Deriving from Gtk::EntryBuffer

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1

Hi, I am trying to derive and use Gtk::EntryBuffer with the following code:

class TimeBuffer : Gtk::EntryBuffer{
public:
	void on_inserted_text (guint position, const char * chars, guint n_chars){
		if ( (position == 2) || (position == 5) ){
			gtk_entry_buffer_insert_text(gobj(), (position +1), ((const char*) chars[position]), -1 /* see docs */); // reffer to EntryBuffer::insert_text
			gtk_entry_buffer_insert_text(gobj(), position, (const char*) ':', -1);
		}
		if ( ( chars[position] < 48) || ( chars[position] > 57) ) gtk_entry_buffer_insert_text(gobj(), position, (const char*) '0', -1);
	}
	Glib::RefPtr<Gtk::EntryBuffer> get_entry_buffer(){
		return Glib::RefPtr<Gtk::EntryBuffer>(dynamic_cast<Gtk::EntryBuffer*>(this));
	}
};

It does even compile and I am able to attribute a variable to it. However I am having issue on getting the described behaviour of time formatting out of it. I believe my problem is that Gtk::Entry::set_buffer expects a shared pointer of Gtk::EntryBuffer type, however as it does it, it ignores the overloading of the default handler for inserted text

2

Regarding your get_entry_buffer() method, see

See the api documentation for Glib::make_refptr_for_instance() at glibmm: Glib Namespace Reference

I’d recommend making a ::create() method, and then whatever object you’ve composed this EntryBuffer into should have a member variable holding the refptr, rather than using the xxx_from_this approach.

–
As for your on_inserted_text method, I’m not sure that chars[position] is valid; the size of chars is n_chars. I think position is not related to chars at all, so using it as an index seems wrong.

3

right but anyway I should override the set_buffer function to work with the other type of parameter right?

4

No, I wouldn’t derive a Gtk::Entry just to take your TimeBuffer. As the documentation for Glib::RefPtr points out, if you have a Glib::RefPtr<Derived> you can std::dynamic_pointer_cast<Base>, e.g. entry->set_buffer(std::dynamic_pointer_cast<Gtk::EntryBuffer>(ptr_timeBuffer))

In this case I would std::static_pointer_cast, but maybe while you are exploring polymorphism it might be more helpful to use the dynamic error checking version

5

thanks, now it is using the function and indeed there is problem with the gtk_entry_buffer_insert_text function that I was using

6

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