Checkboxes in a Tree Control

void TreeCtrl_SetStateImage(CTreeCtrl & tree, HTREEITEM item, int stateImage)
{
tree.SetItemState(item, INDEXTOSTATEIMAGEMASK(stateImage), TVIS_STATEIMAGEMASK);
}

int TreeCtrl_GetStateImage(CTreeCtrl & tree, HTREEITEM item)
{
return tree.GetItemState(item, TVIS_STATEIMAGEMASK) >> 12;
}

// .h:

#define UWM_TV_CHECKBOX    WM_APP   // the custom message we post to ourself
class CDlgOrWhatever
{
// ...
CTreeCtrl    m_tree;
afx_msg LRESULT OnTvCheckbox(WPARAM wp, LPARAM lp); // our message handler for the posted message
};

// .cpp
#include "windowsx.h"  // required for GET_X_LPARAM, GET_Y_LPARAM)

// ----- Message map ------
BEGIN_MESSAGE_MAP(...)
ON_MESSAGE(UWM_TV_CHECKBOX, OnTvCheckbox)
// ... and, of course, the message handlers for NM_CLICK and TVN_KEYDOWN notifications
END_MESSAGE_MAP()

// ----- NM_CLICK Message Handler: ------
void CCheckTreeDlg::OnClickTree1(NMHDR* pNMHDR, LRESULT* pResult)
{
DWORD dw = GetMessagePos();                   // retrieve mouse cursor position when msg was sent
CPoint p(GET_X_LPARAM(dw), GET_Y_LPARAM(dw)); // ..and put into point structure
m_tree.ScreenToClient(&p);                    // make coords local to tree client area
UINT htFlags = 0;
HTREEITEM it = m_tree.HitTest(p, &htFlags);   // See where the click was on
if (it != NULL && ( htFlags & TVHT_ONITEMSTATEICON)) {
// the check box was hit - we just post a message for later processing
PostMessage(UWM_TV_CHECKBOX, pNMHDR->idFrom, (LPARAM) it);
}
*pResult = 0;
}

// ----- Handle checkbox changed here: ------
LRESULT CCheckTreeDlg::OnTvCheckbox(WPARAM wp, LPARAM lp)
{
CTreeCtrl & tree = GetDlgItem(wp);  // if we have multiple trees
HTREEITEM hitem = (HTREEITEM) lp;
int checked = (tree.GetItemState(hitem, TVIS_STATEIMAGEMASK) >> 12) - 1;
// "checked" now contains the check state.
// the sample does the following:
CString s = tree.GetItemText(hitem);
if (checked==0) s += " unchecked";
else if (checked==1) s+= " checked";
else if (checked==2) s+= " dunno";
else s+= " ???";
SetDlgItemText(IDC_INFO, s);
return 0;
}