CONTRIBUTING.org


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#+HTML_HEAD: <link rel="stylesheet" href="../../static/style.css">
#+HTML_HEAD: <link rel="icon" href="../../static/perseus/favicon.png" type="image/png">
#+EXPORT_FILE_NAME: contributing
#+TITLE: Contributing - Perseus

Perseus is a simple link aggregation and discussion program. It is written in Go
& uses sqlite3 for storage.

| Project Home    | [[https://andinus.nand.sh/perseus][Perseus]]           |
| Source Code     | [[https://tildegit.org/andinus/perseus][Andinus / Perseus]] |
| GitHub (Mirror) | [[https://github.com/andinus/perseus][Perseus - GitHub]]  |

* Branches
** master
Master branch always contains the code that compiles and has passed tests. Users
must be able to pull the master branch anything and expect that everything
works. Everything works doesn't mean that previous setup will work, i.e. if user
has setup for 0.X.a then master will work if last tagged version was 0.X.b but
if the last tagged version is 0.Y then 0.X's setup may not work.
** develop
Develop branch shouldn't be used in production, it may contain code that doesn't
work or even insecure. Everyone should makes pull requests against develop
branch.
* Patches
Contributors can send their patches to my email address (see commits), a public
mailing list will be considered if this is used often.
type sandbox {
  data: (handle gap-buffer)
  value: (handle stream byte)
  trace: (handle trace)
  screen-var: (handle cell)
  keyboard-var: (handle cell)
  cursor-in-data?: boolean
  cursor-in-trace?: boolean
  cursor-in-keyboard?: boolean
}

fn initialize-sandbox _self: (addr sandbox), fake-screen-width: int, fake-screen-height: int {
  var self/esi: (addr sandbox) <- copy _self
  var data-ah/eax: (addr handle gap-buffer) <- get self, data
  allocate data-ah
  var data/eax: (addr gap-buffer) <- lookup *data-ah
  initialize-gap-buffer data, 0x40000/default-gap-buffer-size=256KB
  #
  var value-ah/eax: (addr handle stream byte) <- get self, value
  populate-stream value-ah, 0x1000/4KB
  #
  {
    compare fake-screen-width, 0
    break-if-=
    var screen-ah/eax: (addr handle cell) <- get self, screen-var
    new-fake-screen screen-ah, fake-screen-width, fake-screen-height, 1/enable-pixel-graphics
    var keyboard-ah/eax: (addr handle cell) <- get self, keyboard-var
    new-fake-keyboard keyboard-ah, 0x10/keyboard-capacity
  }
  #
  var trace-ah/eax: (addr handle trace) <- get self, trace
  allocate trace-ah
  var trace/eax: (addr trace) <- lookup *trace-ah
  initialize-trace trace, 4/max-depth, 0x8000/lines, 0x80/visible
  var cursor-in-data?/eax: (addr boolean) <- get self, cursor-in-data?
  copy-to *cursor-in-data?, 1/true
}

## some helpers for tests

fn initialize-sandbox-with _self: (addr sandbox), s: (addr array byte) {
  var self/esi: (addr sandbox) <- copy _self
  var data-ah/eax: (addr handle gap-buffer) <- get self, data
  allocate data-ah
  var data/eax: (addr gap-buffer) <- lookup *data-ah
  initialize-gap-buffer-with data, s
  var value-ah/eax: (addr handle stream byte) <- get self, value
  populate-stream value-ah, 0x1000/4KB
  var trace-ah/eax: (addr handle trace) <- get self, trace
  allocate trace-ah
  var trace/eax: (addr trace) <- lookup *trace-ah
  initialize-trace trace, 3/max-depth, 0x8000/lines, 0x80/visible
  var cursor-in-data?/eax: (addr boolean) <- get self, cursor-in-data?
  copy-to *cursor-in-data?, 1/true
}

fn allocate-sandbox-with _out: (addr handle sandbox), s: (addr array byte) {
  var out/eax: (addr handle sandbox) <- copy _out
  allocate out
  var out-addr/eax: (addr sandbox) <- lookup *out
  initialize-sandbox-with out-addr, s
}

fn write-sandbox out: (addr stream byte), _self: (addr sandbox) {
  var self/eax: (addr sandbox) <- copy _self
  var data-ah/eax: (addr handle gap-buffer) <- get self, data
  var data/eax: (addr gap-buffer) <- lookup *data-ah
  {
    var len/eax: int <- gap-buffer-length data
    compare len, 0
    break-if-!=
    return
  }
  write out, "  (sandbox . ["
  append-gap-buffer data, out
  write out, "])\n"
}

