GTK/Glade text entry string to global variable in C

Question

I am creating a Menu GUI for a game using glade and GTK in C. I have a text entry box and a button. When the button is pressed, the value inside the text entry needs to be saved as a global variable. I don't know how to get the value inside the text entry so I'm a bit stuck. Any help would be great.

Function

void on_okButton_clicked (GtkButton *object, gpointer user_data)
{
//???????
}

EDIT:

This is what my current code looks like

#include <stdio.h>
#include <gtk/gtk.h>
#include <python2.7/Python.h>


void on_window1_destroy (GtkObject *object, gpointer user_data)
{
gtk_main_quit();
}

void on_okButton_clicked (GtkButton *object, gpointer user_data)
{

gchar *entry_value;//this can be a global variable, too, of course
entry_value = gtk_entry_get_text(//get text function
    GTK_ENTRY(//use GTK_ENTRY widget
        (GtkWidget *) user_data //cast to GtkWidget pointer
    )
);

}


int main(int argc, char *argv[])
{
    GtkBuilder *gtkBuilder;
    GtkWidget *window;
    GtkWidget *Quit;
    GtkWidget *OK;
    GtkWidget *entry = gtk_entry_new();
    gtk_init(&argc, &argv);

    gtkBuilder = gtk_builder_new();
    gtk_builder_add_from_file(gtkBuilder, "IPenter.glade", NULL);
    window = GTK_WIDGET(gtk_builder_get_object(gtkBuilder, "window1"));

    OK = GTK_WIDGET(gtk_builder_get_object(gtkBuilder, "okButton"));
    g_signal_connect(G_OBJECT(OK),"clicked",G_CALLBACK(on_okButton_clicked),entry);

    g_object_unref(G_OBJECT(gtkBuilder));
    gtk_widget_show(window);
    gtk_main();

    return 0;
}

Answer 1

Assuming you connected the signal correctly, this ought to work just fine:

gchar *entry_value;//this can be a global variable, too, of course
entry_value = gtk_entry_get_text(//get text function
    GTK_ENTRY(//use GTK_ENTRY widget
        (GtkWidget *) user_data //cast to GtkWidget pointer
    )
);

Just to be sure, this is how you should connect the signal:

g_signal_connect(
    G_OBJECT(your_btn),
    "clicked",
    G_CALLBACK(
        on_okButton_clicked
    ),
    txt_entry_pointer
);

Where txt_entry_pointer is, of course, a pointer to the entry widget. Do not, however, make the surprisingly common mistake of passing the address of a local pointer here. If you create the entry widget like so:

GtkWidget *entry = gtk_entry_new();

And then attempt to connect the signal like so:

g_signal_connect(
    G_OBJECT(your_btn),
    "clicked",
    G_CALLBACK(
        on_okButton_clicked
    ),
    &entry// <=== WRONG!!
);

You are passing a pointer to a stack pointer, very likely resulting in undefined behaviour. Just drop the ampersand from the code above.

Also worth mentioning is that gchar is just a typedef for the char type. That means that:

gchar *foobar;

is the same as writing

char *foobar;

As you can see here.