Using a Combobox to edit cells in the Grid Control

gridctrl with combo example image
Download sample project.

Environment: VC++ 5.0 (SP3) NT 4.0 (SP4) – CGridCtrl version 1.12

Since I posted my MFC grid control I’ve had a lot
of requests asking how to use other methods of editing cells in the grid. I’ve
created a demo project that shows how to replace the default editing with a
dropdown list of choices. This is achieved by deriving a new class from CGridCtrl
and overridding CGridCtrl::CreateInPlaceEditControl.

The In-Place list that I use to edit the cells instead of the in-place edit
control is not the greatest – but it does demonstrate how to replace the default
editting.

Thanks go to Roelf Werkman for his work in
extending the CInPlaceList to allow the CBS_DROPDOWN and CBS_SIMPLE styles
to be used.

The first step is to derive a new class from CGridCtrl – I call it
CComboGridCtrl – and override CreateInPlaceEditControl. There are a number of things
to be aware of when you override this function. CreateInPlaceEditControl receives the
row and column to be edited, the dimensions and location of the in-place edit
control, the style of control to create, the original text in the cell plus the
initial character that caused editing to commence (or VK_LBUTTON if the mouse
was clicked on the current cell).

  • Your editing control must self-delete when it loses input focus.
  • Your editing object should handle mouse keys in a way that allows
    the user to navigate between cells while editing. If the control gets an
    arrow key for instance, it should cancel editing and return the last key
    it encountered back to the grid via the GVN_ENDLABELEDIT notification
    message.

    Note that the grid control (as of version 1.08) accepts Ctrl+<arrows>
    for navigation, so if your in-place edit control needs to use the arrows,
    you can always reserve Ctrl+<arrows> to move to other cells.

To pass the necessary data back to the parent grid once editing has been completed,
use the following code snippet in your in-place edit control:


// Send Notification to parent
GV_DISPINFO dispinfo;

dispinfo.hdr.hwndFrom = GetSafeHwnd(); // Handle of window
dispinfo.hdr.idFrom = GetDlgCtrlID(); // control ID
dispinfo.hdr.code = GVN_ENDLABELEDIT; // Message

dispinfo.item.mask = LVIF_TEXT|LVIF_PARAM; // Not used in default mode
dispinfo.item.row = m_nRow; // Row – previously stored
dispinfo.item.col = m_nCol; // column – previously stored
dispinfo.item.szText = str; // New text
dispinfo.item.lParam = (LPARAM) m_nLastChar; // Last character encountered

I pass the character that initiated editing to the edit control itself so
that it can deal with keys appropriately. For instance in the default edit control,
if the edit control is passed a normal character or arrow key as the “initiating”
key, then it will cease editing when it encounters an arrow key (to allow navigation
using the keyboard). If the edit control is passed VK_LBUTTON (meaning editing
was initiated by a mouse click) then arrow keys will not cause the editing to
cease.

Once you have an edit control ready to be used, override CreateInPlaceEditControl
and use your own edit control instead of the default in-place edit control.


void CComboGridCtrl::CreateInPlaceEditControl(CRect& rect, DWORD dwStyle, UINT nID,
int nRow, int nCol,
LPCTSTR szText, int nChar)
{
CStringArray Items;
Items.Add(“Choice 1”);
Items.Add(“Choice 2”);
Items.Add(“Choice 3”);
Items.Add(“Choice 4”);
Items.Add(“Choice 5”);

// InPlaceList and auto-deletes itself
new CInPlaceList(this, rect,
//CBS_DROPDOWNLIST, // Uncomment for dropdown list style
CBS_DROPDOWN, // Uncomment for dropdown style
//CBS_SIMPLE, // Uncomment for simple style
nID, // ID of control being created
nRow, nCol,
Items, szText, nChar);
}

The sample project includes the source code for the CInPlaceList control presented
above.

Last Updated: Aug 11, 1998.

More by Author

Must Read