To make the dialog bar resizable when using versions of MFC earlier
than version 4.0:

To make the dialog bar resizable when using MFC version 4.0 or
later, you can use the built-in support for resizable control bars. However,
dialog bars do not get this behavior by default. To make a dialog bar
resizable:

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For versions of MFC earlier than version 4.0

CDialogBar contains an embedded member variable m_sizeDefault of
type CSize. On creation, m_sizeDefault is set to the size of the dialog
template embedded in the dialog bar. Whenever the dialog bar is resized or
repositioned, MFC calls CDialogBar::CalcFixedLayout(). This member function is
intended to return the appropriate size of the control bar; for CDialogBar,
CalcFixedLayout() usually returns m_sizeDefault. This causes the dialog bar to
always snap back to its default size.

To create a resizable dialog
bar, you must ensure that the following things are handled in some manner by an
application:

With the appropriate tests, both 1 and 3 can be implemented in
CalcFixedLayout(). See the "Sample Code" section of this article for an example
of this.

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For MFC version 4.0 and later

In MFC 4.0 and higher, control bars support the new
CBRS_SIZE_DYNAMIC style. CBRS_SIZE_DYNAMIC allows a floating control bar to be
dynamically resized when the user drags the control bar's border. The virtual
function CControlBar::CalcDynamicLayout() has been added to determine the size
that a control bar should be resized to.

CalcDynamicLayout() is
called for CBRS_SIZE_DYNAMIC control bars when the border of a floating control
bar is dragged and when the control bar is docked or floated. The default
CControlBar implementation simply calls CalcFixedLayout(), which prevents
control bar objects from resizing unless CalcDynamicLayout() is overridden.
CDialogBar does not override CalcDynamicLayout(), so by default, dialog bars
are not resizable.

Therefore, to make a resizable dialog bar using
MFC 4.0:

      if (!m_wndDialogBar.Create(this, IDD_DIALOGBAR,
                                 CBRS_TOP | CBRS_SIZE_DYNAMIC, 777))
      {
         TRACE0("Failed to create dialogbar/n");
         return -1;
      }

      m_wndDialogBar.EnableDocking(CBRS_ALIGN_ANY);
      DockControlBar(&m_wndDialogBar); 

Note You must use the WS_CHILD style with the IDD_DIALOGBAR dialog
template. Do not use the WS_VISIBLE style or any other style.

See the
"Sample Code" section in this article for a examples of this.

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Sample code

Sample code for MFC versions prior to Visual C++ 4.0

   /* Compile options needed: Default
   */ 

   // RSZDLGBR.H : header file
   // 

   class CResizableDlgBar : public CDialogBar
   {
   // Construction
   public:
        BOOL Create( CWnd* pParentWnd, UINT nIDTemplate, UINT nStyle,
                    UINT nID, BOOL = TRUE);
        BOOL Create( CWnd* pParentWnd, LPCTSTR lpszTemplateName,
                 UINT nStyle, UINT nID, BOOL = TRUE);

   // Attributes
   public:
        CSize m_sizeDocked;
        CSize m_sizeFloating;
        BOOL m_bChangeDockedSize;   // Indicates whether to keep
                                 // a default size for docking

   // Operations
   public:

   // Overrides
       virtual CSize CalcFixedLayout(BOOL bStretch, BOOL bHorz);

   // Implementation
   public:
   };

   ///////////////////////////////////////////////////////////////////// 

   // RSZDLGBR.CPP : implementation file
   // 

   #include "stdafx.h"
   #include <afxpriv.h>
   #include "ResizableDlgBar.h"
   #include "resource.h"

   //////////////////////////////////////////////////////////////////// 
   // CResizableDlgBar Construction/Destruction

   BOOL CResizableDlgBar::Create( CWnd* pParentWnd, UINT nIDTemplate,
                                  UINT nStyle, UINT nID, BOOL bChange)
   {
        if(!CDialogBar::Create(pParentWnd,nIDTemplate,nStyle,nID))
             return FALSE;

        m_bChangeDockedSize = bChange;
        m_sizeFloating = m_sizeDocked = m_sizeDefault;
        return TRUE;
   }

   BOOL CResizableDlgBar::Create( CWnd* pParentWnd,
                                  LPCTSTR lpszTemplateName,
                                  UINT nStyle, UINT nID, BOOL bChange)
   {
        if (!CDialogBar::Create( pParentWnd, lpszTemplateName,
                                nStyle, nID))
             return FALSE;

        m_bChangeDockedSize = bChange;
        m_sizeFloating = m_sizeDocked = m_sizeDefault;
        return TRUE;
   }

   //////////////////////////////////////////////////////////////////// 
   // Overloaded functions


