winex11: Create a dummy parent window for composite child windows to avoid using the root.

[Chris Robinson]

Alexandre Julliard wrote:
> -        attrib.override_redirect = True;
>          attrib.colormap = data->colormap;
>          XInstallColormap(gdi_display, attrib.colormap);
>
>          if(data->gl_drawable) XDestroyWindow(gdi_display, 
data->gl_drawable);
> -        data->gl_drawable = XCreateWindow(gdi_display, parent, -w, 0, w, h, 
0,
> +        data->gl_drawable = XCreateWindow(gdi_display, dummy_parent, -w, 0, 
w, h, 0,
>                                            vis->depth, InputOutput, 
vis->visual,
>                                            CWColormap | CWOverrideRedirect,
>                                            &attrib);

Did you mean to remove setting the override_redirect attribute? I remember 
having some alignment issues without it (the GL rendering was offset on the 
unseen window by the size of the decorations). But even if so, you'd need to 
remove the CWOverrideRedirect flag, because it's now taking the setting from 
the uninitialized override_redirect field.