MFC CTreeCtrl鼠标滑过节点显示图片

要实现鼠标滑过节点显示图片，可以使用CTreeCtrl的NM_CUSTOMDRAW消息来自定义绘制节点。具体实现步骤如下：

1. 响应CTreeCtrl的NM_CUSTOMDRAW消息，并在OnCustomDraw函数中处理。

2. 判断绘制的节点是否是鼠标滑过的节点，可以使用CTreeCtrl的HitTest函数。

3. 如果是鼠标滑过的节点，就在该节点的位置显示图片，可以使用CImageList的Draw函数。

下面是代码示例：

void CMyTreeCtrl::OnCustomDraw(NMHDR* pNMHDR, LRESULT* pResult)
{
    NMTVCUSTOMDRAW* pNMCD = reinterpret_cast<NMTVCUSTOMDRAW*>(pNMHDR);
    *pResult = CDRF_DODEFAULT;

    switch (pNMCD->nmcd.dwDrawStage)
    {
    case CDDS_PREPAINT:
        *pResult = CDRF_NOTIFYITEMDRAW;
        break;
    case CDDS_ITEMPREPAINT:
        *pResult = CDRF_NOTIFYITEMDRAW;
        break;
    case CDDS_ITEMPREPAINT | CDDS_SUBITEM:
        {
            HTREEITEM hItem = reinterpret_cast<HTREEITEM>(pNMCD->nmcd.dwItemSpec);
            if (hItem == GetHoverItem())
            {
                CRect rect;
                GetItemRect(hItem, rect, TRUE);
                rect.left += m_nIndent + 2;
                rect.top += 1;
                rect.bottom -= 1;

                int nImage = GetItemImage(hItem, FALSE);
                if (nImage != -1)
                {
                    CImageList* pImageList = GetImageList(TVSIL_NORMAL);
                    if (pImageList != NULL)
                    {
                        pImageList->Draw(&pNMCD->nmcd.hdc, nImage, rect.TopLeft(), ILD_NORMAL);
                    }
                }
            }
        }
        break;
    }

    *pResult |= CDRF_NOTIFYPOSTPAINT;
}

HTREEITEM CMyTreeCtrl::GetHoverItem() const
{
    HTREEITEM hItem = NULL;
    CPoint pt;
    GetCursorPos(&pt);
    ScreenToClient(&pt);
    UINT uFlags;
    hItem = HitTest(pt, &uFlags);
    if ((uFlags & TVHT_ONITEM) == 0)
    {
        hItem = NULL;
    }
    return hItem;
}

在OnMouseMove函数中，可以调用RedrawWindow函数来刷新树形控件，以便及时显示鼠标滑过的节点的图片。

void CMyTreeCtrl::OnMouseMove(UINT nFlags, CPoint point)
{
    HTREEITEM hHoverItem = GetHoverItem();
    if (hHoverItem != m_hHoverItem)
    {
        m_hHoverItem = hHoverItem;
        RedrawWindow();
    }

    CTreeCtrl::OnMouseMove(nFlags, point);
}