##

fn render-sandbox screen: (addr screen), _self: (addr sandbox), xmin: int, ymin: int, xmax: int, ymax: int, show-cursor?: boolean {
  clear-rect screen, xmin, ymin, xmax, ymax, 0xc5/bg=blue-bg
  add-to xmin, 1/padding-left
  add-to ymin, 1/padding-top
  subtract-from xmax, 1/padding-right
  var self/esi: (addr sandbox) <- copy _self
  # data
  var data-ah/eax: (addr handle gap-buffer) <- get self, data
  var _data/eax: (addr gap-buffer) <- lookup *data-ah
  var data/edx: (addr gap-buffer) <- copy _data
  var x/eax: int <- copy xmin
  var y/ecx: int <- copy ymin
  y <- maybe-render-empty-screen screen, self, xmin, y
  y <- maybe-render-keyboard screen, self, xmin, y
  var cursor-in-editor?/ebx: boolean <- copy show-cursor?
  {
    compare cursor-in-editor?, 0/false
    break-if-=
    var cursor-in-data-a/eax: (addr boolean) <- get self, cursor-in-data?
    cursor-in-editor? <- copy *cursor-in-data-a
  }
  x, y <- render-gap-buffer-wrapping-right-then-down screen, data, x, y, xmax, ymax, cursor-in-editor?, 7/fg, 0xc5/bg=blue-bg
  y <- increment
  # trace
  var trace-ah/eax: (addr handle trace) <- get self, trace
  var _trace/eax: (addr trace) <- lookup *trace-ah
  var trace/edx: (addr trace) <- copy _trace
  var cursor-in-trace?/eax: (addr boolean) <- get self, cursor-in-trace?
  y <- render-trace screen, trace, xmin, y, xmax, ymax, *cursor-in-trace?
  # value
  $render-sandbox:value: {
    compare y, ymax
    break-if->=
    var value-ah/eax: (addr handle stream byte) <- get self, value
    var _value/eax: (addr stream byte) <- lookup *value-ah
    var value/esi: (addr stream byte) <- copy _value
    rewind-stream value
    var done?/eax: boolean <- stream-empty? value
    compare done?, 0/false
    break-if-!=
    var x/eax: int <- copy 0
    x, y <- draw-text-wrapping-right-then-down screen, "=> ", xmin, y, xmax, ymax, xmin, y, 7/fg, 0xc5/bg=blue-bg
    var x2/edx: int <- copy x
    var dummy/eax: int <- draw-stream-rightward screen, value, x2, xmax, y, 7/fg=grey, 0xc5/bg=blue-bg
  }
  y <- add 2  # padding
  maybe-render-screen screen, self, xmin, y
}

fn render-sandbox-menu screen: (addr screen), _self: (addr sandbox) {
  var self/esi: (addr sandbox) <- copy _self
  var cursor-in-data?/eax: (addr boolean) <- get self, cursor-in-data?
  compare *cursor-in-data?, 0/false
  {
    break-if-=
    render-sandbox-edit-menu screen, self
    return
  }
  var cursor-in-trace?/eax: (addr boolean) <- get self, cursor-in-trace?
  compare *cursor-in-trace?, 0/false
  {
    break-if-=
    render-trace-menu screen
    return
  }
  var cursor-in-keyboard?/eax: (addr boolean) <- get self, cursor-in-keyboard?
  compare *cursor-in-keyboard?, 0/false
  {
    break-if-=
    render-keyboard-menu screen
    return
  }
}

