Add a listener when a widget closes

[admin]

Not directly, but as a work-around you can create a timer which checks widget state each second:

Code:

var widget = $('#widget-1'), visible = false;

setInterval(function() {
  var state = widget.is(':visible');
  if (state != visible) {
    visible = state;
    console.log('widget visibility state', visible);
  }
}, 1000);