I just wanted to say that this looks like a fantastic and very cool project! Congratulations on the speed.
Personally, the lack of scrollback and tabs is a dealbreaker for me. I know that I'm supposed to use tmux for that, but I can never remember how tmux scrollback and tab switching work without thinking about them. Plus I rely heavily on mouse selection of multi-screen text in the scrollback buffer. So I'm unlikely to be part of your target audience. (However, I could live without GUI config and menus, because I configure my terminals once every few years at most.)
Also, a silly question: Do you support color emoji in the Terminal? I've never quite managed to get it working on Linux.
I like opinionated software. If scrollback is better implemented on a different layer, leaving it out is reasonable.
But I'm not using tmux because I use i3 as wm which does all the tiling/splitting. Now using a new tmux instance for each of my terminal (can be dozens) only for scrollback seems not the right way though. Any recommendations what would be The Right Way here? Anything that only implements scrollback maybe?
Just to present an alternate opinion here: I haven't used my terminal's scrollback on purpose in 5+ years now, and it's fine. To me, Alacritty's trade off is perfectly acceptable, and even desirable.
As far as I can tell, using Tmux's scrollback instead has no downsides of note, but some _very_ significant upsides. For example, (1) shared buffer between terminal windows, and (2) copy/paste modes that are usable with Vim shortcuts.
Hm. So, for that to work, I'd basically have to forever hardcode the terminal to launch tmux every single time. Basically, this new terminal + tmux = the old terminal behavior.
I'm not saying this is necessarily a bad thing (haven't tried it), I'm just saying this is the way to get my scrollback... uh... back.
Might as well ship the terminal with tmux as a hard dependency and launch a tmux child process by default.
> Hm. So, for that to work, I'd basically have to forever hardcode the terminal to launch tmux every single time.
Yeah, but it's not as bad as it sounds once you "move down a layer" and treat Tmux like your terminal manager rather than your terminal. When I need to a new shell, I don't open a new terminal window; instead I open a new Tmux "window" (the spiritual equivalent to a tab) and do the work there. I keep the same two terminal windows open with nested Tmux sessions for months at a time. By extension, opening new Tmux sessions is also an extremely rare event because the ones I already have are persistent.
> Might as well ship the terminal with tmux as a hard dependency and launch a tmux child process by default.
I think it's still nice to leave some room for customization here. Screen is still a pretty good Tmux alternative for example (in fact, five years ago you would have said that Tmux was a screen alternative rather than vice versa), and some people might prefer to use that instead.
You can also set tmux as your default shell with chsh. I've been doing this for a while on macOS and have enjoyed it (other than user namespace issues that still drive me crazy)
I may be reconsidering this position[0]. If scrolling support can be added in a non-intrusive way behind a feature flag (so it could be completely compiled out), it could potentially have a place in Alacritty.
Sounds great! I totally understand the motivations behind the decision to leave it out, but it's a great candidate for a compile time flag. I would love to throw out gnome-terminal for this!
the use case seems to be using tmux inside the terminal emulator, with tmux you'd use its own scrollback buffer
(edit) from the project's github page in fact
The simplicity goal means that it doesn't have many features like tabs or scroll back as in other terminals. Instead, it is expected that users of Alacritty make use of a terminal multiplexer such as tmux.
The problem with this is using tmux screws with using mouse for selection (since tmux takes over the mouse and does its own selection thing, which usually doesn't do what I want).
This approach also means you can't do anything interesting like what Terminal.app does with detecting prompts, marking them, and letting you jump back to them (or clear history back to them).
This approach could be excused if the terminal actually natively integrated with tmux, thus providing its own gui splits/tabs that represent tmux's panes/windows, but it doesn't sound like it does that.
I just disable tmux's mouse usage by putting "bind m set -g mouse off" into my tmux.conf: tmux is useful enough just with key shortcuts, and I generally dislike terminal programs that use the mouse anyways.
Also, some terminal emulators (iTerm2 on Mac) let you disable mouse grabbing by holding a special key while clicking, maybe Alacritty could implement something like this?
It does, but it's not completely reliable for me. Also, you have to configure it to make it actually work.
