support for OSC 4

[cgsdev0]

hi!

i've been messing around with OSC 4 sequences lately to change the terminal's color palette on the fly. i noticed asciinema doesn't support it

it's kinda difficult to find good documentation for these sequences, but the best i've seen so far is https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h3-Operating-System-Commands

i created a short demo:

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[0.107432, "o", "\u001b]2;applesauce\u001b\\"]
[0.140703, "o", "\u001b[0m\u001b[27m\u001b[24m\u001b[J\u001b[38;5;242msarah\u001b[39m\u001b[38;5;242m@applesauce\u001b[39m \u001b[34m~\u001b[39m\r\n\r\u001b[35m❯\u001b[39m \u001b[K"]
[0.140784, "o", "\u001b[?1h\u001b="]
[0.141187, "o", "\u001b[?2004h"]
[0.92006, "o", "\u001b[32mc\u001b[39m"]
[0.924449, "o", "\b\u001b[32mc\u001b[39m\u001b[90mlear\u001b[39m\b\b\b\b"]
[1.010068, "o", "\b\u001b[1m\u001b[31mc\u001b[1m\u001b[31mu\u001b[0m\u001b[39m\u001b[39m \u001b[39m \u001b[39m \b\b\b"]
[1.013263, "o", "\u001b[90mrl -LN party.hotdogstand.lol\u001b[39m\u001b[28D"]
[1.13193, "o", "\b\b\u001b[1m\u001b[31mc\u001b[1m\u001b[31mu\u001b[1m\u001b[31mr\u001b[0m\u001b[39m"]
[1.243904, "o", "\b\b\b\u001b[0m\u001b[32mc\u001b[0m\u001b[32mu\u001b[0m\u001b[32mr\u001b[32ml\u001b[39m"]
[1.589589, "o", "\u001b[39m \u001b[39m-\u001b[39mL\u001b[39mN\u001b[39m \u001b[39mp\u001b[39ma\u001b[39mr\u001b[39mt\u001b[39my\u001b[39m.\u001b[39mh\u001b[39mo\u001b[39mt\u001b[39md\u001b[39mo\u001b[39mg\u001b[39ms\u001b[39mt\u001b[39ma\u001b[39mn\u001b[39md\u001b[39m.\u001b[39ml\u001b[39mo\u001b[39ml"]
[1.984949, "o", "\u001b[?1l\u001b>"]
[1.990999, "o", "\u001b[?2004l"]
[1.991892, "o", "\r\r\n"]
[2.050787, "o", "\u001b]4;0;#ff0000\u001b\\\u001b]4;1;#ffff00\u001b\\\u001b]4;2;#ffff00\u001b\\\u001b]4;3;#ffff00\u001b\\\u001b]4;4;#ffff00\u001b\\\u001b]4;5;#ffff00\u001b\\\u001b]4;6;#ffff00\u001b\\\u001b]4;7;#ffff00\u001b\\\u001b]4;8;#ffff00\u001b\\\u001b]4;9;#ffff00\u001b\\\u001b]4;10;#ffff00\u001b\\\u001b]4;11;#ffff00\u001b\\\u001b]4;12;#ffff00\u001b\\\u001b]4;13;#ffff00\u001b\\\u001b]4;14;#ffff00\u001b\\\u001b]4;15;#ffff00\u001b\\\u001b]10;#ffff00\u001b\\\u001b]11;#ff0000\u001b\\\u001b]12;#ffff00\u001b\\\u001b]13;#ffff00\u001b\\\u001b]17;#ffff00\u001b\\\u001b]19;#ff0000\u001b\\\u001b]4;232;#ff0000\u001b\\\u001b]4;256;#ffff00\u001b\\\u001b]708;#ff0000\u001b\\"]
[3.051149, "o", "\u001b]4;0;#ffff00\u001b\\\u001b]4;1;#ff0000\u001b\\\u001b]4;2;#ff0000\u001b\\\u001b]4;3;#ff0000\u001b\\\u001b]4;4;#ff0000\u001b\\\u001b]4;5;#ff0000\u001b\\\u001b]4;6;#ff0000\u001b\\\u001b]4;7;#ff0000\u001b\\\u001b]4;8;#ff0000\u001b\\\u001b]4;9;#ff0000\u001b\\\u001b]4;10;#ff0000\u001b\\\u001b]4;11;#ff0000\u001b\\\u001b]4;12;#ff0000\u001b\\\u001b]4;13;#ff0000\u001b\\\u001b]4;14;#ff0000\u001b\\\u001b]4;15;#ff0000\u001b\\\u001b]10;#ff0000\u001b\\\u001b]11;#ffff00\u001b\\\u001b]12;#ff0000\u001b\\\u001b]13;#ff0000\u001b\\\u001b]17;#ff0000\u001b\\\u001b]19;#ffff00\u001b\\\u001b]4;232;#ffff00\u001b\\\u001b]4;256;#ff0000\u001b\\\u001b]708;#ffff00\u001b\\"]
