move gap buffer code to top-level

Now that it's been used in a second app without needing any changes.

2 files changed, 0 insertions, 2026 deletions

diff --git a/browse-slack/gap-buffer.mu b/browse-slack/gap-buffer.mu
deleted file mode 100644
index 0077d6fd..00000000
--- a/browse-slack/gap-buffer.mu
+++ /dev/null
@@ -1,1470 +0,0 @@
-# primitive for editing text
-
-type gap-buffer {
-  left: grapheme-stack
-  right: grapheme-stack
-  # some fields for scanning incrementally through a gap-buffer
-  left-read-index: int
-  right-read-index: int
-}
-
-fn initialize-gap-buffer _self: (addr gap-buffer), capacity: int {
-  var self/esi: (addr gap-buffer) <- copy _self
-  var left/eax: (addr grapheme-stack) <- get self, left
-  initialize-grapheme-stack left, capacity
-  var right/eax: (addr grapheme-stack) <- get self, right
-  initialize-grapheme-stack right, capacity
-}
-
-fn clear-gap-buffer _self: (addr gap-buffer) {
-  var self/esi: (addr gap-buffer) <- copy _self
-  var left/eax: (addr grapheme-stack) <- get self, left
-  clear-grapheme-stack left
-  var right/eax: (addr grapheme-stack) <- get self, right
-  clear-grapheme-stack right
-}
-
-fn gap-buffer-empty? _self: (addr gap-buffer) -> _/eax: boolean {
-  var self/esi: (addr gap-buffer) <- copy _self
-  # if !empty?(left) return false
-  {
-    var left/eax: (addr grapheme-stack) <- get self, left
-    var result/eax: boolean <- grapheme-stack-empty? left
-    compare result, 0/false
-    break-if-!=
-    return 0/false
-  }
-  # return empty?(right)
-  var left/eax: (addr grapheme-stack) <- get self, left
-  var result/eax: boolean <- grapheme-stack-empty? left
-  return result
-}
-
-fn gap-buffer-capacity _gap: (addr gap-buffer) -> _/edx: int {
-  var gap/esi: (addr gap-buffer) <- copy _gap
-  var left/eax: (addr grapheme-stack) <- get gap, left
-  var left-data-ah/eax: (addr handle array grapheme) <- get left, data
-  var left-data/eax: (addr array grapheme) <- lookup *left-data-ah
-  var result/eax: int <- length left-data
-  return result
-}
-
-# just for tests
-fn initialize-gap-buffer-with self: (addr gap-buffer), keys: (addr array byte) {
-  initialize-gap-buffer self, 0x40/capacity
-  var input-stream-storage: (stream byte 0x40/capacity)
-  var input-stream/ecx: (addr stream byte) <- address input-stream-storage
-  write input-stream, keys
-  {
-    var done?/eax: boolean <- stream-empty? input-stream
-    compare done?, 0/false
-    break-if-!=
-    var g/eax: grapheme <- read-grapheme input-stream
-    add-grapheme-at-gap self, g
-    loop
-  }
-}
-
-fn load-gap-buffer-from-stream self: (addr gap-buffer), in: (addr stream byte) {
-  rewind-stream in
-  {
-    var done?/eax: boolean <- stream-empty? in
-    compare done?, 0/false
-    break-if-!=
-    var key/eax: byte <- read-byte in
-    compare key, 0/null
-    break-if-=
-    var g/eax: grapheme <- copy key
-    edit-gap-buffer self, g
-    loop
-  }
-}
-
-fn emit-gap-buffer self: (addr gap-buffer), out: (addr stream byte) {
-  clear-stream out
-  append-gap-buffer self, out
-}
-
-fn append-gap-buffer _self: (addr gap-buffer), out: (addr stream byte) {
-  var self/esi: (addr gap-buffer) <- copy _self
-  var left/eax: (addr grapheme-stack) <- get self, left
-  emit-stack-from-bottom left, out
-  var right/eax: (addr grapheme-stack) <- get self, right
-  emit-stack-from-top right, out
-}
-
-# dump stack from bottom to top
-fn emit-stack-from-bottom _self: (addr grapheme-stack), out: (addr stream byte) {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var data-ah/edi: (addr handle array grapheme) <- get self, data
-  var _data/eax: (addr array grapheme) <- lookup *data-ah
-  var data/edi: (addr array grapheme) <- copy _data
-  var top-addr/ecx: (addr int) <- get self, top
-  var i/eax: int <- copy 0
-  {
-    compare i, *top-addr
-    break-if->=
-    var g/edx: (addr grapheme) <- index data, i
-    write-grapheme out, *g
-    i <- increment
-    loop
-  }
-}
-
-# dump stack from top to bottom
-fn emit-stack-from-top _self: (addr grapheme-stack), out: (addr stream byte) {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var data-ah/edi: (addr handle array grapheme) <- get self, data
-  var _data/eax: (addr array grapheme) <- lookup *data-ah
-  var data/edi: (addr array grapheme) <- copy _data
-  var top-addr/ecx: (addr int) <- get self, top
-  var i/eax: int <- copy *top-addr
-  i <- decrement
-  {
-    compare i, 0
-    break-if-<
-    var g/edx: (addr grapheme) <- index data, i
-    write-grapheme out, *g
-    i <- decrement
-    loop
-  }
-}
-
-fn word-at-gap _self: (addr gap-buffer), out: (addr stream byte) {
-  var self/esi: (addr gap-buffer) <- copy _self
-  clear-stream out
-  {
-    var g/eax: grapheme <- grapheme-at-gap self
-    var at-word?/eax: boolean <- is-ascii-word-grapheme? g
-    compare at-word?, 0/false
-    break-if-!=
-    return
-  }
-  var left/ecx: (addr grapheme-stack) <- get self, left
-  var left-index/eax: int <- top-most-word left
-  emit-stack-from-index left, left-index, out
-  var right/ecx: (addr grapheme-stack) <- get self, right
-  var right-index/eax: int <- top-most-word right
-  emit-stack-to-index right, right-index, out
-}
-
-fn test-word-at-gap-single-word-with-gap-at-end {
-  var _g: gap-buffer
-  var g/esi: (addr gap-buffer) <- address _g
-  initialize-gap-buffer-with g, "abc"
-  # gap is at end (right is empty)
-  var out-storage: (stream byte 0x10)
-  var out/eax: (addr stream byte) <- address out-storage
-  word-at-gap g, out
-  check-stream-equal out, "abc", "F - test-word-at-gap-single-word-with-gap-at-end"
-}
-
-fn test-word-at-gap-single-word-with-gap-at-start {
-  var _g: gap-buffer
-  var g/esi: (addr gap-buffer) <- address _g
-  initialize-gap-buffer-with g, "abc"
-  gap-to-start g
-  #
-  var out-storage: (stream byte 0x10)
-  var out/eax: (addr stream byte) <- address out-storage
-  word-at-gap g, out
-  check-stream-equal out, "abc", "F - test-word-at-gap-single-word-with-gap-at-start"
-}
-
-fn test-word-at-gap-multiple-words-with-gap-at-non-word-grapheme-at-end {
-  var _g: gap-buffer
-  var g/esi: (addr gap-buffer) <- address _g
-  initialize-gap-buffer-with g, "abc "
-  # gap is at end (right is empty)
-  var out-storage: (stream byte 0x10)
-  var out/eax: (addr stream byte) <- address out-storage
-  word-at-gap g, out
-  check-stream-equal out, "", "F - test-word-at-gap-multiple-words-with-gap-at-non-word-grapheme-at-end"
-}
-
-fn test-word-at-gap-multiple-words-with-gap-at-non-word-grapheme-at-start {
-  var _g: gap-buffer
-  var g/esi: (addr gap-buffer) <- address _g
-  initialize-gap-buffer-with g, " abc"
-  gap-to-start g
-  #
-  var out-storage: (stream byte 0x10)
-  var out/eax: (addr stream byte) <- address out-storage
-  word-at-gap g, out
-  check-stream-equal out, "", "F - test-word-at-gap-multiple-words-with-gap-at-non-word-grapheme-at-start"
-}
-
-fn test-word-at-gap-multiple-words-with-gap-at-end {
-  var _g: gap-buffer
-  var g/esi: (addr gap-buffer) <- address _g
-  initialize-gap-buffer-with g, "a bc d"
-  # gap is at end (right is empty)
-  var out-storage: (stream byte 0x10)
-  var out/eax: (addr stream byte) <- address out-storage
-  word-at-gap g, out
-  check-stream-equal out, "d", "F - test-word-at-gap-multiple-words-with-gap-at-end"
-}
-
-fn test-word-at-gap-multiple-words-with-gap-at-initial-word {
-  var _g: gap-buffer
-  var g/esi: (addr gap-buffer) <- address _g
-  initialize-gap-buffer-with g, "a bc d"
-  gap-to-start g
-  #
-  var out-storage: (stream byte 0x10)
-  var out/eax: (addr stream byte) <- address out-storage
-  word-at-gap g, out
-  check-stream-equal out, "a", "F - test-word-at-gap-multiple-words-with-gap-at-initial-word"
-}
-
-fn test-word-at-gap-multiple-words-with-gap-at-final-word {
-  var _g: gap-buffer
-  var g/esi: (addr gap-buffer) <- address _g
-  initialize-gap-buffer-with g, "a bc d"
-  var dummy/eax: grapheme <- gap-left g
-  # gap is at final word
-  var out-storage: (stream byte 0x10)
-  var out/eax: (addr stream byte) <- address out-storage
-  word-at-gap g, out
-  check-stream-equal out, "d", "F - test-word-at-gap-multiple-words-with-gap-at-final-word"
-}
-
-fn test-word-at-gap-multiple-words-with-gap-at-final-non-word {
-  var _g: gap-buffer
-  var g/esi: (addr gap-buffer) <- address _g
-  initialize-gap-buffer-with g, "abc "
