This message is only sent at the time the menu control is created. When the owner receives this message, it must calculate and return the height of an item to the control.

All items in a menu must have the same height, and that must be greater than or equal to the height of the current font.

In particular, this notification is sent to the owner of a menu that has a style of MIS_OWNERDRAW, to offer the owner an opportunity to establish the height of an item that accommodates any special requirements for the drawing of items in that menu. When the owner receives this message, it must calculate and return the height and width of an item to the control. Typically, the client window procedure processes WM_MEASUREITEM by filling in the yTop and Right fields of the RECTL structure specified by the rclItem field of the OWNERITEM structure; this specifies the size of the rectangle needed to enclose the item when it is drawn.