fn clear-sandbox-output screen: (addr screen), _self: (addr sandbox), xmin: int, ymin: int, xmax: int, ymax: int {
  # render just enough of the sandbox to figure out what to erase
  var self/esi: (addr sandbox) <- copy _self
  var data-ah/eax: (addr handle gap-buffer) <- get self, data
  var _data/eax: (addr gap-buffer) <- lookup *data-ah
  var data/edx: (addr gap-buffer) <- copy _data
  var x/eax: int <- copy xmin
  var y/ecx: int <- copy ymin
  y <- maybe-render-empty-screen screen, self, xmin, y
  y <- maybe-render-keyboard screen, self, xmin, y
  var cursor-in-sandbox?/ebx: (addr boolean) <- get self, cursor-in-data?
  x, y <- render-gap-buffer-wrapping-right-then-down screen, data, x, y, xmax, ymax, *cursor-in-sandbox?, 3/fg, 0xc5/bg=blue-bg
  y <- increment
  clear-rect screen, xmin, y, xmax, ymax, 0xc5/bg=blue-bg
}

fn maybe-render-empty-screen screen: (addr screen), _self: (addr sandbox), xmin: int, ymin: int -> _/ecx: int {
  var self/esi: (addr sandbox) <- copy _self
  var screen-obj-cell-ah/eax: (addr handle cell) <- get self, screen-var
  var screen-obj-cell/eax: (addr cell) <- lookup *screen-obj-cell-ah
  compare screen-obj-cell, 0
  {
    break-if-!=
    return ymin
  }
  var screen-obj-cell-type/ecx: (addr int) <- get screen-obj-cell, type
  compare *screen-obj-cell-type, 5/screen
  {
    break-if-=
    return ymin  # silently give up on rendering the screen
  }
  var y/ecx: int <- copy ymin
  var screen-obj-ah/eax: (addr handle screen) <- get screen-obj-cell, screen-data
  var _screen-obj/eax: (addr screen) <- lookup *screen-obj-ah
  var screen-obj/edx: (addr screen) <- copy _screen-obj
  var x/eax: int <- draw-text-rightward screen, "screen:   ", xmin, 0x99/xmax, y, 0x17/fg, 0xc5/bg=blue-bg
  x <- copy xmin
  x <- add 2
  y <- increment
  y <- render-empty-screen screen, screen-obj, x, y
  return y
}

fn maybe-render-screen screen: (addr screen), _self: (addr sandbox), xmin: int, ymin: int {
  var self/esi: (addr sandbox) <- copy _self
  var screen-obj-cell-ah/eax: (addr handle cell) <- get self, screen-var
  var screen-obj-cell/eax: (addr cell) <- lookup *screen-obj-cell-ah
  compare screen-obj-cell, 0
  {
    break-if-!=
    return
  }
  var screen-obj-cell-type/ecx: (addr int) <- get screen-obj-cell, type
  compare *screen-obj-cell-type, 5/screen
  {
    break-if-=
    return  # silently give up on rendering the screen
  }
  var screen-obj-ah/eax: (addr handle screen) <- get screen-obj-cell, screen-data
  var _screen-obj/eax: (addr screen) <- lookup *screen-obj-ah
  var screen-obj/edx: (addr screen) <- copy _screen-obj
  {
    var screen-empty?/eax: boolean <- fake-screen-empty? screen-obj
    compare screen-empty?, 0/false
    break-if-=
    return
  }
  var x/eax: int <- draw-text-rightward screen, "screen:   ", xmin, 0x99/xmax, ymin, 0x17/fg, 0xc5/bg=blue-bg
  x <- copy xmin
  x <- add 2
  var y/ecx: int <- copy ymin
  y <- increment
  render-screen screen, screen-obj, x, y
}

fn render-empty-screen screen: (addr screen), _target-screen: (addr screen), xmin: int, ymin: int -> _/ecx: int {
  var target-screen/esi: (addr screen) <- copy _target-screen
  var screen-y/edi: int <- copy ymin
  # screen
  var height/edx: (addr int) <- get target-screen, height
  var y/ecx: int <- copy 0
  {
    compare y, *height
    break-if->=
    set-cursor-position screen, xmin, screen-y
    var width/edx: (addr int) <- get target-screen, width
    var x/ebx: int <- copy 0
    {
      compare x, *width
      break-if->=
      draw-code-point-at-cursor-over-full-screen screen, 0x20/space, 0x18/fg, 0/bg
      x <- increment
      loop
    }
    y <- increment
    screen-y <- increment
    loop
  }
  return screen-y
}

