Re: passing #define'd value to callback

[Darin Adler <darin eazel com>]

on 10/10/00 5:22 AM, Peter Wurmsdobler at peter wurmsdobler ctm-france com
wrote:

> When I want to pass a usual variable to a handler connected
> to an object, only the following code works:
> ----------common.h----------
> #define OFF         ( 0 )
> #define ON          ( 1 )
> -------------x.c------------
> static int off = OFF;
> static int on  = ON;
> void mm_spin_radiobutton_clicked( GtkButton *button, gpointer data ) {
> if ( GTK_TOGGLE_BUTTON(button)->active )
> do_something(data);
> }
> void create( void ) {
> :
> gtk_signal_connect(
> GTK_OBJECT( mm_off_radiobutton ), "clicked",
> GTK_SIGNAL_FUNC( mm_state_radiobutton_clicked ), &off );
> gtk_signal_connect(
> GTK_OBJECT( mm_on_radiobutton ), "clicked",
> GTK_SIGNAL_FUNC( mm_state_radiobutton_clicked ), &on );
> :
> }
>
> If the variable off/on is declared inside the create function,
> it works sometimes. However, I would prefer something without
> extra declaration of each value passed.
>
> Any ideas?

Have the integer itself masquerade as a pointer, using the glib macros, like
this (I tried to imitate your formatting):

-------------x.c------------
void mm_spin_radiobutton_clicked( GtkButton *button, gpointer data ) {
    if ( GTK_TOGGLE_BUTTON(button)->active )
        do_something(GPOINTER_TO_INT(data));
}
void create( void ) {
    :
    gtk_signal_connect(
        GTK_OBJECT( mm_off_radiobutton ), "clicked",
        GTK_SIGNAL_FUNC( mm_state_radiobutton_clicked ),
        GINT_TO_POINTER(OFF) );
    gtk_signal_connect(
        GTK_OBJECT( mm_on_radiobutton ), "clicked",
    GTK_SIGNAL_FUNC( mm_state_radiobutton_clicked ),
        GINT_TO_POINTER(ON) );
    :
}

    -- Darin