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   <TITLE>Controls - Adding Horizontal Extent handling to a CListBox</TITLE>
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<CENTER><H3><FONT COLOR="#AOAO99">
How to add Horizontal Extent handling for a CListBox
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This article was contributed by <A HREF="mailto:rhollis@keypoint.demon.co.uk">Richard Hollis</A>.

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<P><A HREF="listbox_extent.zip">Download Source Code</A></p>
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<p>The following code illustrates how to implement Horizonal Extent handling
for a CListBox. For more information you can look at Q66370.
This class implements a derived CListBox which automatically sets the
horizontal extent.

<h4>CListBoxEx.h</h4>

<FONT COLOR="#990000"><TT><PRE>
//
// CListBoxEx.h     v1.0
//

#ifndef _LISTBOX_EX_H
#define _LISTBOX_EX_H

#include <afxwin.h>

class CListBoxEx : public CListBox
{
public:
     //virtual functions
     virtual int AddString( LPCTSTR sString );
     virtual int DeleteString( UINT nIndex );
     virtual int InsertString( int nIndex, LPCTSTR lpszItem );
     virtual void ResetContent();
     virtual int Dir( UINT attr, LPCTSTR lpszWildCard );

private:
     //helpers
     LONG GetExtentForString( LPCTSTR sText );
     LONG GetExtentForEntireControl();
};


#endif
</tt></PRE></FONT>
<br><br><br>

<h4>CListBoxEx.cpp</h4>

<FONT COLOR="#990000"><TT><PRE>
// CListBoxEx.cpp   v1.0
//

#include "stdafx.h"
#include "listboxex.h"


//
// see Q66370 for more information
//

///////////////////////////////////////////////////////////////////////////
///////
//
//override functions
///////////////////////////////////////////////////////////////////////////
///////

int CListBoxEx::AddString(LPCTSTR lpszItem)
{

     LONG lStringExtent = GetExtentForString(lpszItem);
     if(GetHorizontalExtent() < lStringExtent)
          SetHorizontalExtent(lStringExtent);

     return CListBox::AddString(lpszItem);
}

int CListBoxEx::DeleteString( UINT nIndex )
{
     int nCountLeft = CListBox::DeleteString(nIndex);
     if(nCountLeft == LB_ERR)
          return LB_ERR;

     LONG lMaxExtent = GetExtentForEntireControl();
     SetHorizontalExtent(lMaxExtent);

     return nCountLeft;
}

int CListBoxEx::InsertString( int nIndex, LPCTSTR lpszItem )
{
     int nInsertPos = InsertString(nIndex, lpszItem);
     if(nInsertPos == LB_ERR)
          return LB_ERR;

     LONG lStringExtent = GetExtentForString(lpszItem);
     if(GetHorizontalExtent() < lStringExtent)
          SetHorizontalExtent(lStringExtent);

     return nInsertPos;
}

void CListBoxEx::ResetContent()
{
     SetHorizontalExtent(0);

     CListBox::ResetContent();

     return;
}

int CListBoxEx::Dir( UINT attr, LPCTSTR lpszWildCard )
{
     int nReturn = Dir( attr, lpszWildCard );

     if(nReturn == LB_ERR || nReturn == LB_ERRSPACE)
          return nReturn;

     LONG lMaxExtent = GetExtentForEntireControl();
     SetHorizontalExtent(lMaxExtent);

     return nReturn;
}


///////////////////////////////////////////////////////////////////////////
///////
//
//helper functions
///////////////////////////////////////////////////////////////////////////
///////

LONG CListBoxEx::GetExtentForString(LPCTSTR lpszItem)
{
     CDC* cdc = this->GetDC();
     CFont* font = this->GetFont();
     CFont* pOldFont;

    if (font)
     {
        pOldFont = cdc->SelectObject(font);

          TEXTMETRIC tm;
          cdc->GetTextMetrics(&tm);

          CSize size = cdc->GetTextExtent(lpszItem, lstrlen(lpszItem) );
          size.cx += tm.tmAveCharWidth;

          cdc->SelectObject(pOldFont);
          this->ReleaseDC(cdc);

          return (LONG) size.cx;
     }

     this->ReleaseDC(cdc);

     return 0L;
}

LONG CListBoxEx::GetExtentForEntireControl()
{
     CDC* cdc = this->GetDC();
     CFont* font = this->GetFont();
     CFont* pOldFont;

    if (font)
     {
        pOldFont = cdc->SelectObject(font);

          TEXTMETRIC tm;
          cdc->GetTextMetrics(&tm);
          CString sText;
          LONG max_cx = 0;

          for(int n = 0; n<=GetCount(); n++)
          {
               this->GetText(n, sText);
               if(sText == "")
                    continue;

               CSize size = cdc->GetTextExtent(sText, sText.GetLength() );
               size.cx += tm.tmAveCharWidth;

               if(max_cx <= size.cx)
                    max_cx = size.cx;
          }

          cdc->SelectObject(pOldFont);
          this->ReleaseDC(cdc);

          return max_cx;
     }

     this->ReleaseDC(cdc);

     return 0L;
}
</tt></PRE></FONT>

<p>BUGFIX (28 June 1998): In function GetExtentForEntireControl() changed SText = "" ro SText == "".

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<p>Last updated: 28 June 1998

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