Re: how to handle an array of Pixbuf?

[Kjell Ahlstedt <kjell ahlstedt bredband net>]

In the code snippet that you've shown, image2 is allocated on the stack. 
Then of course it's deleted when the creating method is terminated. The 
reference count of Gdk::Pixbuf is decreased, when 
Glib::RefPtr<Gdk::Pixbuf> is deleted. If the reference count reaches 0, 
Gdk::Pixbuf is also deleted. The next question is: How do you copy 
image2 in XMLSeq's constructor? If you use memcpy() or a similar 
function, neither RefPtr's copy constructor nor its assignment operator 
will be called. The reference count of Gdk::Pixbuf is not increased as 
it should be when Glib::RefPtr<Gdk::Pixbuf> is copied. And if you only 
copy a pointer to the array, you will have a dangling pointer after the 
array has been deleted in the creating method.

If it works with std::vector, and you are satisfied with that, we need 
not try to find out exactly what happened to your array, unless you're 
interested.

2013-03-01 21:03, jody skrev:
> I just passed the array to a constructor of an object who later draws itself
>      XLMSeq *pXLM3 = new XLMSeq(77, 1.0, 1, EAST, 3, image2);
>
> in the constructor i copy the array 'image2' to the object's member
> variable 'image2',
> which is later used for drawing.
>
> If i understand it correctly, by passing the pointer, the images were
> deleted after the method which created them terminated?
>
> But now I tried it  with a std::vector and that worked - thank you!
>   jody
>
> On Fri, Mar 1, 2013 at 8:30 PM, Kjell Ahlstedt
> <kjell ahlstedt bredband net> wrote:
> > How do you transfer the array from the creating method to the painting
> > method? With arrays it's easy to (by mistake) copy a pointer to the array
> > when you should have copied the whole array. A std::vector is often safer,
> >
> > std::vector< Glib::RefPtr<Gdk::Pixbuf> > image2(3);
> >
> > Kjell
> >
> > 2013-03-01 19:17, jody skrev:
> > > Follow up:
> > > when i fill the PixBuf array in the same method where i paint its
> > > element this works...
> > > Jody
> > >
> > > On Fri, Mar 1, 2013 at 7:10 PM, jody <jody xha gmail com> wrote:
> > > > Hi
> > > >
> > > > When i do
> > > >      Glib::RefPtr<Gdk::Pixbuf> image1 =
> > > > Gdk::Pixbuf::create_from_file("base1.png");
> > > >
> > > > i can later (in a different method) paint this into a cairo context like
> > > > this:
> > > >      Gdk::Cairo::set_source_pixbuf(cr, image1, 0, 0);
> > > >
> > > >
> > > > Now i wanted to do the same with an array of PixBufs:
> > > >       Glib::RefPtr<Gdk::Pixbuf> image2[3];
> > > >       image2[0] =  Gdk::Pixbuf::create_from_file("hexT1.png");
> > > >       image2[1] =  Gdk::Pixbuf::create_from_file("hexT2.png");
> > > >       image2[2] =  Gdk::Pixbuf::create_from_file("hexT3.png");
> > > > this compiles and seems to work, but painting (in a different method) :
> > > >       Gdk::Cairo::set_source_pixbuf(cr, image2[0], 0, 0);
> > > > fails with a segmentation fault.
> > > >
> > > > I suspect that for some reason the RefPtr died, but i actually have no
> > > > idea.
> > > >
> > > > Can anybody help me?
> > > >
> > > > Thank You
> > > >     Jody
> > > _______________________________________________