fn render-screen screen: (addr screen), _target-screen: (addr screen), xmin: int, ymin: int {
  var target-screen/esi: (addr screen) <- copy _target-screen
  convert-screen-cells-to-pixels target-screen  # might overwrite existing pixel data with screen cells
                                                # overlapping the two is not supported
  # pixel data
  {
    # screen top left pixels x y width height
    var tmp/eax: int <- copy xmin
    tmp <- shift-left 3/log2-font-width
    var left: int
    copy-to left, tmp
    tmp <- copy ymin
    tmp <- shift-left 4/log2-font-height
    var top: int
    copy-to top, tmp
    var pixels-ah/eax: (addr handle array byte) <- get target-screen, pixels
    var _pixels/eax: (addr array byte) <- lookup *pixels-ah
    var pixels/edi: (addr array byte) <- copy _pixels
    compare pixels, 0
    break-if-=
    var y/ebx: int <- copy 0
    var height-addr/edx: (addr int) <- get target-screen, height
    var height/edx: int <- copy *height-addr
    height <- shift-left 4/log2-font-height
    {
      compare y, height
      break-if->=
      var width-addr/edx: (addr int) <- get target-screen, width
      var width/edx: int <- copy *width-addr
      width <- shift-left 3/log2-font-width
      var x/eax: int <- copy 0
      {
        compare x, width
        break-if->=
        {
          var idx/ecx: int <- pixel-index target-screen, x, y
          var color-addr/ecx: (addr byte) <- index pixels, idx
          var color/ecx: byte <- copy-byte *color-addr
          var color2/ecx: int <- copy color
          var x2/eax: int <- copy x
          x2 <- add left
          var y2/ebx: int <- copy y
          y2 <- add top
          pixel screen, x2, y2, color2
        }
        x <- increment
        loop
      }
      y <- increment
      loop
    }
  }
}

fn has-keyboard? _self: (addr sandbox) -> _/eax: boolean {
  var self/esi: (addr sandbox) <- copy _self
  var keyboard-obj-cell-ah/eax: (addr handle cell) <- get self, keyboard-var
  var keyboard-obj-cell/eax: (addr cell) <- lookup *keyboard-obj-cell-ah
  compare keyboard-obj-cell, 0
  {
    break-if-!=
    return 0/false
  }
  var keyboard-obj-cell-type/ecx: (addr int) <- get keyboard-obj-cell, type
  compare *keyboard-obj-cell-type, 6/keyboard
  {
    break-if-=
    return 0/false
  }
  var keyboard-obj-ah/eax: (addr handle gap-buffer) <- get keyboard-obj-cell, keyboard-data
  var _keyboard-obj/eax: (addr gap-buffer) <- lookup *keyboard-obj-ah
  var keyboard-obj/edx: (addr gap-buffer) <- copy _keyboard-obj
  compare keyboard-obj, 0
  {
    break-if-!=
    return 0/false
  }
  return 1/true
}

fn maybe-render-keyboard screen: (addr screen), _self: (addr sandbox), xmin: int, ymin: int -> _/ecx: int {
  var self/esi: (addr sandbox) <- copy _self
  var keyboard-obj-cell-ah/eax: (addr handle cell) <- get self, keyboard-var
  var keyboard-obj-cell/eax: (addr cell) <- lookup *keyboard-obj-cell-ah
  compare keyboard-obj-cell, 0
  {
    break-if-!=
    return ymin
  }
  var keyboard-obj-cell-type/ecx: (addr int) <- get keyboard-obj-cell, type
  compare *keyboard-obj-cell-type, 6/keyboard
  {
    break-if-=
    return ymin  # silently give up on rendering the keyboard
  }
  var keyboard-obj-ah/eax: (addr handle gap-buffer) <- get keyboard-obj-cell, keyboard-data
  var _keyboard-obj/eax: (addr gap-buffer) <- lookup *keyboard-obj-ah
  var keyboard-obj/edx: (addr gap-buffer) <- copy _keyboard-obj
  var y/ecx: int <- copy ymin
  y <- increment  # padding
  var x/eax: int <- draw-text-rightward screen, "keyboard: ", xmin, 0x99/xmax, y, 0x17/fg, 0xc5/bg=blue-bg
  var cursor-in-keyboard?/esi: (addr boolean) <- get self, cursor-in-keyboard?
  y <- render-keyboard screen, keyboard-obj, x, y, *cursor-in-keyboard?
  y <- increment  # padding
  return y
}

