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SplitBit-Emulator/Tests/video.sh
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AnachronautandClaude Opus 5 13b20c8834 Give the screen a bitmap mode 
V4. Mode 2 is 320 by 200 with a byte a pixel: no tile to look up and no attribute to add,
the byte IS the palette index. Programs/Examples/picture.asm fills a whole one in 127 bytes
of program and 47,498 cycles.

IT IS THE SAME MEMORY AS THE TILES AND THE MAP, which is what shared video memory has always
been, and there is nowhere else it could be - 64,000 bytes of picture in a 65,536 byte bank
leaves room for nothing beside it. Going to bitmap mode does not clear the text screen, it
stops calling it one, and coming back finds the tiles holding whatever the picture put there.
Taking the screen means taking it.

The palette moves to 0xFC00, the top of video memory, because it is the one thing that has to
mean the same in every mode and 64,000 bytes of picture leaves nowhere in the middle for it
to hide. That is a documented address, so the example, the tests and the manual move with it.

A BITMAP HAS NO COLUMNS AND NO ROWS, and both registers read zero rather than a leftover from
the last mode. The console asks: told there is no character screen, it has nowhere to put a
glyph and draws nothing, while still saying everything down the serial line. The honest
alternative is what a machine with shared video memory really does, which is scribble marks
nobody can read across somebody's picture - honest and useless, since a program that has
taken the screen has not stopped wanting to print.

Six checks in Tests/video.sh, to 55: that the mode is 320 by 200, that a byte is one pixel's
colour and only that pixel, that printing leaves a picture alone while the letter still goes
out, and that the columns register says nought and then forty again.

The example is worth reading for one thing beyond the mode: Fill leaves its destination past
what it touched, so two hundred rows are drawn from one address set once. Working out where
row n begins would be n times 320, and this machine has no multiply.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
2026-08-29 10:44:15 -04:00

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#!/usr/bin/env bash
# Checks what the video device actually draws.
#
# THE SUITE HAS NO DISPLAY, and a screen nothing can look at is a screen nothing checks. So
# the device renders into a buffer that is a pure function of video memory, and the machine
# can be asked to save it with --screen. Every check below runs a program, saves the picture
# and reads pixels out of it - no window, no display server, and the same answer every time.
#
# Each check is a named claim about one behaviour rather than a comparison against a
# recorded image. A recorded image would say "something changed" and leave which of the
# palette, the tile, the attribute, the map or the scroll register broke to be found by
# hand, which for a screen is the hardest kind of bug to see.
#
# Written by Anachronaut
set -u
ROOT="$(cd "$(dirname "$0")/.." && pwd)"
BUILD="$ROOT/Tests/build/video"
ASM="$ROOT/Assembler"
EMU="$ROOT/SplitBit"
for tool in "$ASM" "$EMU"; do
[ -x "$tool" ] || { echo "$(basename "$tool") is not built."; exit 1; }
done
rm -rf "$BUILD"; mkdir -p "$BUILD"
PASS=0
FAIL=0
FAILED_NAMES=()
GREEN=$'\033[32m'; RED=$'\033[31m'; RESET=$'\033[0m'
[ -t 1 ] || { GREEN=""; RED=""; RESET=""; }
result() {
# result <ok|no> <name> <detail>
if [ "$1" = "ok" ]; then
PASS=$((PASS + 1)); printf " [%sok %s] %-38s %s\n" "$GREEN" "$RESET" "$2" "$3"
else
FAIL=$((FAIL + 1)); FAILED_NAMES+=("$2")
printf " [%sFAIL%s] %-38s %s\n" "$RED" "$RESET" "$2" "$3"
fi
}
# ---- Writing to video memory from a program ----
#
# Through the controller, because that is the only way to reach a device's bank: the CPU
# never touches it directly. The Data port puts a byte at the destination and steps the
# address on, which is what makes a poke six instructions instead of a loop.
prologue() {
cat <<'ASM'
#Program
start:
