Expanding and collapsing subtrees
As you have probably already noticed, when a subtree is collapsed, only its root node is visible and there is a small box icon to its left containing a "+", signifying that there are additional nodes hidden from view. When the subtree has been expanded, the child nodes are visible and the sign inside the box changes to a "-".
Since a subtree can be several levels deep, at times you will want to expand just the top level, while at others you will want to view the whole subtree even though it may be large enough to require scrolling. Therefore it is useful to have terms that distinguish between the two actions.
From now on we will apply the terms Opening ⁄ Closing to mean expanding ⁄ collapsing just the top level of the subtree, and Exploding ⁄ Imploding to mean expanding ⁄ collapsing all levels. The terms Expand ⁄ Collapse will be used generically to cover both opening⁄closing and exploding ⁄ imploding.
Some commands perform opposite functions depending on the state of the tree, e.g. they open a subtree if it is closed and close it if it is open. These commands are said to toggle the particular action. Refer to the Glossary for more information on this and any other unfamiliar terms.
To toggle a subtree between its closed and open state
- Click the box icon as above; or
- Double-click the node or its icon
Note: Since closing a subtree affects only its top level and does not close any opened subtrees underneath, this enables you to conceal a multilevel, fully expanded subtree by simply closing the top level, yet reveal all levels of the subtree upon reopening it. Likewise, if you want to reopen an expanded subtree to only the top level, you should collapse it rather than close it, before opening it.