fn render-keyboard screen: (addr screen), _keyboard: (addr gap-buffer), xmin: int, ymin: int, render-cursor?: boolean -> _/ecx: int {
  var keyboard/esi: (addr gap-buffer) <- copy _keyboard
  var width/edx: int <- copy 0x10/keyboard-capacity
  var y/edi: int <- copy ymin
  # keyboard
  var x/eax: int <- copy xmin
  var xmax/ecx: int <- copy x
  xmax <- add 0x10
  var ymax/edx: int <- copy ymin
  ymax <- add 1
  clear-rect screen, x, y, xmax, ymax, 0/bg
  x <- render-gap-buffer screen, keyboard, x, y, render-cursor?, 3/fg, 0/bg
  y <- increment
  return y
}

fn print-screen-cell-of-fake-screen screen: (addr screen), _target: (addr screen), x: int, y: int {
  var target/ecx: (addr screen) <- copy _target
  var data-ah/eax: (addr handle array screen-cell) <- get target, data
  var data/eax: (addr array screen-cell) <- lookup *data-ah
  var index/ecx: int <- screen-cell-index target, x, y
  var offset/ecx: (offset screen-cell) <- compute-offset data, index
  var src-cell/esi: (addr screen-cell) <- index data, offset
  var src-code-point/eax: (addr code-point) <- get src-cell, data
  var src-color/ecx: (addr int) <- get src-cell, color
  var src-background-color/edx: (addr int) <- get src-cell, background-color
  draw-code-point-at-cursor-over-full-screen screen, *src-code-point, *src-color, *src-background-color
}

fn render-sandbox-edit-menu screen: (addr screen), _self: (addr sandbox) {
  var _width/eax: int <- copy 0
  var height/ecx: int <- copy 0
  _width, height <- screen-size screen
  var width/edx: int <- copy _width
  var y/ecx: int <- copy height
  y <- decrement
  var height/ebx: int <- copy y
  height <- increment
  clear-rect screen, 0/x, y, width, height, 0xc5/bg=blue-bg
  set-cursor-position screen, 0/x, y
  draw-text-rightward-from-cursor screen, " ^r ", width, 0/fg, 0x5c/bg=menu-highlight
  draw-text-rightward-from-cursor screen, " run main  ", width, 7/fg, 0xc5/bg=blue-bg
  draw-text-rightward-from-cursor screen, " ^s ", width, 0/fg, 0x5c/bg=menu-highlight
  draw-text-rightward-from-cursor screen, " run sandbox  ", width, 7/fg, 0xc5/bg=blue-bg
  draw-text-rightward-from-cursor screen, " ^g ", width, 0/fg, 0x5c/bg=menu-highlight
  draw-text-rightward-from-cursor screen, " go to  ", width, 7/fg, 0xc5/bg=blue-bg
  $render-sandbox-edit-menu:render-ctrl-m: {
    var self/eax: (addr sandbox) <- copy _self
    var has-trace?/eax: boolean <- has-trace? self
    compare has-trace?, 0/false
    {
      break-if-=
      draw-text-rightward-from-cursor screen, " ^m ", width, 0/fg, 0x38/bg=trace
      draw-text-rightward-from-cursor screen, " to trace  ", width, 7/fg, 0xc5/bg=blue-bg
      break $render-sandbox-edit-menu:render-ctrl-m
    }
    draw-text-rightward-from-cursor screen, " ^m ", width, 0/fg, 3/bg=keyboard
    draw-text-rightward-from-cursor screen, " to keyboard  ", width, 7/fg, 0xc5/bg=blue-bg
  }
  draw-text-rightward-from-cursor screen, " ^a ", width, 0/fg, 0x5c/bg=menu-highlight
  draw-text-rightward-from-cursor screen, " <<  ", width, 7/fg, 0xc5/bg=blue-bg
  draw-text-rightward-from-cursor screen, " ^b ", width, 0/fg, 0x5c/bg=menu-highlight
  draw-text-rightward-from-cursor screen, " <word  ", width, 7/fg, 0xc5/bg=blue-bg
  draw-text-rightward-from-cursor screen, " ^f ", width, 0/fg, 0x5c/bg=menu-highlight
  draw-text-rightward-from-cursor screen, " word>  ", width, 7/fg, 0xc5/bg=blue-bg
  draw-text-rightward-from-cursor screen, " ^e ", width, 0/fg, 0x5c/bg=menu-highlight
  draw-text-rightward-from-cursor screen, " >>  ", width, 7/fg, 0xc5/bg=blue-bg
}

