Problem: An accidental key press can dismiss a routed message to be
shown in full before the user was able to read it.
'verbose' message routing based on an outdated condition results
in "last_set" messages being separated from its message pair.
Solution: Show a message to be shown in full in the cmdline window instead
of the pager. Keep it there and update the spill indicator when
the message is dismissed.
Remove the 'verbose' message routing.
Problem: Messages routed to the pager to be shown in full, enter the
pager automatically, yielding another "press-q-prompt".
Solution: Only enter the pager when requested explicitly. Otherwise,
close the pager on the next typed mapping, unless that mapping
entered the pager.
Problem: vim._extui unconditionally creates windows, buffers and the
Vimscript cmdline highlighter when it is first loaded.
Solution: Schedule first creation of the window so that first redraw
happens sooner (still need to create at least the cmdline
window asap as it can have a different highlight through
hl-MsgArea; thus further delaying until the first event that
needs a particular target seems redundant). Load the cmdline
highlighter on the first cmdline_show event.
Problem: ext_messages cannot tell when the screen was cleared, which is
needed to clear visible messages. An empty message is also
never emitted, but clears messages from the message grid.
Solution: Repurpose the "msg_clear" event to be emitted when the screen
was cleared. Emit an empty message with the `empty` kind to
hint to a UI to clear the cmdline area.
Problem: OptionSet autocmd emitted with invalid grids after entering
tabpage with different 'cmdheight'.
Solution: First call `tabpage_check_windows()` before changing 'cmdheight'.
Add a test that exercises the `vim._extui` cmdline.
Problem: UI buffers may be 'unmodifiable' and use a 'swapfile'.
Solution: Set the 'modifiable' and 'noswapfile' options.
Co-authored-by:phanium <91544758+phanen@users.noreply.github.com>
Problem: No ext_messages kind for the :command, :version commands.
:version is emitted as multiple events.
Solution: Assign them the "list_cmd" kind. Use `msg_put*` to properly
format the message as a single event.
