Adding Checkboxes to a list control

A list view gives the GUI designer many options. One of the best is the ability to display tabular data in columns, sort columns, add images and more. This is well implemented by CListView in MFC.

A checked list box enables the GUI designer to get the users picked options via a checkbox on every list item. This is well implemented by CCheckListBox in MFC.

How to combine them both into one control?

Basically, there are two options: either you use owner drawn list view controls and draw your own check boxes as small images OR you can use the new control introduced in Microsoft's IE 3.0. To use the new features of a list view control you must install IE 3.0 (or above) to get the newest version of COMCTL32.DLL (the common controls library).

This control introduces some new flags in the ListView style and adds accepts some macros defined in the windows header files.

Bear in mind, the new flags and macros DO NOT APPEAR in VC++ 4.2 help files and started to exists in help files only from MSDN Jan 97 version and V++ 5.0

Well, here goes:

First, you have to set the new style in the list view control. This can be done by:

ListView_SetExtendedListViewStyle 
   (m_lvTestList.m_hWnd, LVS_EX_CHECKBOXES | LVS_EX_FULLROWSELECT);

This sets the list view to support check boxes and also a full row select (not only the 1st column).

How to get notification when an item is checked / unchecked:

void DemoDlg::OnItemchangedLinksList(NMHDR* pNMHDR, LRESULT* pResult) 
{
    NM_LISTVIEW* pNMListView = (NM_LISTVIEW*)pNMHDR;
    *pResult = 0;

    if (pNMListView->uOldState == 0 && pNMListView->uNewState == 0)
        return;    // No change


    // Old check box state
    BOOL bPrevState = (BOOL)(((pNMListView->uOldState & 
                LVIS_STATEIMAGEMASK)>>12)-1);  
    if (bPrevState < 0)    // On startup there's no previous state 
        bPrevState = 0; // so assign as false (unchecked)

    // New check box state
    BOOL bChecked = <BR>            (BOOL)(((pNMListView->uNewState & LVIS_STATEIMAGEMASK)>>12)-1);   
    if (bChecked < 0) // On non-checkbox notifications assume false
        bChecked = 0; 

    if (bPrevState == bChecked) // No change in check box
        return;
    
    // Now bChecked holds the new check box state

    // ....
}

for this to work, you must map the following message:

ON_NOTIFY(LVN_ITEMCHANGED, IDC_MYLIST, OnItemchangedLinksList)

Setting the check box state of an item:

Try the following piece of code

void SetLVCheck (WPARAM ItemIndex, BOOL bCheck)
{
    ListView_SetItemState (m_lvTestList.m_hWnd, ItemIndex, 
        UINT((int(bCheck) + 1) << 12), LVIS_STATEIMAGEMASK);
}

Getting the check box state of an item:

Use the macro ListView_GetCheckState(hwndLV, i) defined in commctl.h (hwndLV is the window handle of the list view member - i.e, m_lvTestList.m_hWnd and i is the list view index)