For example, here's my mouse-related tmux config:
set -g mouse on
# enter copy-mode by scrolling, but don't select the pane
# The usage of #{mouse_any_flag} just forwards mouse events when in a fullscreen app that wants them
bind -n WheelUpPane if -F -t = "#{mouse_any_flag}" "send-keys -M -t =" "if -F -t = '#{alternate_on}' 'send-keys -t = Up' \"if -F -t = '#{pane_in_mode}' '' 'copy-mode -e -t ='; send-keys -M -t =\""
bind -n WheelDownPane if -F -t = "#{alternate_on}" "send-keys -t = Down" "send-keys -M -t ="
# Start copy-mode with PageUp
# For PageDown, if we're not in copy-mode, discard it
bind -n PageUp if -F "#{alternate_on}" "send-keys PageUp" "copy-mode -eu"
bind -n PageDown if -F "#{alternate_on}" "send-keys PageDown" "if -F '#{pane_in_mode}' 'send-keys PageDown'"
tmux handles mouse events very well. Scrolling, pane resizing (in tmux and vim), selection work once you add one line in config. For me it works so perfectly that it successfully goes in nested tmux sessions over ssh.
However, some people complain about mouse issues. I would suspect that some terminal emulators are trying way too hard to properly handle mouse events.
Hey, nice project :) I do have a question: you mentioned that urxvt is difficult to configure (because of .Xresources format?), but then you also say that "GUI-based configuration is unnecessary", so how exactly is Alacritty easier than urxvt?
One feature that I really miss in rxvt is an easy/fast way to change the color scheme, or at least reverse colors (like with xterm, which if correctly configured it's just ~3 times slower than urxvt). This is something really important when your screen receives direct sunlight.
Specifically this. Without being above-average proficiency with X, the format and available options are likely to be difficult to figure out.
> "GUI-based configuration is unnecessary", so how exactly is Alacritty easier than urxvt
The config file is well documented and in a human-friendly format. Most flags will also take effect immediately without restarting the program.
> One feature that I really miss in rxvt is an easy/fast way to change the color scheme, or at least reverse colors (like with xterm, which if correctly configured it's just ~3 times slower than urxvt). This is something really important when your screen receives direct sunlight.
You could have two `colors` sections in the config file and just uncomment one or the other. Not quite as convenient I suppose. One thing I'm considering as a key-binding option is to exec a command. This could be anything like `sh swap_config.sh` and then you could bind it to whatever you like.
You don't need to implement this in the terminal. You can bind macros to keys in anything that uses readline. Search for "inputrc" and the READLINE section in bash(1). While this is usually used for binding builtin functions (i.e. editing, history), you can simply provide the literal expansion.
# in ~/.inputrc
$if Bash
# <f12> - find this with "<Control-v>{KEY}"
"\e[24~": "sh \"${HOME}\"/path/to/swap_config.sh
"
# (the newline is included, which is
# usually bound to accept-line)
$endif
The string indicating the key to binding to (left of the ":") can change depending on the environment (terminal, os, etc), so use <Control-v> to investigate what is actually being sent by the terminal into readline.
Cool project, but I have literally never thought a terminal was excessively low-performing enough to prevent work from getting done. What applications benefit from a terminal that's even an order of magnitude faster than the alternative?
Have you even had Control-C take forever to kill that `cat` you accidentally ran against a 1GB log file? I have. Most terminal emulators are 'dumb' and try to render the whole backbuffer sequentially even if what you are seeing is no longer the tail of the output stream.
It's not so much that this is 'fast' (because even gnome-terminal which is not what I'd call crazy fast is 'fast enough' most days), but that it's much more responsive as a result. By locking the terminal refresh to your screen refresh rate and only rendering 'current' data this removes a lot of headaches you can run into with other terminal emulators (like the aforementioned cat of a 1GB text file).
I've done that (we all did), but "can't reproduce". So this seems to depend a lot on the emulator, eg. I'm using Konsole, which is superb, and don't see that problem there.
Konsole is the only emulator I've used (other than actual tty) that doesn't have this problem. It's actually been frustrating, becasue there is plenty about it that I don't like.
I'll be giving Alacritty a try shortly - if it does what it says on the tin, it's exactly what I've been looking for.
Thanks, though I've been on linux for the last couple of years.
On the mac side I had other performance issues with Terminal.app (particularly when using all of widescreen + tmux - lots of flicker during move/refresh operations). iTerm2 did well for me though, iirc.
The only real issue I run into is clipboard wonkiness when console apps integrate the clipboard (nvim+twmux).
Beyond that, it has a ton of features - none of which I use since I manage my sessions with tmux. So I guess it's mostly a matter of not wanting a sledgehammer when the right tool is a finishing hammer?
I use nvim inside Konsole/Yakuake and I don't have any issue with the clipboard.
"+p and "+y works fine
Also Shift+Inst and Shift+Supr keeps working fine.
Terminal performance is fine at smaller sizes and with less going on.
In a multi-pane tmux window with vim, performance issues start to become noticeable. Many people I've talked to have experienced a situation where a bunch of output is being written to the screen, they panic to hit C-c, and then all you can do is wait for it to finish. This just isn't an issue with Alacritty.