-  var dummy/eax: grapheme <- gap-left g
-  # gap is at final word
-  var out-storage: (stream byte 0x10)
-  var out/eax: (addr stream byte) <- address out-storage
-  word-at-gap g, out
-  check-stream-equal out, "", "F - test-word-at-gap-multiple-words-with-gap-at-final-non-word"
-}
-
-fn grapheme-at-gap _self: (addr gap-buffer) -> _/eax: grapheme {
-  # send top of right most of the time
-  var self/esi: (addr gap-buffer) <- copy _self
-  var right/edi: (addr grapheme-stack) <- get self, right
-  var data-ah/eax: (addr handle array grapheme) <- get right, data
-  var data/eax: (addr array grapheme) <- lookup *data-ah
-  var top-addr/ecx: (addr int) <- get right, top
-  {
-    compare *top-addr, 0
-    break-if-<=
-    var top/ecx: int <- copy *top-addr
-    top <- decrement
-    var result/eax: (addr grapheme) <- index data, top
-    return *result
-  }
-  # send top of left only if right is empty
-  var left/edi: (addr grapheme-stack) <- get self, left
-  var data-ah/eax: (addr handle array grapheme) <- get left, data
-  var data/eax: (addr array grapheme) <- lookup *data-ah
-  var top-addr/ecx: (addr int) <- get left, top
-  {
-    compare *top-addr, 0
-    break-if-<=
-    var top/ecx: int <- copy *top-addr
-    top <- decrement
-    var result/eax: (addr grapheme) <- index data, top
-    return *result
-  }
-  # send null if everything is empty
-  return 0
-}
-
-fn top-most-word _self: (addr grapheme-stack) -> _/eax: int {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var data-ah/edi: (addr handle array grapheme) <- get self, data
-  var _data/eax: (addr array grapheme) <- lookup *data-ah
-  var data/edi: (addr array grapheme) <- copy _data
-  var top-addr/ecx: (addr int) <- get self, top
-  var i/ebx: int <- copy *top-addr
-  i <- decrement
-  {
-    compare i, 0
-    break-if-<
-    var g/edx: (addr grapheme) <- index data, i
-    var is-word?/eax: boolean <- is-ascii-word-grapheme? *g
-    compare is-word?, 0/false
-    break-if-=
-    i <- decrement
-    loop
-  }
-  i <- increment
-  return i
-}
-
-fn emit-stack-from-index _self: (addr grapheme-stack), start: int, out: (addr stream byte) {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var data-ah/edi: (addr handle array grapheme) <- get self, data
-  var _data/eax: (addr array grapheme) <- lookup *data-ah
-  var data/edi: (addr array grapheme) <- copy _data
-  var top-addr/ecx: (addr int) <- get self, top
-  var i/eax: int <- copy start
-  {
-    compare i, *top-addr
-    break-if->=
-    var g/edx: (addr grapheme) <- index data, i
-    write-grapheme out, *g
-    i <- increment
-    loop
-  }
-}
-
-fn emit-stack-to-index _self: (addr grapheme-stack), end: int, out: (addr stream byte) {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var data-ah/edi: (addr handle array grapheme) <- get self, data
-  var _data/eax: (addr array grapheme) <- lookup *data-ah
-  var data/edi: (addr array grapheme) <- copy _data
-  var top-addr/ecx: (addr int) <- get self, top
-  var i/eax: int <- copy *top-addr
-  i <- decrement
-  {
-    compare i, 0
-    break-if-<
-    compare i, end
-    break-if-<
-    var g/edx: (addr grapheme) <- index data, i
-    write-grapheme out, *g
-    i <- decrement
-    loop
-  }
-}
-
-fn is-ascii-word-grapheme? g: grapheme -> _/eax: boolean {
-  compare g, 0x21/!
-  {
-    break-if-!=
-    return 1/true
-  }
-  compare g, 0x30/0
-  {
-    break-if->=
-    return 0/false
-  }
-  compare g, 0x39/9
-  {
-    break-if->
-    return 1/true
-  }
-  compare g, 0x3f/?
-  {
-    break-if-!=
-    return 1/true
-  }
-  compare g, 0x41/A
-  {
-    break-if->=
-    return 0/false
-  }
-  compare g, 0x5a/Z
-  {
-    break-if->
-    return 1/true
-  }
-  compare g, 0x5f/_
-  {
-    break-if-!=
-    return 1/true
-  }
-  compare g, 0x61/a
-  {
-    break-if->=
-    return 0/false
-  }
-  compare g, 0x7a/z
-  {
-    break-if->
-    return 1/true
-  }
-  return 0/false
-}
-
-# We implicitly render everything editable in a single color, and assume the
-# cursor is a single other color.
-fn render-gap-buffer-wrapping-right-then-down screen: (addr screen), _gap: (addr gap-buffer), xmin: int, ymin: int, xmax: int, ymax: int, render-cursor?: boolean, color: int, background-color: int -> _/eax: int, _/ecx: int {
-  var gap/esi: (addr gap-buffer) <- copy _gap
-  var left/edx: (addr grapheme-stack) <- get gap, left
-  var highlight-matching-open-paren?/ebx: boolean <- copy 0/false
-  var matching-open-paren-depth/edi: int <- copy 0
-  highlight-matching-open-paren?, matching-open-paren-depth <- highlight-matching-open-paren? gap, render-cursor?
-  var x2/eax: int <- copy 0
-  var y2/ecx: int <- copy 0
-  x2, y2 <- render-stack-from-bottom-wrapping-right-then-down screen, left, xmin, ymin, xmax, ymax, xmin, ymin, highlight-matching-open-paren?, matching-open-paren-depth, color, background-color
-  var right/edx: (addr grapheme-stack) <- get gap, right
-  x2, y2 <- render-stack-from-top-wrapping-right-then-down screen, right, xmin, ymin, xmax, ymax, x2, y2, render-cursor?, color, background-color
-  # decide whether we still need to print a cursor
-  var fg/edi: int <- copy color
-  var bg/ebx: int <- copy background-color
-  compare render-cursor?, 0/false
-  {
-    break-if-=
-    # if the right side is empty, grapheme stack didn't print the cursor
-    var empty?/eax: boolean <- grapheme-stack-empty? right
-    compare empty?, 0/false
-    break-if-=
-    # swap foreground and background
-    fg <- copy background-color
-    bg <- copy color
-  }
-  # print a grapheme either way so that cursor position doesn't affect printed width
-  var space/edx: grapheme <- copy 0x20
-  x2, y2 <- render-grapheme screen, space, xmin, ymin, xmax, ymax, x2, y2, fg, bg
-  return x2, y2
-}
-
-fn render-gap-buffer screen: (addr screen), gap: (addr gap-buffer), x: int, y: int, render-cursor?: boolean, color: int, background-color: int -> _/eax: int {
-  var _width/eax: int <- copy 0
-  var _height/ecx: int <- copy 0
-  _width, _height <- screen-size screen
-  var width/edx: int <- copy _width
-  var height/ebx: int <- copy _height
-  var x2/eax: int <- copy 0
-  var y2/ecx: int <- copy 0
-  x2, y2 <- render-gap-buffer-wrapping-right-then-down screen, gap, x, y, width, height, render-cursor?, color, background-color
-  return x2  # y2? yolo
-}
-
-fn gap-buffer-length _gap: (addr gap-buffer) -> _/eax: int {
-  var gap/esi: (addr gap-buffer) <- copy _gap
-  var left/eax: (addr grapheme-stack) <- get gap, left
-  var tmp/eax: (addr int) <- get left, top
-  var left-length/ecx: int <- copy *tmp
-  var right/esi: (addr grapheme-stack) <- get gap, right
-  tmp <- get right, top
-  var result/eax: int <- copy *tmp
-  result <- add left-length
-  return result
-}
-
-fn add-grapheme-at-gap _self: (addr gap-buffer), g: grapheme {
-  var self/esi: (addr gap-buffer) <- copy _self
-  var left/eax: (addr grapheme-stack) <- get self, left
-  push-grapheme-stack left, g
-}
-
-fn add-code-point-at-gap self: (addr gap-buffer), c: code-point {
-  var g/eax: grapheme <- copy c
-  add-grapheme-at-gap self, g
-}
-
-fn gap-to-start self: (addr gap-buffer) {
-  {
-    var curr/eax: grapheme <- gap-left self
-    compare curr, -1
-    loop-if-!=
-  }
-}
-
-fn gap-to-end self: (addr gap-buffer) {
-  {
-    var curr/eax: grapheme <- gap-right self
-    compare curr, -1
-    loop-if-!=
-  }
-}
-
-fn gap-at-start? _self: (addr gap-buffer) -> _/eax: boolean {
-  var self/esi: (addr gap-buffer) <- copy _self
-  var left/eax: (addr grapheme-stack) <- get self, left
-  var result/eax: boolean <- grapheme-stack-empty? left
-  return result
-}
-
-fn gap-at-end? _self: (addr gap-buffer) -> _/eax: boolean {
-  var self/esi: (addr gap-buffer) <- copy _self
-  var right/eax: (addr grapheme-stack) <- get self, right
-  var result/eax: boolean <- grapheme-stack-empty? right
-  return result
-}
-
-fn gap-right _self: (addr gap-buffer) -> _/eax: grapheme {
-  var self/esi: (addr gap-buffer) <- copy _self
-  var g/eax: grapheme <- copy 0
-  var right/ecx: (addr grapheme-stack) <- get self, right
-  g <- pop-grapheme-stack right
-  compare g, -1
-  {
-    break-if-=
-    var left/ecx: (addr grapheme-stack) <- get self, left
-    push-grapheme-stack left, g
-  }
-  return g
-}
-
-fn gap-left _self: (addr gap-buffer) -> _/eax: grapheme {
-  var self/esi: (addr gap-buffer) <- copy _self
