Advanced MFC Programming

Chapter 5. Common Controls
The first step of enabling label editing is to set “Edit labels” style when adding tree control resource to
the dialog template. The following lsts necessary steps of doing this: 1) Invoke “Tree Control Properties”
property sheet, click “Styles” tab. 2) Check “Edit labels” check box (Figure 5-11).
Label editing will be enabled if this style is selected. However, if we do not add code to change the
label at the end of editing, the label will remain unchanged after it is edited. To make this happen, we must
handle message TVN_ENDLABELEDIT.
Standard TVN_ENDLABELEDIT message handler added by Class Wizard will have the following format:
void MCTreeCtrl::OnEndlabeledit(NMHDR *pNMHDR, LRESULT *pResult)
{
TV_DISPINFO *pTVDispInfo = (TV_DISPINFO*)pNMHDR;
}
*pResult=0;
Figure 5-11. Check “Edit labels” to enable label
Here pTVDispInfo is a pointer to TV_DISPINFO type object, which can be obtained from the message
parameter. The most useful member of TV_DISPINFO is item, which is a TV_ITEM type object. Three
members of item contain valid information: hItem, lParam, and pszText. We could use hItem to identify
the node and use pszText to obtain the updated text string. If pszText is a NULL pointer, this means the
editing is canceled (Label editing can be canceled through pressing ESC key). Otherwise it will contain a
NULL-terminated string. The following is the implementation of this message handler:
void MCTreeCtrl::OnEndlabeledit(NMHDR *pNMHDR, LRESULT *pResult)
{
TV_DISPINFO *pTVDispInfo = (TV_DISPINFO*)pNMHDR;
}
if(pTVDispInfo->item.pszText != NULL)
{
SetItemText
(
pTVDispInfo->item.hItem,
pTVDispInfo->item.pszText
);
}
*pResult=0;
If the editing is not canceled, we need to call function CTreeCtrl::SetItemText(…) to set the node’s
new text, which has the following format:
BOOL CTreeCtrl::SetItemText(HTREEITEM hItem, LPCTSTR lpszItem);
This function is similar to CTreeCtrl::SetItemImage(…). Its first parameter is the handle of tree
control, and the second parameter is a string pointer to the new label text.
There are other messages associated with label editing, one useful message is TVN_BEGINLABELEDIT,
which will be sent when the editing is about to begin. We can handle this message to disable label editing
for certain nodes. In the message handler, if we assign a non-zero value to the content of pResult, the edit
will stop. Otherwise the label editing will go on as usual.
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