Re: Gtk2::SpinButton with blank value

[muppet <scott asofyet org>]

On Nov 10, 2008, at 3:19 PM, Jeffrey Ratcliffe wrote:

> I'd like to set a Gtk2::SpinButton to a blank value in certain
> situations.
>
> set_value() complains that "" isn't numeric, but Gtk2::SpinButton
> inherits from Gtk2::Entry, so set_text() should work, but is simply
> ignored (or possibly set, and updated to the nearest numeric value, as
> happens when entering a blank value manually and hitting return).
>
> Is it doable?


Looking at the C code in gtkspinbutton.c, i think you could override  
the GtkEditable's insert_text method with your own thing that allows  
you to slip a BlankableSpinButton into a "blank" state.

But we don't have the infrastructure you need to implement your own  
overrides for Gtk2::Editable methods.

D'oh.

You could override the insert-text signal, but to get stuff to happen  
correctly, you'd either have to reimplement the whole thing from  
gtkspinbutton.c or chain up -- and in chaining up, you bump into a  
deficiency of Glib::Object::signal_chain_from_overridden(), namely  
that it doesn't know how to unmarshal the stuff we give to custom  
signal marshalers.  In other words, we crash.

Double d'oh.


So, without binding work, no, not doable by "clean" methods.

You could do dirty stuff like hook into focus-out and prevent it  
restoring the numeric value, but that'll be tedious and fragile.


The obvious question is, why do you want to do this?  What are these  
certain situations?  Maybe there's another solution that doesn't  
involve hackery here...


--
Teeter tots are shaped like marshmallows.
  -- Zella.