WM_MEASUREITEM  V_G68G 

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 MEASUREITEMSTRUCT5K1K_8R 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 MEASUREITEMSTRUCT5K1K_8R 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