[Octave-bug-tracker] [bug #43651] special character (diameter sign) in plot produces warning or doesn't show up

[Rik]

Follow-up Comment #6, bug #43651 (project octave):

Thanks for doing such careful debugging.  I think you've discovered the root
issue which is that FLTK adheres strictly to the user's stated font, while
gnuplot and Matlab substitute a font specifically for symbols.  They may also
be running some sort of substitution for glyphs not found as well.  I can tell
because Octave is requesting the circle division slash glyph, and gnuplot is
responding with the emptyset glyph which is a different.

Since gnuplot is going to ignore Octave anyways I don't see any point in
checking on Octave's side whether the given font has the correct glyph.  I
believe you're right that the glyph warning can be eliminated when the toolkit
is gnuplot.

On the broader issue of whether FLTK should follow gnuplot/Matlab and use a
different font entirely for special symbols, I'm not certain how to proceed. 
One choice would be to try and use the default font, '*', for all symbols in
the hope that the default has the largest number of glyphs of the available
fonts.  Otherwise, I'm not sure how to find the best font to use for symbols
on a given platform.


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