- Classes: #wxTreeCtrl, #wxImageList
- The tree control displays its items in a tree like structure. Each item has its
- own (optional) icon and a label. An item may be either collapsed (meaning that
- its children are not visible) or expanded (meaning that its children are
- shown). Each item in the tree is identified by its @e itemId which is of
- opaque data type @e wxTreeItemId. You can test whether an item is valid
- by calling wxTreeItemId::IsOk.
- The items text and image may be retrieved and changed with
- #GetItemText/#SetItemText
- and
- #GetItemImage/#SetItemImage.
- In fact, an item may even have two images associated with it: the normal one
- and another one for selected state which is set/retrieved with
- #SetItemSelectedImage/#GetItemSelectedImage
- functions, but this functionality might be unavailable on some platforms.
- Tree items have several attributes: an item may be selected or not, visible or
- not, bold or not. It may also be expanded or collapsed. All these attributes
- may be retrieved with the corresponding functions:
- #IsSelected,
- #IsVisible, #IsBold
- and #IsExpanded. Only one item at a time may be
- selected, selecting another one (with
- #SelectItem) automatically unselects the
- previously selected one.
- In addition to its icon and label, a user-specific data structure may be associated
- with all tree items. If you wish to do it, you should derive a class from @e wxTreeItemData which is a very simple class having only one function @e GetId() which returns the id of the item this data is associated with. This
- data will be freed by the control itself when the associated item is deleted
- (all items are deleted when the control is destroyed), so you shouldn't delete
- it yourself (if you do it, you should call
- #SetItemData(@NULL) to prevent the tree from
- deleting the pointer second time). The associated data may be retrieved with
- #GetItemData() function.
- Working with trees is relatively straightforward if all the items are added to
- the tree at the moment of its creation. However, for large trees it may be
- very inefficient. To improve the performance you may want to delay adding the
- items to the tree until the branch containing the items is expanded: so, in the
- beginning, only the root item is created (with
- #AddRoot). Other items are added when
- EVT_TREE_ITEM_EXPANDING event is received: then all items lying immediately
- under the item being expanded should be added, but, of course, only when this
- event is received for the first time for this item - otherwise, the items would
- be added twice if the user expands/collapses/re-expands the branch.
- The tree control provides functions for enumerating its items. There are 3
- groups of enumeration functions: for the children of a given item, for the
- sibling of the given item and for the visible items (those which are currently
- shown to the user: an item may be invisible either because its branch is
- collapsed or because it is scrolled out of view). Child enumeration functions
- require the caller to give them a @e cookie parameter: it is a number which
- is opaque to the caller but is used by the tree control itself to allow
- multiple enumerations to run simultaneously (this is explicitly allowed). The
- only thing to remember is that the @e cookie passed to
- #GetFirstChild and to
- #GetNextChild should be the same variable (and
- that nothing should be done with it by the user code).
- Among other features of the tree control are: item sorting with
- #SortChildren which uses the user-defined comparison
- function #OnCompareItems (by default the
- comparison is the alphabetic comparison of tree labels), hit testing
- (determining to which portion of the control the given point belongs, useful
- for implementing drag-and-drop in the tree) with
- #HitTest and editing of the tree item labels in
- place (see #EditLabel).
- Finally, the tree control has a keyboard interface: the cursor navigation (arrow) keys
- may be used to change the current selection. HOME and END are used to go to
- the first/last sibling of the current item. '+', '-' and '*' expand, collapse
- and toggle the current branch. Note, however, that DEL and INS keys do
- nothing by default, but it is common to associate them with deleting an item from
- a tree and inserting a new one into it.
projects / wxWidgets.git / blobdiff