bug 548 graphics '*' (PR#549)

A little more followup.  The gtk() device uses gdk_string_width to
find the character extents. That seems undocumented anywhere in the
gtk+ sources.  It is returning the maximal descent for the font for all
input strings on my system.  Looking at the current gtk+-1.2.7 sources it
appears to call XTextExtents, and that _should_ give the
string descent.

Since gdk fonts are private opaque structures I see no way around this.
Without any documentation I do not even know if it is a gdk bug (although
I suspect it is or was).  The gdk docs in gtk+ seem seriously incomplete.

The best thing that can be said about the GNOME API documentation is
that it is getting better.  Documentation on glib, gdk and gtk+ is
available from here:

http://developer.gnome.org/doc/API/

but is still quite sparse.  

This is not, in fact, a gdk bug, but is due to a permutation in
the arguments of gdk_string_extents in GTK_MetricInfo 
(file src/gnome/devGTK.c). It currently reads

    gdk_string_extents(gtkd->font, tmp,
                       &lbearing, &rbearing,
                       &iascent, &idescent, &iwidth);

but should be

    gdk_string_extents(gtkd->font, tmp,
                       &lbearing, &rbearing,
                       &iwidth, &iascent, &idescent);

See
http://developer.gnome.org/doc/API/gdk/gdk-fonts.html#GDK-STRING-EXTENTS

Martyn
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