Hacker News Reader

Comment by nomel | Hacker News Reader

The newest Apple Pencil is apparently around 9ms [1]. It really does fool your brain into thinking something is coming out of the tip.

[1] https://www.macworld.com/article/3402336/apple-pencil-change...

View on HN

If only they cared about such things for Terminal.app, so we didn't have the extra step of installing Alacritty on every single machine to improve the situation (and not to anywhere near 9ms, even).

I've always found this a bit funny - why are people so concerned with input latency at the terminal? (I get why I care with a phone, or gaming). It's not like anyone's typing hundreds of characters a second. I use Alacritty, but mostly because I like the way it's config file works and it does nice font rendering. The latency thing barely even registers.

The same reason people are concerned with input latency when scrolling on a touchscreen. Lag is annoying, and the less you have, the more satisfying it is to use the device. Latency is detectible on even a single character, "hundreds of characters per second" has nothing to do with it.

It's the same reason I'm not a big fan of mushy keyboards, or having to ssh between continents.

Sure, maybe I need to add "within reason". I agree I want my keystroke to appear reasonably quickly, let's say under 200ms to fit some of the stuff in the post.

Alacritty used to make kind of a big deal of these "benchmarks" on it's main page, and they don't any longer because the software improvements in the terminal are likely completely overwhelmed by whatever keyboard/monitor/OS you happen to be using.

That's the point. If you really care about this stuff, the terminal isn't exactly the place to go improve stuff unless it was way worse than it should've been in the first place.

Also note that alacritty's benchmark are throughput oriented, not latency oriented. The benchmarks measure how fast it can tear through data, not how quickly pixels change on screen.

But, rendering the entire terminal buffer is slightly overkill when only a few pixels changed, and the time it takes can end up significant on weaker devices driving high resolution displays.

As a result, Alacritty doesn't have the best "time to light" performance, and there have been long debates in the issues about it.

200ms is a lot of lag. When trying to hjkl in to a specific character on the screen (yes, I know I should be using the 'f' verb more) that can add up quick.

200ms is really, really slow. You almost certainly type familiar words faster than at 5cps. You'd notice and feel it, even if you don't. The thresholds are obviously different for what one typically perceives as slow or insufficiently responsive but at 200ms, almost everything stops feeling responsive.

The exact number really isn't the point. The point is if the terminal emulator is 1% of that 200ms (or 100, or whatever), then who gives a shit. You should be buying a better monitor first.

I don't think the terminal emulator matters that much below some number, it's just that you picked a really high number and that the perception of slowness is neither linear nor the same across types of activities. I think this is generally a little bit of a weakness in the article itself.

Some of us love CLI programs or using ncurses. Rougelike video games which can be played in a terminal (nethack) would profit heavily from a fast terminal

At least for me, the terminal is the only place where latency is tolerable on underpowered, crappy machines. This is because my keyboard input stream will always trigger behavior deterministically in the terminal.

Isn't Terminal.app famously pretty speedy compared with most other terminal emulators? In fact, there's a link from this article to another of Dan's posts that's precisely about terminal performance - https://danluu.com/term-latency/

It's a few years old now so I've no doubt that Alacritty's performance has improved, but I'm suspicious of the idea that Terminal.app is noticeably slow.

I've always loved the low latency of Terminal.app (particularly over iTerm2, which I find unusable), but recently noticed that it has gotten a little worse in Big Sur now that the "Antialias Text" option is broken on non-retina displays.

I assume the extra forced compositing/rendering/whatever being imposed by antialiasing is to blame, though I could be wrong.

Catalina: https://i.imgur.com/G66HpJ6.png

Big Sur: https://i.imgur.com/R5dlzdj.png

rdar://FB8901170 if any apple employees happen to see this :)

Huh? Terminal.app is one of the fastest ones. iTerm2 is much slower in comparison.

URxvt on a 144hz gaming monitor is excellent.

URxvt is fast, but still has a mean input latency of 18.3 ms. Try Xterm it only adds 1.7 ms to the stack. I find the difference very noticeable. I switched from URxvt to Xterm a few years back, although I had to give up on proper UTF-8 glyph rendering.

Low latency is important for me, because I use Vim inside Tmux inside Xterm inside Xorg and latencies add up.

https://lwn.net/Articles/751763/

Reply on news.ycombinator.com