Re: [gtkmm] signal_key_press_event() question

["Daniel J. Lauk" <Daniel Lauk Student FH-Reutlingen de>]

Well, actually...
...if you had return on_key_press_event(event); at the end of your event handler
(where I put the Gtk::Entry::on_...), then you created an infinite loop, yes.

...if you had it at the place where it is in your sample code below, than the
following occurs: If <ENTER> is pressed the key code gets changed to <TAB> and
the handler is reinvoked. That's perfectly fine. Only, for all non-<ENTER> keys
the handler simply does nothing (besides returning false).

What the call Gtk::Entry::on_... does, is: it calls the (overridden) method
of the base class (I think the correct c.s. terminology is a "super call").
This is very important if you derive classes that "add" special behaviour or
vary the original one only a little bit (e.g. modifying/ignoring a certain key).
If you'd like your derived class to handle the event totally different, you
wouldn't call the base classes method.

I hope that helped you a little bit and you'll have a lot of fun with this awful
language. I myself really hate C++ for giving the programmer so many possibilities...
no, wait... that's actually the reason why I love it... or hate? ... Eh, anyway,
you better make up your mind and decide for yourself, what you like and what
not :^)

Regards,

DJ

>thanks for your reply,
>
>I tried almost the same:
>    return on_key_press_event(event);  //this of course resulted in an
>endless loop
>instead of
>    return Gtk::Entry::on_key_press_event(event);
>I think this will bypass my NumberEntry::on_key_press_event() and thus avoid

>the endless loop, (i still have to learn some things about c++).
>I will try this.
>
>thank you,
>Marco
>
>----- Original Message ----- 
>From: "Daniel J. Lauk" <Daniel Lauk Student FH-Reutlingen de>
>To: <schwein chello nl>;
><"gtkmm-list gnome org"@loginmail.fh-reutlingen.de>; <gtkmm-list gnome org>

>Sent: Thursday, October 07, 2004 9:10 AM
>Subject: Re: [gtkmm] signal_key_press_event() question
>
>
>> Hi.
>>
>> First of all, I think, that your Gdk event handler is not doing all it
>should,
>> but I'm not sure.
>> Anyway, what you'd probably like is, to have the same behaviour as with a

>regular
>> Gtk::Entry except for the thing with the <ENTER> to <TAB> conversion,
>right?
>>
>> I'm not absolutely sure on this, but you might like to experiment with the

>following
>> code:
>>
>> <code>
>> bool NumberEntry::on_key_press_event(GdkEventKey* event)
>> {
>>   /* first (if necessary) change the key code */
>>   //36 = enter, 108 = keypad enter, 13 = tab
>>   if (event->hardware_keycode==36 ||
>>       event->hardware_keycode==108)
>>   {
>>     event->hardware_keycode = 13;
>>   }
>>
>>   /* and now do, what Gtk::Entry would have done */
>>   return Gtk::Entry::on_key_press_event(event);
>> }
>> </code>
>>
>> Best regards,
>>
>> DJ
>>
>> >I want to catch a keypress of enter and turn it into a tab (to go to the

>> >next entry) to enable the user to quickly enter lots of numbers with the

>> >numerical keypad.
>> >
>> >Then i tried this code to catch a keypress in a Gtk::Entry, but this only

>>
>> >works with non-printable keys (tab, function keys etc.)
>> >So i think that all printable characters get processed by the entry's
>> >on_key_press_event() and never make it to OnKeyPress() ?.
>> >
>> >class NumberEntry : public Gtk::Entry
>> >{ public:
>> > NumberEntry();
>> > ~NumberEntry();
>> > bool OnKeyPress(GdkEventKey* event);
>> >};
>> >
>> >NumberEntry::NumberEntry()
>> >{ signal_key_press_event().connect(sigc::mem_fun(*this,
>> >&NumberEntry::OnKeyPress));
>> >}
>> >
>> >bool NumberEntry::OnKeyPress(GdkEventKey* event)
>> >{ cout << "Pressed " << event->hardware_keycode << endl;
>> > return false;
>> >}
>> >
>> >
>> >I also tried overriding the on_key_press_event() function and was able to

>>
>> >turn an enter into a tab, however no printable characters made it into
>the
>>
>> >entry box.
>> >
>> >bool NumberEntry::on_key_press_event(GdkEventKey* event)
>> >{ cout << "Pressed " << event->hardware_keycode << endl;
>> > //36 = enter, 108 = keypad enter, 13 = tab
>> > if (event->hardware_keycode==36 || event->hardware_keycode==108)
>> > { event->hardware_keycode = 23;
>> > return on_key_press_event(event); //tab to next
>> > }
>> > return false;
>> >}
>> >
>> >i'm kinda stuck now, what am i doing wrong?, or is there maybe a much
>> >simpler way to achieve what i want?
>> >
>> >thanks for any help,
>> >Marco
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>
>