SortableStackedInline not working if inline has collapse class

[aacimov]

When using django-admin-sortable2 with Django 5.2 and Django CMS 4+ with inline that has a collapsed class (in my case called Multimedia), after expanding the collapsed inline, drag and drop does not work, nor does the arrow repositioning.

Using it for images sorting like so...

class MultimediaInline(SortableStackedInline):
    model = Multimedia
    readonly_fields = ('image_tag',)
    fields = ('image_tag', 'type', 'image', 'video_url', 'panorama')
    extra = 0
    classes = ['collapse']

My parent class has SortableAdminBase of course.

When the class is removed it works as expected.

[jrief]

This probably is due to the fact, that CSS class collapse hides (ie. sets display: none;) the sortable element and hence Sortable.js can't initialize. Please try to use an alternative CSS class which sets width: 1px; height: 1px; border: none; and try again.

[aacimov]

Most probably this is the scenario, I will try using a different class since collapse is Django's default but even better I will try fixing the root cause and get back with the solution (hopefully). Then I can make a PR request or just put a snippet (should be 1-2 liner), it will be faster.