-  var g/eax: grapheme <- copy 0
-  {
-    var left/ecx: (addr grapheme-stack) <- get self, left
-    g <- pop-grapheme-stack left
-  }
-  compare g, -1
-  {
-    break-if-=
-    var right/ecx: (addr grapheme-stack) <- get self, right
-    push-grapheme-stack right, g
-  }
-  return g
-}
-
-fn index-of-gap _self: (addr gap-buffer) -> _/eax: int {
-  var self/eax: (addr gap-buffer) <- copy _self
-  var left/eax: (addr grapheme-stack) <- get self, left
-  var top-addr/eax: (addr int) <- get left, top
-  var result/eax: int <- copy *top-addr
-  return result
-}
-
-fn first-grapheme-in-gap-buffer _self: (addr gap-buffer) -> _/eax: grapheme {
-  var self/esi: (addr gap-buffer) <- copy _self
-  # try to read from left
-  var left/eax: (addr grapheme-stack) <- get self, left
-  var top-addr/ecx: (addr int) <- get left, top
-  compare *top-addr, 0
-  {
-    break-if-<=
-    var data-ah/eax: (addr handle array grapheme) <- get left, data
-    var data/eax: (addr array grapheme) <- lookup *data-ah
-    var result-addr/eax: (addr grapheme) <- index data, 0
-    return *result-addr
-  }
-  # try to read from right
-  var right/eax: (addr grapheme-stack) <- get self, right
-  top-addr <- get right, top
-  compare *top-addr, 0
-  {
-    break-if-<=
-    var data-ah/eax: (addr handle array grapheme) <- get right, data
-    var data/eax: (addr array grapheme) <- lookup *data-ah
-    var top/ecx: int <- copy *top-addr
-    top <- decrement
-    var result-addr/eax: (addr grapheme) <- index data, top
-    return *result-addr
-  }
-  # give up
-  return -1
-}
-
-fn grapheme-before-cursor-in-gap-buffer _self: (addr gap-buffer) -> _/eax: grapheme {
-  var self/esi: (addr gap-buffer) <- copy _self
-  # try to read from left
-  var left/ecx: (addr grapheme-stack) <- get self, left
-  var top-addr/edx: (addr int) <- get left, top
-  compare *top-addr, 0
-  {
-    break-if-<=
-    var result/eax: grapheme <- pop-grapheme-stack left
-    push-grapheme-stack left, result
-    return result
-  }
-  # give up
-  return -1
-}
-
-fn delete-before-gap _self: (addr gap-buffer) {
-  var self/eax: (addr gap-buffer) <- copy _self
-  var left/eax: (addr grapheme-stack) <- get self, left
-  var dummy/eax: grapheme <- pop-grapheme-stack left
-}
-
-fn pop-after-gap _self: (addr gap-buffer) -> _/eax: grapheme {
-  var self/eax: (addr gap-buffer) <- copy _self
-  var right/eax: (addr grapheme-stack) <- get self, right
-  var result/eax: grapheme <- pop-grapheme-stack right
-  return result
-}
-
-fn gap-buffer-equal? _self: (addr gap-buffer), s: (addr array byte) -> _/eax: boolean {
-  var self/esi: (addr gap-buffer) <- copy _self
-  # complication: graphemes may be multiple bytes
-  # so don't rely on length
-  # instead turn the expected result into a stream and arrange to read from it in order
-  var stream-storage: (stream byte 0x10/capacity)
-  var expected-stream/ecx: (addr stream byte) <- address stream-storage
-  write expected-stream, s
-  # compare left
-  var left/edx: (addr grapheme-stack) <- get self, left
-  var result/eax: boolean <- prefix-match? left, expected-stream
-  compare result, 0/false
-  {
-    break-if-!=
-    return result
-  }
-  # compare right
-  var right/edx: (addr grapheme-stack) <- get self, right
-  result <- suffix-match? right, expected-stream
-  compare result, 0/false
-  {
-    break-if-!=
-    return result
-  }
-  # ensure there's nothing left over
-  result <- stream-empty? expected-stream
-  return result
-}
-
-fn test-gap-buffer-equal-from-end {
-  var _g: gap-buffer
-  var g/esi: (addr gap-buffer) <- address _g
-  initialize-gap-buffer g, 0x10
-  #
-  add-code-point-at-gap g, 0x61/a
-  add-code-point-at-gap g, 0x61/a
-  add-code-point-at-gap g, 0x61/a
-  # gap is at end (right is empty)
-  var result/eax: boolean <- gap-buffer-equal? g, "aaa"
-  check result, "F - test-gap-buffer-equal-from-end"
-}
-
-fn test-gap-buffer-equal-from-middle {
-  var _g: gap-buffer
-  var g/esi: (addr gap-buffer) <- address _g
-  initialize-gap-buffer g, 0x10
-  #
-  add-code-point-at-gap g, 0x61/a
-  add-code-point-at-gap g, 0x61/a
-  add-code-point-at-gap g, 0x61/a
-  var dummy/eax: grapheme <- gap-left g
-  # gap is in the middle
-  var result/eax: boolean <- gap-buffer-equal? g, "aaa"
-  check result, "F - test-gap-buffer-equal-from-middle"
-}
-
-fn test-gap-buffer-equal-from-start {
-  var _g: gap-buffer
-  var g/esi: (addr gap-buffer) <- address _g
-  initialize-gap-buffer g, 0x10
-  #
-  add-code-point-at-gap g, 0x61/a
-  add-code-point-at-gap g, 0x61/a
-  add-code-point-at-gap g, 0x61/a
-  var dummy/eax: grapheme <- gap-left g
-  dummy <- gap-left g
-  dummy <- gap-left g
-  # gap is at the start
-  var result/eax: boolean <- gap-buffer-equal? g, "aaa"
-  check result, "F - test-gap-buffer-equal-from-start"
-}
-
-fn test-gap-buffer-equal-fails {
-  # g = "aaa"
-  var _g: gap-buffer
-  var g/esi: (addr gap-buffer) <- address _g
-  initialize-gap-buffer g, 0x10
-  add-code-point-at-gap g, 0x61/a
-  add-code-point-at-gap g, 0x61/a
-  add-code-point-at-gap g, 0x61/a
-  #
-  var result/eax: boolean <- gap-buffer-equal? g, "aa"
-  check-not result, "F - test-gap-buffer-equal-fails"
-}
-
-fn gap-buffers-equal? self: (addr gap-buffer), g: (addr gap-buffer) -> _/eax: boolean {
-  var tmp/eax: int <- gap-buffer-length self
-  var len/ecx: int <- copy tmp
-  var leng/eax: int <- gap-buffer-length g
-  compare len, leng
-  {
-    break-if-=
-    return 0/false
-  }
-  var i/edx: int <- copy 0
-  {
-    compare i, len
-    break-if->=
-    {
-      var tmp/eax: grapheme <- gap-index self, i
-      var curr/ecx: grapheme <- copy tmp
-      var currg/eax: grapheme <- gap-index g, i
-      compare curr, currg
-      break-if-=
-      return 0/false
-    }
-    i <- increment
-    loop
-  }
-  return 1/true
-}
-
-fn gap-index _self: (addr gap-buffer), _n: int -> _/eax: grapheme {
-  var self/esi: (addr gap-buffer) <- copy _self
-  var n/ebx: int <- copy _n
-  # if n < left->length, index into left
-  var left/edi: (addr grapheme-stack) <- get self, left
-  var left-len-a/edx: (addr int) <- get left, top
-  compare n, *left-len-a
-  {
-    break-if->=
-    var data-ah/eax: (addr handle array grapheme) <- get left, data
-    var data/eax: (addr array grapheme) <- lookup *data-ah
-    var result/eax: (addr grapheme) <- index data, n
-    return *result
-  }
-  # shrink n
-  n <- subtract *left-len-a
-  # if n < right->length, index into right
-  var right/edi: (addr grapheme-stack) <- get self, right
-  var right-len-a/edx: (addr int) <- get right, top
-  compare n, *right-len-a
-  {
-    break-if->=
-    var data-ah/eax: (addr handle array grapheme) <- get right, data
-    var data/eax: (addr array grapheme) <- lookup *data-ah
-    # idx = right->len - n - 1
-    var idx/ebx: int <- copy n
-    idx <- subtract *right-len-a
-    idx <- negate
-    idx <- subtract 1
-    var result/eax: (addr grapheme) <- index data, idx
-    return *result
-  }
-  # error
-  abort "gap-index: out of bounds"
-  return 0
-}
-
-fn test-gap-buffers-equal? {
-  var _a: gap-buffer
-  var a/esi: (addr gap-buffer) <- address _a
-  initialize-gap-buffer-with a, "abc"
-  var _b: gap-buffer
-  var b/edi: (addr gap-buffer) <- address _b
-  initialize-gap-buffer-with b, "abc"
-  var _c: gap-buffer
-  var c/ebx: (addr gap-buffer) <- address _c
-  initialize-gap-buffer-with c, "ab"
-  var _d: gap-buffer
-  var d/edx: (addr gap-buffer) <- address _d
-  initialize-gap-buffer-with d, "abd"
-  #
-  var result/eax: boolean <- gap-buffers-equal? a, a
-  check result, "F - test-gap-buffers-equal? - reflexive"
-  result <- gap-buffers-equal? a, b
-  check result, "F - test-gap-buffers-equal? - equal"
-  # length not equal
-  result <- gap-buffers-equal? a, c
-  check-not result, "F - test-gap-buffers-equal? - not equal"
-  # contents not equal
-  result <- gap-buffers-equal? a, d
-  check-not result, "F - test-gap-buffers-equal? - not equal 2"
-  result <- gap-buffers-equal? d, a
-  check-not result, "F - test-gap-buffers-equal? - not equal 3"
-}
-
-fn test-gap-buffer-index {
-  var gap-storage: gap-buffer
-  var gap/esi: (addr gap-buffer) <- address gap-storage
-  initialize-gap-buffer-with gap, "abc"
-  # gap is at end, all contents are in left
-  var g/eax: grapheme <- gap-index gap, 0
