en la documentación del magnific popup pone "preloader: true" antes de los callbacks
Código Javascript
:
Ver original$('.image-link').magnificPopup({
// you may add other options here, e.g.:
preloader: true,
callbacks: {
open: function() {
// Will fire when this exact popup is opened
// this - is Magnific Popup object
},
close: function() {
// Will fire when popup is closed
}
// e.t.c.
}
});