This is a new convention pioneered by tmux. It does not do much for
nvim; since nvim always looks to see whether it should be making up
"setrgbf" and "setrgbb" capabilities. But it is a way for terminfo to
force this, irrespective of the hardwired list in the code, for more
terminal types. On the gripping hand, updating terminfo descriptions to
actually have "setrgbf" and "setrgbb" capabilities so that nvim never
has to try to invent them in the first place, is as good if not better
an approach for overriding what is baked into the code.
From observation, there are several different possible behaviours:
1. Deferred wrap like a real DEC VT. The cursor stays visible in the last
column, and CUB is calculated relative to that column.
Examples: xterm, Unicode rxvt, PuTTY, nosh console-terminal-emulator,
FreeBSD kernel's built-in emulator, Linux's built-in emulator
2. Deferred wrap like a real DEC VT. CUB is calculated relative to the last
column. But the cursor is invisible.
Examples: emulators using newer libvte
3. Non-deferred wrap. The cursor has already wrapped to the next line and CUB
does not wrap back.
Examples: cygwin, Interix
4. Non-deferred wrap that acts like deferred wrap. The cursor has already
visibly wrapped to the next line, but CUB can wrap back around the left
margin.
Examples: Konsole
5. Deferred wrap with visibly out of bounds cursor. The cursor visibly moves
outwith the screen boundaries. CUB is calculated relative to a cursor
column that has overflowed the end of the screen grid array.
Examples: iTerm2
6. Deferred wrap with invisibly out of bounds cursor. CUB is calculated
relative to a cursor column that has overflowed the end of the screen grid
array. And the cursor is invisible.
Examples: emulators using older libvte
In many cases, nvim does not have enough information to know which behaviour
the terminal will exhibit, and thus the correct amount of CUB to issue.
Partly undo 8ab08a65ba3bc9a44741a2ec9aa81fbcc77467fb. Further testing
by Enrico Ghirardi suggests limiting the non-deferred automatic wrap to
only the bottom line, whose rightmost column is not printed for iTerm.
They are now in their own nvim/tui/terminfo.c file.
Also turn the TERMINAL_FAMILY macro into a function. Use the terminfo_
prefix for its name as other parts of the program are unlikely to want
that namespace, and the prefix is already used for some other TUI
functions.
Testing by Enrico Ghirardi and review of the source indicates that
iTerm2 is a second terminal emulator that does not defer automatic wrap
at the right margin.
The example used &term which is no longer meaningful.
Fortunately, we can change this into a useful example using $TERM that also
shows how to address a common need with termguicolors at the same time.
PM...ST actually sends the string to screen's message area. Sending the
string to the status line requires a different control sequence peculiar to
screen.
Also make iTerm2 SGR 38/48 consistent.
The Interix termcap entry is missing the carriage_return capability which nvim
relies upon. And Interix is one of the few terminal emulators that does not
defer automatic wrap at the right margin, which is now accounted for when
moving the cursor left and when outputting whole lines at a time.
tmux has its own code path, now; and the tmux wrapping was not the ideal thing
to do in the first place.
Also improve the commentary on the built-in terminfo records.
The details are in the on-line help under :help true-color .
The brief precis is that nvim is (I hope.) converging with tmux and libvte.
It is taking the same approach with setrgbf and setrgbb terminfo capabilities
that it does with the Ss and Se terminfo capabilities.
The details are in the on-line help under :help cursor-shape .
The brief precis is that nvim is following the lead of tmux, and going
beyond what tmux does to make cursor shape changes work on a broad range of
terminals. This includes on tmux itself, which is no longer bypassed.
Ironically, higher layers trying to be "smart" about the terminal type
but not actually being very smart at all, makes it more difficult rather
than less to correct the TUI layer.
Note that this orphans the os_term_is_nice() function and down the road,
presuming that we do not have to revert this, that function can be removed.
It incorporates knowledge of terminal types and behaviours in the wrong place.
There are now a few built-in terminfo entries, taken either from unibilium
or ncurses terminfo, for falling back upon when there is no terminfo database
or when it is missing stuff. In an ideal world, these would be in unibilium
itself.
The ultimate fallback, for no terminfo database and no built-in terminfo
record that matches the terminal type, is now the "ansi" terminal type; so
unknown terminal types are now considered to have at minimum the basic
ECMA-48 colour, motion, and editing capabilities.
The terminfo records are just blobs, raw images of the equivalent terminfo file
created with the od command. No longer are incomplete terminfo records built
up with code. These blobs are the full, real, records; already built.
The post-processing of the terminfo record, once found, is split into the
part where we fix known errors and deficiencies in terminfo, and the part
where we add extensions that we need that terminfo does not define
capabilities for. In an ideal world, the former would be a no-op.
No part of the TUI layer apart from these is aware of terminal type or has
conditional code based upon checking environment variables at runtime. It
is all pre-calculated and written into unibilium (or the TUIData object) at
initialization time.
This is fairly aggressive about turning on 256-colour and true colour support.
This also positively decodes genuine xterm for turning on DECSLRM use, rather
than assuming that anything that says that it is xterm is actually xterm,
fixing scrolling problems with vertically split windows.
This documents 256-colour and true colour handling, cursor shapes,
and scrolling regions.
Almost all of these headings are taken from the Vim doco, so that
the :help commands that people learn are a transferable skill.
