Things to do, roughly in order of importance:

- Find out for sure whether it's safe to use g_strsplit et al. to split
  UTF-8 strings on ASCII characters - e.g. ','. This FAQ seems to say it's
  okay: http://www.cl.cam.ac.uk/~mgk25/unicode.html#utf-8

    "All UCS characters >U+007F are encoded as a sequence of several bytes,
    each of which has the most significant bit set. Therefore, no ASCII byte
    (0x00-0x7F) can appear as part of any other character."

- Is the gettext stuff set up correctly?

- Option not to change a card's box and expiry date twice in one day.
  (Or should that policy be automatic/assumed?)

- Context menus on the category and card lists (Cut/Copy/Paste/Add/Remove/...)

- Ability to duplicate cards and categories.

- The Card Editor needs an Edit menu with Cut/Copy/Paste/Undo/Redo.

- Basic markup in cards - e.g. <b/>, <i/>, <big/>, <small/>, <tt/>,
  and/or *bold*, _italic_. (Remember that pango has routines to remove
  pango markup from strings - maybe useful for the card treeview.)

- In search results, show the category of each card found.

- A "match case" option in the search dialog.

- Sort category and card lists on column header clicks.

- Allow hidden comments (e.g. search keywords) in cards, e.g. # CHECKME

- Is it practical to use gtkhtml to display quiz cards? (Maybe using XSL to
  transform cards into HTML?) If so, that'd facilitate both markup (<i/>, etc.)
  and display of attachments (images, etc.) in cards.

- Nested categories.

- Some kind of pretty statistics view/window, with an option to reset the
  statistics of the entire file.

- Import/export "real" CSV files (see Wikipedia's article on CSV).

- Allow categories as an optional 3rd column for CSV/TSV import/export.

- Preference option to make a backup when saving, maybe.

- Update editor and quiz colours and fonts immediately if preferences change.

- Ability to specify which columns are displayed in the card list, maybe
  via a right-click menu on the column headers.

- Reduce the amount of duplicated code (e.g. app-window.c:
  cb_m_reset_stats and cb_m_switch_sides), and general cleanup.

- Attachment of files to cards (sounds, pictures, movies). Nice if media files
  could be dragged and dropped onto cards.

- Ability to spell check card contents and category titles.

- Figure out how to do drag-n-drop properly between card and category treeviews.

- Per-category card styles, maybe.

- Ability to print, and save lists of words (e.g. troublesome words) as plain
  text (er, UTF-8).

- Maybe a command line option to start up with a quiz window only.

