gnome - Start vino-server (VNC) before login on Linux CentOS

I'm using the default vino-server package to access my CentOS 6 workstation via VNC.

It works ok, but only AFTER I locally login on the workstation. I need to have vino-server start BEFORE the login, right at the Gnome login screen where I choose username and password.

Due to personal reasons, I need to use Vino and not vnc-server or any other packages.

I already tried to insert /usr/libexec/vino-server & in /etc/gdm/Init/Default but this didn't solve the issue.

Create the desktop file that's going to start vino:

# cat > /usr/share/gdm/autostart/LoginWindow/vino-server.desktop << 'EOF'
[Desktop Entry]
Name=Remote Desktop
Comment=GNOME Remote Desktop Server
Exec=/usr/libexec/vino-server
Icon=preferences-desktop-remote-desktop
Terminal=false
Type=Application
EOF

Change some of the vino's settings¹ for the gdm user (vino runs under it):

# su -s /bin/sh -l gdm -c               \
     'gconftool-2 --set --type=bool     \
                  /desktop/gnome/remote_access/enabled true'
# su -s /bin/sh -l gdm -c               \
     'gconftool-2 --set --type=bool     \
                  /desktop/gnome/remote_access/prompt_enabled false'

Note that all you can do is login. After the user logins, the VNC sesssion ends. At the end of the session, you'll be able to reconnect to GDM.

You'll also need to disable SELinux² or preferable write the required rules to let user gdm run vino-server.

_{¹ I got the details from an answer to "Enable remote VNC from the commandline?" from the Ask Ubuntu SE.}

_{² Modify /etc/selinux/config so that SELINUX=permissive or use setenforce.}