admingen_sortable.yml

# MyModel-generator.yml (admingen)
# you might want to add a pos. label. If not, ignore this part
params:
    fields:
        Rank:
            label:      Pos.

# Change list to nested_list and add rank if needed
builders:
    nested_list:
        params:
            display:
                - Rank


# admingenerator.yml (routing)
# Change admingen routing type from admingenerator to admingenerator_nested to enable the *_nested_move route
my_namespace_admin_gen_my_model:
    resource: "@MyNamespaceAdminGenBundle/Controller/MyModel/"
#   type:     admingenerator
    type:     admingenerator_nested
    prefix:   /my_model

php_classes.php

<?php

// Model class
// Fake tree (flat list)
class MyModelQuery extends BaseMyModelQuery
{
    public function findTree()
    {
        return $this
            ->orderByRank()
            ->find()
        ;
    }
}

// Model query class
// Fake parent call (there is none)
class MyModel extends BaseMyModel
{
    public function getParent()
    {
        return null;
    }
}

// Admingen list controller class
// Generic override of the existing nested_moveAction() to sort instead of move
class ListController extends BaseListController
{
    public function nested_moveAction($dragged, $action, $dropped)
    {
        if(!in_array($action, array('before', 'after'))) {
            throw new NotFoundHttpException("Unknown action");
        }

        $dragged = $this->buildQuery()->findPk($dragged);
        $dropped = $this->buildQuery()->findPk($dropped);

        if (!$dragged || !$dropped) {
            throw new NotFoundHttpException("Could not find the nodes");
        }

        switch($action) {
          case 'before':
              $dragged->moveToRank($dragged->getRank() > $dropped->getRank() ? $dropped->getRank() : $dropped->getRank() - 1);
              break;
          case 'after':
              $dragged->moveToRank($dragged->getRank() > $dropped->getRank() ? $dropped->getRank() + 1 : $dropped->getRank());
              break;
        }

        $dragged->save();

        return new Response();
    }
}

stylesheet.less

// unfortunately the existing tree stylesheet is a mess of !important statements, making it impossible to
// override any borders, so we have to improvise by defining background radients used as insertion markers

.treeTable tbody tr.droppable-before
{
    #gradient > .vertical-three-colors(@start-color: rgba(0, 0, 0, 0.4); @mid-color: rgba(255, 255, 255, 0.1); @color-stop: 30%; @end-color: rgba(255, 255, 255, 0.0))
}

.treeTable tbody tr.droppable-after
{
    #gradient > .vertical-three-colors(@start-color: rgba(255, 255, 255, 0.0); @mid-color: rgba(255, 255, 255, 0.1); @color-stop: 70%; @end-color: rgba(0, 0, 0, 0.4))
}

.table-striped > tbody > tr.droppable-before:nth-child(2n+1) > td, .table-striped > tbody > tr.droppable-before:nth-child(2n+1) > th {
    background-color: transparent;
}

.table-striped > tbody > tr.droppable-after:nth-child(2n+1) > td, .table-striped > tbody > tr.droppable-after:nth-child(2n+1) > th {
    background-color: transparent;
}

templates.twig

{# MyModelList/index.html.twig #}
{% extends_admingenerated "MyNamespaceAdminGenBundle:MyModelList:index.html.twig" %}

{# Adding patched library source #}
{% block javascripts %}
    {{ parent() }}
    <script type="text/javascript" src="{{ asset("bundles/c33score/js/nestedset-override.js") }}"></script>
{% endblock javascripts %}


{# MyModelList/results.html.twig #}
{% extends_admingenerated "MyNamespaceAdminGenBundle:MyModelList:results.html.twig" %}

{# By default the count is reduced by 1 because the tree root would be hidden. To fix this, override this block #}
{% block list_nbresults %}
<div class="list_nbresults">
    {% trans with {'%count%': Services.count,} from "Admingenerator" %}list.display.all{% endtrans %}
</div>
{% endblock list_nbresults %}

{# Overriding the included js library to use our patched one #}
{% block endform_batch_actions %}
{{ parent() }}
<script type="text/javascript">
    ;(function(window, $, undefined){
        $(function(){
            var original = $.fn['agen$nestedTree'];

            $.fn['agen$nestedTree'] = function() {
                return $.fn['agen$nestedTreeOverride'].apply(this, arguments);
            };
        });
    })(this, jQuery);
</script>
{% endblock endform_batch_actions %}