I have problem with many2one fields in calendar view 

for example 

class x_x (osv.osv):

      _name = 'x.x'

        _columns= {

           'x_field' : fields.many2one('res.partner' , 'Partner'),

           'date' ; fields.datetime('date'),

          'note' : fields.char('Note')

}

and build my xml like the following :

<record id="calendar" model="ir.ui.view"> 
  <field name="name">calendar</field>  
 <field name="model">x.x</field> 
 <field name="arch" type="xml"> 
 <calendar string="Calendar" color="x_field" date_start='date'> 
  <field name="note"/> 
   </calendar>
  </field>
</record>

but in the calendar right hand side (color property) just retrieve the recorded partners in this object

any solution for list all partners ?????