docs/doxygen/overviews/treectrl.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        treectrl
   3 // Purpose:     topic overview
   4 // Author:      wxWidgets team
   5 // RCS-ID:      $Id$
   6 // Licence:     wxWindows license
   7 /////////////////////////////////////////////////////////////////////////////
   8
   9 /*!
  10
  11  @page treectrl_overview wxTreeCtrl overview
  12
  13  Classes: #wxTreeCtrl, #wxImageList
  14  The tree control displays its items in a tree like structure. Each item has its
  15  own (optional) icon and a label. An item may be either collapsed (meaning that
  16  its children are not visible) or expanded (meaning that its children are
  17  shown). Each item in the tree is identified by its @e itemId which is of
  18  opaque data type @e wxTreeItemId. You can test whether an item is valid
  19  by calling wxTreeItemId::IsOk.
  20  The items text and image may be retrieved and changed with
  21  #GetItemText/#SetItemText
  22  and
  23  #GetItemImage/#SetItemImage.
  24  In fact, an item may even have two images associated with it: the normal one
  25  and another one for selected state which is set/retrieved with
  26  #SetItemSelectedImage/#GetItemSelectedImage
  27  functions, but this functionality might be unavailable on some platforms.
  28  Tree items have several attributes: an item may be selected or not, visible or
  29  not, bold or not. It may also be expanded or collapsed. All these attributes
  30  may be retrieved with the corresponding functions:
  31  #IsSelected,
  32  #IsVisible, #IsBold
  33  and #IsExpanded. Only one item at a time may be
  34  selected, selecting another one (with
  35  #SelectItem) automatically unselects the
  36  previously selected one.
  37  In addition to its icon and label, a user-specific data structure may be associated
  38  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
  39  data will be freed by the control itself when the associated item is deleted
  40  (all items are deleted when the control is destroyed), so you shouldn't delete
  41  it yourself (if you do it, you should call
  42  #SetItemData(@NULL) to prevent the tree from
  43  deleting the pointer second time). The associated data may be retrieved with
  44  #GetItemData() function.
  45  Working with trees is relatively straightforward if all the items are added to
  46  the tree at the moment of its creation. However, for large trees it may be
  47  very inefficient. To improve the performance you may want to delay adding the
  48  items to the tree until the branch containing the items is expanded: so, in the
  49  beginning, only the root item is created (with
  50  #AddRoot). Other items are added when
  51  EVT_TREE_ITEM_EXPANDING event is received: then all items lying immediately
  52  under the item being expanded should be added, but, of course, only when this
  53  event is received for the first time for this item - otherwise, the items would
  54  be added twice if the user expands/collapses/re-expands the branch.
  55  The tree control provides functions for enumerating its items. There are 3
  56  groups of enumeration functions: for the children of a given item, for the
  57  sibling of the given item and for the visible items (those which are currently
  58  shown to the user: an item may be invisible either because its branch is
  59  collapsed or because it is scrolled out of view). Child enumeration functions
  60  require the caller to give them a @e cookie parameter: it is a number which
  61  is opaque to the caller but is used by the tree control itself to allow
  62  multiple enumerations to run simultaneously (this is explicitly allowed). The
  63  only thing to remember is that the @e cookie passed to
  64  #GetFirstChild and to
  65  #GetNextChild should be the same variable (and
  66  that nothing should be done with it by the user code).
  67  Among other features of the tree control are: item sorting with
  68  #SortChildren which uses the user-defined comparison
  69  function #OnCompareItems (by default the
  70  comparison is the alphabetic comparison of tree labels), hit testing
  71  (determining to which portion of the control the given point belongs, useful
  72  for implementing drag-and-drop in the tree) with
  73  #HitTest and editing of the tree item labels in
  74  place (see #EditLabel).
  75  Finally, the tree control has a keyboard interface: the cursor navigation (arrow) keys
  76  may be used to change the current selection. HOME and END are used to go to
  77  the first/last sibling of the current item. '+', '-' and '*' expand, collapse
  78  and toggle the current branch. Note, however, that DEL and INS keys do
  79  nothing by default, but it is common to associate them with deleting an item from
  80  a tree and inserting a new one into it.
  81
  82  */
  83
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