[GtkGLExt] segfault - offscreen rendering

[Toon Verstraelen <Toon Verstraelen UGent be>]

Hi,

I tried to implement an offscreen rendering feature in my project, but 
I'm stuck on an segmentation fault. The problem is always reproducable 
and I have reimplemented the same problem in the share-list.py example 
by adding the following lines in the __init__ method of ShareListDemo class:

# Now repeat the same on an offscreen rendering surface
pixmap = gtk.gdkgl.ext(gtk.gdk.Pixmap(None, 120, 120, 24))
gldrawable = pixmap.set_gl_capability(self.glconfig)
glcontext = gtk.gdkgl.Context(gldrawable, share_list=self.glcontext, 
direct=False)

A modified version of share-list.py is attached to this mail. The 
segmentation fault is generated during the last line in the snippet 
above. When I'm using the nvidia dri, the program just segfaults. When 
switch off direct rendering, this error is spawned on the output and 
then my X-server crashes.

The program 'share-lists.py' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadWindow (invalid Window parameter)'.
  (Details: serial 277 error_code 3 request_code 146 minor_code 5)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the --sync command line
   option to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() 
function.)

I don't understand the error message, appart from the fact that I'm 
probably doing something stupid. :-) I tried to follow the note in the 
error message, but I don't know what libraries I should recompile with 
debugging symbols in order to get some usefull debuginfo. Can someone 
give me a hint on how to solve this problem?

regards,

Toon

#!/usr/bin/env python

# This program is a mapping of the share-lists.c program
# written by Naofumi. It should provide a good test case for the
# relevant gtk.gtkgl.*/gtk.gdkgl.* classes and functions in PyGtkGLExt.
#
# Alif Wahid, May 2003.

import sys

import pygtk
pygtk.require('2.0')
import gtk
import gtk.gtkgl

from OpenGL.GL import *
from OpenGL.GLU import *

# Due to the low level nature of this
# program, I think aggregating Gtk
# classes is a better idea rather
# than inheriting. This class is really
# intended to provide a namespace rather
# than an object heirarchy.

class ShareListsDemo(object):

    def __init__(self):
        self.display_mode = gtk.gdkgl.MODE_RGB    | \
                            gtk.gdkgl.MODE_DEPTH  | \
                            gtk.gdkgl.MODE_DOUBLE

        # Try to create a double buffered framebuffer,
        # if not successful then create a single
        # buffered one.
        try:
            self.glconfig = gtk.gdkgl.Config(mode=self.display_mode)
        except gtk.gdkgl.NoMatches:
            self.display_mode &= ~gtk.gdkgl.MODE_DOUBLE
            self.glconfig = gtk.gdkgl.Config(mode=self.display_mode)

        # Create the window for the app.
        self.win = gtk.Window()
        self.win.set_title('share-lists')
        if sys.platform != 'win32':
            self.win.set_resize_mode(gtk.RESIZE_IMMEDIATE)
        self.win.set_reallocate_redraws(gtk.TRUE)
        self.win.set_border_width(10)
        self.win.connect('destroy', lambda quit: gtk.main_quit())

        # VBox to hold everything.
        vbox = gtk.VBox()
        self.win.add(vbox)
        vbox.show()

        # DrawingArea-1 for OpenGL rendering (main: creates display list).
        glarea = gtk.gtkgl.DrawingArea( glconfig=self.glconfig,
                                        share_list=None,
                                        render_type=gtk.gdkgl.RGBA_TYPE)
        glarea.set_size_request(120, 120)
        red = (1.0, 0.0, 0.0, 0.0)
        glarea.connect_after('realize', self.__realize_main, red)
        glarea.connect('configure_event', self.__configure_event)
        glarea.connect('expose_event', self.__expose_event)
        vbox.pack_start(glarea, expand=gtk.TRUE, fill=gtk.TRUE, padding=5)
        glarea.show()

        # Get OpenGL context.
        glarea.realize()
        self.glcontext = glarea.get_gl_context()

        # DrawingArea-2 for OpenGL rendering (sub: shares display list).
        glarea = gtk.gtkgl.DrawingArea( glconfig=self.glconfig,
                                        share_list=self.glcontext,
                                        render_type=gtk.gdkgl.RGBA_TYPE)
        glarea.set_size_request(120, 120)
        green = (0.0, 1.0, 0.0, 0.0)
        glarea.connect_after('realize', self.__realize, green)
        glarea.connect('configure_event', self.__configure_event)
        glarea.connect('expose_event', self.__expose_event)
        vbox.pack_start(glarea, expand=gtk.TRUE, fill=gtk.TRUE, padding=5)
        glarea.show()

