var home_mvid;
var previous_onSetFocus = wb.onSetFocus;
var previous_onClearAll = wb.onClearAll;

wb.onSetFocus = function(id, isFocus) {
    if (isFocus  &&  wb.getFindInfo().find == "") {
        home_mvid = id;
    }
    previous_onSetFocus(id, isFocus);
};

wb.onClearAll = function(){
    previous_onClearAll();
    if (wb.getFindInfo().find == ""  &&  wb.getFocusThum() != home_mvid) {
        wb.focusThum(home_mvid);
        setTimeout(function(){ wb.scrollTo(0); }, 100);
    }
};