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.
deprecate ncvisual_geom() in favor of new ncvisual_blitter_geom(), which allows caller to get the blitter used. replace the checks and calculations in ncvisual_render() with a call to ncvisual_blitter_geom(), unifying the two paths (and eliminating several bugs in the unloved ncvisual_geom()).
Deprecate ncplane_align(), after rewriting it as a passthrough
to new function ncplane_halign(). Add ncplane_valign(). Update
all callers. Closes#1468.
Add `notcurses_check_pixel_support()` and
`ncdirect_check_pixel_support()` per #1367. Removes
NCOPTION_VERIFY_SIXEL, again per #1367. Adds
`free_terminfo_cache()`, and calls it from both
`notcurses_stop_minimal()` and `ncdirect_stop()`.
Update all documentation. Closes#1371 and #1367.
nick black