This plugin raises two events, much like normal the Commerce add to cart, which you can listen for in the same way. They are:
onBeforeMultiAddToCart
and onMultiAddToCart
In each case the event parameters are:
order
(CommerceOrderModel)
lineItems
(an array of CommerceLineItemModel)
craft()->on('multiAdd_cart.onBeforeMultiAddToCart', function($event) {
$order = $event->params['order'];
$lineItems = $event->params['lineItems'];
$event->performAction = false;
});
Available for Craft 2, unlimited use, free forever. Coming soon for Craft 3.