Editable subitems


The default implementation of the ListView control allows editing of the first column label only. You have to create your own edit control to allow editing of subitems.

Step 1: Derive a class from CListCtrl

In the code below, CMyListCtrl is the name used for the derived class. You can also derive a class from CListView if you need this functionality in a CView rather than in a control. If you are already working with a sub-class of CListCtrl, you can make the modifications to that class.

Step 2: Define HitTestEx()

Define an extended HitTest function for the CMyListCtrl class. This function will determine the row index that the point falls over and also determine the column. The HitTestEx() has already been listed and explained in an earlier section and is listed here again for completeness. We need this function if the user interface to initiate the edit is a mouse click or a double click. See the section "Detecting column index of the item clicked".
// HitTestEx	- Determine the row index and column index for a point
// Returns	- the row index or -1 if point is not over a row
// point	- point to be tested.
// col		- to hold the column index
int CMyListCtrl::HitTestEx(CPoint &point, int *col) const
{
	int colnum = 0;
	int row = HitTest( point, NULL );
	
	if( col ) *col = 0;

	// Make sure that the ListView is in LVS_REPORT
	if( (GetWindowLong(m_hWnd, GWL_STYLE) & LVS_TYPEMASK) != LVS_REPORT )
		return row;

	// Get the top and bottom row visible
	row = GetTopIndex();
	int bottom = row + GetCountPerPage();
	if( bottom > GetItemCount() )
		bottom = GetItemCount();
	
	// Get the number of columns
	CHeaderCtrl* pHeader = (CHeaderCtrl*)GetDlgItem(0);
	int nColumnCount = pHeader->GetItemCount();

	// Loop through the visible rows
	for( ;row <=bottom;row++)
	{
		// Get bounding rect of item and check whether point falls in it.
		CRect rect;
		GetItemRect( row, &rect, LVIR_BOUNDS );
		if( rect.PtInRect(point) )
		{
			// Now find the column
			for( colnum = 0; colnum < nColumnCount; colnum++ )
			{
				int colwidth = GetColumnWidth(colnum);
				if( point.x >= rect.left 
					&& point.x <= (rect.left + colwidth ) )
				{
					if( col ) *col = colnum;
					return row;
				}
				rect.left += colwidth;
			}
		}
	}
	return -1;
}

Step 3: Add function to initiate the edit

The user interface to initiate an edit for a sub item may be click on an already selected row, a double click or even a push button. We define a helper function to set up the edit control. The helper function takes only the row and column index of the subitem. EditSubLabel() ensures that the row as well as the column is visible before it creates the edit control. It then creates the edit control of the right size and with the proper text justification. The edit control created is of the class CInPlaceEdit which we will define later.
// EditSubLabel		- Start edit of a sub item label
// Returns		- Temporary pointer to the new edit control
// nItem		- The row index of the item to edit
// nCol			- The column of the sub item.
CEdit* CMyListCtrl::EditSubLabel( int nItem, int nCol )
{
	// The returned pointer should not be saved

	// Make sure that the item is visible
	if( !EnsureVisible( nItem, TRUE ) ) return NULL;

	// Make sure that nCol is valid
	CHeaderCtrl* pHeader = (CHeaderCtrl*)GetDlgItem(0);
	int nColumnCount = pHeader->GetItemCount();
	if( nCol >= nColumnCount || GetColumnWidth(nCol) < 5 )
		return NULL;

	// Get the column offset
	int offset = 0;
	for( int i = 0; i < nCol; i++ )
		offset += GetColumnWidth( i );

	CRect rect;
	GetItemRect( nItem, &rect, LVIR_BOUNDS );

	// Now scroll if we need to expose the column
	CRect rcClient;
	GetClientRect( &rcClient );
	if( offset + rect.left < 0 || offset + rect.left > rcClient.right )
	{
		CSize size;
		size.cx = offset + rect.left;
		size.cy = 0;
		Scroll( size );
		rect.left -= size.cx;
	}

	// Get Column alignment
	LV_COLUMN lvcol;
	lvcol.mask = LVCF_FMT;
	GetColumn( nCol, &lvcol );
	DWORD dwStyle ;
	if((lvcol.fmt&LVCFMT_JUSTIFYMASK) == LVCFMT_LEFT)
		dwStyle = ES_LEFT;
	else if((lvcol.fmt&LVCFMT_JUSTIFYMASK) == LVCFMT_RIGHT)
		dwStyle = ES_RIGHT;
	else dwStyle = ES_CENTER;

	rect.left += offset+4;
	rect.right = rect.left + GetColumnWidth( nCol ) - 3 ;
	if( rect.right > rcClient.right) rect.right = rcClient.right;

	dwStyle |= WS_BORDER|WS_CHILD|WS_VISIBLE|ES_AUTOHSCROLL;
	CEdit *pEdit = new CInPlaceEdit(nItem, nCol, GetItemText( nItem, nCol ));
	pEdit->Create( dwStyle, rect, this, IDC_IPEDIT );


	return pEdit;
}

Step 4: Handle the scroll messages

The CInPlaceEdit class is designed to destroy the edit control and delete the object when it loses focus. Clicking on the scrollbars of the ListView control does not take away the focus from the edit control. We therefore add handlers for the scrollbar messages which force focus away from the edit control by setting the focus to the list view control itself.
void CMyListCtrl::OnHScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar)
{
	if( GetFocus() != this ) SetFocus();
	CListCtrl::OnHScroll(nSBCode, nPos, pScrollBar);
}

void CMyListCtrl::OnVScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar)
{
	if( GetFocus() != this ) SetFocus();
	CListCtrl::OnVScroll(nSBCode, nPos, pScrollBar);
}

