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WM_MEASUREITEM message

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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.

WM_MEASUREITEM

    WPARAM wParam;
    LPARAM lParam;

Parameters

wParam

Contains the value of the CtlID member of the MEASUREITEMSTRUCT structure pointed to by the lParam parameter. This value identifies the control that sent the WM_MEASUREITEM message. If the message was sent by a menu, this parameter is zero. If the value is nonzero or the value is zero and the value of the CtlType member of the MEASUREITEMSTRUCT pointed to by lParam is not ODT_MENU, 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 lParam is (UINT) 1, the message was sent by a combo edit field.

lParam

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 lParam 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.

Requirements

Requirement Value
Minimum supported client
 Windows Vista [desktop apps only]
Minimum supported server
 Windows Server 2003 [desktop apps only]
Header
Winuser.h (include Windows.h)

See also

Reference

MEASUREITEMSTRUCT

Other Resources

WM_INITDIALOG