INIA 0d3
OUTA 0xE3
INIA 0x30
OUTA 0xE2
INIA 0x03
OUTA 0xE8 ; Video memory becomes bank 3
ASM
# ---- Said rather than assumed ----
#
# The machine wakes up with a palette so that it can show text before any program has
# run, so palette entry 0 is the console's paper rather than black. A check that wanted
# black and got paper would be a check that had quietly depended on a default. These
# tests are about the device, so they set what they are about to look at.
poke 0xFC00 0x00; poke 0xFC01 0x00; poke 0xFC02 0x00
}
poke() {
# poke <address> <byte>
printf ' INIA 0x%02X\n OUTA 0xE4\n INIA 0x%02X\n OUTA 0xE5\n INIA 0x%02X\n OUTA 0xE9\n' \
$(( ($1 >> 8) & 0xFF )) $(( $1 & 0xFF )) $(( $2 & 0xFF ))
}
port() {
# port <port> <byte>
printf ' INIA 0x%02X\n OUTA 0x%02X\n' $(( $2 & 0xFF )) $(( $1 & 0xFF ))
}
show() {
# show <port> - sends a port's value to the console, so a test can read a register.
# INA reads straight into A, so there is nothing to move first.
printf ' INA 0x%02X\n OUTA 0x00\n' $(( $1 & 0xFF ))
}
epilogue() {
printf ' HALT\n#Vectors\n Boot start\n'
}
# One byte to the console, by its number.
emit() {
printf ' INIA 0d%d\n OUTA 0x00\n' "$1"
}
# About 262,000 cycles of nothing. A DECA is one byte and a BNA is three, so four cycles a
# turn, 256 times 256. The label suffix is so that two of these can sit in one program.
spin() {
printf ' RSTB\nspinOuter%s:\n RSTA\nspinInner%s:\n DECA\n BNA spinInner%s\n DECB\n BNB spinOuter%s\n' \
"$1" "$1" "$1" "$1"
}
# A string to the console, which is all a program has ever had to do to put text on a
# SplitBit. That it now appears on a screen is the whole of this rung.
say() {
local i
for (( i = 0; i < ${#1}; i++ )); do
printf ' INIA 0d%d\n OUTA 0x00\n' "'${1:$i:1}"
done
}
# Waits, as a keyboard file: a zero is a moment of nobody typing, which is the commonest
# thing that happens behind a window and the only thing a file otherwise cannot say.
waiting() {
python3 -c "import sys; sys.stdout.buffer.write(b'\\x00' * int(sys.argv[1]) + b'x')" "$1" \
> "$BUILD/waits.keys"
echo "$BUILD/waits.keys"
}
# Assembles what is on standard input, runs it, and leaves the picture in $BUILD/<name>.ppm.
# A second argument names a keyboard file to feed it.
run() {
local name="$1"
cat > "$BUILD/$name.asm"
"$ASM" "$BUILD/$name.asm" -o "$BUILD/$name.bin" >"$BUILD/$name.log" 2>&1 || {
echo "could not assemble $name"; sed 's/^/ /' "$BUILD/$name.log"; return 1; }
# ---- Bounded, the way run.sh bounds things ----
#
# A program here can WAIT for something that never comes, and one did: breaking the frame
# interrupt on purpose left a machine asleep for ever and took the whole suite with it,
# which is a worse way to be told than a failing check. Ten seconds, and a test that hangs
# says so instead of hanging.
if [ -n "${2:-}" ]; then
timeout 10 "$EMU" --fast --keyboard "$2" --screen "$BUILD/$name.ppm" \
"$BUILD/$name.bin" > "$BUILD/$name.out" 2>&1
else
timeout 10 "$EMU" --fast --screen "$BUILD/$name.ppm" "$BUILD/$name.bin" \
> "$BUILD/$name.out" 2>&1
fi
if [ $? -eq 124 ]; then
echo " $name did not finish within ten seconds"
fi
}
# One pixel out of a PPM, as "r,g,b".
pixel() {
python3 - "$BUILD/$1.ppm" "$2" "$3" <<'PY'
import sys
data = open(sys.argv[1], "rb").read()
# P6, width height, maxval, then the bytes. The header is three whitespace-separated
# fields after the magic, which is all this needs to know about the format.
fields = data.split(b"\n", 3)
width, height = (int(n) for n in fields[1].split())
body = fields[3]
x, y = int(sys.argv[2]), int(sys.argv[3])
at = (y * width + x) * 3
print("%d,%d,%d" % tuple(body[at:at + 3]))
PY
}
size() {
head -c 20 "$BUILD/$1.ppm" | sed -n '2p'
}
# ---- What a program said, as numbers ----
#
# With two things taken out that are not the program's: the cursor sequences the console
# generates to drive a host terminal, and the emulator's own halt line. Counting bytes from
# either end of the raw file worked until the console started announcing the cursor, and
# then quietly measured an escape.
said() {
python3 - "$BUILD/$1.out" <<'PY'
import re, sys
data = open(sys.argv[1], "rb").read()
data = re.sub(rb"\x1b\[[0-9;]*[A-Za-z]", b"", data)
data = re.sub(rb"Execution [^\n]*\n$", b"", data)
print(" ".join(str(byte) for byte in data))
PY
}
echo "Checking what the video device draws."
