Re: XForms: Problems with Mesa in a glcanvas object (2nd posting)

Eef Hartman (E.J.M.Hartman@math.tudelft.nl)
Wed, 27 May 1998 08:59:47 +0200 (METDST)

# To subscribers of the xforms list from Eef Hartman <E.J.M.Hartman@math.tudelft.nl> :

In a message to me Steve Lamont wrote:
> > The "glBegin" _always_ returns INVALID_OPERATION.
> > So I never get to the real drawing part (which is actually rather simple).
>
> Does the program draw anything at all?

No, just the empty window (which is made by XForms, not Mesa).

> Do you have a corresponding glEnd() call?

Of course, and some "vertex2f" calls in between. I'm trying to draw line
strips.

> the callback a second time, you're going to get the GL_INVALID_OPERATION
> error.

It already happens the FIRST time the "expose" handler is entered and
the very first glBegin in that. So the "state" of the OpenGL engine is
such that it _seems_ to think it cannot draw anything yet.
I must be missing something in the initialisation part, at least, that
is what I'm thinking.

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