7fa3c42046
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@52048 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
93 lines
4.5 KiB
C
93 lines
4.5 KiB
C
/////////////////////////////////////////////////////////////////////////////
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// Name: treectrl
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// Purpose: topic overview
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// Author: wxWidgets team
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// RCS-ID: $Id$
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// Licence: wxWindows license
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/////////////////////////////////////////////////////////////////////////////
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/*!
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@page overview_treectrl wxTreeCtrl overview
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Classes: #wxTreeCtrl, #wxImageList
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The tree control displays its items in a tree like structure. Each item has its
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own (optional) icon and a label. An item may be either collapsed (meaning that
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its children are not visible) or expanded (meaning that its children are
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shown). Each item in the tree is identified by its @e itemId which is of
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opaque data type @e wxTreeItemId. You can test whether an item is valid
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by calling wxTreeItemId::IsOk.
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The items text and image may be retrieved and changed with
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#GetItemText/#SetItemText
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and
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#GetItemImage/#SetItemImage.
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In fact, an item may even have two images associated with it: the normal one
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and another one for selected state which is set/retrieved with
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#SetItemSelectedImage/#GetItemSelectedImage
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functions, but this functionality might be unavailable on some platforms.
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Tree items have several attributes: an item may be selected or not, visible or
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not, bold or not. It may also be expanded or collapsed. All these attributes
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may be retrieved with the corresponding functions:
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#IsSelected,
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#IsVisible, #IsBold
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and #IsExpanded. Only one item at a time may be
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selected, selecting another one (with
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#SelectItem) automatically unselects the
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previously selected one.
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In addition to its icon and label, a user-specific data structure may be associated
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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
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data will be freed by the control itself when the associated item is deleted
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(all items are deleted when the control is destroyed), so you shouldn't delete
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it yourself (if you do it, you should call
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#SetItemData(@NULL) to prevent the tree from
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deleting the pointer second time). The associated data may be retrieved with
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#GetItemData() function.
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Working with trees is relatively straightforward if all the items are added to
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the tree at the moment of its creation. However, for large trees it may be
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very inefficient. To improve the performance you may want to delay adding the
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items to the tree until the branch containing the items is expanded: so, in the
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beginning, only the root item is created (with
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#AddRoot). Other items are added when
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EVT_TREE_ITEM_EXPANDING event is received: then all items lying immediately
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under the item being expanded should be added, but, of course, only when this
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event is received for the first time for this item - otherwise, the items would
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be added twice if the user expands/collapses/re-expands the branch.
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The tree control provides functions for enumerating its items. There are 3
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groups of enumeration functions: for the children of a given item, for the
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sibling of the given item and for the visible items (those which are currently
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shown to the user: an item may be invisible either because its branch is
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collapsed or because it is scrolled out of view). Child enumeration functions
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require the caller to give them a @e cookie parameter: it is a number which
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is opaque to the caller but is used by the tree control itself to allow
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multiple enumerations to run simultaneously (this is explicitly allowed). The
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only thing to remember is that the @e cookie passed to
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#GetFirstChild and to
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#GetNextChild should be the same variable (and
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that nothing should be done with it by the user code).
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Among other features of the tree control are: item sorting with
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#SortChildren which uses the user-defined comparison
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function #OnCompareItems (by default the
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comparison is the alphabetic comparison of tree labels), hit testing
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(determining to which portion of the control the given point belongs, useful
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for implementing drag-and-drop in the tree) with
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#HitTest and editing of the tree item labels in
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place (see #EditLabel).
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Finally, the tree control has a keyboard interface: the cursor navigation (arrow) keys
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may be used to change the current selection. HOME and END are used to go to
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the first/last sibling of the current item. '+', '-' and '*' expand, collapse
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and toggle the current branch. Note, however, that DEL and INS keys do
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nothing by default, but it is common to associate them with deleting an item from
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a tree and inserting a new one into it.
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*/
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