Hexadecimal value entry

kharrison · **Posted:** Wed Oct 10, 2007 5:42 pm

Does anyone have a recommended solution (or example) for capturing user entry for hexadecimal values as is commonly used to specify hardware addresses?
I was thinking of using a modified GtkEntry or GtkSpinButton widget to do this... but it looks like a lot of work.

Micah Carrick · **Posted:** Wed Oct 10, 2007 6:57 pm

Do you mean you want the gchar* from a GtkEntry to be converted to a hexidecimal value?

Code:

#include <glib-2.0/glib.h>

int
main (int argc, char *argv[])
{
    g_print("0x00ff=%d\n", (guint)g_strtod("0x00ff", NULL));
    g_print("0xfafa=%d\n", (guint)g_strtod("0xfafa", NULL));
    g_print("0x1c1c1c1c1c=%d\n", (guint)g_strtod("0x1c1c1c1c1c", NULL));
    
    return 0;
}

// gcc -Wall -g `pkg-config --cflags --libs glib-2.0` -o example example.c

kharrison · **Posted:** Wed Oct 10, 2007 7:11 pm

Thanks for the quick response...
Actually, I am looking for a widget to accept (and manage) entry of hexadecimal values. Preferably with a static prefix ("0x" or even '#').

openldev · **Posted:** Wed Oct 10, 2007 7:46 pm

If you want a multi-lined hex editor widget, you will have to use GtkTextView. GtkEntry will work for a single lined hex editor. However, there aren't any widgets currently for this. (If you give a more detailed description of what exactly you want to do with this, I can point you in the right direction.)

kharrison · **Posted:** Mon Oct 29, 2007 1:34 pm

Actually, I was simply looking for a GtkEntry widget that manages hexadecimal entry. I was able to find a good example of using the "key-press-event" in your book, "Foundations of GTK+ Development" which helped me to quickly resolve this. (I should note that I wanted to preserve a '0x' prefix on the entry field of the widget.)
By the way... I've purchased a LOT of technical books over the past 20 years of my career and this one is among the better written. Have you considered tackling more advanced topics in a sequel?

Here is the code which manages hexadecimal input for a GtkEntry widget:

Code:

gboolean validate_hex_entry
(
   GtkEntry     *entry,
   GdkEventKey  *event
)
{
   gboolean  status = TRUE;

   guint keyval = event->keyval;

   /*
    * Get the current entry value and string length
    */
   const gchar *current_text = gtk_entry_get_text( entry );
   size_t entry_length = strlen(current_text);

   /*
    * If the key a valid hexadecimal diget then append it to the entry
    */
   if (  g_ascii_isxdigit( keyval ) )
   {
      /*
       * Limit the number of caharacters to 10 characters
       * 0x00000000 through 0xFFFFFFFF
       */
      if ( entry_length < 10 )
      {
         status = FALSE;
      }
   }
   else if ( keyval == GDK_BackSpace )
   {
      if ( entry_length > 2 ) /* preserve "0x" hex prefix */
      {
         gchar *new_text = g_strndup( current_text, entry_length );
         gtk_entry_set_text( entry, new_text );
         g_free( new_text );
         gtk_entry_set_position( entry, entry_length );
         status = FALSE;
      }
   }
   else if ( ( keyval == GDK_Return ) || ( keyval == GDK_KP_Enter ) )
   {
      gtk_widget_activate( GTK_WIDGET( entry ) );
      status = FALSE;
   }
   return status;

} /* validate_hex_entry */

I then set up the callback as follows:

Code:

   g_signal_connect
     (
        G_OBJECT( widget ), "key-press-event",
        G_CALLBACK( validate_hex_entry ),
        NULL
     );

openldev · **Posted:** Mon Oct 29, 2007 4:08 pm

I currently wasn't planning a sequel just because it's senior year of college and I'm so very busy. However, I am writing articles on other concepts that weren't covered in the book, so if you have any suggestions, just let me know.

Also, when you are done reading the book, I would appreciate if you took a moment to review it at Amazon or B&N if you enjoyed it! :)

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