Re: [Plib-users] multiple windows

[Steve B. <sjb...@ai...>]

Anthony Corriveau wrote:
> 
> Yes, I probably mean textures. Do you think it is a glut command? If you
> find it let me know.

OK - I found a few moments to check this out...

The third parameter to glXCreateContext specifies that display lists
and textures are to be shared between two or more OpenGL "rendering contexts"
(ie windows).

I don't think GLUT does this - the only place that glXCreateContext is called
in GLUT is 'glut_win.c' which has:

 window->ctx = glXCreateContext(__glutDisplay, window->vis, None, __glutTryDirect);

...the 'None' parameter is that 'share list'...so I think that nothing is shared. :-(

I also checked the 'freeglut' sources - it does the same thing as GLUT:

 window->Window.Context = glXCreateContext(
        fgDisplay.Display, window->Window.VisualInfo,
        NULL, TRUE ) ;

PrettyPoly (which *does* share textures between multiple windows) uses the FLTK
library instead of GLUT - and looking into the FLTK source code, it calls
glXCreateContext as:

  context = glXCreateContext(fl_display, fl_visual, fl_first_context, 1);

...which looks more convincing.

Somehow, I thought it was easier than this...and it's possible that it is - but
I don't know how.

> I have the source to PrettyPoly but it uses a few other libs, and it will
> take a while to sort through it.

Don't bother - it won't tell you anything.  The difference is inside FLTK
with that glXCreateContext call.

So, it seems like you have two choices:

  1) Take a copy of 'freeglut' (which has very liberal licensing conditions)
     and hack it to make it share display lists and textures.  I don't think
     this is all *that* hard to do...but it's a pain because you now have
     a non-standard library.

  2) Switch to a different window library.  We know that FLTK is good in
     this regard...I have no idea about the other alternatives.

I confess that I'm suprised that GLUT doesn't share textures by default.

----------------------------- Steve Baker -------------------------------
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