Toolkit Pro - CXTListBase::AddColumn -- ItemCount = 0?

CXTListBase::AddColumn -- ItemCount = 0?

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Topic: CXTListBase::AddColumn -- ItemCount = 0?

Posted By: scruzer
Subject: CXTListBase::AddColumn -- ItemCount = 0?
Date Posted: 19 May 2008 at 2:42pm

From toolkit v11 -- In AddColumn, this code:

int iIndex = pHeaderCtrl->GetItemCount();
if (nWidth == -1 && iIndex >= 0 )
{
  // Get the column width of the previous column from header control
  HD_ITEM hd_item;
  hd_item.mask = HDI_WIDTH;               //indicate that we want the width
  pHeaderCtrl->GetItem(iIndex - 1, &hd_item);
  nWidth = hd_item.cxy;
}

doesn't get a valid hd_item when iIndex = 0!

Replies:

Posted By: Smucker
Date Posted: 19 May 2008 at 6:11pm

Perhaps because you asked it to get item iIndex - 1.

As good practice, you may also want to zero any structure you pass to APIs. (I don't think it matters for the header control):

HD_ITEM hd_item = {0};

-------------
Product: Xtreme Toolkit Pro version 13.2 (Unicode, static build)

Platform: Windows 200x/XP/Vista/Win7 (32/64 bit)

Language: Visual C++ 9.0 (Studio 2008)

Posted By: scruzer
Date Posted: 29 May 2008 at 2:21pm

Or, perhaps -- using the default parameter leads to the bug in the code?

virtual int AddColumn(
    LPCTSTR lpszColHeading,
    int nWidth = -1,
    int nFormat = LVCFMT_LEFT
);

again, looking at this code. If you call this function the first time, with nWidth as the default parameter (-1)... The call to GetItem will request item "-1".

int CXTListBase::AddColumn(LPCTSTR lpszColHeading, int nWidth/*= -1*/, int nFormat/*= LVCFMT_LEFT*/)
{
// if we are not in report mode return error.
if ((GetWindowLong(m_pListCtrl->m_hWnd, GWL_STYLE) & LVS_TYPEMASK) != LVS_REPORT)
return -1;

// get a pointer to the header control, if NULL return error.
CHeaderCtrl* pHeaderCtrl = _xtGetHeaderCtrl();

if (pHeaderCtrl == NULL)
return -1;

   int iIndex = pHeaderCtrl->GetItemCount();   // could be 0!
   if (nWidth == -1 && iIndex >= 0 )
   {
      // Get the column width of the previous column from header control
      HD_ITEM hd_item;
      hd_item.mask = HDI_WIDTH; //indicate that we want the width
      pHeaderCtrl->GetItem(iIndex - 1, &hd_item);
      nWidth = hd_item.cxy;
   }
   return m_pListCtrl->InsertColumn(iIndex, lpszColHeading, nFormat, nWidth, iIndex);
}

My fix, "don't use the default parameter".