Re: leading
James Clark (jjc@jclark.com)
Tue, 1 Aug 1995 11:19:58 +0000
> Date: Mon, 31 Jul 1995 14:37:23 +0800
> From: Jon_Bosak@novell.com
>
> [Glenn Adams:]
>
> > If your font size is 12pt and the distance between base lines is 14
> > pt, is leading then 2pt or 14pt?
> >
> > Leading is 2pts. The line is set 12/14 (12 on 14). Line separation is 14.
>
> Exactly. Here's why.
>
> Visualize type set in metal (namely lead, Pb). You want to increase
> the space between lines; this is done by inserting a thin strip of the
> same metal between the lines. The strip is called a "lead"
> (pronounced "led"). Leads come in various thicknesses: you have 1pt
> leads, 2pt leads, and so on. Thus, 12 on 14 is leaded 2 points,
> because you have inserted a 2pt lead after each line. 12pt type set
> solid is leaded 0 points, because no additional space has been
> inserted.
>
> [Paul Grosso:]
>
> > Though both have at times been used, by far the more common in use
> > recently--especially in the computerized typesetting world--is the
> > latter, i.e., baseline-to-baseline measure, e.g., 14pt in your example.
> >
> > TeX, the Output Specification (aka FOSIs), and DSSSL are among those
> > that measure "leading" as baseline-to-baseline.
>
> This is an unfortunate error, understandable from folks who have never
> actually handled type, but an error nonetheless. The parameter called
> "leading" should have been named something like "line separation". We
> can't do anything about FOSI or TeX, but we should try to fix it in
> DSSSL.
In the current DSSSL draft, the main characteristic for controlling
the distance between baselines is called line-spacing. This is very
similar to baselineskip in TeX. There's also a characteristic called
min-leading which specifies the minimum space between the bottom edge
of one line and the top edge of the next line, and allows the space
between lines to be automatically adjusted for tall objects within
lines. This is very similar to lineskiplimit in TeX. See pages 33
and 37 of ftp://ftp.jclark.com/pub/dsssl/clstyle.PS.Z for details.
James Clark
jjc@jclark.com