MFC: Have CDockablePane receive ON_NOTIFY_REFLECT messages for a CTreeCtrl? - winapi

Question

The MFC Wizard created a project with a CWorkSpaceBar which in my case is actually based on CBCGPDockingControlBar, the MFC equivalent is CDockablePane. The wizard also created a m_wndTree based on CBCGPTreeCtrl (CTreeCtrl). It created it in its OnCreate() like this:
CRect rectDummy;
rectDummy.SetRectEmpty();
// Create tree control:
const DWORD dwViewStyle = WS_CHILD | WS_VISIBLE | TVS_HASLINES | TVS_LINESATROOT | TVS_HASBUTTONS | TVS_SHOWSELALWAYS;
if (!m_wndTree.Create(dwViewStyle, rectDummy, this, 1))
{
TRACE0("Failed to create workspace view\n");
return -1; // fail to create
}
Now I would like to handle some of the TreeView notifications so I added these to the CWorkSpaceBar message map:
ON_NOTIFY_REFLECT(TVN_ITEMEXPANDING, &CWorkSpaceBar::OnTvnItemExpanding)
ON_NOTIFY_REFLECT(TVN_GETDISPINFO, &CWorkSpaceBar::OnTvnGetDispInfo)
However, I'm not getting the notification messages? Is there something else I need to do to make it work?

Answer 1

You appear to be confusing the ON_NOTIFY_REFLECT and ON_NOTIFY handlers; or rather, the windows for which those handlers should be defined.
From what you have described, your CWorkSpaceBar class/object is the parent of the tree-view (CTreeCtrl) object; so, when an item is expanded in that tree-view, that parent pane receives a WM_NOTIFY message and the relevant ON_NOTIFY handler (if defined in the message-map) is called. The ON_NOTIFY_REFLECT handler allows the actual tree-view itself to intercept/receive the notification.
In my projects, I have a similar situation, and the class(es) derived from CDockablePane (such as my UserPane) have message map entries like the following, which work as expected:
ON_NOTIFY(TVN_ITEMEXPANDING, IDR_USRTV, &UserPane::OnItemExpand)
Note: The IDR_USRTV is the ID value that I give to the tree-view, in its Create function, as shown below; in your example code, you have used the value of 1 (which may or may not be advisable).
int UserPane::OnCreate(CREATESTRUCT *pCreateStruct)
{
CRect rc; rc.SetRectEmpty();
const DWORD trvstyle = WS_CHILD | WS_VISIBLE |
TVS_HASLINES | TVS_LINESATROOT | TVS_HASBUTTONS | TVS_SHOWSELALWAYS | TVS_EDITLABELS;
if (CDockablePane::OnCreate(pCreateStruct) == -1) return -1;
if (!m_wndTView.Create(trvstyle, rc, this, IDR_USRTV)) return -1;
//...
A basic outline for the OnItemExpand member function is as follows:
void UserPane::OnItemExpand(NMHDR *pNotifyStruct, LRESULT *result)
{
*result = 0;
NMTREEVIEW *pTV = reinterpret_cast<NMTREEVIEW *>(pNotifyStruct);
HTREEITEM hItem = pTV->itemNew.hItem;
uintptr_t itemData = m_wndTView.GetItemData(hItem);
if (pTV->action == TVE_EXPAND) {
//...
}
else if (pTV->action == TVE_COLLAPSE) {
//...
}
return;
}