Detect which key is pressed in C - c

Question

I'm trying to find a way to find out which key is pressed down in C. This will be in a graphical environment, written in GTK2, but I don't think the answer lies there. I think I might be able to do this using Xlib, but I haven't been able to find anything conclusive on this.
Does anyone have any suggestions on how to do this?
I've managed to catch a keypress using the follow code:
GtkWidget *window;
void gtk_widget_set_events(window,GDK_KEY_RELEASE_MASK);
g_signal_connect(window,"key_release_event",G_CALLBACK(hello),NULL);
However, I would like to identify which key is pressed. From the link posted by Aditya Kumar, I know the answer lies with using GdkEventKey, since it is a structure which has a keyval field, but I cannot seem to get the syntax right. What is the correct way of getting this number?
This is a method I've tried:
static void hello( GtkWidget *widget,
guint data ){
g_print ("Hello World, %d was pressed\n",data);}
I tried supplying "data" by doing this when I catch the key_release_event:
g_signal_connect(window,"key_release_event",G_CALLBACK(hello),GdkEventKey.keyval);
However, I get a compiler error like so:
hello.c:85:5: error: expected ‘)’ before ‘.’ token
hello.c:85:5: error: expected expression before ‘,’ token

Answer 1

You are correct with your original syntax.
g_signal_connect(window, "key-release-event", G_CALLBACK(key_event), NULL);
Where the key_event function looks something like (note I am using the gdk_keyval_name to convert the keyval int value to a string for printing):
static gboolean
key_event(GtkWidget *widget,
GdkEventKey *event)
{
g_printerr("%s\n",
gdk_keyval_name (event->keyval));
return FALSE;
}
Here's a complete example program:
#include <gtk/gtk.h>
static gboolean
key_event(GtkWidget *widget,
GdkEventKey *event)
{
g_printerr("%s\n",
gdk_keyval_name (event->keyval));
return FALSE;
}
int main( int argc,
char *argv[] )
{
GtkWidget *window;
gtk_init (&argc, &argv);
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
g_signal_connect(window, "key-release-event", G_CALLBACK(key_event), NULL);
gtk_widget_show (window);
gtk_main ();
return 0;
}

Answer 2

while looking at the gdk reference manual i think you can capture the keyboard events using this unless you specifically want to have a 'C' program.
Here is the link to help you out.
http://www.gtk.org/api/2.6/gdk/gdk-Keyboard-Handling.html

Answer 3

event->keyval is a pointer to a struct, where keyval contains a integer value for the key pressed, this has been used above in a function gdk_keyval_name (event->keyval) which gets a actual name for the key.