I am polishing rather old GUI of the application. The window is resizable -- home made layout is programmed via MoveWindow() (created in the pre-window-layout-manager era). One of the used controls is a combo-box. The rectangle of the combo box is set to determine the desired size of the list box when the combo is dropped down. However, the rectangle goes out of the window. It overlaps also the tab rectangle and causes the frame around the tab display area to be erased even when the combo box is closed -- see the circled areas on the image and the missing tab border between the two circles.