Re: Units for "set margin"?

[Ethan M. <merritt@u.washington.edu>]

On Thursday 24 July 2008 12:57:42 Philipp K. Janert wrote:
> 
> According to the manual, the units for the
> 	set ?margin
> commands are "character heights or widths,
> as appropriate", using the default font for the
> current terminal, I assume.
> 
> What does this mean for non-fixed character
> sized fonts, including Helvetica?

Internally, it means the values for width and height stored in the
current terminal's term->h_char and term->v_char.
Each terminal driver is supposed to make a best-effort attempt to
store reasonable numbers for these values, but the accuracy varies.

In the specific case of PostScript, the vertical size is set to the normal
font size in points.  (E.g. for "Helvetica,12" the height is 12 points).
The horizontal size is set to 0.6 of the vertical size.

The libgd-based terminals do not assume that the nominal font size
is correct.  Instead they query the actual dimensions of a test string
and set term->h_char and term->v_char on the empirically determined
values.

The accuracy of the values can be judges by inspecting the output
of the "test" command.  If the values are accurate, then the box around
the central test string will fit nicely.  If the values are garbage, the box
will be too big or too small or improperly proportioned.

-- 
Ethan A Merritt