Are Sixel graphics supported on Windows?

[waf]

Hi, I'm using Windows 10 and Contour 0.2.0.173. Are sixel graphics supported on this platform?

To test, I'm using ImageMagick with a small png image:

> .\magick.exe myFile.png sixel:-

This produces a stream of output like so (this is just an excerpt):

Here's the relevant portion of my contour.yml (it's not modified from the default):

images:
    # Enable or disable sixel scrolling (SM/RM ?80 default)
    sixel_scrolling: true
    # Configures the maximum number of color registers available when rendering Sixel graphics.
    sixel_register_count: 4096
    # If enabled, the ANSI text cursor is placed at the position of the sixel graphics cursor after
    # image rendering, otherwise (if disabled) the cursor is placed underneath the image.
    sixel_cursor_conformance: true
    # maximum width in pixels of an image to be accepted
    max_width: 1280
    # maximum height in pixels of an image to be accepted
    max_height: 720

Contour is really impressive, by the way, thanks for building and working on it.

[data-man]

What version of ImageMagick?
For me, IM 7.1.0.7 crashed with sixel graphics (in Linux).
But IM from git works fine.
Can you try https://github.com/hpjansson/chafa or any other app?

[waf]

I think given @christianparpart's answer it's blocked on a ConPTY issue. But here's the answer to your questions in case it helps:

What version of ImageMagick?

ImageMagick 7.1.0-7 Q16-HDRI x64 2021-09-12

Can you try https://github.com/hpjansson/chafa or any other app?

I did try a few other apps, mainly libsixel and PySixel with the same result.

[christianparpart]

God damn it i would love to get sixel support available on windows. But we need ConPTY to either support that first too, or have DCS passthrough or full passthrough mode. (edit: this ask Chinese from ConPTY that's must provide this)

There may be a workaround maybe that i am thinking of. What shell are you using ? Or are you developing your own command line apps on windows that will need this?

Also, sorry for Windows platform for lagging slightly behind. @skyline75489 did great work here (thanks).

Are you also using any non-windows? (Just curious)

But the long term plan is to have one terminal that works equally nice on all platforms.

(Sent from my smartphone. I apologize for possible auto-correction mistakes ahead of time)

[waf]

Thanks, and no worries! I'm glad that it's not an issue with my system.

For my shell, I'm using PowerShell Core 7.2.0-preview.9, but I'd be happy to try some workarounds. I've also tried WSL2 (Ubuntu / ZSH), though I didn't really expect that to work given the added complexity of that setup. I do have native (i.e. not WSL2) Ubuntu and Mac OS available.

My use case is I'd like to add Sixel support to my own cross-platform application (http://github.com/waf/CSharpRepl). On Windows it won't be usable for the vast majority of users until Windows Terminal / ConPTY support is there, but it'd be nice to point people to Contour if they wanted to try the Sixel support.

[christianparpart]

FYI, the ConPTY-relevant ticket is microsoft/terminal#1173.

Ah nice, I think for the interim time you can continue developing your CSharpRepl on a non-Windows platform (let's say: Linux), e.g. using Contour and then start using Sixel there. Try playing around with img2sixel from the libsixel project, in order to display any arbitrary image in the terminal.

You can find out if Sixel support is available using the VT sequence DA1 (CSI c) that should respond with at least the parameter 4, indicating Sixel support.

How to construct the appropriate VT sequence send your own images to the terminal, see here: https://vt100.net/docs/vt3xx-gp/chapter14.html.

Sixel is sadly pixel dependant, so that means you also need to find out how many pixels a grid cell spans. You can do that usually either via ioctl (does not work on Windows though :D) or via CSI 16 t or CSI 14 t. In case you see something odd, it's always best to also check against xterm (which is used as more or less de-facto way of doing VT, from the developers point of view).

One last thing: The proposal I see to get Sixels into Contour on Windows before ConPTY converges here is to provide the client app (e.g. your app) with a side-channel, e.g. a Windows pipe that you can use to send out VT sequences, too, effectively bypassing ConPTY, and giving you the ability to access 100% of the VT features that contour does support. That pipe would require some negotiation up-front and that side-channel can only be used by supporting client applications as well (so not an unmodified powershell.exe or ImageMagick's magic.exe, but it at lesat would give you access to it.

I'm not having time to implement that right now (i'm already busy in another branch), but if ConPTY takes significant longer than already, then I might want to provide that facility.

[waf]

That's great, thanks for the detailed information. I'll start with Contour on Ubuntu, and whenever ConPTY enables the functionality, try it on Windows.

Agreed, the side-channel approach could work, but given the progress the ConPTY team is making, probably not worth prioritizing for now.

Thanks!

[data-man]

BTW chafa now will use sixels in Contour by default.

[WSLUser]

If you want Sixels on Windows currently, you'd need to use Mintty. I DO NOT RECOMMEND copying their behavior to bypass conhost and ConPTY. They are a fork from Putty which does offer a ton of VT support on Windows but there is far too much hackery going on for a long time. Best bet is to wait on microsoft/terminal#11264.

See microsoft/terminal#1173 (and request priority bump). If enough terminal authors are requesting the feature (and asking on progress) , they'll feel more motivated to finish getting that PR ready to go. Probably also a good idea to review that PR to ensure that it would do everything you need it to without any bugs once it's no longer in draft.

[WSLUser]

Also see https://github.com/csdvrx/sixel-tmux, which provides Sixel support for tmux but more importantly, provides a derasterize fallback option for a terminal that doesn't support Sixels by default such as Windows Terminal. Chafa may be the better alternative but it's yet another approach to making Sixel available to users on Windows (as well as many other terminals on Mac or Linux that don't support Sixel).