Created attachment 166796 [details]
The Patch

Hi,

a Debian user reported the following:

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When exporting to fig format, small linewidths from 2-10 (in XFig 1/80 inch units) can not be generated and all gets mapped to width 1.

This is handled in plug-ins/xfig/xfig-export.c by the following:
...
   if (renderer->linewidth <= 0.3175) width = 1;
   else width = (int)((renderer->linewidth / 2.54) * 80.0);
...

Inserting the threshold-value in the scaling expression gives:
  0.3175/2.54*80 = 10

Changing the threshold to 0.03175 makes it possible to generate fig-files with
linewidths between 1 and 10.
See attached patch.

lines.dia shows some lines of different widths and lines.fig shows the result
of exporting to fig after applying the patch to dia.
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See also http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=590857 and the attached patch from there.