# ---- The machine wakes up able to show text ----
#
# Before any program has done anything: the font is in tile memory and the two colours a
# console needs are in the palette. Checked at the pixel, because a font that loaded into
# the wrong place would still be a font that loaded.
{ printf '#Program\nstart:\n'
# 'A' is ASCII 65, so glyph 33, and its top-left pixel is paper while its middle is ink.
printf ' INIA 0d65\n OUTA 0x00\n'
epilogue
} | run wakeup || exit 1
[ "$(pixel wakeup 0 0)" = "0,0,0" ] \
&& result ok "the machine wakes with paper" "black, before any program set one" \
|| result no "the machine wakes with paper" "got $(pixel wakeup 0 0)"
[ "$(pixel wakeup 2 1)" = "216,216,216" ] \
&& result ok "and with a font to write in" "a letter A, drawn in ink" \
|| result no "and with a font to write in" "got $(pixel wakeup 2 1)"
# ---- A tile lands where it is put ----
#
# Palette entry 1 is red, tile 1 is 64 pixels of index 1, and two cells name it: the corner
# and column 3 of row 2. A tile drawn one cell out is the commonest way a tile engine is
# wrong, so the check is where it is AND where it is not.
{ prologue
poke 0xFC04 0xFF; poke 0xFC05 0x00; poke 0xFC06 0x00
for i in $(seq 0 63); do poke $((0x0040 + i)) 0x01; done
poke 0x4000 0x01; poke 0x4001 0x00
poke $((0x4000 + 2 * 256 + 3 * 2)) 0x01
epilogue
} | run corner || exit 1
[ "$(pixel corner 0 0)" = "255,0,0" ] \
&& result ok "a tile lands where it is put" "cell 0,0 is red" \
|| result no "a tile lands where it is put" "got $(pixel corner 0 0)"
[ "$(pixel corner 7 7)" = "255,0,0" ] \
&& result ok "and fills its whole cell" "pixel 7,7 too" \
|| result no "and fills its whole cell" "got $(pixel corner 7 7)"
[ "$(pixel corner 8 0)" = "0,0,0" ] \
&& result ok "and stops at the cell edge" "pixel 8,0 is not" \
|| result no "and stops at the cell edge" "got $(pixel corner 8 0)"
[ "$(pixel corner 24 16)" = "255,0,0" ] \
&& result ok "row 2 column 3 is where it says" "pixel 24,16" \
|| result no "row 2 column 3 is where it says" "got $(pixel corner 24 16)"
# ---- The palette is what colours it ----
#
# Same tile, same map, a different palette entry. Nothing about the picture changes except
# the three bytes the colour came from.
{ prologue
poke 0xFC04 0x00; poke 0xFC05 0xFF; poke 0xFC06 0x40
for i in $(seq 0 63); do poke $((0x0040 + i)) 0x01; done
poke 0x4000 0x01; poke 0x4001 0x00
epilogue
} | run palette || exit 1
[ "$(pixel palette 0 0)" = "0,255,64" ] \
&& result ok "the palette is what colours it" "entry 1 moved, the tile did not" \
|| result no "the palette is what colours it" "got $(pixel palette 0 0)"
