Re: Drawing with cairo

[Doug Baldwin <baldwin geneseo edu>]

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();