Step 5: Handle EndLabelEdit

Like the built in edit control for the first column, our edit control also sends the LVN_ENDLABELEDIT notification when the edit is completed. If this notification message isnt already being handled, add a handler so that any changes made with the edit control can be accepted.
void CMyListCtrl::OnEndLabelEdit(NMHDR* pNMHDR, LRESULT* pResult)
{
	LV_DISPINFO *plvDispInfo = (LV_DISPINFO *)pNMHDR;
	LV_ITEM	*plvItem = &plvDispInfo->item;

	if (plvItem->pszText != NULL)
	{
		SetItemText(plvItem->iItem, plvItem->iSubItem, plvItem->pszText);
	}
	*pResult = FALSE;
}

Step 6: Add means for the user to initiate the edit

A suggested method for starting an edit of a subitem is to click on a subitem when the item already has the focus. You may choose to provide a different method. The code below is the handler for the WM_LBUTTONDOWN message. An edit control is created to edit a subitem if the subitem is clicked after the item already has the focus. The code checks for the LVS_EDITLABELS style before creating the edit control. It also does not activate the edit control for the first column since editing of the first column is already supported by the list view control.

void CMyListCtrl::OnLButtonDown(UINT nFlags, CPoint point)
{
	int index;
	CListCtrl::OnLButtonDown(nFlags, point);

	int colnum;
	if( ( index = HitTestEx( point, &colnum )) != -1 )
	{
		UINT flag = LVIS_FOCUSED;
		if( (GetItemState( index, flag ) & flag) == flag && colnum > 0)
		{
			// Add check for LVS_EDITLABELS
			if( GetWindowLong(m_hWnd, GWL_STYLE) & LVS_EDITLABELS )
				EditSubLabel( index, colnum );
		}
		else
			SetItemState( index, LVIS_SELECTED | LVIS_FOCUSED ,
				    	LVIS_SELECTED | LVIS_FOCUSED); 
	}
}

Step 7: Subclass the CEdit class

We need to subclass the CEdit class to provide for our special requirement. The main requirements placed on this class is that
  • It should send the LVN_ENDLABELEDIT message when edit is complete
  • It should expand to accommodate the text
  • It should destroy itself when the edit is complete
  • The edit should be terminated when the user presses the Escape or the Enter key or when the edit control loses focus.
The listing of the header file precedes that of the implementation file. The CInPlaceEdit declares four private variables. These are used when the control sends the LVN_ENDLABELEDIT notification.
// InPlaceEdit.h : header file
//

/////////////////////////////////////////////////////////////////////////////
// CInPlaceEdit window

class CInPlaceEdit : public CEdit
{
// Construction
public:
	CInPlaceEdit(int iItem, int iSubItem, CString sInitText);

// Attributes
public:

// Operations
public:

// Overrides
	// ClassWizard generated virtual function overrides
	//{{AFX_VIRTUAL(CInPlaceEdit)
	public:
	virtual BOOL PreTranslateMessage(MSG* pMsg);
	//}}AFX_VIRTUAL

// Implementation
public:
	virtual ~CInPlaceEdit();

	// Generated message map functions
protected:
	//{{AFX_MSG(CInPlaceEdit)
	afx_msg void OnKillFocus(CWnd* pNewWnd);
	afx_msg void OnNcDestroy();
	afx_msg void OnChar(UINT nChar, UINT nRepCnt, UINT nFlags);
	afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
	//}}AFX_MSG

	DECLARE_MESSAGE_MAP()
private:
	int m_iItem;
	int m_iSubItem;
	CString m_sInitText;
	BOOL    m_bESC;	 	// To indicate whether ESC key was pressed
};

/////////////////////////////////////////////////////////////////////////////
The listing of the implementation file now follows. The CInPlaceEdit constructor simply saves the values passed through its arguments and initializes m_bESC to false. The overridden PreTranslateMessage() is to ascertain that certain key strokes do make it to the edit control. The escape key and the enter key are normally pre-translated by the CDialog or the CFormView object, we therefore specifically check for these and pass it on to the edit control. The check for GetKeyState( VK_CONTROL) makes sure that key combinations such as Ctrl-C, Ctrl-V and Ctrl-X get forwarded to the edit control.

