Writing a partial escape can easily lock up a terminal. This
is especially relevant when working with bitmaps, as they're
thousands or even millions of times longer than a typical
escape. Immediately before writing, block SIGINT, SIGQUIT, and
SIGTERM in the writing thread, and unblock them upon emerging
(at which point we'll immediately see any queued signal
get delivered). Don't block signals like SIGSEGV that would
seem indicative of actual problems. For this to actually work,
all other threads must also have the signals masked; we thus
now add them to the signal mask of notcurses_getc(), rather
than deleting them. Closes#1416.
* Paint sprixels in order, bottom-to-top
We don't want to have to track sprixel order whenever someone
moves an ncplane, so just keep a list growing backwards as we
pass top-to-bottom in notcurses_render_internal(). Each time
we hit a sprixel plane, splice it out of the sprixel list, and
add it to the front of our temporary list. When we hit the
bottom, stick this temporary list on the end of our existing
list (any such planes are to be deleted, which comes before
drawing). Closes#1575.
* reorder collected sprixellist; solves kitty but breaks sixel =/ #1575
* remove debugging cruft
* [rust] fix up mergedown mutability
Guard against attempts to output glyphs to a sprixelated
plane in ncplane_putc_yx(), the lowest-level common end
of all ncplane_put*() functions. Add unit test #1572.
Go ahead and allow the standard plane to be used with
NCBLIT_PIXEL, but enforce placement at the origin with
any provided plane. Implement this in ncvisual_blitter_geom()
so that it applies everywhere #1572.