fn render-keyboard-menu screen: (addr screen) {
  var width/eax: int <- copy 0
  var height/ecx: int <- copy 0
  width, height <- screen-size screen
  var y/ecx: int <- copy height
  y <- decrement
  var height/edx: int <- copy y
  height <- increment
  clear-rect screen, 0/x, y, width, height, 0xc5/bg=blue-bg
  set-cursor-position screen, 0/x, y
  draw-text-rightward-from-cursor screen, " ^r ", width, 0/fg, 0x5c/bg=menu-highlight
  draw-text-rightward-from-cursor screen, " run main  ", width, 7/fg, 0xc5/bg=blue-bg
  draw-text-rightward-from-cursor screen, " ^s ", width, 0/fg, 0x5c/bg=menu-highlight
  draw-text-rightward-from-cursor screen, " run sandbox  ", width, 7/fg, 0xc5/bg=blue-bg
  draw-text-rightward-from-cursor screen, " ^g ", width, 0/fg, 0x5c/bg=menu-highlight
  draw-text-rightward-from-cursor screen, " go to  ", width, 7/fg, 0xc5/bg=blue-bg
  draw-text-rightward-from-cursor screen, " ^m ", width, 0/fg, 7/bg
  draw-text-rightward-from-cursor screen, " to sandbox  ", width, 7/fg, 0xc5/bg=blue-bg
}

