- move set_seen to Listing component (instead of having it in Listing's
child Component)
- add default values to shortcut definition macro `shortcut_key_values`
- do not redefine default values in each `shortcuts` method after
getting all valid shortcuts from `context.settings.shortcuts.*.key_values()`
Page movements is an enum that describes the movements of the keyboard
keys "Home, End, PageUp, PageDown". Some mail listing Components
interpret these keys as changes to their cursors.
If a listing lists search results, ie when "filtering" with a filter
term, it sets up its state in filtered_selection, filtered_order etc.
set_coordinates() should reset that state.
By convention the valid values at any time of a cursor_pos in mail
listings is in self.new_cursor_pos, which the listing compares with
self.cursor_pos to detect position changes. Returning
self.cursor_pos values with coordinates() is invalid.
This mail list view shows one entry per thread just like CompactListing,
but the entry is slightly bigger just like in some GUIs, and when the
thread is opened the view becomes 3 columned:
+--+-------+----+
|~~|-------|~~~ |
|~~|-------|~~ |
| |-------| |
| |-------|~~~ |
+--+-------+----+
This is meant to be used with bigger terminal sizes