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0x61/a, "F - test-gap-index/left-1"
-  var g/eax: grapheme <- gap-index gap, 1
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0x62/b, "F - test-gap-index/left-2"
-  var g/eax: grapheme <- gap-index gap, 2
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0x63/c, "F - test-gap-index/left-3"
-  # now check when everything is to the right
-  gap-to-start gap
-  rewind-gap-buffer gap
-  var g/eax: grapheme <- gap-index gap, 0
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0x61/a, "F - test-gap-index/right-1"
-  var g/eax: grapheme <- gap-index gap, 1
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0x62/b, "F - test-gap-index/right-2"
-  var g/eax: grapheme <- gap-index gap, 2
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0x63/c, "F - test-gap-index/right-3"
-}
-
-fn copy-gap-buffer _src-ah: (addr handle gap-buffer), _dest-ah: (addr handle gap-buffer) {
-  # obtain src-a, dest-a
-  var src-ah/eax: (addr handle gap-buffer) <- copy _src-ah
-  var _src-a/eax: (addr gap-buffer) <- lookup *src-ah
-  var src-a/esi: (addr gap-buffer) <- copy _src-a
-  var dest-ah/eax: (addr handle gap-buffer) <- copy _dest-ah
-  var _dest-a/eax: (addr gap-buffer) <- lookup *dest-ah
-  var dest-a/edi: (addr gap-buffer) <- copy _dest-a
-  # copy left grapheme-stack
-  var src/ecx: (addr grapheme-stack) <- get src-a, left
-  var dest/edx: (addr grapheme-stack) <- get dest-a, left
-  copy-grapheme-stack src, dest
-  # copy right grapheme-stack
-  src <- get src-a, right
-  dest <- get dest-a, right
-  copy-grapheme-stack src, dest
-}
-
-fn gap-buffer-is-decimal-integer? _self: (addr gap-buffer) -> _/eax: boolean {
-  var self/esi: (addr gap-buffer) <- copy _self
-  var curr/ecx: (addr grapheme-stack) <- get self, left
-  var result/eax: boolean <- grapheme-stack-is-decimal-integer? curr
-  {
-    compare result, 0/false
-    break-if-=
-    curr <- get self, right
-    result <- grapheme-stack-is-decimal-integer? curr
-  }
-  return result
-}
-
-fn test-render-gap-buffer-without-cursor {
-  # setup
-  var gap-storage: gap-buffer
-  var gap/esi: (addr gap-buffer) <- address gap-storage
-  initialize-gap-buffer-with gap, "abc"
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/edi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-gap-buffer screen, gap, 0/x, 0/y, 0/no-cursor, 3/fg, 0xc5/bg=blue-bg
-  check-screen-row screen, 0/y, "abc ", "F - test-render-gap-buffer-without-cursor"
-  check-ints-equal x, 4, "F - test-render-gap-buffer-without-cursor: result"
-                                                                # abc
-  check-background-color-in-screen-row screen, 3/bg=reverse, 0/y, "    ", "F - test-render-gap-buffer-without-cursor: bg"
-}
-
-fn test-render-gap-buffer-with-cursor-at-end {
-  # setup
-  var gap-storage: gap-buffer
-  var gap/esi: (addr gap-buffer) <- address gap-storage
-  initialize-gap-buffer-with gap, "abc"
-  gap-to-end gap
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/edi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-gap-buffer screen, gap, 0/x, 0/y, 1/show-cursor, 3/fg, 0xc5/bg=blue-bg
-  check-screen-row screen, 0/y, "abc ", "F - test-render-gap-buffer-with-cursor-at-end"
-  # we've drawn one extra grapheme for the cursor
-  check-ints-equal x, 4, "F - test-render-gap-buffer-with-cursor-at-end: result"
-                                                                # abc
-  check-background-color-in-screen-row screen, 3/bg=reverse, 0/y, "   |", "F - test-render-gap-buffer-with-cursor-at-end: bg"
-}
-
-fn test-render-gap-buffer-with-cursor-in-middle {
-  # setup
-  var gap-storage: gap-buffer
-  var gap/esi: (addr gap-buffer) <- address gap-storage
-  initialize-gap-buffer-with gap, "abc"
-  gap-to-end gap
-  var dummy/eax: grapheme <- gap-left gap
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/edi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-gap-buffer screen, gap, 0/x, 0/y, 1/show-cursor, 3/fg, 0xc5/bg=blue-bg
-  check-screen-row screen, 0/y, "abc ", "F - test-render-gap-buffer-with-cursor-in-middle"
-  check-ints-equal x, 4, "F - test-render-gap-buffer-with-cursor-in-middle: result"
-                                                                # abc
-  check-background-color-in-screen-row screen, 3/bg=reverse, 0/y, "  | ", "F - test-render-gap-buffer-with-cursor-in-middle: bg"
-}
-
-fn test-render-gap-buffer-with-cursor-at-start {
-  var gap-storage: gap-buffer
-  var gap/esi: (addr gap-buffer) <- address gap-storage
-  initialize-gap-buffer-with gap, "abc"
-  gap-to-start gap
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/edi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-gap-buffer screen, gap, 0/x, 0/y, 1/show-cursor, 3/fg, 0xc5/bg=blue-bg
-  check-screen-row screen, 0/y, "abc ", "F - test-render-gap-buffer-with-cursor-at-start"
-  check-ints-equal x, 4, "F - test-render-gap-buffer-with-cursor-at-start: result"
-                                                                # abc
-  check-background-color-in-screen-row screen, 3/bg=reverse, 0/y, "|   ", "F - test-render-gap-buffer-with-cursor-at-start: bg"
-}
-
-fn test-render-gap-buffer-highlight-matching-close-paren {
-  var gap-storage: gap-buffer
-  var gap/esi: (addr gap-buffer) <- address gap-storage
-  initialize-gap-buffer-with gap, "(a)"
-  gap-to-start gap
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/edi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-gap-buffer screen, gap, 0/x, 0/y, 1/show-cursor, 3/fg, 0xc5/bg=blue-bg
-  check-screen-row                     screen, 0/y,                   "(a) ", "F - test-render-gap-buffer-highlight-matching-close-paren"
-  check-ints-equal x, 4, "F - test-render-gap-buffer-highlight-matching-close-paren: result"
-  check-background-color-in-screen-row screen, 3/bg=reverse,      0/y, "|   ", "F - test-render-gap-buffer-highlight-matching-close-paren: cursor"
-  check-screen-row-in-color            screen, 0xf/fg=highlight, 0/y, "  ) ", "F - test-render-gap-buffer-highlight-matching-close-paren: matching paren"
-}
-
-fn test-render-gap-buffer-highlight-matching-open-paren {
-  var gap-storage: gap-buffer
-  var gap/esi: (addr gap-buffer) <- address gap-storage
-  initialize-gap-buffer-with gap, "(a)"
-  gap-to-end gap
-  var dummy/eax: grapheme <- gap-left gap
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/edi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-gap-buffer screen, gap, 0/x, 0/y, 1/show-cursor, 3/fg, 0xc5/bg=blue-bg
-  check-screen-row                     screen, 0/y,                   "(a) ", "F - test-render-gap-buffer-highlight-matching-open-paren"
-  check-ints-equal x, 4, "F - test-render-gap-buffer-highlight-matching-open-paren: result"
-  check-background-color-in-screen-row screen, 3/bg=reverse,      0/y, "  | ", "F - test-render-gap-buffer-highlight-matching-open-paren: cursor"
-  check-screen-row-in-color            screen, 0xf/fg=highlight, 0/y, "(   ", "F - test-render-gap-buffer-highlight-matching-open-paren: matching paren"
-}
-
-fn test-render-gap-buffer-highlight-matching-open-paren-of-end {
-  var gap-storage: gap-buffer
-  var gap/esi: (addr gap-buffer) <- address gap-storage
-  initialize-gap-buffer-with gap, "(a)"
-  gap-to-end gap
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/edi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-gap-buffer screen, gap, 0/x, 0/y, 1/show-cursor, 3/fg, 0xc5/bg=blue-bg
-  check-screen-row                     screen, 0/y,                   "(a) ", "F - test-render-gap-buffer-highlight-matching-open-paren-of-end"
-  check-ints-equal x, 4, "F - test-render-gap-buffer-highlight-matching-open-paren-of-end: result"
-  check-background-color-in-screen-row screen, 3/bg=reverse,      0/y, "   |", "F - test-render-gap-buffer-highlight-matching-open-paren-of-end: cursor"
-  check-screen-row-in-color            screen, 0xf/fg=highlight, 0/y, "(   ", "F - test-render-gap-buffer-highlight-matching-open-paren-of-end: matching paren"
-}
-
-# should I highlight a matching open paren? And if so, at what depth from top of left?
-# basically there are two cases to disambiguate here:
-#   Usually the cursor is at top of right. Highlight first '(' at depth 0 from top of left.
-#   If right is empty, match the ')' _before_ cursor. Highlight first '(' at depth _1_ from top of left.
