Re: http://www.gtk.org/tutorial/sec-anupgradedhelloworld.html

[Keith Sharp <kms passback co uk>]

On Thu, 2005-02-17 at 13:05 +0100, Gert Cuykens wrote:
> static void callback( GtkWidget *widget, gpointer   data ){
>     g_print ("Hello again - %s was pressed\n", (gchar *) data);
> }
>
> why do they put () around gchar ?
> why can it not be gchar *data ?

gpointer is a void pointer and the call to g_print is expecting a gchar
pointer, hence the use of (gchar *) to change the pointer type.

> What does %s do ?

Same as in printf, look at the man page: man 3 printf.

> Are gpointer and gchar global variables of gtk ?
> Are gpointer and gchar data types or objects ?
> What does gpointer and gchar represent ?

You should consult a beginners guide to C programming so that you can
understand pointers and data types properly.  There are also a number of
introductory C tutorials on the web, just search Google.

Keith.