From: George Ogata <g_ogata@...>
Date: 2006-02-21T11:53:31+09:00
Subject: Re: can opengl work with an object method?

"anne001" <anne@wjh.harvard.edu> writes:

> I started with robot.rb in the sample folder of opengl-0.32g
>
> It comes with a display proc:
> display = Proc.new {}
>
> which is called by a glut function
>   GLUT.DisplayFunc(display);
>
> When I place the exact same code in a method
> class Node
>   def traversetree
>   end
> end
>
> upperarm = Node.new
> GLUT.DisplayFunc(upperarm.traversetree);
>
> displays the image in a different size, and does not respond to resize
> or keyboard keys
>
> Any option?

It doesn't work because `upperarm.traversetree' calls #traversetree
and returns its value, rather than the method itself.  If you want the
method itself, you need to do `upperarm.method(:traversetree)'.

However, it seems GLUT.DisplayFunc won't accept Method objects; only
Procs.  Do that with Kernel#lambda:

  GLUT.DisplayFunc(lambda{upperarm.traversetree})