Re: How to use a signal

[José Alburquerque <jaalburquerque cox net>]

Jamiil Abduqadir wrote:
> Thanks Jose for your prompt response!
> I have two questions regarding this issue,
> One: what does HTH mean and

HTH = Hope This/That Helps

> Second:
> After doing the modifications your suggested, as shown below, I now 
> get this 3 errors, please at the end of this message.
>
> Please note, that this is the first time I am developing a GUI 
> interface, I have chosen Gtkmm because it is C++, portable and fast, 
> nevertheless, I might make stupid mistakes just because of my poor 
> understanding of the GUI library, not because my lack of understanding 
> of the OOP paradigm. As it is the case now, I am sure that I am not 
> passing the right parameters expected by Gtkmm. However, according to
>
> c:\doc\gtkmm-2.4/docs/tutorial/html/apb.html#id2567896
>
> these, and as far as I understand, are the two parameters that I have 
> to pass.
>
> What am I doing wrong?
>
> Thanks in advance.
>
>
> ================ code snip ========
> namespace jve{
> class Entry: virtual public Gtk::VBox {
>       .......
>       Gtk::Entry* text_box;
> public:
>       MyClass();
>       .........
>       void onBlanck();
> };
> }
> jve::Entry::Entry(){
>       ....
>       text_box  = Gtk::manage(new Gtk::Entry());
>       *text_box->signal_focus_out_event().connect(sigc::mem_fun(*this, 
> &Entry::onBlank)); /<== here is the problem/*
>       ....
> }
> void jve::Entry::onBlank(){ // this->getText() returns a Gtk::ustring 
> object
>    if(this->getText(().empy()){
>       // Display a Dialogbox explaining the problem
>       text_box->grab_focus();
>    }
> }

It looks like your onBlank() method should be of type "bool" and not 
"void".  In other words, it should return a bool value.  See: 
http://www.gtkmm.org/docs/gtkmm-2.4/docs/reference/html/classGtk_1_1Widget.html#928afef862c529586ce0d461598623f1

> =========== errors ===========
> ||=== Console application, default ===|
> D:\XWin\include\sigc++-2.0\sigc++\functors\slot.h|144|instantiated 
> from `static void*(* sigc::internal::slot_call1<T_functor, T_return, 
> T_arg1>::address())(void*) [with T_functor = 
> sigc::bound_mem_functor0<void, jme::Entry>, T_return = bool, T_arg1 = 
> GdkEventFocus*]'|
> D:\XWin\include\sigc++-2.0\sigc++\functors\slot.h|529|instantiated 
> from `sigc::slot1<T_return, T_arg1>::slot1(const T_functor&) [with 
> T_functor = sigc::bound_mem_functor0<void, jme::Entry>, T_return = 
> bool, T_arg1 = GdkEventFocus*]'|
> D:\XWin\include\sigc++-2.0\sigc++\functors\slot.h|1157|instantiated 
> from `sigc::slot<T_return, T_arg1, sigc::nil, sigc::nil, sigc::nil, 
> sigc::nil, sigc::nil, sigc::nil>::slot(const T_functor&) [with 
> T_functor = sigc::bound_mem_functor0<void, jme::Entry>, T_return = 
> bool, T_arg1 = GdkEventFocus*]'|
> D:\c++\Samiira\entry.cpp|12|instantiated from here|
> D:\XWin\include\sigc++-2.0\sigc++\functors\slot.h|136|error: void 
> value not ignored as it ought to be|
> D:\XWin\include\sigc++-2.0\sigc++\adaptors\adaptor_trait.h||In member 
> function `typename 
> sigc::adaptor_functor<T_functor>::deduce_result_type<T_arg1, void, 
> void, void, void, void, void>::type 
> sigc::adaptor_functor<T_functor>::operator()(T_arg1) const [with 
> T_arg1 = GdkEventFocus* const&, T_functor = 
> sigc::bound_mem_functor0<void, jme::Entry>]':|
> D:\XWin\include\sigc++-2.0\sigc++\functors\slot.h|136|instantiated 
> from `static T_return sigc::internal::slot_call1<T_functor, T_return, 
> T_arg1>::call_it(sigc::internal::slot_rep*, typename 
> sigc::type_trait<T_arg3>::take) [with T_functor = 
> sigc::bound_mem_functor0<void, jme::Entry>, T_return = bool, T_arg1 = 
> GdkEventFocus*]'|
> D:\XWin\include\sigc++-2.0\sigc++\functors\slot.h|144|instantiated 
> from `static void*(* sigc::internal::slot_call1<T_functor, T_return, 
> T_arg1>::address())(void*) [with T_functor = 
> sigc::bound_mem_functor0<void, jme::Entry>, T_return = bool, T_arg1 = 
> GdkEventFocus*]'|
> D:\XWin\include\sigc++-2.0\sigc++\functors\slot.h|529|instantiated 
> from `sigc::slot1<T_return, T_arg1>::slot1(const T_functor&) [with 
> T_functor = sigc::bound_mem_functor0<void, jme::Entry>, T_return = 
> bool, T_arg1 = GdkEventFocus*]'|
> D:\XWin\include\sigc++-2.0\sigc++\functors\slot.h|1157|instantiated 
> from `sigc::slot<T_return, T_arg1, sigc::nil, sigc::nil, sigc::nil, 
> sigc::nil, sigc::nil, sigc::nil>::slot(const T_functor&) [with 
> T_functor = sigc::bound_mem_functor0<void, jme::Entry>, T_return = 
> bool, T_arg1 = GdkEventFocus*]'|
> D:\c++\Samiira\entry.cpp|12|instantiated from here|
> D:\XWin\include\sigc++-2.0\sigc++\adaptors\adaptor_trait.h|84|error: 
> no match for call to `(sigc::bound_mem_functor0<void, jme::Entry>) 
> (GdkEventFocus* const&)'|
> D:\XWin\include\sigc++-2.0\sigc++\functors\mem_fun.h|1787|note: 
> candidates are: T_return sigc::bound_mem_functor0<T_return, 
> T_obj>::operator()() const [with T_return = void, T_obj = jme::Entry]|
> D:\XWin\include\sigc++-2.0\sigc++\adaptors\adaptor_trait.h|84|error: 
> return-statement with a value, in function returning 'void'|
> ||=== Build finished: 3 errors, 0 warnings ===|
> --
> Happiness has many doors, and when one of them closes another opens, 
> yet we spent so much time looking at the one that is shut that we 
> don't see the one that just opened.
> ------------------------------------------------------------------------
>
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>   


--
José Alburquerque
jaalburquerque cox net

The path to real wisdom begins with a deep loving respect for the ever living God (Prov. 1:7)