Problem: 8defe1a declared the "more" window the most convenient place to
route messages to if it is already open for msg.pos == 'cmd'.
In usage, this doesn't appear to be the case. Appending messages
as added in that commit is still useful, but should only be done
for messages that spill 'cmdheight'.
Solution: Only append messages exceeding 'cmdheight' to the more window.
To do this, instead of immediately writing to the more buffer,
write to the cmd buffer and calculate its height. Then copy the
text and its highlights to the more buffer.
Problem: When opening a new tabpage, extui windows are initialized with
their default config. Window visiblity/dimensions on other
tabpages may get out of sync with their buffer content.
Solution: Copy the config of the window to the new tabpage.
No longer keep track of the various windows on each tabpage.
Close windows on inactive tabpages instead (moving them could
be more efficient but is currently not supported in the API).
Problem: Buffer setup after moving the message buffer to the "more"
window after ff95d7ff is incomplete.
Solution: Adjust and invoke tab_check_wins() to do the setup instead.
Problem: Closing the "more" window for an entered cmdwin in ff95d7ff9
still requires special casing to properly handle "more" visibility.
Solution: Reposition the "more" window instead; anchoring it to the
cmdwin.
Problem: Message lines from multiple message events that end up
spilling 'cmdheight' end up spread out over the cmdline
and "more" window.
Messages emitted as feedback to a typed :command (rather than
its sole purpose like :echo/:=) are routed to the more window.
The more window isn't closed when entering the cmdwin, and
doesn't allow `vim.hl.on_yank()`.
Solution: When first opening the "more" window for spilled messages,
move the message buffer to the more window.
Restrict routing of typed commands to echo kinds.
Ignore all events but WinLeave and TextYankPost.
Problem: Bulking message lines to write in a single API call is
complicated and still not correct w.r.t. overwriting
highlights.
Solution: Write each chunk pattern separately with it's highlight
such that it will be spliced correctly for message chunks
that contain a carriage return. Go with correctness over
performance until this proves to be too inefficient.
Also add an identifying name to the various extui buffers.
Problem: Unable to discern windows used by the extui interface
to configure their local options.
'winblend' may be detrimental to legibility depending on the
colorscheme and 'background'.
Solution: Assign the "cmdline", "msgmore", "msgprompt" and "msgbox"
'filetype' to the respective windows.
Don't set 'winblend' for the message "box" window.
Problem: Moving the "more" (or any extui)-window to a split with
`wincmd L` does not invalidate it as a tracked window.
Solution: Drop an extui window that is no longer floating.
Problem: The cmdline popupmenu is hidden behind extui windows.
'showmode' message is drawn over the cmdline.
Changing the 'cmdheight' to accommodate space for the text in
the cmdline may change the current cursor position.
Solution: Ensure kZIndexMessages < zindex < kZIndexCmdlinePopupMenu.
Clear the 'showmode' message when the cmdline level is negative.
Temporarily set 'splitkeep' = "screen" when changing the 'cmdheight'.
Problem: We have an unmaintained Vimscript parser and cmdline
highlighting mechanism, with which it is hard to leverage the
treesitter highlighter. Long messages result in a hit-enter-prompt.
Solution: Implement a vim.ui_attach() UI, that replaces the message
grid (orphaning some 3000+ LOC core C code). Introduce an experimental
vim._extui module, because removing the message grid at the same time is
too risky. The new UI leverages the bundled treesitter highlighter and
parser for Vimscript, as well as the matchparen plugin, to highlight the
cmdline. Messages are truncated in the cmdline area, or placed in a
floating message box in the bottom right corner. Special ("list_cmd")
messages and the message history are shown in a, "more prompt" (now a
fully interactive regular window). Various default UI elements ('showcmd',
'ruler') are also placed in the cmdline area, as virtual text.
`require('vim._extui').enable({})` enables the experimental UI.
`{ msg.pos = 'box' }` or `:set cmdheight=0` enables the message
box variant.
Followup:
- Come to a consensus for how best to represent messages (by default).
- Start removing message grid when this is deemed a successful replacement.
When that is finished, make this new UI the default and update a lot of tests.