# ---- The attribute picks a palette bank ----
#
# The tile is drawn in index 1 and never changes. Entry 1 is red and entry 17 is blue, and
# the only difference between the two cells is the attribute nibble: 0 leaves the index
# alone, 1 adds sixteen. This is the whole of the recolouring feature in one check.
{ prologue
poke 0xFC04 0xFF; poke 0xFC05 0x00; poke 0xFC06 0x00
poke 0xFC44 0x00; poke 0xFC45 0x00; poke 0xFC46 0xFF
for i in $(seq 0 63); do poke $((0x0040 + i)) 0x01; done
poke 0x4000 0x01; poke 0x4001 0x00
poke 0x4002 0x01; poke 0x4003 0x01
epilogue
} | run attribute || exit 1
[ "$(pixel attribute 0 0)" = "255,0,0" ] \
&& result ok "attribute 0 leaves the index alone" "still entry 1" \
|| result no "attribute 0 leaves the index alone" "got $(pixel attribute 0 0)"
[ "$(pixel attribute 8 0)" = "0,0,255" ] \
&& result ok "and attribute 1 adds sixteen" "the same tile, entry 17" \
|| result no "and attribute 1 adds sixteen" "got $(pixel attribute 8 0)"
# ---- Scrolling moves a register, not memory ----
#
# The tile is in map row 3 and nothing moves it. Setting the scroll origin to 3 brings that
# row to the top of the screen, which is the whole reason a terminal on this machine is
# affordable at all.
{ prologue
poke 0xFC04 0xFF; poke 0xFC05 0xFF; poke 0xFC06 0x00
for i in $(seq 0 63); do poke $((0x0040 + i)) 0x01; done
poke $((0x4000 + 3 * 256)) 0x01
port 0x34 0x03
epilogue
} | run scroll || exit 1
[ "$(pixel scroll 0 0)" = "255,255,0" ] \
&& result ok "scrolling moves which row is on top" "map row 3 at screen row 0" \
|| result no "scrolling moves which row is on top" "got $(pixel scroll 0 0)"
[ "$(pixel scroll 0 8)" = "0,0,0" ] \
&& result ok "and takes the rest with it" "map row 4 below it" \
|| result no "and takes the rest with it" "got $(pixel scroll 0 8)"
# ---- The map is a ring ----
#
# Origin 127 with 128 rows puts map row 127 at the top and map row 0 immediately under it.
# A map that clipped instead of wrapping would show nothing on the second row.
{ prologue
poke 0xFC04 0xFF; poke 0xFC05 0xFF; poke 0xFC06 0xFF
for i in $(seq 0 63); do poke $((0x0040 + i)) 0x01; done
poke 0x4000 0x01
port 0x34 0x7F
epilogue
} | run ring || exit 1
[ "$(pixel ring 0 8)" = "255,255,255" ] \
&& result ok "the map is a ring" "row 0 follows row 127" \
|| result no "the map is a ring" "got $(pixel ring 0 8)"
# ---- Modes ----
{ prologue; port 0x31 0x01; epilogue; } | run wide || exit 1
[ "$(size wide)" = "640 400" ] \
&& result ok "mode 1 is 640 by 400" "$(size wide)" \
|| result no "mode 1 is 640 by 400" "got $(size wide)"
{ prologue; epilogue; } | run narrow || exit 1
[ "$(size narrow)" = "320 200" ] \
&& result ok "and mode 0 is 320 by 200" "$(size narrow)" \
|| result no "and mode 0 is 320 by 200" "got $(size narrow)"
# The geometry is asked for rather than assumed, so a program can be written once and find
# out what it is running on.
{ prologue; show 0x32; show 0x33; epilogue; } | run geometry || exit 1
GOT="$(said geometry)"
[ "$GOT" = "40 25" ] \
&& result ok "the ports say how big the screen is" "40 columns, 25 rows" \
|| result no "the ports say how big the screen is" "got \"$GOT\""
# ---- A mode that does not exist ----
#
# Not taken, and not fatal either. A screen is a poor place to stop the machine: a program
# that asked for something impossible still has the screen it had.
{ prologue; port 0x31 0x09; show 0x32; epilogue; } | run badmode || exit 1
GOT="$(said badmode)"
[ "$GOT" = "40" ] \
&& result ok "an impossible mode is not taken" "still 40 columns" \
|| result no "an impossible mode is not taken" "got $GOT"