Alacritty is about having tools that don't get in your way and don't distract you from what you're trying to accomplish.
With the C-c issue specifically, I don't think that emulator throughput is the most likely culprit.
It could be that the emulator is not handling inputs fairly: maybe it tries to process all available input from the pseudoterminal before processing the next batch of keyboard input. Or it could be that the pseudoterminal (kernel driver) is not configured to send the signal as expected. Or it could be that the process you're trying to interrupt is not responsive to the signal.
I maintain a terminal emulator that is not optimized at all and I just tested interrupting a process that was dumping one gigabyte of text to the screen. The interrupt was handled instantaneously.
It isn't the most likely culprit. The mosh people point out that the place where people hit this is with a SSH session to another machine. Where the data are actually building up is the SSH connection. It's not a problem with the terminal emulators at all.
It's more of a user comfort / perception thing. Using a slow terminal is basically like playing a game with really inconsistent frame rates. It's a distraction and can cause you to make mistakes from mistimed inputs. In both cases what you're really looking for is consistency more than raw speed.
On Windows "std::cout" can take upwards of 3ms. I noticed this when writing high speed camera software that was supposed to hit my callback every 2ms. Instead it was limited by my print statement!
Windows console is very slow (and terrible in many other ways). I think it is beyond salvageable. The only workarounds is probably write into a disk file or a pipe.
However, keeps being slower that any tty on any *nix. Sometimes fish autocomplete hangs for a few seconds when on the same machine running ubuntu fish autocomplete always is instantaneous. I don't know if it's related to something about the tty emulator or something weird on cygwin.
3ms sounds pretty dire, if you weren't writing very much. Out of curiosity, was this with or without `std::ios::sync_with_stdio(false);` ?
I've found syncing makes a huge difference to IO perf in Windows, e.g. `_getc_nolock` is much faster than `getc`. (Assuming of course that you can get away with it.)
These have little effect, also omitting std::endl has little effect. The effect is somewhat mitigated by buffering, so that if the time between subsequent st::couts is large, you won't see the runtime overhead.
Terminal speed is the primary reason I (and some others) use 'terminology', which is a relatively quick terminal emulator out of the enlightenment project.
However, a terminal emulator + X11 and so on can eat a bit of a CPU with noisy processes, eg. the output of mpv eats maybe 5-10 %, because it updates every(?) frame, so maximum work for the whole display stack. Getting the terminal emulator out of sight can get a bit more battery life in these cases.
(Somewhat related: If you have infinite scrollback it turns out that /tmp is actually very finite and can be filled by the wrong command with a couple dozen MB/s.)
Sounds like an option to slow down output rendering to e.g. one 1 frame/s might be an interesting feature for a terminal emulator. Still enough to keep an eye on a long-running process, but less overhead?
Glyphs are rasterized once and stored in a texture atlas. When rendering a glyph, the fragment shader pulls from that texture. Once loaded, the glyph stays loaded for the duration of the program.
Got it, just a heads-ups that texture atlas tends to hammer your GPU texture upload if you want to support UTF or non-latin(esp glyph-based) character sets.
Not trying to be discouraging just something to keep in mind if that's a direction you want to go. Pretty excited to see a GPU + Rust based stuff making it out into the wild.
Sure, but you're either going to have to generate the whole font up-front(can be many thousand characters) or you need to re-upload as you use/generate new characters which can thrash unless you're very careful about the regions you lock(and you have a driver that behaves appropriately).
Most font renderers I know do a tiered LRU cache of 3-4 texture "pages" which hurts your drawcall batching but tends to be a nice tradeoff in texture usage.
Okay so I dug into this. There is a font cache on the GPU and another in CPU ram. I believe it will fall into the drawcall batching issue you are concerned about... but terminals don't need to get >60FPS in most cases.
You really have nothing better to render on your GPU and store in that video memory than your terminal? I also use a web browser, and feel like it could use a performance boost a lot more than my terminal (particularly as I don't actually believe that using textures in this way is actually the most efficient way to render fonts with OpenGL).
There's Distance Fields[1] and Loop-Blinn[2] aside from standard textures that I'm aware of.
Valve uses the first, very few people use the second because of patent issues. They're more computationally expensive in some cases so there's always tradeoffs to be made depending on your hardware.
Just another vote for scroll back - would not use without. I do use tmux occasionally but it is just too awkward beyond keeping stuff running in SSH. I also have a tiling window manager and since I use mouse a lot in browser and other GUI apps it's too much of a pain to switch to keyboard only navigation for the terminal.
I want to encourage you to keep your product vision. It makes totally sense.