-fn highlight-matching-open-paren? _gap: (addr gap-buffer), render-cursor?: boolean -> _/ebx: boolean, _/edi: int {
-  # if not rendering cursor, return
-  compare render-cursor?, 0/false
-  {
-    break-if-!=
-    return 0/false, 0
-  }
-  var gap/esi: (addr gap-buffer) <- copy _gap
-  var stack/edi: (addr grapheme-stack) <- get gap, right
-  var top-addr/eax: (addr int) <- get stack, top
-  var top-index/ecx: int <- copy *top-addr
-  compare top-index, 0
-  {
-    break-if->
-    # if cursor at end, return (char before cursor == ')', 1)
-    stack <- get gap, left
-    top-addr <- get stack, top
-    top-index <- copy *top-addr
-    compare top-index, 0
-    {
-      break-if->
-      return 0/false, 0
-    }
-    top-index <- decrement
-    var data-ah/eax: (addr handle array grapheme) <- get stack, data
-    var data/eax: (addr array grapheme) <- lookup *data-ah
-    var g/eax: (addr grapheme) <- index data, top-index
-    compare *g, 0x29/close-paren
-    {
-      break-if-=
-      return 0/false, 0
-    }
-    return 1/true, 1
-  }
-  # cursor is not at end; return (char at cursor == ')')
-  top-index <- decrement
-  var data-ah/eax: (addr handle array grapheme) <- get stack, data
-  var data/eax: (addr array grapheme) <- lookup *data-ah
-  var g/eax: (addr grapheme) <- index data, top-index
-  compare *g, 0x29/close-paren
-  {
-    break-if-=
-    return 0/false, 0
-  }
-  return 1/true, 0
-}
-
-fn test-highlight-matching-open-paren {
-  var gap-storage: gap-buffer
-  var gap/esi: (addr gap-buffer) <- address gap-storage
-  initialize-gap-buffer-with gap, "(a)"
-  gap-to-end gap
-  var highlight-matching-open-paren?/ebx: boolean <- copy 0/false
-  var open-paren-depth/edi: int <- copy 0
-  highlight-matching-open-paren?, open-paren-depth <- highlight-matching-open-paren? gap, 0/no-cursor
-  check-not highlight-matching-open-paren?, "F - test-highlight-matching-open-paren: no cursor"
-  highlight-matching-open-paren?, open-paren-depth <- highlight-matching-open-paren? gap, 1/render-cursor
-  check highlight-matching-open-paren?, "F - test-highlight-matching-open-paren: at end immediately after ')'"
-  check-ints-equal open-paren-depth, 1, "F - test-highlight-matching-open-paren: depth at end immediately after ')'"
-  var dummy/eax: grapheme <- gap-left gap
-  highlight-matching-open-paren?, open-paren-depth <- highlight-matching-open-paren? gap, 1/render-cursor
-  check highlight-matching-open-paren?, "F - test-highlight-matching-open-paren: on ')'"
-  dummy <- gap-left gap
-  highlight-matching-open-paren?, open-paren-depth <- highlight-matching-open-paren? gap, 1/render-cursor
-  check-not highlight-matching-open-paren?, "F - test-highlight-matching-open-paren: not on ')'"
-}
-
-## some primitives for scanning through a gap buffer
-# don't modify the gap buffer while scanning
-# this includes moving the cursor around
-
-# restart scan without affecting gap-buffer contents
-fn rewind-gap-buffer _self: (addr gap-buffer) {
-  var self/esi: (addr gap-buffer) <- copy _self
-  var dest/eax: (addr int) <- get self, left-read-index
-  copy-to *dest, 0
-  dest <- get self, right-read-index
-  copy-to *dest, 0
-}
-
-fn gap-buffer-scan-done? _self: (addr gap-buffer) -> _/eax: boolean {
-  var self/esi: (addr gap-buffer) <- copy _self
-  # more in left?
-  var left/eax: (addr grapheme-stack) <- get self, left
-  var left-size/eax: int <- grapheme-stack-length left
-  var left-read-index/ecx: (addr int) <- get self, left-read-index
-  compare *left-read-index, left-size
-  {
-    break-if->=
-    return 0/false
-  }
-  # more in right?
-  var right/eax: (addr grapheme-stack) <- get self, right
-  var right-size/eax: int <- grapheme-stack-length right
-  var right-read-index/ecx: (addr int) <- get self, right-read-index
-  compare *right-read-index, right-size
-  {
-    break-if->=
-    return 0/false
-  }
-  #
-  return 1/true
-}
-
-fn peek-from-gap-buffer _self: (addr gap-buffer) -> _/eax: grapheme {
-  var self/esi: (addr gap-buffer) <- copy _self
-  # more in left?
-  var left/ecx: (addr grapheme-stack) <- get self, left
-  var left-size/eax: int <- grapheme-stack-length left
-  var left-read-index-a/edx: (addr int) <- get self, left-read-index
-  compare *left-read-index-a, left-size
-  {
-    break-if->=
-    var left-data-ah/eax: (addr handle array grapheme) <- get left, data
-    var left-data/eax: (addr array grapheme) <- lookup *left-data-ah
-    var left-read-index/ecx: int <- copy *left-read-index-a
-    var result/eax: (addr grapheme) <- index left-data, left-read-index
-    return *result
-  }
-  # more in right?
-  var right/ecx: (addr grapheme-stack) <- get self, right
-  var _right-size/eax: int <- grapheme-stack-length right
-  var right-size/ebx: int <- copy _right-size
-  var right-read-index-a/edx: (addr int) <- get self, right-read-index
-  compare *right-read-index-a, right-size
-  {
-    break-if->=
-    # read the right from reverse
-    var right-data-ah/eax: (addr handle array grapheme) <- get right, data
-    var right-data/eax: (addr array grapheme) <- lookup *right-data-ah
-    var right-read-index/ebx: int <- copy right-size
-    right-read-index <- subtract *right-read-index-a
-    right-read-index <- subtract 1
-    var result/eax: (addr grapheme) <- index right-data, right-read-index
-    return *result
-  }
-  # if we get here there's nothing left
-  return 0/nul
-}
-
-fn read-from-gap-buffer _self: (addr gap-buffer) -> _/eax: grapheme {
-  var self/esi: (addr gap-buffer) <- copy _self
-  # more in left?
-  var left/ecx: (addr grapheme-stack) <- get self, left
-  var left-size/eax: int <- grapheme-stack-length left
-  var left-read-index-a/edx: (addr int) <- get self, left-read-index
-  compare *left-read-index-a, left-size
-  {
-    break-if->=
-    var left-data-ah/eax: (addr handle array grapheme) <- get left, data
-    var left-data/eax: (addr array grapheme) <- lookup *left-data-ah
-    var left-read-index/ecx: int <- copy *left-read-index-a
-    var result/eax: (addr grapheme) <- index left-data, left-read-index
-    increment *left-read-index-a
-    return *result
-  }
-  # more in right?
-  var right/ecx: (addr grapheme-stack) <- get self, right
-  var _right-size/eax: int <- grapheme-stack-length right
-  var right-size/ebx: int <- copy _right-size
-  var right-read-index-a/edx: (addr int) <- get self, right-read-index
-  compare *right-read-index-a, right-size
-  {
-    break-if->=
-    # read the right from reverse
-    var right-data-ah/eax: (addr handle array grapheme) <- get right, data
-    var right-data/eax: (addr array grapheme) <- lookup *right-data-ah
-    var right-read-index/ebx: int <- copy right-size
-    right-read-index <- subtract *right-read-index-a
-    right-read-index <- subtract 1
-    var result/eax: (addr grapheme) <- index right-data, right-read-index
-    increment *right-read-index-a
-    return *result
-  }
-  # if we get here there's nothing left
-  return 0/nul
-}
-
-fn put-back-from-gap-buffer _self: (addr gap-buffer) {
-  var self/esi: (addr gap-buffer) <- copy _self
-  # more in right?
-  var right/eax: (addr grapheme-stack) <- get self, right
-  var right-size/eax: int <- grapheme-stack-length right
-  var right-read-index-a/eax: (addr int) <- get self, right-read-index
-  compare *right-read-index-a, 0
-  {
-    break-if-<=
-    decrement *right-read-index-a
-    return
-  }
-  # more in left?
