
Columns editor
**************

Each PortaBase file contains one table of a user-defined format.  The
format of this table is determined by a sequence of data columns, each
of which has its own name, data type, and default value. When creating
a new PortaBase file, this dialog is shown so the data columns can be
defined.  The columns of an existing file can also be edited at any
time using this dialog by selecting the "Edit Columns" menu item (in
the *data viewer*, under the "File" menu except on Maemo where the
menus are flattened).

The current column definitions are displayed as rows in a list, in the
order in which they appear in the *row editor*.  These column
definitions are manipulated using the buttons in the dialog:

**Add**
   Create a new column definition at the end of the list.  A small
   dialog is shown which allows you to enter the name, data type, and
   default value of the new column.  (If you select "(New Enum)" from
   the type list in this dialog, the *enum editor* will be launched to
   allow you to add one.)  The default value is what will be entered
   for this column in any already existing data rows, and it will
   appear in the row editor when adding new rows as well.

**Edit**
   Edit the currently selected column definition.  Note that the data
   type cannot be changed.  If the default value is changed, the new
   default will appear in the row editor when adding new rows;
   existing rows are unaffected.

**Delete**
   Delete the currently selected column definition.  All data stored
   in that column will be lost.

**Up**
   Move the currently selected column up one position in the list (and
   hence in the row editor as well).

**Down**
   Move the currently selected column down one position in the list
   (and hence in the row editor as well).

None of the changes made to the table format are applied until the
"OK" ("Done" on Maemo Fremantle) button is pressed; if the dialog is
exited by cancelling instead, the changes are discarded and the file
format is left as it was.  If the dialog is cancelled while defining
the columns of a new file, the file creation is aborted; otherwise,
exiting the dialog takes you to the *data viewer*.
