Tk/Linux: How do I tell whether a font is scalable?

[Ralf Fassel]

I need to display a number in a font 80 pixels high.
This seems no problem on Windows, where I just configure the font

font create -size 80 -weight bold -family Helvetica

and get some nice big letters.

On Linux however, the font is not available in this size, and it comes
out way too tiny. Moreover, the font command decides to be nasty on
my system:

% info patchlevel
8.4.13
% font create -size 80 -weight bold -family Helvetica
font1
% font configure font1 -size
80
% font actual font1
-family helvetica -size 18 -weight bold -slant roman -underline 0 -overstrike 0

Note the difference between the two -size results.

- how do I get a font which is scalable, so it gets displayed at the
size I specify?

I can try to look for some well-known font(s) in [font families], and
maybe iterate until I have found one which gives the correct -size
(and hope it's not Dingbats). Probably also grep the output of
xlsfonts for 0-0-0, which seem to be the scalable fonts on the system
(?).

Is there a better way? Maybe some Digital-Font-package for the canvas?

R'