GTK+ Forums

shri_desai09 · Familiar Face Joined: 24 Jul 2006 Posts: 7

Hi all,
i have a problem with the backspace key. I have a entry for accepting only numbers and special characters, since i want to input IP address. i am able to restrict the entry only to digits and special characters but i am not able to take the backspace character. I am totally clueless upon this.
waiting for some reply
regards,
Shri.

openldev · Posted: Wed Aug 30, 2006 3:14 pm Post subject:

If you are using the key-press-event signal callback, you can use the GdkEventKey structure. For example:

Code: (Plaintext)

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g_signal_connect (G_OBJECT (entry), "key-press-event",
G_CALLBACK (key_pressed), NULL);

/* ... */

static gboolean
key_pressed (GtkWidget *entry, GdkEventKey *event, gpointer data)
{
if (event->keyval == GDK_BackSpace)
return FALSE;
else if ((event->keyval >= GDK_0 && event->keyval <= GDK_9) ||
(event->keyval >= GDK_KP_0 && event->keyval <= GDK_KP_9))
/* Insert the number (event->string) & then return TRUE */
else
return TRUE;
}

In the code above, event->keyval is used to get the key that was entered. These values are available in gdk/gdkkeysyms.h. If it was a backspace (GDK_BackSpace), then handle that & return FALSE so GTK+ will handle the backspace.

If the key was a number of a number on the keypad, you should handle it & then return TRUE so GTK+ will take no further action. In any other case, return TRUE so that all other keys are ignored.

Hope this helps!

shri_desai09 · Familiar Face Joined: 24 Jul 2006 Posts: 7

Hi,
i am using a entry widget and i am using "insert_text" event to connect to the callback function. The body of the callback function is as below: here z is a global int varibale used as a count and IPaddr[] is a global char array which will hold the final string i.e the IP address.

void KeyPressEventHandler (GtkEntry *entry,
const gchar *text,
gint length,
gint *position,
gpointer data)
{
GtkEditable *editable = GTK_EDITABLE(entry);
int i,j, count=0;
int temp;

gchar *result = g_new (gchar, length);

for (i=0; i < length; i++)
{
if (isalpha(text[i]))
continue;
temp = text[i];
result[count++] = islower(text[i]) ? toupper(text[i]) : text[i];
IPaddr[z] = text[i];

if (temp == 8)
{

z=z-2;
}

}
z++;

if (count > 0) {
gtk_signal_handler_block_by_func (GTK_OBJECT (editable),
GTK_SIGNAL_FUNC (KeyPressEventHandler),
data);
gtk_editable_insert_text (editable, result, count, position);
gtk_signal_handler_unblock_by_func (GTK_OBJECT (editable),
GTK_SIGNAL_FUNC (KeyPressEventHandler),
data);
}
gtk_signal_emit_stop_by_name (GTK_OBJECT (editable), "insert_text");

g_free (result);
}

In this callback function im validating the key to be only numbers. here there is a varibale 'temp' in which i have the recent key entered, it works fine for all numbers and even some special characters too, but if i enter backspace that variable holds nothing. The comparision in the code with 8 is to chaeck for the key as backsapce, since 8 is the ASCII value of backspace.

Regards,
shri.

openldev · Posted: Fri Sep 01, 2006 1:11 pm Post subject:

Well, that is because the backspace character does not insert any text. If you want to catch a backspace event, you need to use the backspace signal for that key or delete_from_cursor signal for all types of deletions.