So here it is: trayicon.c

#include <gtk/gtk.h>

int main(int argc, char *argv[])
{
    gtk_init (&argc, &argv);

    GtkStatusIcon *status = gtk_status_icon_new_from_stock(GTK_STOCK_NO);
    gtk_status_icon_set_tooltip(status, "Nice Tooltip");

    gtk_main();
    return 0;
}

As you can see, beside the C-Standard header and footer, and also the GTK header and footer, we have only two lines of code. Without the tooltip it would be only one.

To compile it, you’ll need the GTK libs and their development headers. The gcc command is:

gcc -Wall trayicon.c -o trayicon `pkg-config --cflags --libs gtk+-2.0`

After starting it, you’ll see a red circle in your tray – Good Luck!