The MEASUREITEMSTRUCT data structure informs Windows of the dimensions of an owner-draw control. This allows Windows to process user interaction with the control correctly. The owner of an owner-draw control receives a pointer to this structure as the lParam parameter of an WM_MEASUREITEM message. The owner-draw control sends this message to its owner window when the control is created; the owner then fills in the appropriate fields in the structure for the control and returns. This structure is common to all owner-draw controls.
The MEASUREITEMSTRUCT structure has the following format:
typedef struct tagMEASUREITEMSTRUCT
{
WORD CtlType;
WORD CtlID;
WORD itemID;
WORD itemWidth;
WORD itemHeight;
DWORD itemData
} MEASUREITEMSTRUCT;
The MEASUREITEMSTRUCT structure contains the following fields:
| Field | Description | ||
| CtlType | Is the control type. The values for control types are as follows: | ||
| Value | Meaning | ||
| ODT_BUTTON | Owner-draw button. | ||
| ODT_COMBOBOX | Owner-draw combo box. | ||
| ODT_LISTBOX | Owner-draw list box. | ||
| ODT_MENU | Owner-draw menu. | ||
| CtlID | Is the control ID for a combo box, list box, or button. This field is not used for a menu. | ||
| itemID | Is the menu-item ID for a menu or the list-box item ID for a variable-height combo box or list box. This field is not used for a fixed-height combo box or list box, or for a button. | ||
| itemWidth | Specifies the width of a menu item. The owner of the owner-draw menu item must fill this field before returning from the message. | ||
| itemHeight | Specifies the height of an individual item in a list box or a menu. Before returning from the message, the owner of the owner-draw combo box, list box, or menu item must fill out this field. | ||
| itemData | Contains the value that was passed to the combo box or list box in the lParam parameter of one of the following messages: | ||
| CB_ADDSTRING | |||
| CB_INSERTSTRING | |||
| LB_ADDSTRING | |||
| LB_INSERTSTRING | |||
| Contains the DWORD value passed as the lpNewItem parameter of the AppendMenu, InsertMenu, or ModifyMenu function that added or modified the menu item. Its contents are undefined for buttons. | |||
Failure to fill out the proper fields in the MEASUREITEM structure will cause improper operation of the control.