Comment by kps

4 days ago

That could be done with a few influential terminal emulators adopting a consensus extension to ISO8613-6, like this: ESC[38:99:‹purpose›m for foreground, ESC[48:99:‹purpose›m for background.

e.g.

    Foreground     Background    Purpose
    -----------    -----------   -------
    ESC[38:99:0m    ESC[48:99:0m   normal ( same as ESC[39m and ESC[49m )
    ESC[38:99:1m    ESC[48:99:1m   emphasise
    ESC[38:99:2m    ESC[48:99:2m   de-emphasise
    ESC[38:99:3m    ESC[48:99:3m   error
    ESC[38:99:4m    ESC[48:99:4m   warning
    ESC[38:99:5m    ESC[48:99:5m   caution
    ESC[38:99:6m    ESC[48:99:6m   notice

Then people (themes) could easily choose foreground colour or background highlighting for particular roles. Some terminal emulators might also choose to configure other stylistic choices like bold, italic, etc.

(I believe ISO8613-6 defines sub-modes 0 through 5 (te;db), with 2 (rgb) and 5 (256-color indexed) being most widely implemented. But some terminals historically mess up : and ; in CSI sequences, and I know at least one would interpret ESC[38:6:1m as ESC[6;1m (blinking bold!), so here I pick 99 (ECMA-48 defines modes up to 65).)

6 comments

kps

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hnlmorg  4 days ago

This is a fantastic idea!

I’m working on a terminal emulator. It’s not big like Ghostty but this is something I might adopt

  • kps  4 days ago

    After thinking about it a bit more, I think the specific details of that (i.e. inventing an extended colour mode) are not ideal.

    One alternative: Assign semantics to colour indexes above 256.

    Both of those have the disadvantage that they separate foreground and background colour, but a user really wants a combined semantic presentation. For instance, a user might want a warning message to be black text on a yellow background, and not have to rely on the program remembering to set both foreground and background to ‘warning’ colour.

    So another possibility is just to invent new SGR numbers, e.g.

        Control         Purpose
    ------------    -------
    CSI 2 0 0 m    normal (undoes any CSI 1 x x m)
    CSI 2 0 1 m    emphasise
    CSI 2 0 2 m    de-emphasise
    CSI 2 0 3 m    error
    CSI 2 0 4 m    warning
    CSI 2 0 5 m    caution
    CSI 2 0 6 m    notice
    ⋮

    Then the user can configure those as they please with any combination of foreground, background, weight, slant, etc.

    I'm now thinking about writing up pros and cons of alternatives.

zzo38computer  4 days ago

I like this idea, although I think that they should be only one code, which might program both the foreground and background (and font styles if applicable), rather than separate codes for foreground and for background.