A ~C! override can, if it wants, go put an error code in there,
which ~AT28 does.

This way, after a copy or xcomp process directly to EEPROM, one
can verify whether all bytes were successfully written by checking
whether "~C!ERR C@" is zero.

They're only used once.

Also, turn AT28! and AT28, into ~AT28, pluggable into ~C!.

~AT28 doesn't check for mismatches. It was too complicated to turn
a mismatch into a compiled word we would jump to next. Data
integrity has to be checked through another path.

Also, remove MOVEW. Without indirect memory access, this word
doesn't make sense. Some AVR-specific words will have to be
defined.

I got bitten again, I've over-designed my solution. The last time
it happened, it was that memory mapping thing I was wanting to add.

The indirect memory access feature I was adding was to solve a
specific problem: Allow Collapse OS to cross-compile directly on a
AT28 EEPROM.

It began well. As long as we were staying in the assembler realm,
things were looking good. However, when we got into the xcomp realm
(B260), things became ugly, and I had to creep up indirection where
I didn't want to.

All of this because I wanted to solve my initial problem in a
slightly more generalized way. The broad idea was that these indirect
memory access could allow xcomp into a broad kind of memory-like
devices.

This idea broke on the "@" part of the equation. If I want
indirections to be two-way and allow xcomp to work properly, I have
to add this indirection to FIND (and possibly others) and this just
isn't practical or elegant.

So, I'm taking a step back and accepting that the solution I design
for now is exclusively for the AT28. What I'm thinking is to add a
low-level hook for memory writing, at the assembly level.

Splitting a word into MSB/LSB pairs happens often and is worth, I
think, native words. Also, I'm going to need it in the upcoming
commits.

Also, rename "Addressed devices" to "Indirect memory access".

I do this because I need to add indirect versions of !, @ and ,
to allow boostrapping directly to EEPROM and that A,, thing I've
added to assemblers felt like really bad names.

With this change, I'd like to generalize the use of the * suffix
for aliases.

This brings us a bit closer to TYPE from Forth 2012. I don't think
I'll add TYPE (sig "addr len") anytime soon because there is few
use cases for it, but having "STYPE" instead of "(print)" feels
cleaner.

I hadn't noticed yet, but making CVM use the Grid subsystem made
me lose scrolling. It's fine because that scrolling was "artificial"
in the sense that it was provided by curses, not Collapse OS and I
prefer having something that closer emulates a real machine.

However, CVM didn't properly clear the new line when entering it.
Fixed.

Scrolling behavior will come back when it's implemented in the Grid
subsystem.

This required the change of CURSOR! signature: we now supply it
with both old and new cursor positions.

Also, fix broken _bs in Grid subsystem.

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.

With the move of CVM's forth to the grid protocol, we've lost the
cursor's visual indication. Now, we have it back.

The challenge now is in implementing it in SMS' text mode. In mode
4, it's easy to mark a cell as inverted, but in text mode, that's
not possible.

In VE on the SMS, the first contents line would always be cleared
because of NEWLN being called when the FBUF would spit its last
char. Inconvenient...

I've added a "graphical" mode to the grid subsystem to inhibit this
behavior in a graphical situation such as in VE.

Also, write a more complete Grid documentation.

Also, fixed broken AT-XY in Grid...

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.

I wanted to make CVM's forth use the Grid subsystem, but doing so
would break the stage binary. Hence, this split.

I've noticed that under certain conditions, such as a stack overflow,
I would segfault, something I though was impossible because my memory
size is 0x10000 and all my integer variables are uint16_t.

After having re-read my C handbook, it seems I wasn't sufficiently
knowledgeable about type conversion rules.

It isn't used in there anymore. Moved it to VE, the only place
where it's used.

If a line has a char below 0x20, we consider the line ended, we
stop the EMIT loop for this line and spit our NL.

This makes LIST stop wasting rows in environments with a tight
screen.

NetBSD doesn't have ncurses. Linking to curses doesn't seem to change
anything. Tried on OpenBSD and Ubuntu.

There are many situations where it can be useful. Worth it.

This allows us to remove AMOVE* words.

This would be useful, for example, to allow the assembler to write
straight to an AT28 EEPROM without going to RAM. This would be a
life saver in machines with tight RAM such as the SMS.

With KEY and EMIT being switch words, most of the high layer can
be defined before drivers.

In addition to this change, I've compacted core blocks which were
becoming quite sparse.

This allows us to remove one layer of indirection in (wnf). This is
possible now that EMIT is a switch word.

Slightly larger binary, but clearer code and slightly faster.

I'm pretty happy about how lightweight the implementation turns
out to be.

I think that when I added NL, I had troubles having access to CRLF's
address at boot time, which is why I had this system. But now that
CRLF is easily accessible during BOOT, we can simplify.

(and that will help us in the hopefully-upcoming change, which is
quite nice...)

They were only used in the ti84 recipe and were not worth their cost.

Adding a delay such as the 20ms one we have in AVR programmer's
initialization routine is tricky without a word like TICKS.

This implementation is highly inaccurate, but more accurate and
reliable than a "ballpark" DO..LOOP...

The few extra bytes they save in the core aren't worth the extra
complexity. This was initially done in a context where I had
troubles keeping the RC2014 binary with SDC inside the 8K limit.

At this point, even with the few extra bytes we add here, we're at
7200 bytes, so I'd say we're fine.

This marks the end of wordrefs in stable ABI. Nice.

The ":" now takes care of scanning for ";". Conceptually, having
";" as an immediate word is slightly simpler than the approach in
this commit, but when bootstrapping is involved, this simpler
approach gets murkier.

Moreover, it got even murkier-er when trying to de-stabilize EXIT,
so here we are.

This duplicated feature existed because of bootstrapping issues
with LIT", but again, with careful threading, we can clean things
up.

We can now have a proper "Collapse OS" prompt :)

I've mistakenly broken it in previous commit.

When writing the xcomp documentation, I realized that with careful
threading and by accepting a bit of code duplication in the xcomp
toolset, I could de-stabilize a couple of words.

(n) and EXIT are a bit trickier, but I think it can be done. It
would be nice to get rid of stable wordrefs...

Always returning zero caused test failures not to be properly
detected.

This should help spot bugs due to bad initialization.

They were a bit terse.

The 1 byte limitation has been effective for a while now, but I
hadn't made the move yet, I wanted to see if the limitation would
cause me problems. It doesn't.

Doing this now slightly facilitates the IY->BC move in z80.

Bootstrapping: if you try to recreate the CVM binary from the
previous commit with this code, you'll have bootstrapping problems.
The first bootstrap will compile a binary with 2-bytes wide cells
but branching conditionals that yields 1-byte cells. That's bad.

I got around the issue by temporarily inserting a "397 399 LOADR"
instruction in cvm/xcomp.fs, right before the xcomp overrides. This
way, I force 1-byte cells everywhere on the first compiliation,
which then allows me to apply the logic change in cvm/vm.c and have
a properly running binary.