'"True'" Dynamic Splitter Bar

If you want to implement splitter window in your MFC based application that redraws its panes dynamically (like Microsoft Windows Explorer does when you have IE4.0 installed) then you can use my simple class CDynSplitterWnd. Dragging CDynSplitterWnd splitter bar does not show a hatched line, instead it immediately redraws itself at a new position as well as forces all its panes to redraw themselves.

To implement CDynSplitterWnd window simply:

1. Change declaration of your splitter window instances to be instances of the CDynSplitterWnd class rather than CSplitterWnd class.

2. Or derive your own CSplitterWnd based classes (if you have them) from CDynSplitterWnd instead, and don't forget about BEGIN_MESSAGE_MAP(CYourSplitterWnd, CDynSplitterWnd) macro.

CDynSplitterWnd works best for the "1column 2 rows static splitter" situation. If you have MFC dynamic splitters create them with SIZE sizeMin parameter in CSplitterWnd ::Create(...) function set to CSize(1,1) or CSize(0,0).

// DynSplitterWnd.h file
//
class CDynSplitterWnd : public CSplitterWnd
{
	// Construction
	public:
		CDynSplitterWnd();
		
		// Attributes
	public:
		BOOL	IsDynamic()
			
		{ return m_bDynSplit; }
		void	SetDynamic(BOOL bDynSplit = TRUE) 
		{ m_bDynSplit = bDynSplit; }
		
		// Operations
	public:
		
		// Overrides
		// ClassWizard generated virtual function overrides
		//{{AFX_VIRTUAL(CDynSplitterWnd)
		virtual void OnInvertTracker(const CRect& rect);
		virtual void StartTracking(int ht);
		virtual void StopTracking(BOOL bAccept);
		//}}AFX_VIRTUAL
		
		// Implementation
	public:
		virtual ~CDynSplitterWnd();
		
	protected:
		CPoint  m_OldPoint;
		BOOL	m_bDynSplit;
		
		enum HitTestValue
		{
			noHit                   = 0,
				vSplitterBox            = 1,
				hSplitterBox            = 2,
				bothSplitterBox         = 3,        // just for
				keyboard
				vSplitterBar1           = 101,
				vSplitterBar15          = 115,
				hSplitterBar1           = 201,
				hSplitterBar15          = 215,
				splitterIntersection1   = 301,
				splitterIntersection225 = 525
		};
		
		
		// Generated message map functions
	protected:
		//{{AFX_MSG(CDynSplitterWnd)
		afx_msg void OnMouseMove(UINT nFlags, CPoint point);
		//}}AFX_MSG
		DECLARE_MESSAGE_MAP()
};

#include "stdafx.h"
#include <afxext.h>
#include "DynSplitterWnd.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

#define CX_BORDER	1
#define CY_BORDER	1

#define FAR_POINT_XY		-10000



////////////////////////////////////////////////////////////////////////
/////
// CDynSplitterWnd

CDynSplitterWnd::CDynSplitterWnd() 
:m_OldPoint(FAR_POINT_XY,FAR_POINT_XY),
m_bDynSplit(TRUE)
{
}

CDynSplitterWnd::~CDynSplitterWnd()
{
}


void CDynSplitterWnd::OnInvertTracker(const CRect& rect)
{
	if(!m_bDynSplit)
		CSplitterWnd::OnInvertTracker(rect);
	else
		return;
}

void CDynSplitterWnd::StartTracking(int ht)
{
	if(!m_bDynSplit)
	{
		CSplitterWnd::StartTracking(ht);
		return;
	}
	
	ASSERT_VALID(this);
	if (ht == noHit)
		return;
	
	// GetHitRect will restrict 'm_rectLimit' as appropriate
	GetInsideRect(m_rectLimit);
	
	if (ht >= splitterIntersection1 && ht <=
		splitterIntersection225)
	{
		// split two directions (two tracking
		rectangles)
			int row = (ht - splitterIntersection1) / 15;
		int col = (ht - splitterIntersection1) % 15;
		
		GetHitRect(row + vSplitterBar1, m_rectTracker);
		int yTrackOffset = m_ptTrackOffset.y;
		m_bTracking2 = TRUE;
		GetHitRect(col + hSplitterBar1, m_rectTracker2);
		m_ptTrackOffset.y = yTrackOffset;
	}
	else if (ht == bothSplitterBox)
	{
		// hit on splitter boxes (for keyboard)
		GetHitRect(vSplitterBox, m_rectTracker);
		int yTrackOffset = m_ptTrackOffset.y;
		m_bTracking2 = TRUE;
		GetHitRect(hSplitterBox, m_rectTracker2);
		m_ptTrackOffset.y = yTrackOffset;
		
		// center it
		m_rectTracker.OffsetRect(0,
			m_rectLimit.Height()/2);
		m_rectTracker2.OffsetRect(m_rectLimit.Width()/2,
			0);
	}
	else
	{
		// only hit one bar
		GetHitRect(ht, m_rectTracker);
	}
	
	// steal focus and capture
	SetCapture();
	
	// set tracking state and appropriate cursor
	m_bTracking = TRUE;
	m_htTrack = ht;
	SetSplitCursor(ht);
}


void CDynSplitterWnd::StopTracking(BOOL bAccept)
{
	ASSERT_VALID(this);
	
	if (!m_bTracking)
		return;
	
	ReleaseCapture();
	
