There's an issue with dropdown menus nested inside a scroll view being
very frustrating to scroll to off-screen items. This works around that
to some extent by giving the user more "parent-scrollable" space to
mouse wheel or drag over.
The equality operator is used to determine whether the next background
in the cycle should be loaded, to avoid pointless loads of the same
background several times (see #13362 and #13393). Its omission in the
latter pull caused seasonal backgrounds to no longer cycle.
Closes#13508.