TreeColumn folder icon issue #12229
Description
Hello there!
I think there is a documentation issue around TreeColumn folder icons.
Both collapsedFolderIconCls and expandedFolderIconCls are documented as "The icon to use for the collapse icon in expanded state", which is only correct for the latter setting. The former should read "The icon to use for the expand icon in collapsed state".
On top of that, those config seem to work in reverse: collapsed nodes use the expanded folder icon, and vice-versa. I believe this misunderstanding comes from the misleading naming convention: the related collapseIconCls and expandIconCls properties are named after actions (expand/collapse), where as corresponding folder icon properties are named after states (collapsed/expanded), so they should work in reverse but in fact they don't.
See attached screen recording illustrating of the bug.
Screen Recording 2025-11-14 at 15.44.25.mov
(16.45 MiB) Downloaded 3 times
Thank you!