Tree view: How to indicate that only some sub-items are selected?

Question

I have an application where the client can select items from a tree-like structure using checkboxes. Items with only some sub-items selected show only a "grayed" check mark which transports the "not entirely selected"-information quite clearly and works quite nicely.

Later on a report is generated which contains the selected items of the tree structure only (with the unselected ones omitted). Therefore it is difficult to spot which items are only partially selected on the report (changing the selection at that point is not allowed any more so no checkboxes are shown).

What would be a good visual reminder that a listed item is only partly selected?

Answer 1

^{download bmml source – Wireframes created with Balsamiq Mockups}

Answer 2

A good representation is to use an un-checked checkbox for no items, a check mark for all and a tiny filled square for some items. This is the convention Windows 8 OS.

Answer 3

Since indeterminate checkboxes aren't available natively on the web, I've historically supported this by preventing users from collapsing subtrees with some (but not all) children selected.

We also added a tooltip on the disclosure toggle explaining why it was disabled.

In this way the user could always see all the items that were selected at any given time (at the expense of some space on screen). For our data, that was manageable. Your mileage may vary depending on the contents of your tree.