[GtkGLExt] gdk_gl_config_new_by_mode hangs?

[Lindley M French <lfrench1 gmu edu>]

What could cause gdk_gl_config_new_by_mode() not to return? I'm finding this behavior when my program is spawned by another process, but not when it's started normally.

It's new---this didn't use to happen, and none of the code I've changed should affect this directly.

The call looks like:
config = gdk_gl_config_new_by_mode (GdkGLConfigMode(GDK_GL_MODE_RGB | GDK_GL_MODE_DOUBLE));
and I've ensured it takes place in a callback from the gtk event loop.

I've glanced at the source code, but I'm not familiar enough with it to identify the problem immediately.