fn edit-sandbox _self: (addr sandbox), key: grapheme, globals: (addr global-table), data-disk: (addr disk) {
  var self/esi: (addr sandbox) <- copy _self
  # ctrl-s
  {
    compare key, 0x13/ctrl-s
    break-if-!=
    # if cursor is in trace, skip
    var cursor-in-trace?/eax: (addr boolean) <- get self, cursor-in-trace?
    compare *cursor-in-trace?, 0/false
    break-if-!=
    # minor gotcha here: any bindings created later in this iteration won't be
    # persisted until the next call to ctrl-s.
    store-state data-disk, self, globals
    #
#?     turn-on-debug-print
    run-sandbox self, globals
    return
  }
  # ctrl-m
  {
    compare key, 0xd/ctrl-m
    break-if-!=
    # if cursor in data, switch to trace or fall through to keyboard
    {
      var cursor-in-data?/eax: (addr boolean) <- get self, cursor-in-data?
      compare *cursor-in-data?, 0/false
      break-if-=
      var has-trace?/eax: boolean <- has-trace? self
      compare has-trace?, 0/false
      {
        break-if-=
        var cursor-in-data?/eax: (addr boolean) <- get self, cursor-in-data?
        copy-to *cursor-in-data?, 0/false
        var cursor-in-trace?/eax: (addr boolean) <- get self, cursor-in-trace?
        copy-to *cursor-in-trace?, 1/false
        return
      }
      var has-keyboard?/eax: boolean <- has-keyboard? self
      compare has-keyboard?, 0/false
      {
        break-if-=
        var cursor-in-data?/eax: (addr boolean) <- get self, cursor-in-data?
        copy-to *cursor-in-data?, 0/false
        var cursor-in-keyboard?/eax: (addr boolean) <- get self, cursor-in-keyboard?
        copy-to *cursor-in-keyboard?, 1/false
        return
      }
      return
    }
    # if cursor in trace, switch to keyboard or fall through to data
    {
      var cursor-in-trace?/eax: (addr boolean) <- get self, cursor-in-trace?
      compare *cursor-in-trace?, 0/false
      break-if-=
      copy-to *cursor-in-trace?, 0/false
      var cursor-target/ecx: (addr boolean) <- get self, cursor-in-keyboard?
      var has-keyboard?/eax: boolean <- has-keyboard? self
      compare has-keyboard?, 0/false
      {
        break-if-!=
        cursor-target <- get self, cursor-in-data?
      }
      copy-to *cursor-target, 1/true
      return
    }
    # otherwise if cursor in keyboard, switch to data
    {
      var cursor-in-keyboard?/eax: (addr boolean) <- get self, cursor-in-keyboard?
      compare *cursor-in-keyboard?, 0/false
      break-if-=
      copy-to *cursor-in-keyboard?, 0/false
      var cursor-in-data?/eax: (addr boolean) <- get self, cursor-in-data?
      copy-to *cursor-in-data?, 1/true
      return
    }
    return
  }
  # if cursor in data, send key to data
  {
    var cursor-in-data?/eax: (addr boolean) <- get self, cursor-in-data?
    compare *cursor-in-data?, 0/false
    break-if-=
    var data-ah/eax: (addr handle gap-buffer) <- get self, data
    var data/eax: (addr gap-buffer) <- lookup *data-ah
    edit-gap-buffer data, key
    return
  }
  # if cursor in keyboard, send key to keyboard
  {
    var cursor-in-keyboard?/eax: (addr boolean) <- get self, cursor-in-keyboard?
    compare *cursor-in-keyboard?, 0/false
    break-if-=
    var inner-keyboard-var-ah/eax: (addr handle cell) <- get self, keyboard-var
    var inner-keyboard-var/eax: (addr cell) <- lookup *inner-keyboard-var-ah
    compare inner-keyboard-var, 0
    {
      break-if-!=
      return
    }
    var inner-keyboard-var-type/ecx: (addr int) <- get inner-keyboard-var, type
    compare *inner-keyboard-var-type, 6/keyboard
    {
      break-if-=
      return
    }
    var keyboard-ah/eax: (addr handle gap-buffer) <- get inner-keyboard-var, keyboard-data
    var keyboard/eax: (addr gap-buffer) <- lookup *keyboard-ah
    edit-gap-buffer keyboard, key
    return
  }
  # if cursor in trace, send key to trace
  {
    var cursor-in-trace?/eax: (addr boolean) <- get self, cursor-in-trace?
    compare *cursor-in-trace?, 0/false
    break-if-=
    var trace-ah/eax: (addr handle trace) <- get self, trace
    var trace/eax: (addr trace) <- lookup *trace-ah
    # if expanding the trace, first check if we need to run the sandbox again with a deeper trace
    {
      compare key, 0xa/newline
      break-if-!=
      {
        var need-rerun?/eax: boolean <- cursor-too-deep? trace
        compare need-rerun?, 0/false
      }
      break-if-=
#?       draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, "rerun", 7/fg 0/bg
      # save trace lines at various cached indices
      var save: trace-index-stash
      var save-addr/ecx: (addr trace-index-stash) <- address save
      save-indices trace, save-addr
      # rerun at higher depth
      var max-depth-addr/ecx: (addr int) <- get trace, max-depth
      increment *max-depth-addr
      run-sandbox self, globals
      # recompute cached indices
      recompute-all-visible-lines trace
      var save-addr/ecx: (addr trace-index-stash) <- address save
      restore-indices trace, save-addr
    }
    edit-trace trace, key
    return
  }
}

fn run-sandbox _self: (addr sandbox), globals: (addr global-table) {
  var self/esi: (addr sandbox) <- copy _self
  var data-ah/ecx: (addr handle gap-buffer) <- get self, data
  var eval-result-h: (handle cell)
  var eval-result-ah/edi: (addr handle cell) <- address eval-result-h
  var definitions-created-storage: (stream int 0x10)
  var definitions-created/edx: (addr stream int) <- address definitions-created-storage
  var trace-ah/eax: (addr handle trace) <- get self, trace
  var _trace/eax: (addr trace) <- lookup *trace-ah
  var trace/ebx: (addr trace) <- copy _trace
  clear-trace trace
  var tmp/eax: (addr handle cell) <- get self, screen-var
  var inner-screen-var: (addr handle cell)
  copy-to inner-screen-var, tmp
  clear-screen-var inner-screen-var
  var inner-keyboard-var/eax: (addr handle cell) <- get self, keyboard-var
  rewind-keyboard-var inner-keyboard-var  # don't clear keys from before
  #
  read-and-evaluate-and-save-gap-buffer-to-globals data-ah, eval-result-ah, globals, definitions-created, trace, inner-screen-var, inner-keyboard-var
  var error?/eax: boolean <- has-errors? trace
  {
    compare error?, 0/false
    break-if-=
    return
  }
  # if necessary, initialize a new gap-buffer for sandbox
  {
    compare globals, 0
    break-if-=
    rewind-stream definitions-created
    var no-definitions?/eax: boolean <- stream-empty? definitions-created
    compare no-definitions?, 0/false
    break-if-!=
    # some definitions were created; clear the gap buffer
    var data/eax: (addr gap-buffer) <- lookup *data-ah
    var capacity/edx: int <- gap-buffer-capacity data
    allocate data-ah
    var new-data/eax: (addr gap-buffer) <- lookup *data-ah
    initialize-gap-buffer new-data, capacity
  }
  # print
  var value-ah/eax: (addr handle stream byte) <- get self, value
  var value/eax: (addr stream byte) <- lookup *value-ah
  clear-stream value
  print-cell eval-result-ah, value, trace
}