# ---- The console draws ----
#
# Nothing below asks the video device for anything. Every one of these programs does what
# every SplitBit program has always done - write a byte to port 0x00 - and the picture is
# the point. That is why CosmOS needed no changes to run on a screen.
#
# 'A' has ink at (2,1) inside its cell and paper at the corner, which is what makes a letter
# tellable from an empty cell one pixel at a time.
inked() { [ "$(pixel "$1" "$2" "$3")" = "216,216,216" ]; }
papered() { [ "$(pixel "$1" "$2" "$3")" = "0,0,0" ]; }
{ printf '#Program\nstart:\n'; say "AA"; epilogue; } | run twoletters || exit 1
inked twoletters 2 1 \
&& result ok "a character lands at the cursor" "cell 0 has a letter in it" \
|| result no "a character lands at the cursor" "nothing at 2,1"
inked twoletters 10 1 \
&& result ok "and the cursor moves along" "the second is in cell 1" \
|| result no "and the cursor moves along" "nothing at 10,1"
{ printf '#Program\nstart:\n'; say "A"; emit 10; say "A"; epilogue; } | run newline || exit 1
inked newline 2 9 \
&& result ok "a newline starts the next row" "the second is a row down" \
|| result no "a newline starts the next row" "nothing at 2,9"
papered newline 10 1 \
&& result ok "and goes back to the first column" "cell 1 of row 0 is untouched" \
|| result no "and goes back to the first column" "something at 10,1"
{ printf '#Program\nstart:\n'; say "A"; emit 8; epilogue; } | run backspace || exit 1
papered backspace 2 1 \
&& result ok "backspace rubs the letter out" "the cell is paper again" \
|| result no "backspace rubs the letter out" "still inked at 2,1"
# Forty columns, so the forty-first character is on the next row whether anybody asked for a
# newline or not.
{ printf '#Program\nstart:\n'
for i in $(seq 1 41); do say "A"; done
epilogue
} | run wrap || exit 1
inked wrap 2 9 \
&& result ok "the line wraps at the last column" "character 41 is on row 1" \
|| result no "the line wraps at the last column" "nothing at 2,9"
# ---- Scrolling, which is the reason a terminal is affordable here ----
#
# Twenty-five rows, so a twenty-sixth line moves the screen rather than the cursor. The
# check is the ORIGIN: a console blitting rows instead would leave it at zero, and would
# have moved 1,920 bytes to do the same thing.
{ printf '#Program\nstart:\n'
say "A"
for i in $(seq 1 25); do emit 10; done
show 0x34
say "B"
epilogue
} | run scrolled || exit 1
# COUNTED FROM THE FRONT, not the back: the emulator's own halt line follows whatever the
# program wrote, so the last byte of the file belongs to the machine rather than to the
# program. One 'A', twenty-five newlines, then the origin, which is byte 27. It is below 32
# so it goes to standard output without being drawn, and disturbs no pixel below.
GOT="$(head -c 27 "$BUILD/scrolled.out" | tail -c 1 | od -An -tu1 | tr -d ' ')"
[ "$GOT" = "1" ] \
&& result ok "the screen scrolls by moving a register" "the origin is 1, not 0" \
|| result no "the screen scrolls by moving a register" "the origin is $GOT"
inked scrolled 2 193 \
&& result ok "and the cursor stays on the bottom row" "the last line, row 24" \
|| result no "and the cursor stays on the bottom row" "nothing at 2,193"
papered scrolled 2 1 \
&& result ok "the row that came into view is clear" "not what was there a ring ago" \
|| result no "the row that came into view is clear" "something at 2,1"
# ---- Cursor registers, in place of a protocol ----
#
# The console used to be given escape sequences and parse them. It is not a terminal and the
# screen is not on the other end of a serial line, so it takes registers instead: rows and
# columns are written and READ BACK, which is the thing an escape sequence cannot do without
# sending a query and parsing a reply.
{ printf '#Program\nstart:\n'; say "A"; port 0x05 0x01; epilogue; } | run clearcommand || exit 1
papered clearcommand 2 1 \
&& result ok "the clear command clears the screen" "the letter is gone" \
|| result no "the clear command clears the screen" "still inked at 2,1"
{ printf '#Program\nstart:\n'
emit 10; emit 10; say "A"
port 0x03 0x00; port 0x04 0x00
say "A"
epilogue
} | run cursorhome || exit 1
inked cursorhome 2 1 \
&& result ok "the cursor goes where it is put" "row 0, column 0" \
|| result no "the cursor goes where it is put" "nothing at 2,1"
inked cursorhome 2 17 \
&& result ok "and leaves what was drawn alone" "the first is still on row 2" \
|| result no "and leaves what was drawn alone" "nothing at 2,17"
{ printf '#Program\nstart:\n'; port 0x03 0x02; port 0x04 0x04; say "A"; epilogue
} | run cursorput || exit 1
inked cursorput 34 17 \
&& result ok "row and column are counted from zero" "row 2, column 4" \
|| result no "row and column are counted from zero" "nothing at 34,17"
