vttest

[ghost]

If you haven't run across vttest yet, just wanted to point it out. Feel free to close this issue if it is not a project priority.

If you do want to dig in, some notes:

1. Tests 1, 2, 3.8 (VT100 character sets), 6, and 8 need to be passed before you have full coverage of nearly all terminfo-based applications. For these you will need the rightmost margin VT100 line wrap behavior, and remember that cursor position commands reset that flag.
2. Double-width / double-height (test 4), and VT52 (test 7) can wait. No one uses them AFAIK.
3. VAX / VMS systems rely on the default "no argument" forms of the sequences, e.g. things like "ESC [12;h". EVERY sequence has a default argument that needs to be handled.
4. Scrolling regions need to be honored/ignored as per the VT100 specification.
5. Control characters must be handled separately from the rest of your parser.

There is one spot where a vttest-compliant terminal conflicts with modern convention: SGR 38/48 (RGB colors, T.416 / ISO 8613-3). If you chose to go with vttest compliance then it leads to ugly blinking sequences; modern users will prefer the RGB support instead.

[a-kenji]

Thank you very much, this is incredibly helpful!

[qballer]

We actually played around with vttest we have noticed also that a few terminal emulators don't pass them so we didn't pursue this, thought it can bring a lot of value

[SaintFenix]

#408 shows that the current builds have reached support for vttest 1

@imsnif has there been discussion for passing more of the tests? or has that been moved on from?

[imsnif]

Thanks for the poke @SaintFenix ! I've been meaning to reply to this issue and just forgot. :)

@klamonte, thank you for this issue - it has been incredibly helpful. I previously played a little bit with vttest but was discouraged seeing as every terminal emulator I tried did not pass it in one way or another (alacritty, urxvt and even xterm). After you opened this issue though, I decided it might be valuable to pick it up again.

So my goal now is to try to get Zellij to behave the same way alacritty does in vttest. I already got it to pass test 1 here: #408 and plan to continue iterating through this. It has already proven helpful by solving one or two compatibility issues that were open in this repository.

I hope it's okay if I ask you some questions here if some behaviours down the line are unclear to me. I found that gleaning the right behaviour for certain events has been quite challenging at times :)

[ghost]

@imsnif No problem, would love to help! I don't check github extremely frequently but will aim to keep poking my head in more often.

xterm is generally expected to the be "always passing", but for things like reverse-on-bold-on-blink it behaves differently that DOS would have, so for my terminals I have gone with the DOS behavior, I just like it more. :) (BTW I really like where this project is going, and added a link to it.)

If you're looking for a good Windows-based terminal to compare to, mintty is great. Some others I test occasionally are here.

[imsnif]

Zellij has cleared VTTest (at least as far as xterm itself does) a while ago, so closing this issue. Thanks for all the help!