[Gtk-sharp-list] System.InvalidCastException from generated code

[Martin Willemoes Hansen]

On Mon, 2004-01-26 at 03:25, Ben Maurer wrote:
> Hello,
> 
> While I was playing around with gtksourceview today, i found that
> placing a mark in the text would create an error. The error that was
> thrown was:
> 
> > Unhandled Exception: System.InvalidCastException: Cannot cast from source type to destination type
> > in <0x00085> Gtk.SourceBuffer:CreateMarker (string,string,Gtk.TextIter)

Yes, I have seen that error too, just in some other area (DiaCanvas# and
also gtksourceview#).

> Looking into the code, i found that the generator made the code:
> 
> 
> > 		public Gtk.SourceMarker CreateMarker(string name, string type, Gtk.TextIter where) {
> > 			IntPtr raw_ret = gtk_source_buffer_create_marker(Handle, name, type, ref where);
> > 			Gtk.SourceMarker ret = (Gtk.SourceMarker) GLib.Object.GetObject(raw_ret);
> > 			return ret;
> > 		}

try changing the code to be like this:
Gtk.SourceMarker ret = new Gtk.SourceMarker (raw_ret);

> 
> I placed a Console.WriteLine in there to see the type of the object that
> was coming out of the cache. It was a TextIter.
> 
> I think the problem comes from the folowing C code:
> 
> 
> >  33             GType 
> >  34             gtk_source_marker_get_type (void)
> >  35             {
> >  36             	static GType our_type = 0;
> >  37             
> >  38             	/* this function's solely purpose is to allow us to later
> >  39             	 * derive GtkSourceMarker from other base object and not break
> >  40             	 * ABI compatibility (since this way the type is resolved at
> >  41             	 * runtime) */
> >  42             	if (!our_type) {
> >  43				our_type = GTK_TYPE_TEXT_MARK;
> 
> It seems that Gtk# is confused as to the type of the object. What would
> be the best way to fix this?

Yes, I would like to know that as well :o)

Until it is fixed, you can correct the error by hiding the function and
creating a working function with a .custom file.

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-- 
Martin Willemoes Hansen

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