# Readable, which is the point of them being registers. Three characters put the cursor at
# column 3, and asking says so.
{ printf '#Program\nstart:\n'; say "AAA"; show 0x04; show 0x03; epilogue; } | run cursorread || exit 1
GOT="$(said cursorread)"
[ "$GOT" = "65 65 65 3 0" ] \
&& result ok "and the cursor can be read back" "column 3, row 0" \
|| result no "and the cursor can be read back" "got \"$GOT\""
# A cursor asked to go off the screen has an obvious place to be, and stopping the machine
# over one would be a poor trade.
{ printf '#Program\nstart:\n'; port 0x04 0xFF; show 0x04; epilogue; } | run cursorclamp || exit 1
GOT="$(said cursorclamp)"
[ "$GOT" = "39" ] \
&& result ok "a cursor past the edge is clamped" "column 39, the last one" \
|| result no "a cursor past the edge is clamped" "got $GOT"
# ---- Colour, which costs a nibble and no hardware ----
#
# A glyph is drawn in palette indices 0 and 1, paper and ink, and a cell's attribute nibble
# adds sixteen to both. Sixteen banks is therefore sixteen ink and paper pairs, and the
# default palette is arranged so that XOR 8 turns any of them inside out.
coloured() { [ "$(pixel "$1" "$2" "$3")" = "$4" ]; }
{ printf '#Program\nstart:\n'; port 0x06 0x01; say "A"; epilogue; } | run inkred || exit 1
coloured inkred 2 1 "208,64,56" \
&& result ok "the attribute register colours the ink" "bank 1 is red on black" \
|| result no "the attribute register colours the ink" "got $(pixel inkred 2 1)"
coloured inkred 0 0 "0,0,0" \
&& result ok "and leaves the paper alone" "still black behind it" \
|| result no "and leaves the paper alone" "got $(pixel inkred 0 0)"
# The same colour with one bit more, which is the whole of highlighting.
{ printf '#Program\nstart:\n'; port 0x06 0x09; say "A"; epilogue; } | run highlight || exit 1
coloured highlight 0 0 "208,64,56" \
&& result ok "XOR 8 turns a pair inside out" "red paper now" \
|| result no "XOR 8 turns a pair inside out" "got $(pixel highlight 0 0)"
coloured highlight 2 1 "0,0,0" \
&& result ok "and the ink with it" "black letters on it" \
|| result no "and the ink with it" "got $(pixel highlight 2 1)"
# Readable, like every other console register.
{ printf '#Program\nstart:\n'; port 0x06 0x05; show 0x06; epilogue; } | run attrread || exit 1
[ "$(said attrread)" = "5" ] \
&& result ok "and the attribute reads back" "bank 5" \
|| result no "and the attribute reads back" "got $(said attrread)"
# ---- The cursor ----
#
# Drawn by the device, turned inside out rather than drawn over, so that a person editing a
# line can still see the character they are standing on. Off unless asked for: a program
# painting its own screen does not want one blinking in the middle of it.
{ printf '#Program\nstart:\n'; port 0x02 0x04; epilogue; } | run cursoron || exit 1
coloured cursoron 0 0 "216,216,216" \
&& result ok "a cursor appears where the console is" "an empty cell, inside out" \
|| result no "a cursor appears where the console is" "got $(pixel cursoron 0 0)"
{ printf '#Program\nstart:\n'; epilogue; } | run cursoroff || exit 1
coloured cursoroff 0 0 "0,0,0" \
&& result ok "and there is none unless asked for" "the machine draws what it is told" \
|| result no "and there is none unless asked for" "got $(pixel cursoroff 0 0)"
{ printf '#Program\nstart:\n'; port 0x02 0x04; port 0x03 0x03; port 0x04 0x07; epilogue
} | run cursorwhere || exit 1
coloured cursorwhere 56 24 "216,216,216" \
&& result ok "and it follows the cursor registers" "row 3, column 7" \
|| result no "and it follows the cursor registers" "got $(pixel cursorwhere 56 24)"
# ---- And it blinks on the machine's own clock ----
#
# Which is what makes it deterministic: the phase is a pure function of the cycle count, so
# a screen saved at a given cycle is the same screen every time. Half a million cycles in it
# is dark, and this burns about 524,000 - a DECA and a BNA are four cycles a turn.
{ printf '#Program\nstart:\n'; port 0x02 0x04; spin a; spin b; epilogue; } | run cursorblink || exit 1
coloured cursorblink 0 0 "0,0,0" \
&& result ok "the cursor blinks off again" "half a second later, dark" \
|| result no "the cursor blinks off again" "got $(pixel cursorblink 0 0)"
