Nvim Terminal UI: Color Capabilities, Terminal Resizing, and Cursor Shape Handling

add constructed "setrgbf" and "setrgbb" capabilities as if they had been in the terminfo definition. If terminfo does not (yet) have this flag, Nvim will fall back to $TERM and other environment variables. It will add constructed "setrgbf" and "setrgbb" capabilities in the case of the "rxvt", "linux", "st", "tmux", and "iterm" terminal types, or when Konsole, genuine Xterm, a libvte terminal emulator version 0.36 or later, or a terminal emulator that sets the COLORTERM environment variable to "truecolor" is detected. *xterm-resize* Nvim can resize the terminal display on some terminals that implement an extension pioneered by dtterm. |terminfo| does not have a flag for this extension. So Nvim simply assumes that (all) "dtterm", "xterm", "teraterm", "rxvt" terminal types, and Konsole, are capable of this. *tui-cursor-shape* Nvim will adjust the shape of the cursor from a block to a line when in insert mode (or as specified by the 'guicursor' option), on terminals that support it. It uses the same |terminfo| extensions that were pioneered by tmux for this: "Ss" and "Se". Similarly, if you set the cursor highlight group with blend=100, Nvim hides the cursor through the "cvvis" and "civis" extensions. If your terminfo definition is missing them, then Nvim will decide whether to add them to your terminfo definition, by looking at $TERM and other environment variables. For the "rxvt", "putty", "linux", "screen", "teraterm", and "iterm" terminal types, or when Konsole, a libvte-based terminal emulator, or genuine Xterm are detected, it will add constructed "Ss" and "Se" capabilities. *tui-cursor-tmux* Within tmux it may appear that Nvim is not changing the cursor, but in fact it is tmux receiving instructions from Nvim to change the cursor and not knowing what to do in turn. tmux must translate what it receives from Nvim into whatever control sequence is appropriate for the host terminal. It shares a common mechanism with Nvim, of using the "Ss" and "Se" capabilities from terminfo (for the output terminal) if they are present. Unlike Nvim, if they are not in terminfo you must add them by setting "terminal-overrides" in ~/.tmux.conf . See the tmux(1) manual page for the details of how and what to do in the tmux configuration file. It will look something like: >bash set -ga terminal-overrides '*:Ss=\E[%p1%d

Nvim enhances terminal color support by constructing 'setrgbf' and 'setrgbb' capabilities when the terminfo lacks the 'Tc' flag. It resorts to environment variables like $TERM for terminals like 'rxvt', 'linux', 'st', 'tmux', and 'iterm', or when Konsole, Xterm, or libvte are detected. Nvim resizes the terminal display on emulators like 'dtterm', 'xterm', 'teraterm', 'rxvt', and Konsole, assuming they support the dtterm extension. It also adjusts the cursor shape in insert mode using 'Ss' and 'Se' terminfo extensions, constructing them if missing, and addresses cursor visibility issues in tmux by advising users to configure 'terminal-overrides'.