	// erase tracker rectangle
	OnInvertTracker(m_rectTracker);
	if (m_bTracking2)
		OnInvertTracker(m_rectTracker2);
	m_bTracking = m_bTracking2 = FALSE;
	
	// save old active view
	CWnd* pOldActiveView = GetActivePane();
	
	// m_rectTracker is set to the new splitter position
	(without border)
		// (so, adjust relative to where the border will be)
		m_rectTracker.OffsetRect(-CX_BORDER , -CY_BORDER);
	m_rectTracker2.OffsetRect(-CX_BORDER, -CY_BORDER);
	
	if (bAccept)
	{
		if (m_htTrack == vSplitterBox)
		{
			SplitRow(m_rectTracker.top);
		}
		else if (m_htTrack >= vSplitterBar1 && m_htTrack
			<= vSplitterBar15)
		{
			// set row height
			TrackRowSize(m_rectTracker.top,
				m_htTrack - vSplitterBar1);
			RecalcLayout();
		}
		else if (m_htTrack == hSplitterBox)
		{
			SplitColumn(m_rectTracker.left);
		}
		else if (m_htTrack >= hSplitterBar1 && m_htTrack
			<= hSplitterBar15)
		{
			// set column width
			TrackColumnSize(m_rectTracker.left,
				m_htTrack - hSplitterBar1);
			RecalcLayout();
		}
		else if (m_htTrack >= splitterIntersection1 &&
			m_htTrack <= splitterIntersection225)
		{
			// set row height and column width
			int row = (m_htTrack -
				splitterIntersection1) / 15;
			int col = (m_htTrack -
				splitterIntersection1) % 15;
			
			TrackRowSize(m_rectTracker.top, row);
			TrackColumnSize(m_rectTracker2.left,
				col);
			RecalcLayout();
		}
		else if (m_htTrack == bothSplitterBox)
		{
			// rectTracker is vSplitter (splits
			rows)
				// rectTracker2 is hSplitter (splits
				cols)
				SplitRow(m_rectTracker.top);
			SplitColumn(m_rectTracker2.left);
		}
	}
	
	if ( (pOldActiveView == GetActivePane()) &&
		(pOldActiveView != NULL)
		)
		SetActivePane(-1, -1, pOldActiveView);
	// re-activate
}


BEGIN_MESSAGE_MAP(CDynSplitterWnd, CSplitterWnd)
//{{AFX_MSG_MAP(CDynSplitterWnd)
ON_WM_MOUSEMOVE()
//}}AFX_MSG_MAP
END_MESSAGE_MAP()



////////////////////////////////////////////////////////////////////////
/////
// CDynSplitterWnd message handlers


void CDynSplitterWnd::OnMouseMove(UINT nFlags, CPoint pt) 
{
	if(!m_bDynSplit)
	{
		CSplitterWnd::OnMouseMove(nFlags, pt);
		return;
	}
	
	if (GetCapture() != this)
		StopTracking(FALSE);
	
	if (m_bTracking)
	{
		// move tracker to current cursor position
		pt.Offset(m_ptTrackOffset); // pt is the upper
		right of hit detect
			// limit the point to the valid split range
			if (pt.y < m_rectLimit.top)
				pt.y = m_rectLimit.top;
			else if (pt.y > m_rectLimit.bottom)
				pt.y = m_rectLimit.bottom;
			if (pt.x < m_rectLimit.left)
				pt.x = m_rectLimit.left;
			else if (pt.x > m_rectLimit.right)
				pt.x = m_rectLimit.right;
			
			if (m_htTrack == vSplitterBox ||
				m_htTrack >= vSplitterBar1 && m_htTrack
				<= vSplitterBar15)
			{
				if (m_rectTracker.top != pt.y)
				{
					OnInvertTracker(m_rectTracker);
					m_rectTracker.OffsetRect(0, pt.y
						- m_rectTracker.top);
					OnInvertTracker(m_rectTracker);
				}
			}
			else if (m_htTrack == hSplitterBox ||
				m_htTrack >= hSplitterBar1 && m_htTrack
				<= hSplitterBar15)
			{
				if (m_rectTracker.left != pt.x)
				{
					OnInvertTracker(m_rectTracker);
					m_rectTracker.OffsetRect(pt.x -
						m_rectTracker.left, 0);
					OnInvertTracker(m_rectTracker);
				}
			}
			else if (m_htTrack == bothSplitterBox ||
				(m_htTrack >= splitterIntersection1 &&
				m_htTrack <= splitterIntersection225))
			{
				if (m_rectTracker.top != pt.y)
				{
					OnInvertTracker(m_rectTracker);
					m_rectTracker.OffsetRect(0, pt.y
						- m_rectTracker.top);
					OnInvertTracker(m_rectTracker);
				}
				if (m_rectTracker2.left != pt.x)
				{
					OnInvertTracker(m_rectTracker2);
					m_rectTracker2.OffsetRect(pt.x -
						m_rectTracker2.left, 0);
					OnInvertTracker(m_rectTracker2);
				}
			}
			
			OnLButtonUp(MK_LBUTTON,pt);
			OnLButtonDown(MK_LBUTTON,pt);
			if(m_OldPoint != pt)
			{
				RedrawWindow(NULL, NULL, RDW_ALLCHILDREN
					| RDW_UPDATENOW);
				m_OldPoint = pt;
			}
	}
	else
	{
		// simply hit-test and set appropriate cursor
		int ht = HitTest(pt);
		SetSplitCursor(ht);
	}
}

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Updated 4 April 1998