onBeforePortletMove

fires before a portlet is moved

void onBeforePortletMove(object source,object parent,object active,object target,string mode);

source	object	the original parent layout
parent	object	a new parent layout
active	object	(also this) a portlet to move
target	object	a target view (highlighted, will be placed beside the active one within the parent layout)
mode	string	drag direction relative to the target

webix.attachEvent("onBeforePortletMove", function(source,parent,active,target,mode){ 
    // some code here
})

Details

Pay attention that the event is attached globally - webix.attachEvent( ).