# ---- Blinking while the machine is stopped ----
#
# THE MACHINE IS NOT RUNNING while it waits for a key, and that is exactly when somebody is
# looking at the cursor. Time still has to reach the devices: a display controller does not
# stop blinking because the processor is waiting on a keyboard, any more than a disk stops
# turning. Waiting is charged as idle cycles and the devices are told as it happens, so the
# phase below is a pure function of how long nobody typed for.
#
# Key mode, so nothing is echoed and the cursor stays in the corner where it can be seen.
BLINKER='#Program
start:
INIA 0x05
OUTA 0x02
INA 0x00
HALT
#Vectors
Boot start'
echo "$BLINKER" | run blinkon "$(waiting 4)" || exit 1
coloured blinkon 0 0 "216,216,216" \
&& result ok "the cursor is lit while waiting" "sixty thousand cycles in" \
|| result no "the cursor is lit while waiting" "got $(pixel blinkon 0 0)"
echo "$BLINKER" | run blinkoff "$(waiting 40)" || exit 1
coloured blinkoff 0 0 "0,0,0" \
&& result ok "and dark half a second later" "the machine's clock, not the host's" \
|| result no "and dark half a second later" "got $(pixel blinkoff 0 0)"
echo "$BLINKER" | run blinkagain "$(waiting 70)" || exit 1
coloured blinkagain 0 0 "216,216,216" \
&& result ok "and lit again after that" "which is what blinking is" \
|| result no "and lit again after that" "got $(pixel blinkagain 0 0)"
# ---- A byte a pixel ----
#
# The other kind of screen. No tile to look up and no attribute to add: the byte IS the
# palette index, and it lives over the top of the tiles and the map, because 64,000 bytes of
# picture leaves room for nothing else in a 65,536 byte bank.
# Palette entry 5, then one pixel of it at row 2, column 3 - which is byte 2*320+3 = 643.
{ prologue
poke 0xFC14 0x20; poke 0xFC15 0xC0; poke 0xFC16 0x90
poke 0x0283 0x05
port 0x31 0x02
epilogue
} | run bitmap || exit 1
[ "$(size bitmap)" = "320 200" ] \
&& result ok "bitmap mode is 320 by 200" "$(size bitmap)" \
|| result no "bitmap mode is 320 by 200" "got $(size bitmap)"
coloured bitmap 3 2 "32,192,144" \
&& result ok "and a byte is a pixel's colour" "byte 643 is row 2, column 3" \
|| result no "and a byte is a pixel's colour" "got $(pixel bitmap 3 2)"
coloured bitmap 4 2 "0,0,0" \
&& result ok "and only that pixel" "the one beside it is untouched" \
|| result no "and only that pixel" "got $(pixel bitmap 4 2)"
# ---- And the console keeps off it ----
#
# There is no character screen in bitmap mode, so there is nowhere to put a glyph. The
# alternative is what a machine with shared video memory really does, which is scribble on
# somebody's picture with marks nobody can read. It still says everything down the serial
# line, which is where it was going as well.
{ prologue
poke 0xFC14 0x20; poke 0xFC15 0xC0; poke 0xFC16 0x90
poke 0x0283 0x05
port 0x31 0x02
say "A"
epilogue
} | run bitmaptext || exit 1
coloured bitmaptext 3 2 "32,192,144" \
&& result ok "printing does not touch a bitmap" "the pixel survived a letter" \
|| result no "printing does not touch a bitmap" "got $(pixel bitmaptext 3 2)"
[ "$(said bitmaptext)" = "65" ] \
&& result ok "and the letter still goes out" "down the serial line" \
|| result no "and the letter still goes out" "got $(said bitmaptext)"
# Asking how many columns there are in bitmap mode is asking about something that is not
# there, and nought is the true answer rather than a leftover from the last mode.
{ prologue; port 0x31 0x02; show 0x32; port 0x31 0x00; show 0x32; epilogue
} | run bitmapsize || exit 1
[ "$(said bitmapsize)" = "0 40" ] \
&& result ok "a bitmap has no columns" "and forty again when it is text" \
|| result no "a bitmap has no columns" "got $(said bitmapsize)"
