Re: Using GLC with Pango

[Behdad Esfahbod <behdad behdad org>]

On Sun, 2007-10-14 at 13:16 +0200, Bertrand Coconnier wrote:
> Hi all,
> 
> I am the developper of QuesoGLC, a free implementation of SGI's GLC library (an 
> OpenGL character renderer). See http://quesoglc.sourceforge.net
> 
> QuesoGLC's main purpose is to render characters (using OpenGL) but not to 
> provide text layout management. From GLC's point of view, layout services are 
> provided by libraries like Pango. My concern is how to interface smoothly 
> QuesoGLC with Pango ?
> 
> I parsed Pango's web site but I could not figure out where the layout management 
> ends and where the rendering task begins. I mean, should QuesoGLC support 
> right-to-left rendering or does Pango sort out the characters so that they can 
> be rendered left-to-right ? The same for vertical rendering ? Should QuesoGLC 
> support all Unicode features (including the BiDi algorithm and/or the various 
> normalizations) or does Pango take care of it ? Etc...
> 
> Genrally speaking, my question is what are the mimimal services that should be 
> provided by QuesoGLC in order to render correctly the layout performed by Pango ?

Pango takes care of all higher level stuff for you.  What you need is to
implement a Pango backend for your OpenGL-based system.  There are a
couple such implementations already available.  See:

  http://bugzilla.gnome.org/show_bug.cgi?id=354860

A more interesting approach is to see if you can use the cairo's glitz
backend with pangocairo.

Of course you can get away without doing this all, just use pangocairo
and then fetch the glyph paths out and push it in OpenGL yourself.  See
pango_cairo_layout_path() for example.


> Regards,
> 
> Bertrand.

-- 
behdad
http://behdad.org/

"Those who would give up Essential Liberty to purchase a little
 Temporary Safety, deserve neither Liberty nor Safety."
        -- Benjamin Franklin, 1759