Re: Callback trouble

> As a test, and to learn about FLTK and classes, I am trying to make a
> dial that control a value input - very simular to the "adjuster" example
> (part of the FLTK distribution), except that I have put the interface
> into a class. The class they belong to is called Tempo, and the controls
> are named "tempo_dial" and "tempo_input". When the dial is changed,
> the callback goes to a global function, tempo_cb(Fl_Dial *o, void *v).
> So here's my problem: how to transfer the value from the tempo_dial
> (which I can read) to the tempo_input? I have made a global variable that
> points to my userinterface, and tried to use the pointer to read out
> the value from within the callback, but just setting up the connection
> proved more difficult than I had expected. Fl_Value_Input *obj =
> (Fl_Value_Input*)tempo_class->tempo_input; It compiles, but results
> in an access violation - what am I doing wrong here? And could there be
> an alternative solution ? 

Hi,

Here is probable solution.

For example if we have:

Fl_Dial *tempo_dial;
Fl_Value_Input *tempo_input;

then:

tempo_dial->callback(dial_cb, tempo_input);

where dial_cb is:

void dial_cb(Fl_Widget*, void* ti)
{
	Fl_Value_Input* tempo_input = (Fl_Value_Input*)ti;
	tempo_input->value(some_global_value);
}

Now, displayed value inside Fl_Value_Input is controlled by Fl_Dial. 
'some_global_value' can be set/changed inside dial_cb or somewhere else.

Works ?