Custom renderer which extends PrimeFaces DataTableRenderer is not invoked

Question

I'm trying to extend the PrimeFaces 1.0 (yep, sadly we are stuck at JSF 1.2) data table, because I want the built-in filter function to search in the whole field, instead of only at the beginning. So I created a class which extendes DataTableRenderer.java (Source code):

package it.myPackage;

import ...

public class CustomDataTableRenderer extends org.primefaces.component.datatable.DataTableRenderer{

    @Override
    protected void decodeAjaxFilterRequest(FacesContext facesContext, DataTable dataTable) {
        // the same method with a "contains" instead of a "startsWith"
    }
}

And I added this entry to the faces-config:

<render-kit>
    <renderer>
        <component-family>org.primefaces.component</component-family>
        <renderer-type>org.primefaces.component.DataTableRenderer</renderer-type>
        <renderer-class>it.myPackage.CustomDataTableRenderer</renderer-class>
    </renderer>
</render-kit>

But the overriden method is never called. What am I doing wrong?

Platform: Java 6, JSF 1.2, Apache 6.0.18, Mojarra 1.2_12