[4.05504, "o", "\u001b]4;0;#ff0000\u001b\\\u001b]4;1;#ffff00\u001b\\\u001b]4;2;#ffff00\u001b\\\u001b]4;3;#ffff00\u001b\\\u001b]4;4;#ffff00\u001b\\\u001b]4;5;#ffff00\u001b\\\u001b]4;6;#ffff00\u001b\\\u001b]4;7;#ffff00\u001b\\\u001b]4;8;#ffff00\u001b\\\u001b]4;9;#ffff00\u001b\\\u001b]4;10;#ffff00\u001b\\\u001b]4;11;#ffff00\u001b\\\u001b]4;12;#ffff00\u001b\\\u001b]4;13;#ffff00\u001b\\\u001b]4;14;#ffff00\u001b\\\u001b]4;15;#ffff00\u001b\\\u001b]10;#ffff00\u001b\\\u001b]11;#ff0000\u001b\\\u001b]12;#ffff00\u001b\\\u001b]13;#ffff00\u001b\\\u001b]17;#ffff00\u001b\\\u001b]19;#ff0000\u001b\\\u001b]4;232;#ff0000\u001b\\\u001b]4;256;#ffff00\u001b\\\u001b]708;#ff0000\u001b\\"]
[5.052719, "o", "\u001b]4;0;#ffff00\u001b\\\u001b]4;1;#ff0000\u001b\\\u001b]4;2;#ff0000\u001b\\\u001b]4;3;#ff0000\u001b\\\u001b]4;4;#ff0000\u001b\\\u001b]4;5;#ff0000\u001b\\\u001b]4;6;#ff0000\u001b\\\u001b]4;7;#ff0000\u001b\\\u001b]4;8;#ff0000\u001b\\\u001b]4;9;#ff0000\u001b\\\u001b]4;10;#ff0000\u001b\\\u001b]4;11;#ff0000\u001b\\\u001b]4;12;#ff0000\u001b\\\u001b]4;13;#ff0000\u001b\\\u001b]4;14;#ff0000\u001b\\\u001b]4;15;#ff0000\u001b\\\u001b]10;#ff0000\u001b\\\u001b]11;#ffff00\u001b\\\u001b]12;#ff0000\u001b\\\u001b]13;#ff0000\u001b\\\u001b]17;#ff0000\u001b\\\u001b]19;#ffff00\u001b\\\u001b]4;232;#ffff00\u001b\\\u001b]4;256;#ff0000\u001b\\\u001b]708;#ffff00\u001b\\"]
[6.053719, "o", "\u001b]4;0;#ff0000\u001b\\\u001b]4;1;#ffff00\u001b\\\u001b]4;2;#ffff00\u001b\\\u001b]4;3;#ffff00\u001b\\\u001b]4;4;#ffff00\u001b\\\u001b]4;5;#ffff00\u001b\\\u001b]4;6;#ffff00\u001b\\\u001b]4;7;#ffff00\u001b\\\u001b]4;8;#ffff00\u001b\\\u001b]4;9;#ffff00\u001b\\\u001b]4;10;#ffff00\u001b\\\u001b]4;11;#ffff00\u001b\\\u001b]4;12;#ffff00\u001b\\\u001b]4;13;#ffff00\u001b\\\u001b]4;14;#ffff00\u001b\\\u001b]4;15;#ffff00\u001b\\\u001b]10;#ffff00\u001b\\\u001b]11;#ff0000\u001b\\\u001b]12;#ffff00\u001b\\\u001b]13;#ffff00\u001b\\\u001b]17;#ffff00\u001b\\\u001b]19;#ff0000\u001b\\\u001b]4;232;#ff0000\u001b\\\u001b]4;256;#ffff00\u001b\\\u001b]708;#ff0000\u001b\\"]
[6.286387, "o", "^C"]
[6.289531, "o", "\r\n"]
[6.322799, "o", "\u001b[0m\u001b[27m\u001b[24m\u001b[J\u001b[38;5;242msarah\u001b[39m\u001b[38;5;242m@applesauce\u001b[39m \u001b[34m~\u001b[39m\r\n\r\u001b[31m❯\u001b[39m \u001b[K"]
[6.322841, "o", "\u001b[?1h\u001b="]
[6.323225, "o", "\u001b[?2004h"]
[6.638575, "o", "\u001b[?2004l\r\r\n"]

the expected behavior is this (i rendered this gif from the demo using gifcast, which uses xterm.js for rendering)

Spoiler because it's quite obnoxious lol

since this is likely a very low priority feature (understandably), i did some digging on my own to see if i could make it work. i was able to hack together some code to parse the sequences, but i got stumped when it came to actually updating the colors in the palette. i messed around with updating the pen's colors, but i couldn't find a way to refresh the entire screen.

i mostly just wanted to document my exploration here. if you can nudge me in the right direction, i might be able to put up a pull request in the future. cheers!

[ku1ik]

Hi,

Indeed OSC 4 is not supported at the moment. To make it work, it would take at least to implement the following:

• recognizing OSC 4 in avt,
• exposing it to the player from avt::Vt
• adding support for dynamic themes in the player (the way the player defines colors today, via CSS custom props, should make it relatively straightforward)
• ensuring that a theme is reset to the initial one when rewinding (seeking back) in the player

This is doable, however non-trivial, and at the moment it doesn't seem like worth the trouble (given other priorities).