Problem: Calculated cmdline cursor position can be smaller than 0.
Prompt part of the cmdline is translated, while it should
support "\t" characters.
Solution: Remove prompt part from the stored "cmdbuff" and get rid of
dubious +/-1 from cmdline cursor calculation.
Problem: Using tracked message column as column in cleared buffer.
Solution: Ensure column does not exceed current line length.
Further work to ensure carriage return and cmdline block mode
work properly.
Problem: <Tab> is not translated on the cmdline, and exposes a wrong
assumption in search messages that may contain multiple chunks.
Solution: Translate unprintable characters in the cmdline content.
Extract the 'search_count' from the last chunk and route
'search_cmd' to cmdline to handle multiple chunks.
Problem: Extui does not route messages emitted as a result of a typed
command to the "more" window.
Command message leading shell messages is missing a kind.
Messages not routed to 'cmdheight' area after it was 0.
Solution: Route messages that were emitted in the same event loop as an
entered command to the "more" window. Also append multiple
messages in an already open more-window.
Assign it the `shell_cmd` kind.
Change message position when 'cmdheight' changes from 0.
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.
