to the gab between a
macron (bar) accent and a lower case "o".

If you have a mixture of fonts, it's generally best to take the lowest
underline position and the modal thickness (weighted by the amount of
text using it), or to use the thickness for the "prevailing" font.

Using the font associated with the containing flow object is thus a
reasonable aproach for underline thickness.  For underline position,
there's always the possibility that you'll put it too close to one
of the included fonts -- e.g. if you have a single phrase in Courier
Bold such as Pascal_Variables, in a passage of Monotype Centaur Italic, 
you'll probably have the underline bump into the base of the Courier
Bold text.  But this is a relatively minor problem.

At any rate, we need to be able to underline things.

We would probably like to be able to cross them out, especially if
we have change bars, and we'll also want overbars, which are higher
up than macron accents and don't go up and down to accommodate taller
and shorter letters.

So I vote for retaining both features, for what it's worth.


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