Re: [gtkmm] Re: How to derive from Gtk::Toolbar_Helpers::ToggleElem ??

[Murray Cumming <murrayc usa net>]

This might be relevant:
http://libsigc.sourceforge.net/libsigc1_2/manual/html/ch02s02.html

But more importantly, I don't think that you should be deriving from
ToggleElem and adding member data. These items are meant to be stored in
a container by value, so they need to all have the same data.

On Mon, 2003-09-29 at 04:32, S. Myles Prather wrote:
> Ok. No surprise. Turns out it was loser error. But PLEASE, will
> someone explain to me why this works:
> 
> class ToolbarMenuElem : public Gtk::Toolbar_Helpers::ToggleElem,
> public SigC::Object {
>   public:
>     ToolbarMenuElem(
>       Gtk::Menu * menu_, const Glib::ustring & text, Gtk::Widget &
> content, 
>       const Glib::ustring & tooltip_text=Glib::ustring(), 
>       const Glib::ustring & tooltip_private_text=Glib::ustring());
> }
> 
> I took the time to actually attempt to figure out the error msg I
> posted previously and something clued me in to adding the public
> derivation of SigC::Object to the ToolbarMenuElem class. Problem is, I
> have no clue why this worked. And how have I been writing Gtkmm
> (sporadically) for a couple of years now and never had to do that
> before? Yeesh this C++ GUI stuff is confusing. I'm such a Noob.
> 
> Myles
> 
> S. Myles Prather wrote:
> > I didn't think this would work when I typed it in, and sure nuf, it
> > don't.  I'm trying to pass arguments to the constructor of my base
> > class (a ToggleElem), but I can't figure out how to pass in the slot
> > (Callback0). 15 lines of code is worth a million words:
> > 
> > class ToolbarMenuElem : public Gtk::Toolbar_Helpers::ToggleElem {
> >   public:
> >     ToolbarMenuElem(
> >       Gtk::Menu * menu_, const Glib::ustring & text, Gtk::Widget &
> > content, 
> >       const Glib::ustring & tooltip_text=Glib::ustring(), 
> >       const Glib::ustring & tooltip_private_text=Glib::ustring());
> > }
> > 
> > ToolbarMenuElem::ToolbarMenuElem(
> >   Gtk::Menu * menu_, const Glib::ustring & text, Gtk::Widget &
> > content, 
> >   const Glib::ustring & tooltip_text, 
> >   const Glib::ustring & tooltip_private_text)
> >   :
> >   Gtk::Toolbar_Helpers::ToggleElem(text, content, SigC::slot(*this,
> > &ToolbarMenuElem::on_toggled),
> >     tooltip_text, tooltip_private_text) {
> > 
> > ...
> > 
> > }
> > 
> > I'm getting a very odd compiler error that points to header files in
> > SigC++, but I'm pretty sure it comes back to me trying to use *this
> > in the argument list for the base class constructor call.
> > Questions:
> > 
> > 1) Is there any way to accomplish what I'm trying to do?
> > 2) If not, how do I generate a NULL slot to appease compilation? I
> > think I can hook up the the toggled signal after I'm off and
> > running. I tried like hell, but couldn't come up with the magic
> > string of greek C++ to make the compiler happy.
> > 3) When does 'this' come into existence? Shouldn't it be the first
> > argument in the call to ToolbarMenuElem::ToolbarMenuElem(...), and
> > therefore, available for use in the base class constructor call?
> > i.e., at the time of the call to the ToolbarMenuElem constructor,
> > the memory has been allocated and a pointer to it should exist,
> > right?
> > 4) Is this a bug/feature-request for gtk/gtkmm? Am I doing something
> > I shouldn't be trying to do? Gtkmm brags about the ability to derive
> > from Gtk objects. What gives? Maybe we just need a constructor that
> > doesn't require a Callback0. Trust me, I'll hook one up later (if I
> > feel the need)!
> > 5) Why can't anything ever go smoothly :( ?
> > 
> > Much appreciation in advance! I'm at a brick wall here. Work-arounds
> > in my head right now totally defeat the purpose of C++.
> > 
> > Here's the (un-intelligible?) compiler error message:
> > 
> > || In file included from
> > /usr/include/sigc++-1.2/sigc++/object_slot.h:73:
> > || /usr/include/sigc++-1.2/sigc++/object_slot.h: In constructor 
> > ||    `SigC::ObjectSlotNode::ObjectSlotNode(void (*)(void*), T*,
> > void*, T2) [with 
> > ||    T = ToolbarMenuElem, T2 = void (ToolbarMenuElem::*)()]':
> > /usr/include/sigc++-1.2/sigc++/slot.h|211| instantiated from
> > `SigC::Slot0<R>::Slot0(SigC::SlotNode*) [with R = void]'
> > /usr/include/sigc++-1.2/sigc++/object_slot.h|73| instantiated from
> > `SigC::Slot0<R> SigC::slot(O1&, R (O2::*)()) [with R = void, O1 =
> > ToolbarMenuElem, O2 = ToolbarMenuElem]'
> > ToolbarMenuElem.cc|14| instantiated from here
> > /usr/include/sigc++-1.2/sigc++/object_slot.h|45| no matching
> > function for call 
> > ||    to `SigC::ObjectSlotNode::init(ToolbarMenuElem*&, void*&, void
> > ||    (SigC::Object::*&)())'
> > /usr/include/sigc++-1.2/sigc++/object_slot.h|46| candidates are:
> > void 
> > ||    SigC::ObjectSlotNode::init(SigC::Object*, void*, void
> > (SigC::Object::*)())
> > || In file included from
> > /usr/include/sigc++-1.2/sigc++/object_slot.h:187:
> > || /usr/include/sigc++-1.2/sigc++/object_slot.h: In constructor 
> > ||    `SigC::ObjectSlotNode::ObjectSlotNode(void (*)(void*), T*,
> > void*, T2) [with 
> > ||    T = ToolbarMenuElem, T2 = void (ToolbarMenuElem::*)(int&,
> > int&, bool&)]':
> > /usr/include/sigc++-1.2/sigc++/slot.h|343| instantiated from
> > `SigC::Slot3<R, P1, P2, P3>::Slot3(SigC::SlotNode*) [with R = void,
> > P1 = int&, P2 = int&, P3 = bool&]'
> > /usr/include/sigc++-1.2/sigc++/object_slot.h|187| instantiated from
> > `SigC::Slot3<R, P1, P2, P3> SigC::slot(O1&, R (O2::*)(P1, P2, P3))
> > [with R = void, P1 = int&, P2 = int&, P3 = bool&, O1 =
> > ToolbarMenuElem, O2 = ToolbarMenuElem]'
> > ToolbarMenuElem.cc|28| instantiated from here
> > /usr/include/sigc++-1.2/sigc++/object_slot.h|45| no matching
> > function for call 
> > ||    to `SigC::ObjectSlotNode::init(ToolbarMenuElem*&, void*&, void
> > ||    (SigC::Object::*&)())'
> > /usr/include/sigc++-1.2/sigc++/object_slot.h|46| candidates are:
> > void 
> > ||    SigC::ObjectSlotNode::init(SigC::Object*, void*, void
> > (SigC::Object::*)())
> > || make: *** [ToolbarMenuElem.o] Error 1
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-- 
Murray Cumming
murrayc usa net
www.murrayc.com