I have found that DECERA/DECFRA do not apply to Sixel within the
specified rectangular region. The documentation I've read
doesn't seem explicit one way or the other:
but perhaps you have documentation beyond this that locks things
down. Alternatively, perhaps the six-row nature of sixel isn't
immediately amenable to rectangular erasure, since it might end
mid-cell? But the possibility remains that this was merely an
oversight, in which case the attached patch ought at least be a
starting point for remedying the issue.
This probably ought apply to DECSERA, DECSEL, etc. If so, the
attached patch ought be easily enough generalized.
It seems to me intuitive and expected that these control sequences
would obliterate all (non-protected) content. Erase Display,
Erase Character, and Erase Line *do* (by test and visual
inspection) apply to Sixel, which seems correct (I've been
unable to get Erase Area working in any capacity, and assume
it's an aixterm-only deal).
This came up in the following Notcurses issue, if you're interested:
Please feel free to use this patch however you see fit, or to
reject it if inappropriate.
BTW, thanks for fixing up the TIOCGWINSZ-on-font-change issue in
Patch 368! I updated the historical reference at
nick black -=- https://www.nick-black.com
to make an apple pie from scratch,
you need first invent a universe.