Re: Strange bug

[muppet <scott asofyet org>]

On Thursday, November 20, 2003, at 08:42 AM, Bjarne Steinsbø wrote:

> Error message is:
> *** unhandled exception in callback:
> ***   variable is not of type Gtk2::Gdk::Drawable at t line 23.
> ***  ignoring at t line 31.
>
> Something to do with ..._ornull typemap?

only in a roundabout way.

gtk doesn't define a GType for GdkBitmap, but instead just typedefs it 
to be the same as GdkDrawable.  because of this, the typemap, variant 
typedefs, and SV macros don't get generated by CodeGen; instead we have 
to create them by hand.

gdk.typemap adds the typemap for GdkBitmap.  the typemap, 
T_GPERL_GENERIC_WRAPPER, does "Sv$type ($arg)", which, for 
GdkBitmap_ornull, turns into SvGdkBitmap_ornull (ST (2)).

in gtk2perl.h, you can find the variant typedefs and macros for 
GdkBitmap.  a bug is on line 58.

#define SvGdkBitmap_ornull(sv)        (((sv) == &PL_sv_undef) ? NULL : 
SvGdkBitmap(sv))

should be

#define SvGdkBitmap_ornull(sv)        (((sv) && SvTRUE (sv)) ? NULL : 
SvGdkBitmap(sv))


that may not be *the* bug, but it should help.  let me know.


to finish the GdkBitmap story...  since there's no GType for GdkBitmap, 
we have to do a couple of hacks to round out the object support.  the 
Perl-to-C path uses the standard macros-around-gperl_get_object trick, 
but without a GType gperl_new_object would bless into the wrong class.  
so, newSVGdkBitmap and newSVGdkBitmap_noinc are actual functions, 
implemented in Gtk2/xs/GdkPixmap.xs ...  the basic trick is to create 
the object with gperl_new_object, let it get blessed into the 
bottommost known GType, and then re-bless it into Gtk2::Gdk::Bitmap, 
for which we added an @ISA to Gtk2::Gdk::Pixmap in the BOOT section.

as you can see, it's all very straightforward.  *cough*


in general, however, i just avoid the use of GdkBitmaps, because 
GdkPixbuf is a lot easier, especially when you already have to transfer 
all the data to the server anyway. you could replace most of that 
loading code with:

  my $pixbuf = Gtk2::Gdk::Pixbuf->new_from_file ($filename);
  $image->set_from_pixbuf ($pixbuf);

--
muppet <scott at asofyet dot org>