BCN_HOTITEMCHANGE notification is not getting called with CMFCButton class - c++

Question

BCN_HOTITEMCHANGE notification code is not getting called with CMFCButton class.
I'm using Visual Studio 2010
Steps performed:
1) Add a CButton to my dialog from the resource editor.
2) Use my own derived class CMFCButtonEx derived from CMFCButton class (which in turn is derived from CButton class).
3) Declare CMFCButtonEx 'm_btn_ex' instance variable to my dialog.
4) Add DDX_Control(pDX, IDC_BUTTON_EX, m_btn_ex);
5) When I click this button all my message handlers in the derived class are called except BCN_HOTITEMCHANGE notification associated with OnButtonItemChange function. The breakpoint in that function never hits. All the other message handlers (OnMouseMove, OnMouseLeave, and OnButtonClicked) are called correctly, and the breakpoints in them get hit.
As a note if I derive by CMFCButtonEx class from CButton class, then I can hit the breakpoint in OnButtonItemChange function i.e. BCN_HOTITEMCHANGE notification code is handled correctly
For some reason my BCN_HOTITEMCHANGE notification code is not being handled correctly by CMFCButton class. I can't understand what am I doing wrong here. I have also tried to use TBN_HOTITEMCHANGE notification code instead of BCN_HOTITEMCHANGE but the breakpoint in the OnButtonItemChange function never hits.
Thanks!
CMFCButtonEx class code:
IMPLEMENT_DYNAMIC(CMFCButtonEx, CMFCButton)
CMFCButtonEx::CMFCButtonEx()
{
m_bMouseTracking = FALSE
}
CMFCButtonEx::~CMFCButtonEx()
{
}
BEGIN_MESSAGE_MAP(CMFCButtonEx, CMFCButton)
//{{AFX_MSG_MAP(CMFCButtonEx)
ON_WM_MOUSEMOVE()
ON_WM_MOUSELEAVE()
ON_NOTIFY_REFLECT_EX(BCN_HOTITEMCHANGE, OnButtonItemChange)
//ON_NOTIFY_REFLECT_EX(TBN_HOTITEMCHANGE, OnButtonItemChange)
ON_CONTROL_REFLECT_EX(BN_CLICKED, OnButtonClicked)
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
BOOL CMFCButtonEx::OnButtonClicked()
{
AfxMessageBox("MFC Button Clicked");
return FALSE;
}
BOOL CMFCButtonEx::OnButtonItemChange(NMHDR* pNMHDR, LRESULT* pResult)
{
NMBCHOTITEM* pnmbchotitem = (NMBCHOTITEM*)pNMHDR;
AfxMessageBox("MFC Button Item Change");
*pResult = 0;
return FALSE;
}
void CMFCButtonEx::OnMouseMove(UINT nFlags, CPoint point)
{
if (!m_bMouseTracking)
{
TRACKMOUSEEVENT tme;
tme.cbSize = sizeof(TRACKMOUSEEVENT);
tme.dwFlags = TME_LEAVE;
tme.hwndTrack = this->m_hWnd;
if (::_TrackMouseEvent(&tme))
{
m_bMouseTracking = TRUE;
AfxMessageBox("MFC Button Mouse Move");
}
}
CMFCButton::OnMouseMove(nFlags, point);
}
void CMFCButtonEx::OnMouseLeave()
{
m_bMouseTracking = FALSE;
AfxMessageBox("MFC Button Mouse Move");
CMFCButton::OnMouseLeave();
}

Answer 1

BCN_HOTITEMCHANGE is not triggered for CMFCButton, or any classes derived from CMFCButton
As stated in documentation, Visual Style must be enabled otherwise BCN_HOTITEMCHANGE is not triggered. CMFCButton relies on owner draw method, so visual style is disabled for this button.
You could remove BS_OWNERDRAW from your CMFCButtonEx class. But this is not recommended because CMFCButtonEx relies on BS_OWNERDRAW.
A better solution is derive your class from CButton (and make sure Visual Styles is enabled), use custom draw instead of owner draw. You may not need OnMouseMove and OnMouseLeave.
class CMyButton : public CButton {}
...
BOOL CMyButton::OnButtonItemChange(NMHDR* pNMHDR, LRESULT* pResult)
{
auto ptr = (NMBCHOTITEM*)pNMHDR;
bool enter = ptr->dwFlags & HICF_ENTERING;
if (enter)
TRACE(L"CMyButton... enter\n");
else
TRACE(L"CMyButton... exit\n");
*pResult = 0;
return FALSE;
}