GTK Linux C Get Input from Entry Box via Button Widget - c

Question

I have a table that is filled with entry boxes, labels, and buttons.
Currently, if I compile the code, I can get input from a text box but only if the users presses the enter key, and the text only comes from the box they are currently typing in.
I would like to be able to get input from both text boxes when the "Login" button is pushed. I've tried using the same callback function that's used for enter key on the entry box, but GTK gives me an error.
If anyone could show me some code that would allow for me to get text from my entry boxes that are within tables (I know the method for retrieving data from tables and v/boxes is different) it would be greatly appreciated, as I can't seem to find it in any tutorials.
Will update w/working code.
Error when trying to attach status bar to table:
(Entry:5526): Gtk-CRITICAL **: gtk_table_attach: assertion `child->parent == NULL' failed
(Entry:5526): GLib-GObject-WARNING **: invalid cast from GtkTable' toGtkStatusbar'

Answer 1

Your callback function (named callback) needs to access both GtkEntry widgets in order to obtain their values. There are several ways this can be accomplished. Many GTK C programs use global variables, or global variables with file scope (ie a variable declared as static outside of any function within a file).
Remove your entry1 and entry2 variables near the top of the file before any functions:
static GtkWidget *entry1 = 0;
static GtkWidget *entry2 = 0;
And then modify the callback like so:
/* Our callback.
* The data passed to this function is printed to stdout */
static void callback( GtkWidget *widget, gpointer data)
{
const gchar *entry_text1;
const gchar *entry_text2;
g_print ("Hello again - %s was pressed\n", (char *) data);
entry_text1 = gtk_entry_get_text (GTK_ENTRY (entry1));
entry_text2 = gtk_entry_get_text (GTK_ENTRY (entry2));
g_print ("Contents of entries:\n%s\n%s\n", entry_text1, entry_text2);
}
You should additionally make similar modifications to the enter_callback function, and don't forget to remove the GtkWidget pointers to both GtkEntry from main.
As an alternative to using (static) global variables, create a data structure to hold the entries:
typedef struct login_data
{
GtkWidget *entry1;
GtkWidget *entry2;
} login_data;
This then gets passed to the callback (rather than text string as before), and the callback changes like so:
static void callback( GtkWidget *widget, gpointer data)
{
login_data* ld = (login_data*)data;
const gchar *entry_text1;
const gchar *entry_text2;
entry_text1 = gtk_entry_get_text (GTK_ENTRY (ld->entry1));
entry_text2 = gtk_entry_get_text (GTK_ENTRY (ld->entry2));
g_print ("Contents of entries:\n%s\n%s\n", entry_text1, entry_text2);
}
The data structure is dynamically allocated to prevent it going out of scope (not strictly necessary in simple applications) and this is done before using g_signal_connect to connect the callback to the entries:
login_data* ld = g_malloc(sizeof(*ld));
// callback function to execute when login is clicked
g_signal_connect (LoginButton, "clicked", G_CALLBACK (callback), (gpointer) ld);
Using this method, you must change all references to entry1 and entry2 to ld->entry1 and ld->entry2. Lastly, before the program exits, you should call g_free on the dynamically allocated struct ie g_free(ld).
BTW, for this program you don't need two separate callbacks, remove enter_callback and just use callback for both.