   CSize CResizableDlgBar::CalcFixedLayout(BOOL bStretch, BOOL bHorz)
   {
        if (IsFloating())
       {
           // Get the parent mini frame wnd
           CMiniDockFrameWnd* pFrame =
             ((CMiniDockFrameWnd*)m_pDockBar->GetParent());
           CRect rcFrame;
           pFrame->GetClientRect(&rcFrame);
           // Is its size (0,0)? If so, it was just floated
           CSize sizerc(rcFrame.right - rcFrame.left,
                        rcFrame.bottom - rcFrame.top);
           if (!((sizerc.cx <= 0) && (sizerc.cy <= 0)))
               return ((m_bChangeDockedSize) ?
                           m_sizeDocked = m_sizeFloating = sizerc :
                           m_sizeFloating = sizerc);
           else
           {
               // Modify Style when dialog bar is first floated
               pFrame->ModifyStyle(MFS_MOVEFRAME, WS_THICKFRAME, 0);
               m_dwStyle |= MFS_THICKFRAME;
               m_dwStyle |= WS_THICKFRAME;
               m_dwStyle &= ~MFS_MOVEFRAME;
               // Return last floated size
               return m_sizeFloating;
           }
       }

        if (bStretch) // if not docked stretch to fit
             return CSize(bHorz ? 32767 : m_sizeDocked.cx,
                  bHorz ? m_sizeDocked.cy : 32767);
        else
             return m_sizeDocked;
   }

Sample code for MFC included with Visual C++ 4.0 and above

   /* Compile options needed: Default
   */ 

   // ResizableDlgBar.h : header file
   // 

   class CResizableDlgBar : public CDialogBar
   {
   // Construction
   public:
        BOOL Create( CWnd* pParentWnd, UINT nIDTemplate, UINT nStyle,
                     UINT nID, BOOL = TRUE);
        BOOL Create( CWnd* pParentWnd, LPCTSTR lpszTemplateName,
                     UINT nStyle, UINT nID, BOOL = TRUE);

   // Attributes
   public:
        CSize m_sizeDocked;
        CSize m_sizeFloating;
        BOOL m_bChangeDockedSize;   // Indicates whether to keep
                                    // a default size for docking

   // Operations
   public:

   // Overrides
       // ClassWizard generated virtual function overrides
       //{{AFX_VIRTUAL(CResizableDlgBar)
       //}}AFX_VIRTUAL
       virtual CSize CalcDynamicLayout( int nLength, DWORD dwMode );

   // Implementation
   public:

   // Generated message map functions
   protected:
       //{{AFX_MSG(CResizableDlgBar)
       // NOTE - the ClassWizard will add and remove member functions here.
       //}}AFX_MSG
       DECLARE_MESSAGE_MAP()
   };

   ///////////////////////////////////////////////////////////////////// 


   // ResizableDlgBar.cpp : implementation file
   // 

   #include "stdafx.h"
   #include "ResizableDlgBar.h"

   //////////////////////////////////////////////////////////////////// 
   // CResizableDlgBar Construction/Destruction

   BOOL CResizableDlgBar::Create( CWnd* pParentWnd, UINT nIDTemplate,
                                  UINT nStyle, UINT nID, BOOL bChange)
   {
        if(!CDialogBar::Create(pParentWnd,nIDTemplate,nStyle,nID))
             return FALSE;

        m_bChangeDockedSize = bChange;
        m_sizeFloating = m_sizeDocked = m_sizeDefault;
        return TRUE;
   }

   BOOL CResizableDlgBar::Create( CWnd* pParentWnd,
                                  LPCTSTR lpszTemplateName, UINT nStyle,
                                  UINT nID, BOOL bChange)
   {
       if (!CDialogBar::Create( pParentWnd, lpszTemplateName,
                                                 nStyle, nID))
           return FALSE;

       m_bChangeDockedSize = bChange;
       m_sizeFloating = m_sizeDocked = m_sizeDefault;
       return TRUE;
   }

   //////////////////////////////////////////////////////////////////// 
   // Overloaded functions

   CSize CResizableDlgBar::CalcDynamicLayout(int nLength, DWORD dwMode)
   {
       // Return default if it is being docked or floated
       if ((dwMode & LM_VERTDOCK) || (dwMode & LM_HORZDOCK))
       {
           if (dwMode & LM_STRETCH) // if not docked stretch to fit
               return CSize((dwMode & LM_HORZ) ? 32767 : m_sizeDocked.cx,
                            (dwMode & LM_HORZ) ? m_sizeDocked.cy : 32767);
             else
               return m_sizeDocked;
       }
       if (dwMode & LM_MRUWIDTH)
           return m_sizeFloating;
       // In all other cases, accept the dynamic length
       if (dwMode & LM_LENGTHY)
           return CSize(m_sizeFloating.cx, (m_bChangeDockedSize) ?
                        m_sizeFloating.cy = m_sizeDocked.cy = nLength :
                        m_sizeFloating.cy = nLength);
        else
           return CSize((m_bChangeDockedSize) ?
                        m_sizeFloating.cx = m_sizeDocked.cx = nLength :
                        m_sizeFloating.cx = nLength, m_sizeFloating.cy);
   }

   BEGIN_MESSAGE_MAP(CResizableDlgBar, CDialogBar)
       //{{AFX_MSG_MAP(CResizableDlgBar)
           // NOTE - the ClassWizard will add and remove mapping macros
here.
       //}}AFX_MSG_MAP
   END_MESSAGE_MAP()

   ///////////////////////////////////////////////////////////////////// 
   // CResizableDlgBar message handlers
   ///////////////////////////////////////////////////////////////////// 

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