        # DrawingArea-3 for OpenGL rendering (sub: shares display list).
        glarea = gtk.gtkgl.DrawingArea( glconfig=self.glconfig,
                                        share_list=self.glcontext,
                                        render_type=gtk.gdkgl.RGBA_TYPE)
        glarea.set_size_request(120, 120)
        blue = (0.0, 0.0, 1.0, 0.0)
        glarea.connect_after('realize', self.__realize, blue)
        glarea.connect('configure_event', self.__configure_event)
        glarea.connect('expose_event', self.__expose_event)
        vbox.pack_start(glarea, expand=gtk.TRUE, fill=gtk.TRUE, padding=5)
        glarea.show()
        
        # Now repeat the same on an offscreen rendering surface
        pixmap = gtk.gdkgl.ext(gtk.gdk.Pixmap(None, 120, 120, 24))
        gldrawable = pixmap.set_gl_capability(self.glconfig)
        glcontext = gtk.gdkgl.Context(gldrawable, share_list=self.glcontext, direct=False)
		
        # A quit button.
        button = gtk.Button('Quit')
        button.connect('clicked', lambda quit: self.win.destroy())
        vbox.pack_start(button, expand=gtk.FALSE, fill=gtk.FALSE, padding=5)
        button.show()

    def __init_gl (self, light_diffuse):
        # OpenGL context initialisation.
        # Only call this while having a valid context!
        light_position = (1.0, 1.0, 1.0, 0.0)

        glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse)
        glLightfv(GL_LIGHT0, GL_POSITION, light_position)
        glEnable(GL_LIGHTING)
        glEnable(GL_LIGHT0)
        glEnable(GL_DEPTH_TEST)

        glClearColor(1.0, 1.0, 1.0, 1.0)
        glClearDepth(1.0)

        glMatrixMode(GL_PROJECTION)
        glLoadIdentity()
        gluPerspective(40.0, 1.0, 1.0, 10.0)

        glMatrixMode(GL_MODELVIEW)
        glLoadIdentity()
        gluLookAt(0.0, 0.0, 3.0,
                  0.0, 0.0, 0.0,
                  0.0, 1.0, 0.0)
        glTranslatef(0.0, 0.0, -3.0)

    def __realize_main(self, widget, light_diffuse):
        # Get GLContext and GLDrawable
        glcontext = widget.get_gl_context()
        gldrawable = widget.get_gl_drawable()

        # OpenGL begin.
        if not gldrawable.gl_begin(glcontext): return

        # Create display list #1.
        qobj = gluNewQuadric()
        gluQuadricDrawStyle(qobj, GLU_FILL)
        glNewList(1, GL_COMPILE)
        gluSphere(qobj, 1.0, 20, 20)
        glEndList()

        # Initialise rendering context.
        self.__init_gl(light_diffuse)

        # OpenGL end
        gldrawable.gl_end()

    def __realize(self, widget, light_diffuse):
        # Get GLContext and GLDrawable
        glcontext = widget.get_gl_context()
        gldrawable = widget.get_gl_drawable()

        # GL calls
        if not gldrawable.gl_begin(glcontext): return

        # Initialise rendering context.
        self.__init_gl(light_diffuse)

        # OpenGL end
        gldrawable.gl_end()

    def __configure_event(self, widget, event):
        # Get GLContext and GLDrawable
        glcontext = widget.get_gl_context()
        gldrawable = widget.get_gl_drawable()

        # GL calls
        if not gldrawable.gl_begin(glcontext): return

        # OpenGL begin.

        glViewport(0, 0, widget.allocation.width, widget.allocation.height)
        
        # OpenGL end
        gldrawable.gl_end()
        
        return gtk.TRUE

    def __expose_event(self, widget, event):
        # Get GLContext and GLDrawable
        glcontext = widget.get_gl_context()
        gldrawable = widget.get_gl_drawable()
        
        # GL calls
        if not gldrawable.gl_begin(glcontext): return
        
        # OpenGL begin.
        
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
        glCallList(1)

        if gldrawable.is_double_buffered():
            gldrawable.swap_buffers()
        else:
            glFlush()

        # OpenGL end
        gldrawable.gl_end()

        return gtk.TRUE

    def run(self):
        self.win.show()
        gtk.main()


if __name__ == '__main__':
    app = ShareListsDemo()
    app.run()