Doing SPI bit-banging through a controller port is already really
slow, but doing so with the Forth version of (spix) was really,
really slow.
With this pure z80 version of (spix), it's more bearable.
I do this by adding an inverted version of all glyphs in the upper
range of the pattern memory. This is a big waste of the pattern
space (only one inverted character is needed at once), but it's the
simplest way to proceed. I'll change this if I ever need more
pattern space.
Also, remove _blank. It was wastefully blanking the whole memory.
Only the name table needs to be blanked on initialization.
Replace the "g" arg (glyph) with "c" (character). The reason why "g"
was used was to save a "0x20 -" operation at all CELL! implementations,
but this came with too big a drawback: it made CELL! hardly usable
outside of the Grid subsystem, mostly because the user of CELL! would
often have to do "0x20 -".
For example, I want the SMS's Pad driver to use CELL! directly instead
of having to do EMIT+XYPOS-messing-around. I would have had to do a
"0x20 -" there.
Working in "blk/" folder from a modern system is harder than it
should be. Moving blocks around is a bit awkward, grepping is a
bit less convenient than it could be, git blame has troubles
following, etc.
In this commit, we modify blkpack and blkunpack to work with single
text files with blocks being separated by a special markup.
I think this will make the code significantly more convenient to
work into.
