[BRLTTY] Linux console hacking (was: Re: Footsteps towards better accessibility in Linux)

[Samuel Thibault]

Nicolas Pitre, le lun. 30 mars 2026 01:16:39 -0400, a ecrit:
> #### Cell format
> 
> Each cell in the array represents one screen position:
> 
> ```c
> struct kmscon_shm_cell {
>     uint32_t codepoint;    /* Unicode codepoint (UCS-4)       */
>     uint16_t flags;        /* Width + attribute flags          */
>     uint8_t  fr, fg, fb;   /* Foreground color (RGB)           */
>     uint8_t  br, bg, bb;   /* Background color (RGB)           */
> };
> ```

There is one missing thing here: unicode include combining codepoints,
which mix with the base codepoint within the same cell. That's
required for quite a few scripts. In theory there is no limit in the
number of combining letters used, but usually there aren't that many
combining codepoints for cell. Some reference says “The longest known
natural-language grapheme cluster is the Tibetan Hakṣhmalawarayaṁ at
1 base plus 8 combiners”

https://stackoverflow.com/questions/11978912/how-to-protect-against-diacritics-such-as-zalgo-text/11983435#11983435

Samuel