checkbox.pt

<div tal:define="
     oid oid|field.oid;
     true_val true_val|field.widget.true_val;"
     i18n:domain="deform">
  <p class="deform-readonly-true" 
       id="${oid}"
       tal:condition="cstruct == true_val"
       i18n:translate=""><i class="fas fa-check-square" aria-hidden="true" style="color:green;"></i></p>
  <p class="deform-readonly-false" 
       id="${oid}"
       tal:condition="cstruct != true_val"
       i18n:translate=""><i class="fas fa-window-close" aria-hidden="true" style="color:red;"></i></p>
</div>