Advanced MFC Programming

Chapter 3. Splitter Window
WM_LBUTTONDOWN message handler. Instead of calling the message handler implemented by CSplitterWnd,
we can call the default function implemented by class CWnd, which is the base class of CSplitterWnd. For a
dynamic splitter window, the WM_LBUTTONDBLCLK message handler should not be overridden because after
we disable the tracking, double clicking becomes the only way that can be used by the user to dynamically
add or delete panes. For WM_MOUSEMOVE and WM_LBUTTONUP messages, we don’t need to modify their
handlers because after message WM_LBUTTONDOWN is bypassed, the tracking will not happen anymore.
Sample 3.5\Spw demonstrates how to implement splitter window that cannot be resized through
tracking the split bar. It is based on sample 3.4\Spw.
To let class MCSplitterWnd support both resizable and non-resizable split bars, a new Boolean type
variable m_bResizable is declared in the class. Along with this variable a new member function
MCSplitterWnd::SetResizable(…) is also declared, which can be called to set m_bResizable flag and
indicate if tracking resize feature is currently supported. At the beginning variable
MCSplitterWnd::m_bResizable is initialized to TRUE in the constructor. The following code fragment
shows the modified class:
class MCSplitterWnd : public CSplitterWnd
{
DECLARE_DYNCREATE(MCSplitterWnd)
public:
MCSplitterWnd();
void SetResizable(BOOL bResizable){m_bResizable=bResizable;}
virtual void DeleteRow(int);
virtual void DeleteColumn(int);
……
protected:
BOOL m_bResizable;
}
A WM_LBUTTONDOWN message handler is added to the application. This includes function declaration,
adding ON_WM_LBUTTONDOWN message mapping macro, and the implementation of member function. Before
adding message mapping, we need to make sure that DECLARE_MESSAGE_MAP macro is included in the class.
This will enable massage mapping for the class. The following lists necessary steps for implementing the
above message mapping:
1) Declare an afx_msg type member function OnLButtonDown(…) in the class. This function is originally
declared in class CWnd, here we must declare it again in order to override it:
……
……
class MCSplitterWnd : public CSplitterWnd
{
protected:
};
afx_msg void OnLButtonDown(UINT, CPoint);
DECLARE_MESSAGE_MAP()
2) In the implementation file, add ON_WM_LBUTTONDOWN macro between BEGIN_MESSAGE_MAP and
END_MESSAGE_MAP macros:
BEGIN_MESSAGE_MAP(MCSplitterWnd, CSplitterWnd)
//{{AFX_MSG_MAP(MCSplitterWnd)
//}}AFX_MSG_MAP
ON_WM_LBUTTONDOWN()
END_MESSAGE_MAP()
Macro ON_WM_LBUTTONDOWN maps message WM_LBUTTONDOWN to function OnLButtonDown(…).
3) Implement the message handler as follows:
void MCSplitterWnd::OnLButtonDown(UINT uFlags, CPoint point)
{
if(m_bResizable == TRUE)CSplitterWnd::OnLButtonDown(uFlags, point);
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