Re: Invalid UTF-8 string passed to pango_layout_set_text()

[Randy <randyqiuxy hotmail com>]

Hi Kristian,
  Thank you and Mr Liu.
  Thanks for your explicit instrument.
> On Fri, Dec 25, 2009 at 9:14 AM, Randy <randyqiuxy hotmail com> wrote:
> > {
> > const gchar *textLabel=gtk_label_get_text(GTK_LABEL(label));
> > const gchar         *textWindow=gtk_window_get_title(GTK_WINDOW(window));
> >
> > if(keyEvent->keyval==GDK_Shift_L)
> > {
> >                 //surprise,if I skip(via "//") one of the two lines, another
> >                 //will work fine.....
> >        gtk_window_set_title(GTK_WINDOW(window),textLabel);
> >        gtk_label_set_text(GTK_LABEL(label),textWindow);
> > }
> > return FALSE;
> > }
> 
> This is a bit tricky :)  You have to note that textLabel and
> textWindow both point to a string that is internal to the
> GtkLabel/GtkWindow widgets.  
Right,this is the key.I forgot the memory which  wouldn't be used no
longer would be freed by its widget.
> This is why the string has to the const,
> you are not allowed to modify that internal string directly.  The
> point is that when you set another title or text, this internal string
> will be replaced with the new string.  So as soon as you call
> gtk_window_set_title(), the internal title string will be replaced and
> after this call your textWindow pointer is no longer valid (because it
> points to this internal string that has been replaced).  But you still
> have to use it for the call to gtk_label_set_text().  Swapping the
> calls will not help, because gtk_label_set_text() does the same and
> textLabel will become invalid.
> 
> The easiest solution is probably to just duplicate the strings you get
> from gtk_label_get_text() and gtk_window_get_title() using g_strdup()
> (and free them at the end of the function with g_free() !).  This way
> you will have a copy that will persist when the set_title() and
> set_text() functions replace their internal strings.
> 
> Hope this helps.
> 
> 
> regards,
> 
> -kris.
> 
Thanks so much!

Best regards,
Randy