Re: GTK signals question.

[Chris Moller <moller mollerware com>]

I was actually writing that testcase when I found a correlation: I'm 
using gcc and my callbacks were nested functions.  Pull the callbacks 
out and make them normal, top-level, functions, and it all works even 
without no blocking of any kind.  So, if this is a bug at all, I suppose 
it could be a compiler bug.

One way or the other, thanks for all the responses.

-cm

On 03/05/14 04:21, A. Walton wrote:
> On Tue, Mar 4, 2014 at 10:43 PM, Chris Moller <moller mollerware com 
> <mailto:moller mollerware com>> wrote:
>
>     Okay, I'm out of ideas...
>
>     I'm writing an app, that among a lot of other stuff, has three
>     mutually interacting spinbuttuns, i.e., if I increment spinbutton
>     A, its callback then updates values in B and C.  B and then would
>     try to update A, and C, etc., resulting in a bottomless recursion.
>      So, what I need to do is, while I'm in A's callback, block the B
>     and C callbacks; while in in B, block A and C and so on.
>
>     Every combination of g_signal_handler_block(),
>     g_signal_handlers_block_matched(), etc, I've tried just results in
>     seg faults--all that stuff works fine outside the callbacks, but
>     the moment I stick them in a callback, death happens.
>
>     Any suggestions?
>
>
> I'm surprised g_signal_handler_block() or g_signal_stop_emission() 
> didn't work. This was actually a concern when we added the GBinding 
> code to GObject - making sure that these kinds of signal loops were 
> well documented and that you have to prevent against them yourself 
> using one of these methods.
>
> My first suggestion would be to post a minimal test case demonstrating 
> how this failed for you - might have stepped on a bug, but either way 
> it'd make it easier to see why it failed for you.
>
> My second suggestion is along the same line as Tristan's suggestion: 
> create a GObject that holds the value as a property (the model), and 
> bind the property to the views instead of binding the views' values 
> together. (I think this object would be more boilerplate than code, 
> woe is our lives as Gtk+ C developers.) You can use the GBinding code 
> with an appropriate GBindingTransformFunc applied to scale the value 
> correctly for each view, which cuts down the amount of code this 
> approach would take. If these controls are in the same place in the 
> UI, you could bake it all (the three spin buttons, any labels, and the 
> one true value property) into one composite GtkWidget and save 
> yourself a bit of boilerplate too.
>
> -A. Walton
>
>     Thanks.
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