Re: about contibuting to octave

[Michael Goffioul]

On Tue, Mar 3, 2009 at 8:18 AM, Ben Abbott <address@hidden> wrote:
> The fltk backend is primarily in src/fltk_backend.cc
>
> The gnuplot backend is primarily written as m-files. They are in
> scripts/plot (there is a lot of other files having nothing to do with
> gnuplot, in particular, there as well).
>
> Regarding the text object's "extent"s, I've been under the assumption that
> this could/would be handled independent of the backend, and that all
> backends would rely upon a unified solution for calculating the extents of a
> text object.
>
> Am I off in my expectation? ... if so, if anyone has a thought on how the
> extents for the gnuplot backend might be determined, please advise.

Basically, the only thing you need is font metrics information. From that,
you should be able to compute text extent in an independent way. Even a
simple TeX text layouter could be written independently. Font metrics
information is also required to correctly layout axes (title, labels, ticks...).
Once you have that information, the rest is (should be) backend-agnostic.

The OpenGL renderer already uses FTGL, which depends on freetype, so
the most natural choice would be to use freetype to get font metrics.
If freetype is not available (but honestly, are there systems supported by
octave that do not have freetype...?), we might use a very basic font
metrics computation based on the font height: it'll be wrong for non-standard
fonts, but you need a backup solution.

Michael.