Modernizing the OpenBSD Console

Re:Modernizing the OpenBSD Console by asveikau on Monday August 31, 2020 @10:10PM (#24337874)

Some of the code linked in the article seems to emulate the VGA style text console (1 value for char value, 1 value for color and attributes) and render it onto a 32bit framebuffer.

The diffs that are attributed to Carmack seem to deal with this. scr->rs_bs[off].uc and scr->rs_bs[off].attr appear to represent the gylph and attributes/color respectively.

So I would expect that would severely limit the amount of colors available to the input buffer. OTOH I just found the declaration in the code and the attributes are 32 bits wide which is more than the 8 that VGA provides:

    struct wsdisplay_charcell {
       u_int       uc;
       uint32_t    attr;
    };

Note I would expect the 32 bits of attr to be divided between fg and bg color, and it seems like they carved out bits for things like underline.

Edit: after reading some more it seems like the color values range from 0-7.

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Re:Modernizing the OpenBSD Console by JdeBP on Tuesday September 01, 2020 @03:57AM (#24339519)

32 bits isn't really enough. One uses 24 bits for RGB, and the remaining 8 bits aren't really enough for the remaining graphics renditions that a modern terminal emulator should support.

Factor in things like the KiTTY underlining system, invisible, the little-recognized new (sic!) ECMA-48:1991 graphic renditions (encircled, framed, and overlined), and strikethrough; and one actually needs 13 to 14 bits (depending from how far one takes the KiTTY underlining system).

Moreover: No-one doing this style of terminal emulator really does Unicode properly. To do so actually involves having a string of one or more code points per cell, not simply exactly one. Some of the terminal emulators based upon external GUIs (e.g. X11) do do that, or approach it. (Although at the same time they take a giant leap backwards from video terminal semantics to paper terminal semantics, so it is a matter of swings and roundabouts. See https://unix.stackexchange.com/a/593613/5132 .)

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Re:Modernizing the OpenBSD Console by asveikau on Tuesday September 01, 2020 @12:12PM (#24343363)

> 32 bits isn't really enough. One uses 24 bits for RGB,

Yes, and as I mentioned you need to divide between FG and BG colors.

All a little moot because it seems to me like the code uses 3 bits for color.

> No-one doing this style of terminal emulator really does Unicode properly

Indeed, both multi-char and multi-codepoint glyphs. I also think the whole "matrix of glyphs" thing breaks down pretty severely when you want BiDi support for instance. The article mentions someone working on UTF-8 support. I wonder what that looks like.

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