I have read the Void wiki to configure my keyboard :
I put 'KEYMAP=fr' in the file '/etc/rc.conf'
I edit the file '.xinitrc' in my "Home directory' and I put 'setxkbmap fr' in it.
But when my Xfce session starts I got the US keyboard layout instead !
~ ~ ~ ~
According to the Xorg website :
I find this solution to have my keyboard in French !
create the file '/etc/X11/xorg.conf.d/90-custom-kbd.conf' with this settings:
Identifier "keyboard defaults"
Option "XkbModel" "pc105"
Option "XkbLayout" "fr"
Option "XKbOptions" ""