CListBox::MeasureItem

Статья
10/16/2008

Called by the framework when a list box with an owner-draw style is created.

virtual void MeasureItem(
   LPMEASUREITEMSTRUCT lpMeasureItemStruct 
);

Параметры

lpMeasureItemStruct
A long pointer to a MEASUREITEMSTRUCT structure.

Заметки

By default, this member function does nothing. Override this member function and fill in the MEASUREITEMSTRUCT structure to inform Windows of the list-box dimensions. If the list box is created with the LBS_OWNERDRAWVARIABLE style, the framework calls this member function for each item in the list box. Otherwise, this member is called only once.

For further information about using the LBS_OWNERDRAWFIXED style in an owner-draw list box created with the SubclassDlgItem member function of CWnd, see the discussion in Technical Note 14.

See CWnd::OnMeasureItem for a description of the MEASUREITEMSTRUCT structure**.**

Пример

// CMyODListBox is my owner-drawn list box derived from CListBox. This 
// example measures an item and sets the height of the item to twice the 
// vertical extent of its text. The list box control was created with the 
// following code:
//   m_myODListBox.Create(
//      WS_CHILD|WS_VISIBLE|WS_BORDER|WS_HSCROLL|WS_VSCROLL|
//      LBS_SORT|LBS_MULTIPLESEL|LBS_OWNERDRAWVARIABLE|LBS_WANTKEYBOARDINPUT,
//      CRect(10,250,200,450), pParentWnd, IDC_MYODLISTBOX);
//
void CMyODListBox::MeasureItem(LPMEASUREITEMSTRUCT lpMeasureItemStruct)
{
   ASSERT(lpMeasureItemStruct->CtlType == ODT_LISTBOX);
   LPCTSTR lpszText = (LPCTSTR) lpMeasureItemStruct->itemData;
   ASSERT(lpszText != NULL);
   CSize   sz;
   CDC*    pDC = GetDC();

   sz = pDC->GetTextExtent(lpszText);

   ReleaseDC(pDC);

   lpMeasureItemStruct->itemHeight = 2*sz.cy;
}