WM_MEASUREITEM Overview  Group

The WM_MEASUREITEM message is sent to the owner window of an owner-drawn button, combo box, list box, list view control, or menu item when the control or menu is created.

WM_MEASUREITEM 

idCtl = (UINT) wParam;                // control identifier 

lpmis = (LPMEASUREITEMSTRUCT) lParam; // item-size information 

 

Parameters

idCtl

Value of wParam. Contains the value of the CtlID member of the MEASUREITEMSTRUCT structure pointed to by the lpmis parameter. This value identifies the control that sent the WM_MEASUREITEM message.

If the value is zero, the message was sent by a menu. If the value is nonzero, the message was sent by a combo box or by a list box. If the value is nonzero, and the value of the itemID member of the MEASUREITEMSTRUCT pointed to by lpmis is (UINT) -1, the message was sent by a combo edit field.

lpmis

Value of lParam. Points to a MEASUREITEMSTRUCT structure that contains the dimensions of the owner-drawn control or menu item.

Return Values

If an application processes this message, it should return TRUE.

Remarks

When the owner window receives the WM_MEASUREITEM message, the owner fills in the MEASUREITEMSTRUCT structure pointed to by the lParam parameter of the message and returns; this informs Windows of the dimensions of the control. If a list box or combo box is created with the LBS_OWNERDRAWVARIABLE or CBS_OWNERDRAWVARIABLE style, this message is sent to the owner for each item in the control; otherwise, this message is sent once.

Windows sends the WM_MEASUREITEM message to the owner window of combo boxes and list boxes created with the OWNERDRAWFIXED style before sending the WM_INITDIALOG message. As a result, when the owner receives this message, Windows has not yet determined the height and width of the font used in the control; function calls and calculations requiring these values should occur in the main function of the application or library.

See Also

MEASUREITEMSTRUCT, WM_INITDIALOG