I am using the CComboBoxEx control in MFC to implement an address box for a browser application which shows the address and the related site icon.
According this link:
I once encountered a similar problem. Later I found that the cause is the CImageList when I created it.
After I changed
m_pImgLst->Create(32,20,ILC_COLOR32,2,2);
to
m_pImgLst->Create(32,20,ILC_COLOR16,2,2);
the phenomenon of updating until WM_KILLFOCUS
received disappeared. But it's a pity that the image is a little less beautiful than before.
Probably you need to call CComboBoxEx::SetImageList again.