p:selectOneListbox ajax item selection changes scroll position

Question

There is a <p:selectOneListbox> with about 20 items. The first 5 items can be viewed in the list and then the remaining can be scrolled to and selected. The list is ajaxified. When the item numbers greater than 5 is selected (after scrolling to it) the scrollbar does not remain at its place; it moves to the top position. This makes the selected item (for example item 9) invisible. The program uses a ajax listener. The app uses PrimeFaces 5.0.

But, when the ajax listener is removed the selected (item 9) is visible and the scroller does not move to top (remove the p:ajax tag's listener attribute in the below JSF page).

I would like to know how to make the scrollbar not move when any item is selected while using the ajax listener.

The JSF page:

<p:selectOneListbox id="list"
                    scrollHeight="100"
                    value="#{bean.todo}">

    <f:selectItems value="#{bean.data}"
                   var="t"
                   itemLabel="#{t.name}"
                   itemValue="#{t.name}"/>

    <p:ajax process="@this"
            update="@this msg"
            listener="#{bean.valueChanged}" />
</p:selectOneListbox>

<br /><h:outputText id="msg" value="#{bean.message}" />

The bean's code:

import javax.faces.bean.*;
import java.io.Serializable;
import java.util.*;
import javax.faces.event.AjaxBehaviorEvent;
import javax.faces.component.UIOutput;

@ManagedBean(name="bean")
@SessionScoped
public class TodosBean implements Serializable {

    private List<Todo> data;
    private String todo; // selected item value
    private String msg;

    public TodosBean() {
        loadData();
        if (data.size() == 0) {
            return;
        }

        Todo t = data.get(0);
        String name = t.getName();
        setTodo(name); // select the first item in the list
        setMessage(name);
    }

    private void loadData() {
        data = new ArrayList<>();
        data.add(new Todo("1first", "1"));
        data.add(new Todo("2second", "2"));
        data.add(new Todo("3third", "3"));
        data.add(new Todo("4fourth", "4"));
        data.add(new Todo("5fifth", "5"));
        data.add(new Todo("6sixth", "6"));
        data.add(new Todo("7seventh", "7"));
        data.add(new Todo("8eighth", "8"));
    }

    public List<Todo> getData() {
        return data;
    }

    public void setMessage(String msg) {
        this.msg = msg;
    }

    public String getMessage() {
        return msg;
    }

    public String getTodo() {
        return todo;
    }

    public void setTodo(String t) {
        todo = t;
    }

    public void valueChanged(AjaxBehaviorEvent e) {
        String name = (String) ((UIOutput) e.getSource()).getValue();
        setMessage(name + " selected.");
    }
}

public class Todo {

    private String name;
    private String desc;

    public Todo() {}

    public Todo(String name, String desc) {
        this.name = name;
        this.desc = desc;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    @Override
    public String toString() {
        return this.name;
    }
}

Answer 1

Remove the update="@this will solve it. Updating a control will move it to a default state. It might also be that in a newer version of PF this default state is improved and it still is at the correct position