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List:       gtkmm
Subject:    Re: const version of Gdk::Pixbuf::save()
From:       Florian Philipp <lists () binarywings ! net>
Date:       2012-06-21 19:28:43
Message-ID: 4FE375EB.70407 () binarywings ! net
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Am 21.06.2012 19:45, schrieb Kjell Ahlstedt:
> Gdk::Pixbuf::save() and save_to_buffer() are C++ wrappers around the C
> functions gdk_pixbuf_savev() and gdk_pixbuf_save_to_buffer(), resp.
> Those C functions take a "GdkPixbuf* pixbuf" parameter (i.e. not const
> GdkPixbuf* pixbuf). I don't know why. It's unintuitive that they should
> modify the GdkPixbuf, but perhaps they do. Anyway, that's the reason why
> there are no const versions of the corresponding C++ member functions.
> 
> A solution (not very attractive, I admit) is to take a copy of the
> Pixbuf with Gdk::Pixbuf::copy() and save the copy.
> 
> If you don't get a better answer here, you can try asking on a gtk+ list
> (e.g. gtk-app-devel-list) why the gdk_pixbuf_save*() functions don't
> take const GdkPixbuf*.
> 

Why don't you simply cast the const away?

Gtk::Image const&  img (my_canvas->getImage());
Glib::RefPtr<const Gdk::Pixbuf>  pix_buf (img.get_pixbuf());
Glib::RefPtr<Gdk::Pixbuf> mutable_pix_buf =
	Glib::RefPtr<Gdk::Pixbuf>::cast_const (pix_buf);
mutable_pix_buf.save(fname, "png");

Regards,
Florian Philipp


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