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[wxWidgets.git] / docs / doxygen / overviews / treectrl.h

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// Name:        treectrl
// Purpose:     topic overview
// Author:      wxWidgets team
// RCS-ID:      $Id$
// Licence:     wxWindows license
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/*!

 @page overview_treectrl wxTreeCtrl overview

 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.

 */