-  var left/eax: (addr grapheme-stack) <- get self, left
-  var left-size/eax: int <- grapheme-stack-length left
-  var left-read-index-a/eax: (addr int) <- get self, left-read-index
-  decrement *left-read-index-a
-}
-
-fn test-read-from-gap-buffer {
-  var gap-storage: gap-buffer
-  var gap/esi: (addr gap-buffer) <- address gap-storage
-  initialize-gap-buffer-with gap, "abc"
-  # gap is at end, all contents are in left
-  var done?/eax: boolean <- gap-buffer-scan-done? gap
-  check-not done?, "F - test-read-from-gap-buffer/left-1/done"
-  var g/eax: grapheme <- read-from-gap-buffer gap
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0x61/a, "F - test-read-from-gap-buffer/left-1"
-  var done?/eax: boolean <- gap-buffer-scan-done? gap
-  check-not done?, "F - test-read-from-gap-buffer/left-2/done"
-  var g/eax: grapheme <- read-from-gap-buffer gap
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0x62/b, "F - test-read-from-gap-buffer/left-2"
-  var done?/eax: boolean <- gap-buffer-scan-done? gap
-  check-not done?, "F - test-read-from-gap-buffer/left-3/done"
-  var g/eax: grapheme <- read-from-gap-buffer gap
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0x63/c, "F - test-read-from-gap-buffer/left-3"
-  var done?/eax: boolean <- gap-buffer-scan-done? gap
-  check done?, "F - test-read-from-gap-buffer/left-4/done"
-  var g/eax: grapheme <- read-from-gap-buffer gap
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0/nul, "F - test-read-from-gap-buffer/left-4"
-  # now check when everything is to the right
-  gap-to-start gap
-  rewind-gap-buffer gap
-  var done?/eax: boolean <- gap-buffer-scan-done? gap
-  check-not done?, "F - test-read-from-gap-buffer/right-1/done"
-  var g/eax: grapheme <- read-from-gap-buffer gap
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0x61/a, "F - test-read-from-gap-buffer/right-1"
-  var done?/eax: boolean <- gap-buffer-scan-done? gap
-  check-not done?, "F - test-read-from-gap-buffer/right-2/done"
-  var g/eax: grapheme <- read-from-gap-buffer gap
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0x62/b, "F - test-read-from-gap-buffer/right-2"
-  var done?/eax: boolean <- gap-buffer-scan-done? gap
-  check-not done?, "F - test-read-from-gap-buffer/right-3/done"
-  var g/eax: grapheme <- read-from-gap-buffer gap
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0x63/c, "F - test-read-from-gap-buffer/right-3"
-  var done?/eax: boolean <- gap-buffer-scan-done? gap
-  check done?, "F - test-read-from-gap-buffer/right-4/done"
-  var g/eax: grapheme <- read-from-gap-buffer gap
-  var x/ecx: int <- copy g
-  check-ints-equal x, 0/nul, "F - test-read-from-gap-buffer/right-4"
-}
-
-fn skip-spaces-from-gap-buffer self: (addr gap-buffer) {
-  var done?/eax: boolean <- gap-buffer-scan-done? self
-  compare done?, 0/false
-  break-if-!=
-  var g/eax: grapheme <- peek-from-gap-buffer self
-  {
-    compare g, 0x20/space
-    break-if-=
-    return
-  }
-  g <- read-from-gap-buffer self
-  loop
-}
-
-fn edit-gap-buffer self: (addr gap-buffer), key: grapheme {
-  var g/edx: grapheme <- copy key
-  {
-    compare g, 8/backspace
-    break-if-!=
-    delete-before-gap self
-    return
-  }
-  {
-    compare g, 0x80/left-arrow
-    break-if-!=
-    var dummy/eax: grapheme <- gap-left self
-    return
-  }
-  {
-    compare g, 0x83/right-arrow
-    break-if-!=
-    var dummy/eax: grapheme <- gap-right self
-    return
-  }
-  {
-    compare g, 6/ctrl-f
-    break-if-!=
-    gap-to-start-of-next-word self
-    return
-  }
-  {
-    compare g, 2/ctrl-b
-    break-if-!=
-    gap-to-end-of-previous-word self
-    return
-  }
-  {
-    compare g, 1/ctrl-a
-    break-if-!=
-    gap-to-previous-start-of-line self
-    return
-  }
-  {
-    compare g, 5/ctrl-e
-    break-if-!=
-    gap-to-next-end-of-line self
-    return
-  }
-  {
-    compare g, 0x81/down-arrow
-    break-if-!=
-    gap-down self
-    return
-  }
-  {
-    compare g, 0x82/up-arrow
-    break-if-!=
-    gap-up self
-    return
-  }
-  {
-    compare g, 0x15/ctrl-u
-    break-if-!=
-    clear-gap-buffer self
-    return
-  }
-  {
-    compare g, 9/tab
-    break-if-!=
-    # tab = 2 spaces
-    add-code-point-at-gap self, 0x20/space
-    add-code-point-at-gap self, 0x20/space
-    return
-  }
-  # default: insert character
-  add-grapheme-at-gap self, g
-}
-
-fn gap-to-start-of-next-word self: (addr gap-buffer) {
-  var curr/eax: grapheme <- copy 0
-  # skip to next space
-  {
-    curr <- gap-right self
-    compare curr, -1
-    break-if-=
-    compare curr, 0x20/space
-    break-if-=
-    compare curr, 0xa/newline
-    break-if-=
-    loop
-  }
-  # skip past spaces
-  {
-    curr <- gap-right self
-    compare curr, -1
-    break-if-=
-    compare curr, 0x20/space
-    loop-if-=
-    compare curr, 0xa/space
-    loop-if-=
-    curr <- gap-left self
-    break
-  }
-}
-
-fn gap-to-end-of-previous-word self: (addr gap-buffer) {
-  var curr/eax: grapheme <- copy 0
-  # skip to previous space
-  {
-    curr <- gap-left self
-    compare curr, -1
-    break-if-=
-    compare curr, 0x20/space
-    break-if-=
-    compare curr, 0xa/newline
-    break-if-=
-    loop
-  }
-  # skip past all spaces but one
-  {
-    curr <- gap-left self
-    compare curr, -1
-    break-if-=
-    compare curr, 0x20/space
-    loop-if-=
-    compare curr, 0xa/space
-    loop-if-=
-    curr <- gap-right self
-    break
-  }
-}
-
-fn gap-to-previous-start-of-line self: (addr gap-buffer) {
-  # skip past immediate newline
-  var dummy/eax: grapheme <- gap-left self
-  # skip to previous newline
-  {
-    dummy <- gap-left self
-    {
-      compare dummy, -1
-      break-if-!=
-      return
-    }
-    {
-      compare dummy, 0xa/newline
-      break-if-!=
-      dummy <- gap-right self
-      return
-    }
-    loop
-  }
-}
-
-fn gap-to-next-end-of-line self: (addr gap-buffer) {
-  # skip past immediate newline
-  var dummy/eax: grapheme <- gap-right self
-  # skip to next newline
-  {
-    dummy <- gap-right self
-    {
-      compare dummy, -1
-      break-if-!=
-      return
-    }
-    {
-      compare dummy, 0xa/newline
-      break-if-!=
-      dummy <- gap-left self
-      return
-    }
-    loop
-  }
-}
-
-fn gap-up self: (addr gap-buffer) {
-  # compute column
-  var col/edx: int <- count-columns-to-start-of-line self
-  #
-  gap-to-previous-start-of-line self
-  # skip ahead by up to col on previous line
-  var i/ecx: int <- copy 0
-  {
-    compare i, col
-    break-if->=
-    var curr/eax: grapheme <- gap-right self
-    {
-      compare curr, -1
-      break-if-!=
-      return
-    }
-    compare curr, 0xa/newline
-    {
-      break-if-!=
-      curr <- gap-left self
-      return
-    }
-    i <- increment
-    loop
-  }
-}
-
-fn gap-down self: (addr gap-buffer) {
-  # compute column
-  var col/edx: int <- count-columns-to-start-of-line self
-  # skip to start of next line
-  gap-to-end-of-line self
-  var dummy/eax: grapheme <- gap-right self
-  # skip ahead by up to col on previous line
-  var i/ecx: int <- copy 0
-  {
-    compare i, col
-    break-if->=
-    var curr/eax: grapheme <- gap-right self
-    {
-      compare curr, -1
-      break-if-!=
-      return
-    }
-    compare curr, 0xa/newline
-    {
-      break-if-!=
-      curr <- gap-left self
-      return
-    }
-    i <- increment
-    loop
-  }
-}
-
-fn count-columns-to-start-of-line self: (addr gap-buffer) -> _/edx: int {
-  var count/edx: int <- copy 0
-  var dummy/eax: grapheme <- copy 0
-  # skip to previous newline
-  {
-    dummy <- gap-left self
-    {
-      compare dummy, -1
-      break-if-!=
-      return count
-    }
-    {
-      compare dummy, 0xa/newline
-      break-if-!=
-      dummy <- gap-right self
-      return count
-    }
-    count <- increment
-    loop
-  }
-  return count
-}
-
-fn gap-to-end-of-line self: (addr gap-buffer) {
-  var dummy/eax: grapheme <- copy 0
-  # skip to next newline
-  {
-    dummy <- gap-right self
-    {
-      compare dummy, -1
-      break-if-!=
-      return
-    }
-    {
-      compare dummy, 0xa/newline
-      break-if-!=
-      dummy <- gap-left self
-      return
-    }
-    loop
-  }
-}
diff --git a/browse-slack/grapheme-stack.mu b/browse-slack/grapheme-stack.mu
deleted file mode 100644
index 13f0e31c..00000000
--- a/browse-slack/grapheme-stack.mu
+++ /dev/null
@@ -1,556 +0,0 @@
-# grapheme stacks are the smallest unit of editable text
-
-type grapheme-stack {
-  data: (handle array grapheme)
-  top: int
-}
-
-fn initialize-grapheme-stack _self: (addr grapheme-stack), n: int {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var d/edi: (addr handle array grapheme) <- get self, data
-  populate d, n
-  var top/eax: (addr int) <- get self, top
-  copy-to *top, 0
-}
-
-fn clear-grapheme-stack _self: (addr grapheme-stack) {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var top/eax: (addr int) <- get self, top
-  copy-to *top, 0
-}
-
-fn grapheme-stack-empty? _self: (addr grapheme-stack) -> _/eax: boolean {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var top/eax: (addr int) <- get self, top
-  compare *top, 0
-  {
-    break-if-!=
-    return 1/true
-  }
-  return 0/false
-}
-
-fn grapheme-stack-length _self: (addr grapheme-stack) -> _/eax: int {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var top/eax: (addr int) <- get self, top
-  return *top
-}
-
-fn push-grapheme-stack _self: (addr grapheme-stack), _val: grapheme {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var top-addr/ecx: (addr int) <- get self, top
-  var data-ah/edx: (addr handle array grapheme) <- get self, data
-  var data/eax: (addr array grapheme) <- lookup *data-ah
-  var top/edx: int <- copy *top-addr
-  var dest-addr/edx: (addr grapheme) <- index data, top
-  var val/eax: grapheme <- copy _val
-  copy-to *dest-addr, val
-  add-to *top-addr, 1
-}
-
-fn pop-grapheme-stack _self: (addr grapheme-stack) -> _/eax: grapheme {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var top-addr/ecx: (addr int) <- get self, top
-  {
-    compare *top-addr, 0
-    break-if->
-    return -1
-  }
-  subtract-from *top-addr, 1
-  var data-ah/edx: (addr handle array grapheme) <- get self, data
-  var data/eax: (addr array grapheme) <- lookup *data-ah
-  var top/edx: int <- copy *top-addr
-  var result-addr/eax: (addr grapheme) <- index data, top
-  return *result-addr
-}
-
-fn copy-grapheme-stack _src: (addr grapheme-stack), dest: (addr grapheme-stack) {
-  var src/esi: (addr grapheme-stack) <- copy _src
-  var data-ah/edi: (addr handle array grapheme) <- get src, data
-  var _data/eax: (addr array grapheme) <- lookup *data-ah
-  var data/edi: (addr array grapheme) <- copy _data
-  var top-addr/ecx: (addr int) <- get src, top
-  var i/eax: int <- copy 0
-  {
-    compare i, *top-addr
-    break-if->=
-    var g/edx: (addr grapheme) <- index data, i
-    push-grapheme-stack dest, *g
-    i <- increment
-    loop
-  }
-}
-
-# dump stack to screen from bottom to top
-# hardcoded colors:
-#   matching paren
-fn render-stack-from-bottom-wrapping-right-then-down screen: (addr screen), _self: (addr grapheme-stack), xmin: int, ymin: int, xmax: int, ymax: int, _x: int, _y: int, highlight-matching-open-paren?: boolean, open-paren-depth: int, color: int, background-color: int -> _/eax: int, _/ecx: int {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var matching-open-paren-index/edx: int <- get-matching-open-paren-index self, highlight-matching-open-paren?, open-paren-depth
-  var data-ah/edi: (addr handle array grapheme) <- get self, data
-  var _data/eax: (addr array grapheme) <- lookup *data-ah
-  var data/edi: (addr array grapheme) <- copy _data
-  var x/eax: int <- copy _x
-  var y/ecx: int <- copy _y
-  var top-addr/esi: (addr int) <- get self, top
-  var i/ebx: int <- copy 0
-  {
-    compare i, *top-addr
-    break-if->=
-    {
-      var g/esi: (addr grapheme) <- index data, i
-      var fg: int
-      {
-        var tmp/eax: int <- copy color
-        copy-to fg, tmp
-      }
-      {
-        compare i, matching-open-paren-index
-        break-if-!=
-        copy-to fg, 0xf/highlight
-      }
-      x, y <- render-grapheme screen, *g, xmin, ymin, xmax, ymax, x, y, fg, background-color
-    }
-    i <- increment
-    loop
-  }
-  return x, y
-}
-
-# helper for small words
-fn render-stack-from-bottom screen: (addr screen), self: (addr grapheme-stack), x: int, y: int, highlight-matching-open-paren?: boolean, open-paren-depth: int -> _/eax: int {
-  var _width/eax: int <- copy 0
-  var _height/ecx: int <- copy 0
-  _width, _height <- screen-size screen
-  var width/edx: int <- copy _width
-  var height/ebx: int <- copy _height
-  var x2/eax: int <- copy 0
-  var y2/ecx: int <- copy 0
-  x2, y2 <- render-stack-from-bottom-wrapping-right-then-down screen, self, x, y, width, height, x, y, highlight-matching-open-paren?, open-paren-depth, 3/fg=cyan, 0xc5/bg=blue-bg
-  return x2  # y2? yolo
-}
-
-# dump stack to screen from top to bottom
-# optionally render a 'cursor' with the top grapheme
-# hard-coded colors:
-#   matching paren
-#   cursor
-fn render-stack-from-top-wrapping-right-then-down screen: (addr screen), _self: (addr grapheme-stack), xmin: int, ymin: int, xmax: int, ymax: int, _x: int, _y: int, render-cursor?: boolean, color: int, background-color: int -> _/eax: int, _/ecx: int {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var matching-close-paren-index/edx: int <- get-matching-close-paren-index self, render-cursor?
