Keep a list of callbacks to allow registering multiple callbacks to the same event. This is consistent with eg. jQuery.Deferred and is needed for example to open multiple dialogs showing the progress of installing a package at the same time.
Keep a list of callbacks to allow registering multiple callbacks to the same event. This is consistent with eg. jQuery.Deferred and is needed for example to open multiple dialogs showing the progress of installing a package at the same time.