muk_web/muk_web_theme/template/web.xml

<?xml version="1.0" encoding="UTF-8"?>

<!--     
	Copyright (C) 2018 MuK IT GmbH
	
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 of the
    License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>. 
-->

<odoo>
	
	<template id="webclient_bootstrap" name="Web Client" inherit_id="web.webclient_bootstrap">
        <xpath expr="//t[@t-set='body_classname']" position="after">
            <t t-set="body_classname" t-value="'o_web_client mk_sidebar_type_' + request.env.user.sidebar_type or 'large'"/>
        </xpath>
        <xpath expr="//*[hasclass('o_main')]" position="attributes">
            <attribute name="t-attf-class">o_main mk_chatter_position_#{request.env.user.chatter_position or 'normal'}</attribute>
        </xpath>
    </template>
	
</odoo>