I am a heavy tmux + vim user, developing on a remote server. So, I have all my dev sessions always running and can access them on any client. I never needed scrollback or tabs in my terminal. tmux has it all. Excellent window and pane management + scrollback included.
And even on a remote connection I feel speed differences between terminal emulators as I wrote in another post. So, there is a strong need for such a product and great that somebody is innovating a console app in a time of locked-down fancy touch devices.
Well done and keep on going. Don't be intimidated by different requirements. Your product strategy is right (at least for me).
I put this comment elsewhere in the thread, but maybe if I put it in this subthread you'll get to see it.
I tested on my laptop (a ThinkPad X250) and alacritty is slower than xterm. xterm can display find / at 80x24 in 11 seconds, but alacritty takes 17 seconds or more, depending on how large the window is (smaller seems to be slower) and whether it's on-screen or not (off-screen seems to be slower).
There's a small subset of systems experiencing this. Do you happen to have a Radeon video card? In the profile I looked at, glClear was calling down into (through libxcb) __poll_nocancel which was eating 99% of the CPU time. I'm not sure if there's an issue open for this yet, but it's something we're looking into. One of my testers during development ran into this so we're aware of the problem.
> My current Bash prompt contains a unicode character. I guess this is unsupported?
Multibyte characters are 100% supported, but only if they are available in the chosen font. The fallback fonts feature will resolve this issue for you.
> Possible bug: on macOS when I minimize Alacritty, and I put it on focus again, it tries to select text. Strangely, not always.
Definitely a bug, and it's one that I knowingly shipped with (usually I just resize my terminal once and then it's static). The events triggering selection seem to work slightly different on macOS than Linux. The issue should be easy to resolve, but this comes down to making time.
> Multibyte characters are 100% supported, but only if they are available in the chosen font. The fallback fonts feature will resolve this issue for you.
How do I enable this feature?
The characters and ⑂ don't work in Menlo.
and do work in Cousine for Powerline font.
In Terminal.App and iTerm2 this works in both fonts. Do those applications also have a fallback fonts feature?
For some reason I can't run Emacs in terminal/unwindowed mode in Alacritty. Every "regular" character I type (ie to enter text into a buffer), Emacs says it's "unrecognized".
Control sequences work - ie I can exit with C-x C-e.
Works fine in regular Mac OS X terminal.
Any suggestions appreciated. Looks like an awesome project!
Nevermind -- Turns out I was just trying to type some characters in Emacs' welcome screen, which doesn't allow that in any terminal. I was so focused on kicking the tires of Alacritty I wasn't paying attention.
Nope. The idea is that perf should be good enough that it's not necessary.
withoutboats and I are hopefully going to collaborate and add notty protocol support to Alacritty. This should make text splits as performant as GUI splits.
I (withoutboats) agree. The real problem in terminals is that this goes both ways - if you let tmux or just vim/emacs split the window, you get no GUI integration - but you use the GUI to split the terminal window, you now have two disconnected shell sections, so none of the CLI integration works.
The notty screen splitting protocol should support a "GUI" interface shared by a single process, solving this problem.
cool project, but my question is why? rxvt is plenty fast for general purposes. if your bottleneck is the terminal emulator then you're doing something wrong. can you really read at ~10mbps?
No, of course you can't read all of the text at 10Mbps. The problem is that when you start some task which has a lot of spew, just having all of that text scrolling past can slow everything down to the point where the task actually takes longer! Even a few percentage points of slowdown can add up to minutes just sitting there twiddling your thumb.
Just a few weeks ago I accidentally ran a command on a remote machine that generated so much spew in the few seconds it ran before I hit control-c that it took 5 minutes to scroll through before I could do anything else.
But yes, you probably want to avoid that much text spew even if your terminal is super fast.
You think that your bottleneck is the terminal emulator, but you are wrong. As the mosh people pointed out a few years ago, the output from the remote machine has to scroll for 5 minutes because it is all backed up in the SSH connection between your machine and the remote one. Your bottleneck isn't in the terminal emulator at all, and changing terminal emulators to whizzy new ones will not make any difference to it.
This initial release should be considered to be pre-alpha
software--it will have issues. Once Alacritty reaches an
alpha level of readiness, precompiled binaries will be
provided for supported operating systems.
Might be a bit early, but will the Windows support be good for Bash on Ubuntu on Windows? Right now I use xming and run xterm inside it, but that is not a perfect solution, especially for things like vim. It works for now, but I am definitely looking for a good alternative.
Generally continuously, but it depends on how you scroll. If you're in `less` for example and holding the down key, you will probably see one line at a time, and it should be very smooth. It's possible with high key repeat rates that you might get multiple lines on some frames.
