SaveAsOziWaypoingFileDialog (rev 2)

class SaveAsOziWaypointFileDialog(wx.Dialog):
    def __init__(self, parent, document, path):
        wx.Dialog.__init__(self, parent, -1, 'Save as Ozi waypoint file',
                           style=wx.DEFAULT_DIALOG_STYLE | wx.RESIZE_BORDER)

        self.document = document
        self.path = path

        self.initialize_ui()

        # Increase the width of the dialog and centre it on the screen.
        self.SetSizeWH(600, -1)
        self.CenterOnScreen()

        self.Bind(wx.EVT_BUTTON, self.on_button)
        self.Bind(wx.EVT_RADIOBUTTON, self.on_radio_button)

    def _column_picker_row(self, parent, grid, row_index, label):
        # The label.
        grid.Add(
            wx.StaticText(parent, -1, label), (row_index, 0),
            (1, 1), wx.ALIGN_RIGHT | wx.ALIGN_CENTER_VERTICAL
        )

        # The text control.
        tc = wx.TextCtrl(parent, -1)
        tc.Font = wx.Font(*const.FONT_FIXEDWIDTH)

        grid.Add(
            tc, (row_index, 1), (1, 1),
            wx.ALIGN_LEFT | wx.ALIGN_CENTER_VERTICAL | wx.EXPAND
        )

        # The "add column" button.
        add_btn = wx.Button(parent, -1, '+', style=wx.BU_EXACTFIT)
        self.Bind(
            wx.EVT_BUTTON, partial(self.on_add_to_tc, tc), source=add_btn
        )

        grid.Add(add_btn, (row_index, 2), (1, 1), wx.ALIGN_CENTER_VERTICAL)

        # Tie the add button to the text control for future use.
        tc.add_column_button = add_btn

        return tc

    def initialize_ui(self):
        # Create a main sizer to get padding from the edges of the window, and
        # create a layout sizer inside it for positioning controls.
        main_sizer = wx.BoxSizer(wx.VERTICAL)

        # Add the text controls for the waypoint info.
        waypoint_info_box = wx.StaticBox(self, -1, 'Waypoint info')
        waypoint_info_box_sizer = wx.StaticBoxSizer(waypoint_info_box)
        waypoint_info_layout = wx.GridBagSizer(5, 5)

        self.tc_wpname = self._column_picker_row(
            waypoint_info_box, waypoint_info_layout, 0, 'Waypoint name'
        )
        self.tc_wpdescr = self._column_picker_row(
            waypoint_info_box, waypoint_info_layout, 1, 'Waypoint description'
        )
        waypoint_info_layout.AddGrowableCol(1)

        waypoint_info_box_sizer.Add(
            waypoint_info_layout, 1, wx.ALL | wx.EXPAND, 10
        )
        main_sizer.Add(
            waypoint_info_box_sizer, 0, flag=wx.ALL | wx.EXPAND, border=10
        )

        # Add the controls for waypoint coordinates.
        coords_box = wx.StaticBox(self, -1, 'Waypoint coordinates')
        coords_box_sizer = wx.StaticBoxSizer(coords_box,
                                                      wx.HORIZONTAL)
        waypoint_coords_layout = wx.GridBagSizer(5, 5)

        wgs84_sizer = wx.GridBagSizer(5, 5)

        # The WGS 84 radio button.
        self.rb_wgs84 = wx.RadioButton(coords_box, -1, 'WGS 84 decimals')
        self.rb_wgs84.Value = True
        wgs84_sizer.Add(self.rb_wgs84, (0, 0), (1, 2), wx.BOTTOM, 10)

        # The column WGS 84 column pickers.
        self.tc_lat = self._column_picker_row(
            coords_box, wgs84_sizer, 1, 'Latitude'
        )
        self.tc_lng = self._column_picker_row(
            coords_box, wgs84_sizer, 2, 'Longitude'
        )
        wgs84_sizer.AddGrowableCol(1)

        # The UTM coordinate radio button and column pickers.
        utm_sizer = wx.GridBagSizer(5, 5)

        self.rb_utm = wx.RadioButton(coords_box, -1, 'UTM')
        utm_sizer.Add(self.rb_utm, (0, 0), (1, 2), wx.BOTTOM, 10)

        self.tc_utmz = self._column_picker_row(
            coords_box, utm_sizer, 1, 'Zone'
        )
        self.tc_utmx = self._column_picker_row(
            coords_box, utm_sizer, 2, 'Northing'
        )
        self.tc_utmy = self._column_picker_row(
            coords_box, utm_sizer, 3, 'Easting'
        )
        utm_sizer.AddGrowableCol(1)

        # Disable the UTM controls initially.
        for tc in [self.tc_utmz, self.tc_utmx, self.tc_utmy]:
            tc.Disable()
            tc.add_column_button.Disable()

        coords_box_sizer.Add(wgs84_sizer, 1, wx.EXPAND | wx.ALL, 10)
        coords_box_sizer.Add(utm_sizer, 1, wx.EXPAND | wx.ALL, 10)
        main_sizer.Add(coords_box_sizer, 0, wx.ALL | wx.EXPAND, border=10)

        # Add the save and cancel buttons.
        button_sizer = wx.BoxSizer(wx.HORIZONTAL)
        button_sizer.Add(wx.Button(self, wx.ID_OK, 'Save'), 0, wx.RIGHT, 5)
        button_sizer.Add(wx.Button(self, wx.ID_CANCEL, 'Cancel'), 0)

        main_sizer.AddStretchSpacer()
        main_sizer.Add(wx.StaticLine(self, -1), flag=wx.EXPAND | wx.ALL,
                       border=5)
        main_sizer.Add(button_sizer, flag=wx.ALIGN_RIGHT | wx.ALL,
                       border=5)

        # Set the OK button to the default button.
        self.FindWindowById(wx.ID_OK).SetDefault()

        self.SetSizerAndFit(main_sizer)

    def on_add_to_tc(self, tc, event):
        """Event handler for the small + buttons."""
        # Give the user a list of column headers to choose from.
        headers = self.document.table.column_headers

        dialog = wx.SingleChoiceDialog(
            self, 'Which column would you like to add?', 'Choose a column',
            headers, wx.CHOICEDLG_STYLE
        )

        if dialog.ShowModal() == wx.ID_OK:
            choice = dialog.StringSelection
            tc.AppendText('{{{}}}'.format(choice))

    def on_button(self, event):
        # Validate input when OK is clicked. If there are any errors, inform
        # the user and stop the dialog from closing.
        if event.Id == wx.ID_OK:
            pass
        else:
            event.Skip()

    def on_radio_button(self, event):
        source = self.FindWindowById(event.Id)
        wgs84_checked = source is self.rb_wgs84 and event.Checked()
        utm_checked = not wgs84_checked

        # Set the control states.
        for tc in [self.tc_lat, self.tc_lng]:
            tc.Enable(wgs84_checked)
            tc.add_column_button.Enable(wgs84_checked)

        for tc in [self.tc_utmz, self.tc_utmx, self.tc_utmy]:
            tc.Enable(utm_checked)
            tc.add_column_button.Enable(utm_checked)