From: Lyle Johnson <lyle@...>
Date: 2003-03-26T01:43:38+09:00
Subject: Re: [FXRuby] FXGLViewer and textures

Rasmus wrote:

> I want to use textures in a FXGLViewer. But there seems to be some
> initialization for the OpenGL system missing. When calling
> GL.GenTextures a huge number is returned. The OpenGL samples from the
> samples/opengl folder return 1 or 2 always. The difference is that
> these examples are using GLUT for the GUI -- not FXRuby.
> 
> I have attached an example for my problem. The program prints
> 
>>rubyw gltexture.rbw
> Generated texture number 44171928
> Generate mipmap
> gltexture.rbw:40: [BUG] Segmentation fault
>>Exit code: 3
> 
> when executed. The segmentation fault seems to be a consequence of the
> invalid texture number.
> 
> Does anybody know, what initialization I'm missing?

Yes, you need to make the GL viewer's context the "current" context 
before calling stuff like GL.GenTextures. The least intrusive changes to 
your example program would be to first add an accessor to the TestWindow 
class to return a reference to the FXGLViewer window, i.e.

     class TestWindow < FXMainWindow

         attr_reader :viewer

         # ... remaining code as before ...
     end

and then add calls to FXGLViewer#makeCurrent and 
FXGLViewer#makeNonCurrent before and after the call to TestViewer#scene, 
i.e.

     if __FILE__ == $0
       application = FXApp.new("Test", "Test")
       window = TestWindow.new(application)
       application.create
       viewer = TestViewer.new

       # Make the GL viewer's context current
       window.viewer.makeCurrent

       # Generate textures, etc.
       window.scene viewer.scene(1)

       # Make the GL viewer's context non-current
       window.viewer.makeNonCurrent

       application.run
     end

I see some other problems, e.g. you're trying to pass FXGLPoint objects 
in as arguments to GL.Vertex, which expects an Array. But I'll let you 
debug those yourself first ;) If you run into additional problems, let 
me know.

Hope this helps,

Lyle