self.RegisterDataType(wx.grid.GRID_VALUE_STRING,
                              wx.grid.GridCellStringRenderer(),
                              CCellEditor(self))

        self.CreateGrid(4, 3)           # By default start with a 4 x 3 grid
        self.SetColLabelSize(18)        # Default sizes and alignment
        self.SetRowLabelSize(50)
        self.SetRowLabelAlignment(wx.ALIGN_RIGHT, wx.ALIGN_BOTTOM)
        self.SetColSize(0, 75)          # Default column sizes
        self.SetColSize(1, 75)
        self.SetColSize(2, 75)

        # Sink events
        self.Bind(wx.grid.EVT_GRID_CELL_LEFT_CLICK, self.OnLeftClick)
        self.Bind(wx.grid.EVT_GRID_CELL_RIGHT_CLICK, self.OnRightClick)
        self.Bind(wx.grid.EVT_GRID_CELL_LEFT_DCLICK, self.OnLeftDoubleClick)
        self.Bind(wx.grid.EVT_GRID_RANGE_SELECT, self.OnRangeSelect)
        self.Bind(wx.grid.EVT_GRID_ROW_SIZE, self.OnRowSize)
        self.Bind(wx.grid.EVT_GRID_COL_SIZE, self.OnColSize)
        self.Bind(wx.grid.EVT_GRID_CELL_CHANGE, self.OnCellChange)
        self.Bind(wx.grid.EVT_GRID_SELECT_CELL, self.OnGridSelectCell)

    def OnGridSelectCell(self, event):
        """ Track cell selections """
        # Save the last cell coordinates
        self._lastRow, self._lastCol = event.GetRow(), event.GetCol()
        event.Skip()

    def OnRowSize(self, event):
        event.Skip()

    def OnColSize(self, event):
        event.Skip()

    def OnCellChange(self, event):
        event.Skip()

    def OnLeftClick(self, event):
        """ Override left-click behavior to prevent left-click edit initiation """
        # Save the cell clicked
        currCell = (event.GetRow(), event.GetCol())

        # Suppress event if same cell clicked twice in a row.
        # This prevents a single-click from initiating an edit.
        if currCell != (self._lastRow, self._lastCol): event.Skip()

    def OnRightClick(self, event):
        """ Move grid cursor when a cell is right-clicked """
        self.SetGridCursor( event.GetRow(), event.GetCol() )
        event.Skip()

    def OnLeftDoubleClick(self, event):
        """ Initiate the cell editor on a double-click """
        # Move grid cursor to double-clicked cell
        if self.CanEnableCellControl():
            self.SetGridCursor( event.GetRow(), event.GetCol() )
            self.EnableCellEditControl(True)    # Show the cell editor
        event.Skip()

    def OnRangeSelect(self, event):
        """ Track which cells are selected so that copy/paste behavior can be implemented """
        # If a single cell is selected, then Selecting() returns False (0)
        # and range coords are entire grid.  In this case cancel previous selection.
        # If more than one cell is selected, then Selecting() is True (1)
        # and range accurately reflects selected cells.  Save them.
        # If more cells are added to a selection, selecting remains True (1)
        self._selected = None
        if event.Selecting():
            self._selected = ((event.GetTopRow(), event.GetLeftCol()),
                              (event.GetBottomRow(), event.GetRightCol()))
        event.Skip()

    def Copy(self):
        """ Copy the currently selected cells to the clipboard """
        # TODO: raise an error when there are no cells selected?
        if self._selected == None: return
        ((r1, c1), (r2, c2)) = self._selected

        # Build a string to put on the clipboard
        # (Is there a faster way to do this in Python?)
        crlf = chr(13) + chr(10)
        tab = chr(9)
        s = ""
        for row in range(r1, r2+1):
            for col in range(c1, c2):
                s += self.GetCellValue(row,col)
                s += tab
            s += self.GetCellValue(row, c2)
            s += crlf

        # Put the string on the clipboard
        if wx.TheClipboard.Open():
            wx.TheClipboard.Clear()
            wx.TheClipboard.SetData(wx.TextDataObject(s))
            wx.TheClipboard.Close()

    def Paste(self):
        """ Paste the contents of the clipboard into the currently selected cells """
        # (Is there a better way to do this?)
        if wx.TheClipboard.Open():
            td = wx.TextDataObject()
            success = wx.TheClipboard.GetData(td)
            wx.TheClipboard.Close()
            if not success: return              # Exit on failure
            s = td.GetText()                    # Get the text

            crlf = chr(13) + chr(10)            # CrLf characters
            tab = chr(9)                        # Tab character

            rows = s.split(crlf)               # split into rows
            rows = rows[0:-1]                   # leave out last element, which is always empty
            for i in range(0, len(rows)):       # split rows into elements
                rows[i] = rows[i].split(tab)

            # Get the starting and ending cell range to paste into
            if self._selected == None:          # If no cells selected...
                r1 = self.GetGridCursorRow()    # Start the paste at the current location
                c1 = self.GetGridCursorCol()
                r2 = self.GetNumberRows()-1     # Go to maximum row and col extents
                c2 = self.GetNumberCols()-1
            else:                               # If cells selected, only paste there
                ((r1, c1), (r2, c2)) = self._selected

            # Enter data into spreadsheet cells one at a time
            r = r1                              # Init row and column counters
            c = c1
            for row in rows:                    # Loop over all rows
                for element in row:             # Loop over all row elements
                    self.SetCellValue(r, c, str(element))   # Set cell value
                    c += 1                      # Increment the column counter
                    if c > c2: break            # Do not exceed maximum column
                r += 1
                if r > r2: break                # Do not exceed maximum row
                c = c1

    def Clear(self):
        """ Clear the currently selected cells """
        if self._selected == None:              # If no selection...
            r = self.GetGridCursorRow()         # clear only current cell
            c = self.GetGridCursorCol()
            self.SetCellValue(r, c, "")
        else:                                   # Otherwise clear selected cells
            ((r1, c1), (r2, c2)) = self._selected
            for r in range(r1, r2+1):
                for c in range(c1, c2+1):
                    self.SetCellValue(r, c, "")

    def SetNumberRows(self, numRows=1):
        """ Set the number of rows in the sheet """
        # Check for non-negative number
        if numRows < 0:  return False

        # Adjust number of rows
        curRows = self.GetNumberRows()
        if curRows < numRows:
            self.AppendRows(numRows - curRows)
        elif curRows > numRows:
            self.DeleteRows(numRows, curRows - numRows)

        return True

    def SetNumberCols(self, numCols=1):
        """ Set the number of columns in the sheet """
        # Check for non-negative number
        if numCols < 0:  return False

        # Adjust number of rows
        curCols = self.GetNumberCols()
        if curCols < numCols:
            self.AppendCols(numCols - curCols)
        elif curCols > numCols:
            self.DeleteCols(numCols, curCols - numCols)

        return True