Re: Drawing with cairo

["Diego A. Fons" <diegofons apexar com>]

Doug Baldwin wrote:
> On May 15, 2008, at 11:05 AM, Diego A. Fons wrote:
>
> > Like Theodore I'm using gtkmm. This is an extrac of the code which
> > doesn't work:
> > void Plotter::on_realize( void )
> > {
> >    // Create the GDK window
> >    refGdkWindow = Gdk::Window::create(get_window(), &attributes,
> >            GDK_WA_X | GDK_WA_Y);
> >
> >    // Create Cairo context
> >    Cairo::RefPtr<Cairo::Context> cr = 
> > refGdkWindow->create_cairo_context();
> > }
> >
> >
> > bool Plotter::on_expose_event( GdkEventExpose* event )
> > {
> >    // ... Use cr to do some drawing
> > }
> >
> > Both cr and refGdkWindow are members of the class Plotter....
>
>     Isn't variable cr local to Plotter::on_realize in the above? Even 
> if you declare a similarly-named variable in the class, I'm pretty 
> sure the declaration in the on_realize method will shadow the class 
> member. You might get the result you want if you drop the declaration 
> from the statement that saves the context in cr, i.e., change the 
> second half of Plotter::on_realize to...
>
>     // Create Cairo context
>     cr = refGdkWindow->create_cairo_context();
My mistake!

That's what i meant:

void Plotter::on_realize( void )
{
  // Create the GDK window
  refGdkWindow = Gdk::Window::create(get_window(), &attributes,
          GDK_WA_X | GDK_WA_Y);

  // Create Cairo context
  cr = refGdkWindow->create_cairo_context();
  // cr is a private member of the class
}