Alt-h/j/k/l not working when TERM not xterm* or vt220

[ybc37]

Hey there,

first, thanks for the htop-dev initiative. Cool to see this project going :)

After upgrading to htop 3.0.0 I noticed that some of the added vim bindings do not work for me. I think at least all Alt- bindings. I finally got some time to look at it to be able to provide at least some information.

In my case TERM is set to tmux-256color or alacritty (if not in tmux). I realized it works when using xterm* and was able to pin it down to how the keys are defined in CRT.c

htop/CRT.c

Lines 687 to 706 in f704bae

	if (String_startsWith(CRT_termType, "xterm") || String_eq(CRT_termType, "vt220")) {
	define_key("\033[H", KEY_HOME);
	define_key("\033[F", KEY_END);
	define_key("\033[7~", KEY_HOME);
	define_key("\033[8~", KEY_END);
	define_key("\033OP", KEY_F(1));
	define_key("\033OQ", KEY_F(2));
	define_key("\033OR", KEY_F(3));
	define_key("\033OS", KEY_F(4));
	define_key("\033[11~", KEY_F(1));
	define_key("\033[12~", KEY_F(2));
	define_key("\033[13~", KEY_F(3));
	define_key("\033[14~", KEY_F(4));
	define_key("\033[17;2~", KEY_F(18));
	char sequence[3] = "\033a";
	for (char c = 'a'; c <= 'z'; c++) {
	sequence[1] = c;
	define_key(sequence, KEY_ALT('A' + (c - 'a')));
	}
	}

When skipping the condition it works for other TERM values as well (btw even on VTs; TERM=linux).

I'm not an expert, so not sure what's a valid approach to fix it. Adding every possible TERM that supports these keys most probably isn't ;) Is it somehow possible to check the "capabilities" of a terminal emulator instead of TERM? Or is it safe nowadays to drop this condition without breaking htop for other systems (the condition dates back even before the initial git import 15 years ago (d6231ba). Touched 3 years ago (45f3769) to support for everything that starts with xterm)?

[BenBE]

To make this fully portable the code would have to check the termcap library for the exact mappings.
Cf. https://www.gnu.org/software/termutils/manual/termcap-1.3/html_mono/termcap.html#SEC37
Unfortunately these definitions are regularly broken and thus unreliable …

[fasterit]

Just FTR, vim mode has been removed again in c9ecd0f. The way it was implemented caused too many issues elsewhere.

[ybc37]

I think there's a misunderstanding: AFAIU the bindings I'm talking about are just alternative bindings to the default ones. I didn't use a dedicated "vim mode". I'm using htop 3.0.2 and also tested with current master.

Sorry, I wasn't aware of the difference of the vim key bindings and the vim mode.