Using a drop down list to change a subitem

Step1: Derive a class from CListCtrl

Step 2: Define HitTestEx()

Step 3: Add function to create the Drop Down List

// ShowInPlaceList		- Creates an in-place drop down list for any 
//				- cell in the list view control
// Returns			- A temporary pointer to the combo-box control
// nItem			- The row index of the cell
// nCol				- The column index of the cell
// lstItems			- A list of strings to populate the control with
// nSel				- Index of the initial selection in the drop down list
CComboBox* CMyListCtrl::ShowInPlaceList( int nItem, int nCol, 
					CStringList &lstItems, int nSel )
{
	// 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) < 10 ) 
		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;
	}

	rect.left += offset+4;
	rect.right = rect.left + GetColumnWidth( nCol ) - 3 ;
	int height = rect.bottom-rect.top;
	rect.bottom += 5*height;
	if( rect.right > rcClient.right) rect.right = rcClient.right;

	DWORD dwStyle = WS_BORDER|WS_CHILD|WS_VISIBLE|WS_VSCROLL|WS_HSCROLL
					|CBS_DROPDOWNLIST|CBS_DISABLENOSCROLL;
	CComboBox *pList = new CInPlaceList(nItem, nCol, &lstItems, nSel);
	pList->Create( dwStyle, rect, this, IDC_IPEDIT );
	pList->SetItemHeight( -1, height);
	pList->SetHorizontalExtent( GetColumnWidth( nCol ));


	return pList;
}

Step 4: Handle the scroll messages

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

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

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 )
		{
			// Add check for LVS_EDITLABELS
			if( GetWindowLong(m_hWnd, GWL_STYLE) & LVS_EDITLABELS )
			{
				CStringList lstItems;
				lstItems.AddTail( "First Item");
				lstItems.AddTail( "Second Item");
				lstItems.AddTail( "Third Item");
				lstItems.AddTail( "Fourth Item");
				lstItems.AddTail( "Fifth Item");
				lstItems.AddTail( "Sixth Item");
				ShowInPlaceList( index, colnum, lstItems, 2 );
			}
		}
		else
			SetItemState( index, LVIS_SELECTED | LVIS_FOCUSED , 
					LVIS_SELECTED | LVIS_FOCUSED);
	}
}

Step 7: Subclass the CComboBox class

• It should send the LVN_ENDLABELEDIT message when the user finishes selecting an item
• 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 user selects an item or when the control loses the input focus.

// InPlaceList.h : header file
//

/////////////////////////////////////////////////////////////////////////////
// CInPlaceList window

class CInPlaceList : public CComboBox
{
// Construction
public:
	CInPlaceList(int iItem, int iSubItem, CStringList *plstItems, int nSel);

// Attributes
public:

// Operations
public:

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

// Implementation
public:
	virtual ~CInPlaceList();

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

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

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

The overridden PreTranslateMessage() is to ascertain that the escape and the enter key strokes do make it to the combobox 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 combobox.

OnKillFocus() sends of the LVN_ENDLABELEDIT notification and destroys the combobox 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 selection 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 combobox control to be called. For any other character, the OnChar() function lets the base class function take care of it.

The OnCloseup() function is called when the user has made a selection from the drop down list. This function sets the input focus to its parent thus terminating the item selection.
 

// InPlaceList.cpp : implementation file
//

#include "stdafx.h"
#include "InPlaceList.h"

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

/////////////////////////////////////////////////////////////////////////////
// CInPlaceList

CInPlaceList::CInPlaceList(int iItem, int iSubItem, CStringList *plstItems, int nSel)
{
	m_iItem = iItem;
	m_iSubItem = iSubItem;

	m_lstItems.AddTail( plstItems );
	m_nSel = nSel;
	m_bESC = FALSE;
}

CInPlaceList::~CInPlaceList()
{
}


BEGIN_MESSAGE_MAP(CInPlaceList, CComboBox)
	//{{AFX_MSG_MAP(CInPlaceList)
	ON_WM_CREATE()
	ON_WM_KILLFOCUS()
	ON_WM_CHAR()
	ON_WM_NCDESTROY()
	ON_CONTROL_REFLECT(CBN_CLOSEUP, OnCloseup)
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CInPlaceList message handlers

int CInPlaceList::OnCreate(LPCREATESTRUCT lpCreateStruct) 
{
	if (CComboBox::OnCreate(lpCreateStruct) == -1)
		return -1;
	
	// Set the proper font
	CFont* font = GetParent()->GetFont();
	SetFont(font);

	for( POSITION pos = m_lstItems.GetHeadPosition(); pos != NULL; )
	{
		AddString( (LPCTSTR) (m_lstItems.GetNext( pos )) );
	}
	SetCurSel( m_nSel );
	SetFocus();
	return 0;
}

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

void CInPlaceList::OnKillFocus(CWnd* pNewWnd) 
{
	CComboBox::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 );

	PostMessage( WM_CLOSE );
}

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

void CInPlaceList::OnNcDestroy() 
{
	CComboBox::OnNcDestroy();
	
	delete this;
}

void CInPlaceList::OnCloseup() 
{
	GetParent()->SetFocus();
}