Sugar 7 : how to remove subpanel row_action button on bwc record ?

Hello everyone !

To follow my adventures with panel-top buttons (from here : https://community.sugarcrm.com/ideas/1457#comment-1813 ), I'm struggling with a module 7 subpanel on a bwc record.

What i have :

I've created a custom module through module builder called "ag_ActesDeGestion", so it is built following version 7's intelligence. it is linked with the Contracts module (which is a legacy module) by : Contracts 1-M ag_ActesDeGestion.

So, in a Contract's record, i have a ag_ActesDeGestion subpanel. In bwc display.

What i want :

Making the row action buttons disappear from every line of this subpanel.

What i've tried :

In  custom/Extension/modules/Contracts/Ext/Layoutdefs/contracts_ag_actesdegestion_1_Contracts.php I've tried this :

<?php

// created: 2015-06-12 05:52:53

$layout_defs["Contracts"]["subpanel_setup"]['contracts_ag_actesdegestion_1'] = array (

  'order' => 100,

  'module' => 'ag_ActesDeGestion',

  'subpanel_name' => 'default',

  'sort_order' => 'asc',

  'sort_by' => 'id',

  'title_key' => 'LBL_CONTRACTS_AG_ACTESDEGESTION_1_FROM_AG_ACTESDEGESTION_TITLE',

  'get_subpanel_data' => 'contracts_ag_actesdegestion_1',

  'top_buttons' =>

  array (

    0 =>

    array (

      'widget_class' => 'SubPanelTopButtonQuickCreate',

    ),

  ),

  'list_fields' =>  array(

     'edit_button'=> array(

  'vname' => 'LBL_EDIT_BUTTON',

  'widget_class' => 'SubPanelEditButton',

  'module' => 'Contracts',

  'width' => '5%',

  'css_class'=>'disabled',

  ),

  /*'remove_button'=> array(

  'vname' => 'LBL_REMOVE',

  'widget_class' => 'SubPanelRemoveButton',

  'module' => 'Contracts',

  'width' => '5%',

  'css_class'=>'disabled',

  ),*/

  ),

);

But it does not work.

Which widget_class does they use?

Where can i find these widget classes ?

What file have i to modify ?

By advance, thanks a lot for your help and knowledges.