# ---- The frame, which is the only beat this machine has ----
#
# There is no clock. Every program that wanted to happen at a certain speed has until now
# counted instructions and hoped, which is why Snake's pause silently halved when a cycle
# stopped being an instruction. A screen finishing sixty times a second is a real one, and it
# arrives on the MACHINE'S clock, so the same program sees the same number of frames in the
# same number of cycles however fast the host really went.
FRAMER='#Program
start:
SETD.0 Frames
RSTA
STA.0
INIA 0x01
OUTA 0x35
SIF
loop:
WAIT
SETD.0 Frames
LDA.0
INIB 0d10
CCF
SUB
BRQ done
BRI loop
done:
SETD.0 Frames
LDA.0
INIB 0d48
CCF
ADD
MVQA
OUTA 0x00
HALT
frame:
SETD.0 Frames
LDA.0
INCA
STA.0
RETI
#Data
Frames:
0x00
#Vectors
Boot start
Device 0x30 frame'
echo "$FRAMER" | run frames || exit 1
[ "$(said frames)" = "58" ] \
&& result ok "the screen interrupts once a frame" "ten of them, counted" \
|| result no "the screen interrupts once a frame" "got $(said frames)"
# ---- And the machine was ASLEEP for them ----
#
# Which is the whole point of having a frame to wait for, and the one thing the picture
# cannot show. Ten frames is 166,670 cycles and the program does a few hundred cycles of work
# in them; a machine spinning on the status port instead would show the same characters, take
# the same time, and spend every cycle of it on the bus.
IDLE="$(grep -oE '[0-9]+ of them waiting' "$BUILD/frames.out" | grep -oE '^[0-9]+')"
TOTAL="$(grep -oE 'after [0-9]+' "$BUILD/frames.out" | grep -oE '[0-9]+')"
[ -n "$IDLE" ] && [ "$IDLE" -gt $(( TOTAL - TOTAL / 50 )) ] \
&& result ok "and slept through nearly all of it" "$IDLE of $TOTAL cycles idle" \
|| result no "and slept through nearly all of it" "$IDLE of $TOTAL cycles idle"
# Nothing is asked for, so nothing arrives - and that matters more than it sounds. An
# interrupt with no handler installed is a fault, so a screen that interrupted whether or not
# it was asked would take down every program written before frames existed.
UNARMED='#Program
start:
SIF
INIA 0d100
spin:
DECA
BNA spin
INIA 0d65
OUTA 0x00
HALT
#Vectors
Boot start'
echo "$UNARMED" | run unarmed || exit 1
[ "$(said unarmed)" = "65" ] \
&& result ok "and none arrives unless asked for" "no handler, no fault" \
|| result no "and none arrives unless asked for" "got $(said unarmed)"
# A program with no handler can watch for the frame instead, the way one can poll the console
# rather than being interrupted by it.
POLLER='#Program
start:
SETD.0 Seen
RSTA
STA.0
poll:
INA 0x30
INIB 0x01
AND
BRQ poll
SETD.0 Seen
LDA.0
INCA
STA.0
INIB 0d3
CCF
SUB
BNQ poll
SETD.0 Seen
LDA.0
INIB 0d48
CCF
ADD
MVQA
OUTA 0x00
HALT
#Data
Seen:
0x00
#Vectors
Boot start'
echo "$POLLER" | run poller || exit 1
[ "$(said poller)" = "51" ] \
&& result ok "or watch for it without one" "three frames, polled" \
|| result no "or watch for it without one" "got $(said poller)"
# ---- And looking is what answers it ----
#
# Three frames polled have to have TAKEN three frames. A flag that stayed up once it was
# first set would let this loop through all three without a frame going by, print exactly the
# same character, and look perfectly correct - so the count is not the check, the clock is.
TOTAL="$(grep -oE 'after [0-9]+' "$BUILD/poller.out" | grep -oE '[0-9]+')"
[ "$TOTAL" -gt 33334 ] \
&& result ok "and the flag comes down when looked at" "$TOTAL cycles, so three frames passed" \
|| result no "and the flag comes down when looked at" "$TOTAL cycles, too few to be three frames"
# And what scrolled off the top is still in the map, which is scrollback nothing had to keep.
{ printf '#Program\nstart:\n'
say "A"
for i in $(seq 1 25); do emit 10; done
port 0x34 0x00
epilogue
} | run scrollback || exit 1
inked scrollback 2 1 \
&& result ok "what scrolled off is still there" "the origin went back and found it" \
|| result no "what scrolled off is still there" "nothing at 2,1"
echo
if [ "$FAIL" -eq 0 ]; then
echo "All $PASS video checks passed."
exit 0
fi
echo "$PASS passed, $FAIL failed: ${FAILED_NAMES[*]}"
exit 1
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