-  var data-ah/eax: (addr handle array grapheme) <- get self, data
-  var _data/eax: (addr array grapheme) <- lookup *data-ah
-  var data/edi: (addr array grapheme) <- copy _data
-  var x/eax: int <- copy _x
-  var y/ecx: int <- copy _y
-  var top-addr/ebx: (addr int) <- get self, top
-  var i/ebx: int <- copy *top-addr
-  i <- decrement
-  # if render-cursor?, peel off first iteration
-  {
-    compare render-cursor?, 0/false
-    break-if-=
-    compare i, 0
-    break-if-<
-    var g/esi: (addr grapheme) <- index data, i
-    x, y <- render-grapheme screen, *g, xmin, ymin, xmax, ymax, x, y, background-color, color
-    i <- decrement
-  }
-  # remaining iterations
-  {
-    compare i, 0
-    break-if-<
-    # highlight matching paren if needed
-    var fg: int
-    {
-      var tmp/eax: int <- copy color
-      copy-to fg, tmp
-    }
-    compare i, matching-close-paren-index
-    {
-      break-if-!=
-      copy-to fg, 0xf/highlight
-    }
-    #
-    var g/esi: (addr grapheme) <- index data, i
-    x, y <- render-grapheme screen, *g, xmin, ymin, xmax, ymax, x, y, fg, background-color
-    i <- decrement
-    loop
-  }
-  return x, y
-}
-
-# helper for small words
-fn render-stack-from-top screen: (addr screen), self: (addr grapheme-stack), x: int, y: int, render-cursor?: boolean -> _/eax: int {
-  var _width/eax: int <- copy 0
-  var _height/ecx: int <- copy 0
-  _width, _height <- screen-size screen
-  var width/edx: int <- copy _width
-  var height/ebx: int <- copy _height
-  var x2/eax: int <- copy 0
-  var y2/ecx: int <- copy 0
-  x2, y2 <- render-stack-from-top-wrapping-right-then-down screen, self, x, y, width, height, x, y, render-cursor?, 3/fg=cyan, 0xc5/bg=blue-bg
-  return x2  # y2? yolo
-}
-
-fn test-render-grapheme-stack {
-  # setup: gs = "abc"
-  var gs-storage: grapheme-stack
-  var gs/edi: (addr grapheme-stack) <- address gs-storage
-  initialize-grapheme-stack gs, 5
-  var g/eax: grapheme <- copy 0x61/a
-  push-grapheme-stack gs, g
-  g <- copy 0x62/b
-  push-grapheme-stack gs, g
-  g <- copy 0x63/c
-  push-grapheme-stack gs, g
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/esi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-stack-from-bottom screen, gs, 0/x, 0/y, 0/no-highlight-matching-open-paren, 0/open-paren-depth
-  check-screen-row screen, 0/y, "abc ", "F - test-render-grapheme-stack from bottom"
-  check-ints-equal x, 3, "F - test-render-grapheme-stack from bottom: result"
-  check-background-color-in-screen-row screen, 3/bg=reverse, 0/y, "   ", "F - test-render-grapheme-stack from bottom: bg"
-  #
-  var x/eax: int <- render-stack-from-top screen, gs, 0/x, 1/y, 0/cursor=false
-  check-screen-row screen, 1/y, "cba ", "F - test-render-grapheme-stack from top without cursor"
-  check-ints-equal x, 3, "F - test-render-grapheme-stack from top without cursor: result"
-  check-background-color-in-screen-row screen, 3/bg=reverse, 1/y, "   ", "F - test-render-grapheme-stack from top without cursor: bg"
-  #
-  var x/eax: int <- render-stack-from-top screen, gs, 0/x, 2/y, 1/cursor=true
-  check-screen-row screen, 2/y, "cba ", "F - test-render-grapheme-stack from top with cursor"
-  check-ints-equal x, 3, "F - test-render-grapheme-stack from top with cursor: result"
-  check-background-color-in-screen-row screen, 3/bg=reverse, 2/y, "|   ", "F - test-render-grapheme-stack from top with cursor: bg"
-}
-
-fn test-render-grapheme-stack-while-highlighting-matching-close-paren {
-  # setup: gs = "(b)"
-  var gs-storage: grapheme-stack
-  var gs/edi: (addr grapheme-stack) <- address gs-storage
-  initialize-grapheme-stack gs, 5
-  var g/eax: grapheme <- copy 0x29/close-paren
-  push-grapheme-stack gs, g
-  g <- copy 0x62/b
-  push-grapheme-stack gs, g
-  g <- copy 0x28/open-paren
-  push-grapheme-stack gs, g
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/esi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-stack-from-top screen, gs, 0/x, 2/y, 1/cursor=true
-  check-screen-row                      screen,               2/y, "(b) ", "F - test-render-grapheme-stack-while-highlighting-matching-close-paren"
-  check-background-color-in-screen-row  screen, 3/bg=reverse,  2/y, "|   ", "F - test-render-grapheme-stack-while-highlighting-matching-close-paren: cursor"
-  check-screen-row-in-color             screen, 0xf/fg=white, 2/y, "  ) ", "F - test-render-grapheme-stack-while-highlighting-matching-close-paren: matching paren"
-}
-
-fn test-render-grapheme-stack-while-highlighting-matching-close-paren-2 {
-  # setup: gs = "(a (b)) c"
-  var gs-storage: grapheme-stack
-  var gs/edi: (addr grapheme-stack) <- address gs-storage
-  initialize-grapheme-stack gs, 0x10
-  var g/eax: grapheme <- copy 0x63/c
-  push-grapheme-stack gs, g
-  g <- copy 0x20/space
-  push-grapheme-stack gs, g
-  g <- copy 0x29/close-paren
-  push-grapheme-stack gs, g
-  g <- copy 0x29/close-paren
-  push-grapheme-stack gs, g
-  g <- copy 0x62/b
-  push-grapheme-stack gs, g
-  g <- copy 0x28/open-paren
-  push-grapheme-stack gs, g
-  g <- copy 0x20/space
-  push-grapheme-stack gs, g
-  g <- copy 0x61/a
-  push-grapheme-stack gs, g
-  g <- copy 0x28/open-paren
-  push-grapheme-stack gs, g
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/esi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-stack-from-top screen, gs, 0/x, 2/y, 1/cursor=true
-  check-screen-row                      screen,               2/y, "(a (b)) c ", "F - test-render-grapheme-stack-while-highlighting-matching-close-paren-2"
-  check-background-color-in-screen-row  screen, 3/bg=reverse,  2/y, "|         ", "F - test-render-grapheme-stack-while-highlighting-matching-close-paren-2: cursor"
-  check-screen-row-in-color             screen, 0xf/fg=white, 2/y, "      )   ", "F - test-render-grapheme-stack-while-highlighting-matching-close-paren-2: matching paren"
-}
-
-fn test-render-grapheme-stack-while-highlighting-matching-open-paren-with-close-paren-at-end {
-  # setup: gs = "(b)"
-  var gs-storage: grapheme-stack
-  var gs/edi: (addr grapheme-stack) <- address gs-storage
-  initialize-grapheme-stack gs, 5
-  var g/eax: grapheme <- copy 0x28/open-paren
-  push-grapheme-stack gs, g
-  g <- copy 0x62/b
-  push-grapheme-stack gs, g
-  g <- copy 0x29/close-paren
-  push-grapheme-stack gs, g
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/esi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-stack-from-bottom screen, gs, 0/x, 2/y, 1/highlight-matching-open-paren, 1/open-paren-depth
-  check-screen-row          screen,               2/y, "(b) ", "F - test-render-grapheme-stack-while-highlighting-matching-open-paren-with-close-paren-at-end"
-  check-screen-row-in-color screen, 0xf/fg=white, 2/y, "(   ", "F - test-render-grapheme-stack-while-highlighting-matching-open-paren-with-close-paren-at-end: matching paren"
-}
-
-fn test-render-grapheme-stack-while-highlighting-matching-open-paren-with-close-paren-at-end-2 {
-  # setup: gs = "a((b))"
-  var gs-storage: grapheme-stack
-  var gs/edi: (addr grapheme-stack) <- address gs-storage
-  initialize-grapheme-stack gs, 0x10
-  var g/eax: grapheme <- copy 0x61/a
-  push-grapheme-stack gs, g
-  g <- copy 0x28/open-paren
-  push-grapheme-stack gs, g
-  g <- copy 0x28/open-paren
-  push-grapheme-stack gs, g
-  g <- copy 0x62/b
-  push-grapheme-stack gs, g
-  g <- copy 0x29/close-paren
-  push-grapheme-stack gs, g
-  g <- copy 0x29/close-paren
-  push-grapheme-stack gs, g
