filter_horizontal doesn't use full height when in collapsed fieldset

[Peter Tillema]

Say you have a field field in model X, which is a ManyToMany field. You can use filter_horizontal in the ModelAdmin to display the available and selected options. However, if you use filter_horizontal in combination with a fieldset which is collapsed by default, it won't take the full height.

Example:

@admin.register(X)
class XAdmin(admin.ModelAdmin):
    list_display = ('a', 'b', 'c', 'field')
    filter_horizontal = ('field',)
    
    fieldsets = (
        (None, {
            'fields': ('a', 'b', 'c')
        }),
        ('Other', {
            'classes': ('collapse',),
            'fields': ('field',)
        })
    )

which gets rendered as ​https://i.imgur.com/jZpUHYN.png

[Carlton Gibson]

Hi Peter — OK, thanks. If you'd like to look at an adjustment here, that would be great!

[Shubh Parmar]

PR: ​https://github.com/django/django/pull/15096

[Shubh Parmar]

I think we can solve this issue with just CSS. In that case, we don't need to write javascript for calculating the height of select boxes. I have uploaded a git diff file. Let me know whether this is okay or not.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 51c24d87:

Fixed #33024 -- Fixed height of admin selector boxes in collapsed fieldset.

Thanks Tom Carrick for the review.