ON_MOUSELEAVE and CButton with "Windows XP" desktop theme

[Ben]

Hi there,

I'm writing an MFC dialog-bassed app (with VS .NET 2003) in which I've
had to extend the CButton class to add some simple GUI-related
functionality. I'm using the _TrackMouseEvent function in the usual way
(inside a WM_MOUSEMOVE handler) to process the messages WM_MOUSELEAVE
and WM_MOUSEHOVER.

Here is my code for the WM_MOUSEMOVE, WM_MOUSEHOVER and WM_MOUSELEAVE
message handlers - it's pretty standard stuff:

void CButtonExtend::OnMouseMove(UINT nFlags, CPoint point)
{

if (!m_bTracking)
{
TRACKMOUSEEVENT tme;
tme.cbSize = sizeof(tme);
tme.hwndTrack = m_hWnd;
tme.dwFlags = TME_LEAVE|TME_HOVER;
tme.dwHoverTime = 1;

m_bTracking = _TrackMouseEvent(&tme);
m_point = point;

}

CButton::OnMouseMove(nFlags,point);
}

LRESULT CButtonExtend::OnMouseHover(WPARAM wparam, LPARAM lparam)
{
m_txtInfo->SetWindowText(m_strInformation);
return m_bTracking;
}

LRESULT CButtonExtend::OnMouseLeave(WPARAM wparam,LPARAM lparam)
{
m_txtInfo->SetWindowText("");
m_bTracking = FALSE;
return 0;
}

Now, this is all generally fine and works as expected - the
SetWindowText call just sets/clears a text box that displays
information about a button which when the mouse hovers over it.

My problem has arisen when I've tried to run my app under Windows XP
with the "Windows XP" desktop theme set. (Previously, I had been
developing the app in Win2000). When using this theme, a mouse cursor
hovering over a button (without a click) causes an orangey highlight to
appear around the button's edges, and it disappears when the mouse
leaves the button area. However, when using a button from my
ButtonExtend class, the orange highlight remains even after the cursor
moves away from the button.

The problem goes away if I disable my OnMouseLeave handler and don't
process the WM_MOUSELEAVE message - however, I need this handler to
clear the text in my information box after the mouse leaves a button's
area. I've been fiddling with common controls, manifests, a zillion
message handlers and scouring the MSDN without success. Does anyone
have any suggestions? They would be much appreciated.

Further - there is one message specific to XP (BCN_HOTITEMCHANGE) which
I suspect could be the culprit here. However, when I try to write a
handler for the message in the dialog class that owns the
CButtonExtends, the compiler insists that BCN_HOTITEMCHANGE is an
unresolved symbol, _even though_ when I hover over it in the code
editor, IntelliSense correctly identifies and defines it. I've included
the commctrl.h file in my code.
Any pointers definitely welcome! Thanks.

[Ben]

I should mentioned that I finally solved this problem (thanks to JohnCz
on CodeGuru) by changing the return statement of the OnMouseLeave
message handler to the following:
return DefWindowProc(WM_MOUSELEAVE, wparam, lparam);