[Kde-bindings] Containers passed by reference

[David Palacio]

On Friday 12 December 2008 07:56:42 Richard Dale wrote:
> On Friday 12 December 2008 12:23:12 David Palacio wrote:
> > This is similar to the QImage::bits one. In the Okular bindings a QVector
> > is marshalled to a Ruby array but the original QVector is never updated.
> > This is not the expected behaviour by Okular.
> >
> > virtual bool   loadDocument (const QString &fileName, QVector< Page * >
> > &pagesVector)=0
> > is the c++ signature of a method that needs to be implemented in a
> > generator. pagesVector is a QVector& that will be updated inside this
> > method.
> >
> > I have confirmed, on the C++ side, that the pagesVector has zero size.
> >
> > This would need a special case: create a Ruby Array outside the method
> > and pass it as an argument. When the method finishes, update the QVector.
>
> That should work. In okularhandlers.cpp the QList marshaller is defined
> like this:
>
> DEF_LIST_MARSHALLER( OkularPageList, QVector<Okular::Page*>, Okular::Page )
>
> The macro is defined in qtruby/src/marshall_macros.h, and on line 80 there
> is this code to copy the C++ version of the list to the Ruby one after a
> method has been called:
>
> 			m->item().s_voidp = cpplist;
> 			m->next();
>
> 			if (!m->type().isConst()) {
> 				rb_ary_clear(list);
>
> 				for(int i = 0; i < cpplist->size(); ++i ) {
> 					VALUE obj = getPointerObject( (void *) cpplist->at(i) );
> 					rb_ary_push(list, obj);
> 				}
> 			}
>
> Not that the code after the 'm->next()' call is run after the C++ method
> has has been called.
>
> So I'm not sure why it isn't working in your example.
It seems it is not marshalling back to QVector:
* I run the script and capture it in Gdb
* Set a breakpoint at kdegraphics/okular/core/document.cpp:668
* Set a breakpoint at kdebindings/ruby/qtruby/src/marshall_macros.h:77
( m->item().s_voidp = cpplist; )

It never breaks at the marshall_ItemList method after loadDocument is 
executed. Even if it did marshall it, I am not sure if creating a new list is 
secure:
ItemList *cpplist = new ItemList;