Re: newbie: callback function

["Brian J. Tarricone" <bjt23 cornell edu>]

your prototype here is:

GtkButton *button_create(const char *text, void *callbackfunction)

if you were passing a void * pointer, that would be fine, but you're not.  you want something like this:

GtkButton *button_create(const char *text, void (*callbackfunction)())

because you're passing it a function pointer with a specified signature, not just a void * pointer.

        -brian


F. Kater wrote:

> Hi,
>
> with msvc6.0 I had no problems but mingw/gcc gives me the following
> error in the function call gtk_box_pack_start (see below): "invalid
> conversion from'void(*)()' to'void*'. The problem is the function
> pointer "callback_init" which gcc doesn't accept this way. But what's
> wrong?
>
> Felix
>
>
>
> my callback:
> ------------
>
> void callback_init() { /* ... */ }
>
>
> my button create function (not quite important here):
> -----------------------------------------------------
>
> GtkButton *button_create(
>         const char *text,
>         void *callbackfunction)
> {
>         GtkWidget *gtkwidget1;
>         gtkwidget1 = gtk_button_new_with_label(text);
>         g_signal_connect(
>                 G_OBJECT(gtkwidget1),
>                 "clicked",
>                 G_CALLBACK(callbackfunction),
>                 NULL);
>         gtk_widget_show(gtkwidget1);
>         return GTK_BUTTON(gtkwidget1);
> }
>
>
> the main with the function which causes the error (see description):
> -------------------------------------------------------------------
>
> int main( /*...*/ ){
>
> /*...*/
>
> gtk_box_pack_start(
>         GTK_BOX(hbox2),
>         GTK_WIDGET(
>                 button_create(
>                         "My Button Name",
>                         callback_init   /* error */
>                 )
>         ),
>         INT_EXPAND,
>         cgboolean_fill,
>         cint_padding
>         );
>
>
> /*...*/
>
> }
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