On Mar 25, 6:50 pm, Crispin Wellington <[email protected]>
wrote:
> ... first step would be to just get pyglet.gl OpenGL
> calls working on a Qt OpenGL context.
>
> What I found, at least under Mac OSX leopard, is that the calls
> "work", but somehow, for some reason, importing pyglet.gl freezes the
> QT app window. ...
>
> So now testing under OSX, the display DOES render, I get no error, and
> the window is locked.
> Testing under linux, the pyglet.gl does NOT render, but the window IS
> draggable. It does spit out an error on linux that it doesn't on OSX.
> The traceback on linux is
>
> Traceback (most recent call last):
> File "test.py", line 45, in paintGL
> glClear(GL_COLOR_BUFFER_BIT)
> File "/var/lib/python-support/python2.5/pyglet/gl/lib.py", line 83,
> in errcheck
> raise GLException('No GL context; create a Window first')
> pyglet.gl.lib.GLException: No GL context; create a Window first
>
> Anyone have any ideas how to "unlock" the window on OSX and use the
> pyglet.gl calls? Or how to get the GL drawing on linux?
I get the same error (Intel Mac OS 10.5). I have a (vague) theory
about the cause of all the behaviors you list above: Importing
pyglet.gl (I speculate) doesn't only define symbols, it also does
something to (or using) your current GL context. (Rather than, for
example, requiring you to call an init function and not doing that
stuff until you call that function.) If so, then the behaviors you
describe are consistent with Linux not having any GL context current
when pyglet.gl is imported (which it complains about), but with Mac
having the *wrong* context current -- perhaps one related to being
able to drag the window, thus the freeze. (I.e. either Qt or the Mac
window manager is using OpenGL to drag the window, and has left that
context current when your program starts.)
(It's certain that the context you want (the one owned by the
QGLWidget) can't be current yet, during that import, since it doesn't
even exist yet.)
I've been involved in some Qt OpenGL programming, and seen similar
bugs, for example when we did anything to an OpenGL context outside of
paintGL (e.g. in a mouse event handler) and forgot to first call
makeCurrent on the QGLWidget whose context we wanted to affect. In
that case too, we found different bugs on Linux and Mac.
Based on this theory, I tried fixing this in your example code by just
delaying the import of pyglet.gl until the desired GL context is known
to be current (which is first true inside initializeGL, I think), but
I couldn't get it to work. The problems might be trivial, related to
doing import * inside a function (SyntaxWarning in python 2.5) -- it
might be easier if you did explicit imports rather than import *.
A better fix, if this theory is right, would be to be able to set a
flag which causes pyglet.gl to defer all initialization which depends
on having an OpenGL context current, until a specific function is
called (and ideally to let it be called more than once, in case of non-
resource-sharing contexts, but that's much more work if any global
variables are involved -- they'd need to become attributes of a class
associated with each context -- so for now we can only hope for a
singleton context, just one that doesn't have to exist when your
program starts).
I.e. your program would look like this:
pyglet_gl_no_implicit_init = True
import pyglet.gl # affected by that flag
.....
def initializeGL(self):
pyglet.gl.ok_now_you_can_do_that_init_stuff_that_requires_the_right_GL_context
()
.....
(But I couldn't easily find the right place in pyglet.gl.__init__ or
one of its submodules to do this.)
(I must emphasize that this theory and proposed fix is purely
speculative -- the real issue could be something completely
different.)
- Bruce Smith
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