Re: [gtkmm] Key Snooping / Key_Press_Event Howto?

["Andrew E. Makeev" <andrew solvo ru>]

Jeff Gavin wrote:

> I'm trying to validate an entry while the user types.  I've read all 
> the posts on entry validation and I still don't know an answer.  I 
> would like to create a entry that can validate a date while the user 
> types it in, but to simplify things on the initial version, I decided 
> to create an entry that only allows numbers to be typed in.
>
> Keep in mind I come from a MS/VB background (I know, yech, ptooie, 
> gross!).
>
> From this experience, I have created entries that would intercept each 
> keystroke and decide weather to accept them or not.
>
> For example this VB code snip would not allow the "UserCode" field to 
> accept certain characters.  Changing the KeyAscii code to 0 prevents 
> the entry from accepting the keystroke:
>
> Private Sub txtUserCode_KeyPress(KeyAscii As Integer)
>   ' Check for invalid character and exclude them.
>   If InStr(1, " ~`! #$%^&*()_+-={}[]\|:;<>,./?'""", Chr(KeyAscii)) > 0 
> Then
>     KeyAscii = 0
>   End If
> End Sub
>
> I cannot figure out how to do this with gtk+/gtkmm.  The 
> key_press_event seemed like an obvious candidate, but it only triggers 
> when the user presses shift/esc/ctrl.  Maybe this is not such a good 
> name for this event if that's all it can do.  Is there a way to make 
> all the key presses to be passed to the callback?  I'm sure someone 
> has had to solve this type of problem before.  How did you do it?
>
> Best Regards,
>
> Jeff
1. Try to read tutorial and API reference about signal/event processing.

2. You have to connect to signal with parameter after=false set, like this:

<widget>.signal_key_press_event ().connect (SigC::slot (<callback>), false);

then your callback would be called before Gtk+ keypress event handling.
Keep in mind you could stop event processing just with return value = true.