OnKillFocus() sends of the LVN_ENDLABELEDIT notification and destroys the edit control. The notification is sent to the parent of the list view control and not to the list view control itself. When sending the notification, the m_bESC member variable is used to determine whether to send a NULL string.

The OnNcDestroy() function is the appropriate place to destroy the C++ object.

The OnChar() function ends the edit if the Escape or the Enter key is pressed. It does this by setting focus to the list view control which force the OnKillFocus() of the edit control to be called. For any other character, the OnChar() function lets the base class function take care of it before it tries to determine if the control needs to be resized. The function first gets the extent of the new string using the proper font and then compares it to the current dimension of the edit control. If the string is too long to fit within the edit control, it resizes the edit control after checking the parent window ( the list view control ) to determine if there is space for the edit control to grow.

The OnCreate() function creates the edit control and initializes it with the proper values.

// InPlaceEdit.cpp : implementation file
//

#include "stdafx.h"
#include "InPlaceEdit.h"

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

/////////////////////////////////////////////////////////////////////////////
// CInPlaceEdit

CInPlaceEdit::CInPlaceEdit(int iItem, int iSubItem, CString sInitText)
:m_sInitText( sInitText )
{
	m_iItem = iItem;
	m_iSubItem = iSubItem;
	m_bESC = FALSE;
}

CInPlaceEdit::~CInPlaceEdit()
{
}


BEGIN_MESSAGE_MAP(CInPlaceEdit, CEdit)
	//{{AFX_MSG_MAP(CInPlaceEdit)
	ON_WM_KILLFOCUS()
	ON_WM_NCDESTROY()
	ON_WM_CHAR()
	ON_WM_CREATE()
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CInPlaceEdit message handlers

BOOL CInPlaceEdit::PreTranslateMessage(MSG* pMsg)
{
	if( pMsg->message == WM_KEYDOWN )
	{
		if(pMsg->wParam == VK_RETURN
				|| pMsg->wParam == VK_DELETE
				|| pMsg->wParam == VK_ESCAPE
				|| GetKeyState( VK_CONTROL)
				)
		{
			::TranslateMessage(pMsg);
			::DispatchMessage(pMsg);
			return TRUE;		    	// DO NOT process further
		}
	}

	return CEdit::PreTranslateMessage(pMsg);
}


void CInPlaceEdit::OnKillFocus(CWnd* pNewWnd)
{
	CEdit::OnKillFocus(pNewWnd);

	CString str;
	GetWindowText(str);

	// Send Notification to parent of ListView ctrl
	LV_DISPINFO dispinfo;
	dispinfo.hdr.hwndFrom = GetParent()->m_hWnd;
	dispinfo.hdr.idFrom = GetDlgCtrlID();
	dispinfo.hdr.code = LVN_ENDLABELEDIT;

	dispinfo.item.mask = LVIF_TEXT;
	dispinfo.item.iItem = m_iItem;
	dispinfo.item.iSubItem = m_iSubItem;
	dispinfo.item.pszText = m_bESC ? NULL : LPTSTR((LPCTSTR)str);
	dispinfo.item.cchTextMax = str.GetLength();

	GetParent()->GetParent()->SendMessage( WM_NOTIFY, GetParent()->GetDlgCtrlID(), 
					(LPARAM)&dispinfo );

	DestroyWindow();
}

void CInPlaceEdit::OnNcDestroy()
{
	CEdit::OnNcDestroy();

	delete this;
}


void CInPlaceEdit::OnChar(UINT nChar, UINT nRepCnt, UINT nFlags)
{
	if( nChar == VK_ESCAPE || nChar == VK_RETURN)
	{
		if( nChar == VK_ESCAPE )
			m_bESC = TRUE;
		GetParent()->SetFocus();
		return;
	}


	CEdit::OnChar(nChar, nRepCnt, nFlags);

	// Resize edit control if needed

	// Get text extent
	CString str;

	GetWindowText( str );
	CWindowDC dc(this);
	CFont *pFont = GetParent()->GetFont();
	CFont *pFontDC = dc.SelectObject( pFont );
	CSize size = dc.GetTextExtent( str );
	dc.SelectObject( pFontDC );
	size.cx += 5;			   	// add some extra buffer

	// Get client rect
	CRect rect, parentrect;
	GetClientRect( &rect );
	GetParent()->GetClientRect( &parentrect );

	// Transform rect to parent coordinates
	ClientToScreen( &rect );
	GetParent()->ScreenToClient( &rect );

	// Check whether control needs to be resized
	// and whether there is space to grow
	if( size.cx > rect.Width() )
	{
		if( size.cx + rect.left < parentrect.right )
			rect.right = rect.left + size.cx;
		else
			rect.right = parentrect.right;
		MoveWindow( &rect );
	}
}

int CInPlaceEdit::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
	if (CEdit::OnCreate(lpCreateStruct) == -1)
		return -1;

	// Set the proper font
	CFont* font = GetParent()->GetFont();
	SetFont(font);

	SetWindowText( m_sInitText );
	SetFocus();
	SetSel( 0, -1 );
	return 0;
}