Replacing metacity with xfwm in gnome under Arch Linux

Install xfwm
packer -S xfwm4

Create /usr/share/applications/xfwm4.desktop
[Desktop Entry]
Type=Application
Encoding=UTF-8
Name=Xfwm4
Exec=xfwm4
NoDisplay=true
X-GNOME-WMName=Xfwm4

Change in gconf-editor
/desktop/gnome/session/required_components/windowmanager = xfwm4