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/esi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-stack-from-bottom screen, gs, 0/x, 2/y, 1/highlight-matching-open-paren, 1/open-paren-depth
-  check-screen-row          screen,               2/y, "a((b)) ", "F - test-render-grapheme-stack-while-highlighting-matching-open-paren-with-close-paren-at-end-2"
-  check-screen-row-in-color screen, 0xf/fg=white, 2/y, " (     ", "F - test-render-grapheme-stack-while-highlighting-matching-open-paren-with-close-paren-at-end-2: matching paren"
-}
-
-fn test-render-grapheme-stack-while-highlighting-matching-open-paren {
-  # setup: gs = "(b"
-  var gs-storage: grapheme-stack
-  var gs/edi: (addr grapheme-stack) <- address gs-storage
-  initialize-grapheme-stack gs, 5
-  var g/eax: grapheme <- copy 0x28/open-paren
-  push-grapheme-stack gs, g
-  g <- copy 0x62/b
-  push-grapheme-stack gs, g
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/esi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-stack-from-bottom screen, gs, 0/x, 2/y, 1/highlight-matching-open-paren, 0/open-paren-depth
-  check-screen-row          screen,               2/y, "(b ", "F - test-render-grapheme-stack-while-highlighting-matching-open-paren"
-  check-screen-row-in-color screen, 0xf/fg=white, 2/y, "(  ", "F - test-render-grapheme-stack-while-highlighting-matching-open-paren: matching paren"
-}
-
-fn test-render-grapheme-stack-while-highlighting-matching-open-paren-2 {
-  # setup: gs = "a((b)"
-  var gs-storage: grapheme-stack
-  var gs/edi: (addr grapheme-stack) <- address gs-storage
-  initialize-grapheme-stack gs, 0x10
-  var g/eax: grapheme <- copy 0x61/a
-  push-grapheme-stack gs, g
-  g <- copy 0x28/open-paren
-  push-grapheme-stack gs, g
-  g <- copy 0x28/open-paren
-  push-grapheme-stack gs, g
-  g <- copy 0x62/b
-  push-grapheme-stack gs, g
-  g <- copy 0x29/close-paren
-  push-grapheme-stack gs, g
-  # setup: screen
-  var screen-on-stack: screen
-  var screen/esi: (addr screen) <- address screen-on-stack
-  initialize-screen screen, 5, 4, 0/no-pixel-graphics
-  #
-  var x/eax: int <- render-stack-from-bottom screen, gs, 0/x, 2/y, 1/highlight-matching-open-paren, 0/open-paren-depth
-  check-screen-row          screen,               2/y, "a((b) ", "F - test-render-grapheme-stack-while-highlighting-matching-open-paren-2"
-  check-screen-row-in-color screen, 0xf/fg=white, 2/y, " (    ", "F - test-render-grapheme-stack-while-highlighting-matching-open-paren-2: matching paren"
-}
-
-# return the index of the matching close-paren of the grapheme at cursor (top of stack)
-# or top index if there's no matching close-paren
-fn get-matching-close-paren-index _self: (addr grapheme-stack), render-cursor?: boolean -> _/edx: int {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var top-addr/edx: (addr int) <- get self, top
-  # if not rendering cursor, return
-  compare render-cursor?, 0/false
-  {
-    break-if-!=
-    return *top-addr
-  }
-  var data-ah/eax: (addr handle array grapheme) <- get self, data
-  var data/eax: (addr array grapheme) <- lookup *data-ah
-  var i/ecx: int <- copy *top-addr
-  # if stack is empty, return
-  compare i, 0
-  {
-    break-if->
-    return *top-addr
-  }
-  # if cursor is not '(' return
-  i <- decrement
-  var g/esi: (addr grapheme) <- index data, i
-  compare *g, 0x28/open-paren
-  {
-    break-if-=
-    return *top-addr
-  }
-  # otherwise scan to matching paren
-  var paren-count/ebx: int <- copy 1
-  i <- decrement
-  {
-    compare i, 0
-    break-if-<
-    var g/esi: (addr grapheme) <- index data, i
-    compare *g, 0x28/open-paren
-    {
-      break-if-!=
-      paren-count <- increment
-    }
-    compare *g, 0x29/close-paren
-    {
-      break-if-!=
-      compare paren-count, 1
-      {
-        break-if-!=
-        return i
-      }
-      paren-count <- decrement
-    }
-    i <- decrement
-    loop
-  }
-  return *top-addr
-}
-
-# return the index of the first open-paren at the given depth
-# or top index if there's no matching close-paren
-fn get-matching-open-paren-index _self: (addr grapheme-stack), control: boolean, depth: int -> _/edx: int {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var top-addr/edx: (addr int) <- get self, top
-  # if not rendering cursor, return
-  compare control, 0/false
-  {
-    break-if-!=
-    return *top-addr
-  }
-  var data-ah/eax: (addr handle array grapheme) <- get self, data
-  var data/eax: (addr array grapheme) <- lookup *data-ah
-  var i/ecx: int <- copy *top-addr
-  # if stack is empty, return
-  compare i, 0
-  {
-    break-if->
-    return *top-addr
-  }
-  # scan to matching open paren
-  var paren-count/ebx: int <- copy 0
-  i <- decrement
-  {
-    compare i, 0
-    break-if-<
-    var g/esi: (addr grapheme) <- index data, i
-    compare *g, 0x29/close-paren
-    {
-      break-if-!=
-      paren-count <- increment
-    }
-    compare *g, 0x28/open-paren
-    {
-      break-if-!=
-      compare paren-count, depth
-      {
-        break-if-!=
-        return i
-      }
-      paren-count <- decrement
-    }
-    i <- decrement
-    loop
-  }
-  return *top-addr
-}
-
-# compare from bottom
-# beware: modifies 'stream', which must be disposed of after a false result
-fn prefix-match? _self: (addr grapheme-stack), s: (addr stream byte) -> _/eax: boolean {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var data-ah/edi: (addr handle array grapheme) <- get self, data
-  var _data/eax: (addr array grapheme) <- lookup *data-ah
-  var data/edi: (addr array grapheme) <- copy _data
-  var top-addr/ecx: (addr int) <- get self, top
-  var i/ebx: int <- copy 0
-  {
-    compare i, *top-addr
-    break-if->=
-    # if curr != expected, return false
-    {
-      var curr-a/edx: (addr grapheme) <- index data, i
-      var expected/eax: grapheme <- read-grapheme s
-      {
-        compare expected, *curr-a
-        break-if-=
-        return 0/false
-      }
-    }
-    i <- increment
-    loop
-  }
-  return 1   # true
-}
-
-# compare from bottom
-# beware: modifies 'stream', which must be disposed of after a false result
-fn suffix-match? _self: (addr grapheme-stack), s: (addr stream byte) -> _/eax: boolean {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var data-ah/edi: (addr handle array grapheme) <- get self, data
-  var _data/eax: (addr array grapheme) <- lookup *data-ah
-  var data/edi: (addr array grapheme) <- copy _data
-  var top-addr/eax: (addr int) <- get self, top
-  var i/ebx: int <- copy *top-addr
-  i <- decrement
-  {
-    compare i, 0
-    break-if-<
-    {
-      var curr-a/edx: (addr grapheme) <- index data, i
-      var expected/eax: grapheme <- read-grapheme s
-      # if curr != expected, return false
-      {
-        compare expected, *curr-a
-        break-if-=
-        return 0/false
-      }
-    }
-    i <- decrement
-    loop
-  }
-  return 1   # true
-}
-
-fn grapheme-stack-is-decimal-integer? _self: (addr grapheme-stack) -> _/eax: boolean {
-  var self/esi: (addr grapheme-stack) <- copy _self
-  var data-ah/eax: (addr handle array grapheme) <- get self, data
-  var _data/eax: (addr array grapheme) <- lookup *data-ah
-  var data/edx: (addr array grapheme) <- copy _data
-  var top-addr/ecx: (addr int) <- get self, top
-  var i/ebx: int <- copy 0
-  var result/eax: boolean <- copy 1/true
-  $grapheme-stack-is-integer?:loop: {
-    compare i, *top-addr
-    break-if->=
-    var g/edx: (addr grapheme) <- index data, i
-    result <- decimal-digit? *g
-    compare result, 0/false
-    break-if-=
-    i <- increment
-    loop
-  }
-  return result
-}