In fact, this is the corresponding "cut" down and then "paste" into your control, see the following code location, the so-called transparent background image:
CClientDC CLDC(getParent()); CRect rectangle; CRect rect1; GetClientRect(RECT); GetWindowRect(rect1); getParent() -> ScreenToClient(rect1); if (m_dcBk.m_hDC == NULL){m_dcBk.CreateCompatibleDC(CLDC); m_bmpBk.CreateCompatibleBitmap(CLDC, rect.Width(), rect.Height()); m_pbmpOldBk = m_dcBk.SelectObject(m_bmpBk); m_dcBk.BitBlt(0, 0, rect.Width(), rect.Height(), CLDC, rect1.left, rect1.top, SRCCOPY); } //If pDC->BitBlt(0, 0, rect.Width(), rect.Height(), m_dcBk, 0, 0, SRCCOPY);The above content is just about the core code for verification when the bootstrap input control loses focus. The code is appropriately added, modified and deleted according to personal needs.