Re: Implementing a LED-like widget

[Matthias Langer <mlangc gmx at>]

Marcus Lundblad wrote:

> On Tue, 23 Aug 2005, Antonio Coralles wrote:
>
> > Marcus Lundblad wrote:
> >
> > > I'm trying to implement a widget simulating a LED.
> > > What I have is a widget derived from Gtk::Frame (with style SHADOW_IN).
> > > This frame holds a Gtk::DrawingArea (display in the follwing code..)
> > >
> > > I have the following code intended to turn the inside of the widget
> > > yellow
> > > (as an example).
> > >
> > > --------------------------------
> > >
> > > Constructor contains this:
> > >
> > >    set_shadow_type(Gtk::SHADOW_IN);
> > >    set_size_request(10,10);
> > >    display = new Gtk::DrawingArea;
> > >    display->set_size_request(8,8);
> > >    add(*display);
> >
> > As far as I can tell your constructor should be ok ...
> >
> > > The method setting the LED in on-state:
> >
> > From the nature of the code, I think you are calling this in 
> on_realize()
> > ...
> >
> > >      int width, height;
> > >      Glib::RefPtr<Gdk::Window> win = display->get_window();
> > >      win->get_size(width, height);
> > >      Glib::RefPtr<Gdk::GC> gc = Gdk::GC::create(win);
> > >      gc->set_foreground(Gdk::Color("Yellow"));
> > >      win->draw_rectangle(gc, true, 0, 0, width, height);
> >
> > But as far as I know, you should only do
> >
> > //////////////////////////////////////////////////////////////////////////////////////////////////
> > Glib::RefPtr<Gdk::Window> win = display->get_window();
> > Glib::RefPtr<Gdk::GC> gc = Gdk::GC::create(win);
> > gc->set_foreground(Gdk::Color("Yellow"));
> > //////////////////////////////////////////////////////////////////////////////////////////////////
> >
> > in your overiden version of Gtk::DrawingArea::on_realize().
> > Assuming that gc is a member variable, calling
> >
> > //////////////////////////////////////////////////////////////////////////////////////////////////
> > int width, height;
> > Glib::RefPtr<Gdk::Window> win = display->get_window();
> > win->get_size(width, height);
> > win->draw_rectangle(gc, true, 0, 0, width, height);
> > /////////////////////////////////////////////////////////////////////////////////////////////////
> > from your version of Gtk::DrawingArea::on_expose_event(GdkEventExpose*)
> > should have the desired effect.
> >
> > Antonio
>
> Thanks for your help, but it's still not working correctly.
> Now I have the following:
>
> -----------------------------------------------------------
>
> void
> desk_indicator::led_area::on_realize()
> {

      //This should take care of your SIGSEGV
      Gtk::DrawingArea::on_realize();
      ///////////////////////////////////////////////////////////

>    Glib::RefPtr<Gdk::Window> win = get_window();
>    gc = Gdk::GC::create(win);

      //I'm not sure about this, but i think you should specify a 
colormap for your GC
      gc->set_colormap(get_default_colormap());
      
////////////////////////////////////////////////////////////////////////

>    gc->set_foreground(Gdk::Color("Yellow"));
> }
Hope this helps,
Matthias Langer (alias Antonio)