List Control with OLE Drag '& Drop


This extended list control allow OLE drag and drop between list controls. The programmer can enable/desable local drag and drop of list items inside the same control, automatic scrolling and the removing of dragged items from the source list.

Control Usage

  1. Initialize the OLE libraries in the application InitInstance member function:
  2. BOOL CDdDemoApp::InitInstance()
    #ifdef _AFXDLL
     // Call this when using MFC in a shared DLL
     // Call this when linking to MFC statically
     // Initialize OLE libraries
     if (!AfxOleInit())
      return FALSE;
  3. Insert the #include "DDListCtrl.h" in the dialog C++ file which contains the List Ctrls.
  4. In the OnInitDialog member function of the dialog, initialize and customize the list controls initialization according to the following template:
  5. BOOL CDdDemoDlg::OnInitDialog()
     // 1 - Subclass the list controls
     m_listVars.SubclassDlgItem(IDC_LIST_VAR, this);
     m_listRows.SubclassDlgItem(IDC_LIST_ROWS, this);
     m_listCols.SubclassDlgItem(IDC_LIST_COLS, this);
     m_listData.SubclassDlgItem(IDC_LIST_DATA, this);
     m_listPages.SubclassDlgItem(IDC_LIST_PAGES, this);
     // 2 - Initialize the List view controls
     CString s(TCHAR('M'),29);
     int len = m_listVars.GetStringWidth(s)+15;
     LV_COLUMN lvC;
     lvC.mask = LVCF_FMT | LVCF_WIDTH;
     lvC.fmt  = LVCFMT_LEFT;  // Left-align column   = len;          // Width of column in pixels
     if (m_listVars.InsertColumn(0,&lvC) == -1)
      return FALSE;
     m_listVars.SetLocalDD(FALSE);   // Disable local Drag&Drop
     m_listVars.SetScrolling(FALSE); // and auto scrolling
     // Create a column for the row variables list view control.
     if (m_listRows.InsertColumn(0,&lvC) == -1)
      return FALSE;
     // Create a column for the column variables list view control.
     if (m_listCols.InsertColumn(0,&lvC) == -1)
      return FALSE;
     // Create a column for the data variables list view control.
     if (m_listData.InsertColumn(0,&lvC) == -1)
      return FALSE;
     // Create a column for the page variables view control.
     if (m_listPages.InsertColumn(0,&lvC) == -1)
      return FALSE;
     // 3 - Set the content of the list view controls
     CWordArray aVars;
     int size = m_pSelectInfo->m_asNames.GetSize();
     // Initially the list of available variables contains all variables
     for (int i=0; i<size; i++)
      aVars[i] = i;
     // Fill the list of variables
     m_pData->FillListCtrl(m_listVars, aVars);
     m_pData->FillListCtrl(m_listRows, m_pSelectInfo->m_aRowsVar); 
     m_pData->FillListCtrl(m_listCols, m_pSelectInfo->m_aColsVar);  
     m_pData->FillListCtrl(m_listData, m_pSelectInfo->m_aDataVar); 
     m_pData->FillListCtrl(m_listPages, m_pSelectInfo->m_aPagesVar); 
     // 4 - Initialize the list controls for Drag&Drop
     return TRUE;  


Download source - 9 Kb
Download demo project - 32 Kb


  • Better not to use WM_TIMER

    Posted by Legacy on 01/16/2002 12:00am

    Originally posted by: Robert Dyer

    Because timer messages occur ONLY when the message queue is empty, they are not reliable to use during a drag and drop operation. I found the timer messages were sometimes not getting sent and hence the scrolling did not occur.

    The idea of course here is to make sure scrolling does
    not happen any faster than one line per 300 milliseconds.
    A better approach that also uses less code and fewer resources is to use the WIN32 API function GetTickCount
    in the OnDragOver method of the COleListCtrlDropTarget
    class in DDListCtrl.cpp. Just keep track of the previous tick count when scrolling occurred, and scroll only when the difference between the current and previous tick counts exceeds 300 milliseconds.

    Then there is no need for calls to SetTimer and KillTimer, and you can remove the OnTimer method of CDDListCtrl.

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