By setting the ncurses_builtin_key_parser ui_option to true, we
can disable ncurses parsing of key strokes to get less portable
parsing but support for more complex modifiers.
Ideally, something better should be done (re #2554) but this is a decent
intermediate step for some useful keys.
Note: NCurses supports parsing these keys when shifted (KEY_SR,
_SLEFT, S_RIGHT, etc), but it does not do the same thing for the other
modifiers.
Window can be resized with an "offset_pos" flag, which means that
the resize took place on the top left corner of the window, leading
to a change in current window position. This is treated as temporary
and the position change is stored in a m_position_offset field.
That allows the ncurses UI to offset the position when it displays
a Search menu, so that the window does not constantly scroll when
the search menu open/closes. The window will only scroll if it needs
to in order to keep the main selectin visible.
Because keyboard layouts vary, the shift-modifier `<s-…>` is only supported
for special keys (like `<up>` and `<home>`) and for ASCII lowercase where
we assume the shift-modifier just produces the matching uppercase character.
Even that's not universally true, since in Turkish `i` and `I` are not an
uppercase/lowercase pair, but Kakoune's default keyboard mappings already
assume en-US mappings for mnemonic purposes.
Mappings of the form `<s-x>` are normalized to `<X>` when `x` is an ASCII
character. `<backtab>` is removed, since we can now say `<s-tab>`.
Add a ColumnCount type and use it in place of CharCount whenever
more appropriate, take column size of codepoints into account for
vertical movements and docstring wrapping.
Fixes#811
