Re: g_signal_connect arguments

[Paul Pogonyshev <pogonyshev gmx net>]

franfernandezb coit es wrote:
> Hi all,
>
>       I am new to GTK programming, and I've got a very simple question about
> callbacks. In the application interface that I am encoding the next
> function brings up a window containing several GtkEntries and a
> GtkCheckButton to gather the options chosen by the user:
>
> void menu_qdisc(){
>
> ..
>
> GtkWidget *isRoot;
> GtkWidget *entry1;
> GtkWidget *entry2;
>
> isRoot = gtk_check_button_new_with_label ("root qdisc");
> entry1 = gtk_entry_new();
> entry2 = gtk_entry_new();
>
> ..
>
> g_signal_connect(G_OBJECT (button), "clicked", G_CALLBACK (callback_create), ???);
>
> The problem is that I don't know how to define the signal_connect function
> as all the examples that I've found only pass one widget parameter to the
> callback. Should I pass the window containing all the widgets as an
> argument?

You should pass a pointer to a structure that will allow you to retrieve
all the data you need.  If your window/dialog has its own class, then
pass a pointer to the window/dialog object.  Else do something like

typedef struct _SomeDialogData  SomeDialogData;

struct _SomeDialogData {
  GtkWidget *isRoot;
  GtkWidget *entry1;
  ...
};

Fill this structure (preferably g_malloc'ed) when you create the window
and pass it as your `user_data' as fourth parameter of g_signal_connect().
Then your callback can look like

void
callback_create (GtkWidget *button, SomeDialogData *data)
{
  ...
}

Since you probably don't need the pointer to the button, you can instead
connect using g_signal_connect_swapped() and simplify the callback to

void
callback_create (SomeDialogData *data)
{
  ...
}

> And what is the way to read the user info from the widgets in the callback
> function?

Depends.  For text entries it's like gtk_entry_get_text (entry).  (May need
to cast with GTK_ENTRY() if you are passing generic pointers to `GtkWidget'
around.)  For check/radio/toggle buttons it is gtk_toggle_button_get_active().

Paul