Sixel isn't clearing on Gifs

[raphamorim]

chafa Desktop/peppo.gif -f sixel

It was supposed to clear and maintain gif on top.

[AutumnMeowMeow]

(Just heard about Rio today. Awesome! :) )

I see similar issues testing Rio with jexer, for both sixel and iTerm2 images. Example videos below.

Sixel images below. Also, it appears that transparent pixels in sixel images are replacing/erasing opaque pixels "under" them, rather than being blitted over, which is why the screen goes wonky when the color wheel is dragged into the bottom row. (See here for how the code uses DECSDM for drawing sixel into the bottom row.)

simplescreenrecorder-2025-04-02_23.31.07.mp4

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iTerm2 images below. Looks like the iTerm2 images are not rendering to the bottom row?

simplescreenrecorder-2025-04-02_23.32.54.mp4

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Contrast with same outputs under wezterm. Sixel:

simplescreenrecorder-2025-04-02_23.37.25.mp4

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iTerm2:

simplescreenrecorder-2025-04-02_23.38.08.mp4

[raphamorim]

Very interesting, and very cool project btw

This is rio as well right?

[j4james]

As far I understand it, Rio inherited its Sixel code from Alacritty, so at least some of these bugs are also Alacritty bugs. I'm fairly sure Alacritty used to support transparency, but that broke at some point. The background select parameter does still have some effect, so I think it's still being parsed, but it doesn't seem to preserve the text below it anymore.

As for the issue with images not being cleared, I suspect that might be a z-order problem. The way Sixel is implemented in Alacritty/Rio, an image typically won't erase another image below it - they're just stacked. But if they're rendered in the wrong order, you don't see the "top" image, which gives the impression that the "bottom" image isn't erased. But I'm not seeing this z-order problem on Alacritty - only on Rio - so it might just be a bug fix that Rio hasn't merged. I'm almost sure Alacritty used to have a similar bug that was fixed at some point.

[AutumnMeowMeow]

Very interesting, and very cool project btw

Thanks!

This is rio as well right?

Yes, that is also Rio.

[j4james]

To see a simple example of the z-order issue I mentioned above, you can do something like this:

clear; tput cup 10 10; img2sixel -h 200 snake.png; tput cup 5 20; img2sixel -h 200 snake.png; tput cup 1 1

The second snake ends up below the first snake, when it should be above.

This may be a different issue altogether, but it seems at least a plausible explanation for the glitches seen in jexer.

Btw, this is on version 0.2.10 in case that makes any difference.

[raphamorim]

@j4james thank you for the script! sorry late reply, Finally addressing sixel issues and starting kitty keyboard protocol

[raphamorim]

@j4james side note I plan to work on soft fonts for rio, I have been following some work you have done about it. Started something (incorrectly yet) #1091