A static splitter with the ability to hide/show multiple columns/rows

• Download demo project - 24 Kb

Introduction

When I was working on application I realized that it needed a static splitter with the ability to hide/show several rows or columns simultaneously. Surprisingly I couldn't find such component. The closest solution was proposed by Oleg Galkin http://www.codeguru.com/splitter/show_hide_static_panes.shtml. His splitter can hide/show one of the splitter rows (columns), but only one. A static splitter with ability to hide/show multiple columns/rows is proposed in this article.

Problems with algorithm extension

MFC CSplitterWnd accesses its panes by ID and ID defines the position of a pane in the splitter. Assume that column n is to be hidden. In Oleg Galkin's algorithm, column n gets the last column ID. The columns following n are shifted to the left by 1, i.e. ID of n+1 control is assigned to control n, n+2 ID is assigned to n+1, etc. Attempts to extend this approach for multiple column hiding led to an overcomplicated algorithm. Every time you hide column, the IDs of columns hidden in previous operations are changed again. So if you hide three columns, the IDs of some controls are changed three times. It is a non-trivial problem to trace all of these changes.

New approach

CExtSplitter class uses absolute and relative addresses to operate with splitter panes. The absolute column address is an initial column number and the relative address is current column number in splitter. HideColumn and ShowColumn public functions work with absolute addresses. Relative addresses are used internally. CExtSplitter class saves pointers to all controls in an internal array. The array initialized once when the splitter is created and doesn't change during the splitter existence. Rows and columns of this array are used to access splitter panes by absolute ID. If the splitter was initialized with m rows and n columns then hiding column k (0 < k < n), means hide the column that was column k initially. Note that after several hide operations, column k can appear in the splitter at any position less than k.

Implementation details

CExtSplitter class has list of shown and hidden columns. The value of a list member is an absolute column address and position is and relative column address.

class CExtSplitter : public CSplitterWnd
{
public:
    typedef std::list < int > LIST_INT;

    CExtSplitter();   

    virtual ~CExtSplitter();

    BOOL CreateStatic(CWnd* pParentWnd,
        int nRows, int nCols,
        DWORD dwStyle = WS_CHILD | WS_VISIBLE,
        UINT nID = AFX_IDW_PANE_FIRST);

    virtual BOOL CreateView( int row, int col, 
        CRuntimeClass* pViewClass, SIZE sizeInit,
        CCreateContext* pContext );

    void    HideColumn(int colHide);
    void    ShowColumn(int colShow);
    void    HideRow(int colRow);
    void    ShowRow(int row);

public: 
    LIST_INT m_shown_cols;      //shown  column list
    LIST_INT m_hid_cols;        //hidden column list
    LIST_INT m_shown_rows;      //shown  rows list
    LIST_INT m_hid_rows;        //hidden rows list

protected:
    //array of pointers to splitter panes
    C2DArray m_pane_ptr_array;  
};

Function HideColumn moves column from list of shown columns to list of hidden columns and re-numerate the splitter panes. C++ code for re-numeration rule is shown below

void CExtSplitter::RenumeratePanes()
{
    int i,j,id;

    for(i=0; i < m_nMaxRows; i++)
    {
        for(j=0; j < m_nMaxCols; j++)
        {
            CPoint pos  = RelToAbsPosition(i,j);
            CWnd* pPane = 
                (CWnd*) m_pane_ptr_array(pos.x, pos.y);
            ASSERT(pPane != NULL);

            id=AFX_IDW_PANE_FIRST + i * 16 + j;

            int r=pPane->SetDlgCtrlID(id);
            ASSERT(r);

            if(IsPaneVisible(pos.x,pos.y))
                pPane->ShowWindow(SW_SHOW);
            else
                pPane->ShowWindow(SW_HIDE);

        }
    }
}

where RelToAbsPosition function transform the relative pane position to the absolute pane position.

Demo project

In the demo project you can call the hide and show functions through the "View" submenu. CExtSplitter class depends on C2DArray, which is included to the project.