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 WM_MEASUREITEM

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

A window receives this message through its WindowProc function.

Parameters

• wParam
Contains the value of the CtlID member of the MEASUREITEMSTRUCT structure pointed to by the lpMeasureItem 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 lpMeasureItem is (UINT) –1, the message was sent by a combo edit field.
• lParam
lpMeasureItem Pointer to a MEASUREITEMSTRUCT structure that contains the dimensions of the owner-drawn control or menu item.

Return Value

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 lpMeasureItem parameter of the message and returns; this informs the system 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.

The system 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, the system 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.

Notification Requirements

• Minimum DLL Version None
• Header Declared in Winuser.h, include Windows.h
• Minimum operating systems Windows 95, Windows NT 3.1

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Notebook exported on Monday, 7 July 2008, 18:56:50 PM Eastern Daylight Time