ncplane_as_rgba: genericize across blitters
ncplane_as_rgba() previously was implemented explicitly
in terms of NCBLIT_2x1. it now uses the `egcs` field of the
`blitset`. this supports NCBLIT_2x2 and NCBLIT_3x2 in
ncplane_rgba(). Closes#1490.
Rather than trying to force things in via library constructors
and weak symbols and --whole-archive and pkg-config tricks, just
add new functions ncdirect_core_init() and notcurses_core_init().
libnotcurses has ncdirect_init() and notcurses_init(), which pass
through to these. apps linking against notcurses-core ought use
the _core_ variants directly. This gets exactly the linkage we
want, everywhere. Convert many PoCs to _core_ variants. #1301
Signed-off-by: nick black <dankamongmen@gmail.com>
Extract `libnotcurses-core` from `libnotcurses`. The former contains everything except multimedia code. The latter contains multimedia stuff (a wrapper around FFmpeg or OIIO). If built with `-DUSE_MULTIMEDIA=none`, there will not be any `libnotcurses.so` generated. `libnotcurses.so` uses library constructors/destructors to insert its implementation into the `ncvisual` stack at runtime. Users linking `-lnotcurses` will get the full implementation; users linking `-lnotcurses-core` only will get the stack less multimedia code.
The upshot of this is that someone can compile/install only `libnotcurses-core`, and a program linked against it will work just fine. This eliminates the need to install the full (large) dependency stack of the multimedia code unless necessary. This will hopefully be useful for e.g. installers etc. Closes#339.