fn test-run-integer {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, "1"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen, 1/y, " 1    ", "F - test-run-integer/0"
  check-screen-row screen, 2/y, " ...  ", "F - test-run-integer/1"
  check-screen-row screen, 3/y, " => 1 ", "F - test-run-integer/2"
}

fn test-run-negative-integer {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, "-1"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen, 1/y, " -1    ", "F - test-run-negative-integer/0"
  check-screen-row screen, 2/y, " ...   ", "F - test-run-negative-integer/1"
  check-screen-row screen, 3/y, " => -1 ", "F - test-run-negative-integer/2"
}

fn test-run-error-invalid-integer {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, "1a"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row            screen,               1/y, " 1a                       ", "F - test-run-error-invalid-integer/0"
  check-screen-row            screen,               2/y, " ...                      ", "F - test-run-error-invalid-integer/1"
  check-screen-row-in-color   screen, 0xc/fg=error, 3/y, " unbound symbol: 1a       ", "F - test-run-error-invalid-integer/2"
}

fn test-run-error-unknown-symbol {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, "a"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row            screen,               1/y, " a                  ", "F - test-run-error-unknown-symbol/0"
  check-screen-row            screen,               2/y, " ...                ", "F - test-run-error-unknown-symbol/1"
  check-screen-row-in-color   screen, 0xc/fg=error, 3/y, " unbound symbol: a  ", "F - test-run-error-unknown-symbol/2"
}

fn test-run-with-spaces {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, " 1 \n"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen, 1/y, "  1   ", "F - test-run-with-spaces/0"
  check-screen-row screen, 2/y, "      ", "F - test-run-with-spaces/1"
  check-screen-row screen, 3/y, " ...  ", "F - test-run-with-spaces/2"
  check-screen-row screen, 4/y, " => 1 ", "F - test-run-with-spaces/3"
}

fn test-run-quote {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, "'a"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen, 1/y, " 'a   ", "F - test-run-quote/0"
  check-screen-row screen, 2/y, " ...  ", "F - test-run-quote/1"
  check-screen-row screen, 3/y, " => a ", "F - test-run-quote/2"
}

fn test-run-dotted-list {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, "'(a . b)"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen, 1/y, " '(a . b)   ", "F - test-run-dotted-list/0"
  check-screen-row screen, 2/y, " ...        ", "F - test-run-dotted-list/1"
  check-screen-row screen, 3/y, " => (a . b) ", "F - test-run-dotted-list/2"
}

fn test-run-dot-and-list {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, "'(a . (b))"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen, 1/y, " '(a . (b)) ", "F - test-run-dot-and-list/0"
  check-screen-row screen, 2/y, " ...        ", "F - test-run-dot-and-list/1"
  check-screen-row screen, 3/y, " => (a b)   ", "F - test-run-dot-and-list/2"
}

fn test-run-final-dot {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, "'(a .)"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen, 1/y, " '(a .)               ", "F - test-run-final-dot/0"
  check-screen-row screen, 2/y, " ...                  ", "F - test-run-final-dot/1"
  check-screen-row screen, 3/y, " '. )' makes no sense ", "F - test-run-final-dot/2"
  # further errors may occur
}

fn test-run-double-dot {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, "'(a . .)"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen, 1/y, " '(a . .)             ", "F - test-run-double-dot/0"
  check-screen-row screen, 2/y, " ...                  ", "F - test-run-double-dot/1"
  check-screen-row screen, 3/y, " '. .' makes no sense ", "F - test-run-double-dot/2"
  # further errors may occur
}

fn test-run-multiple-expressions-after-dot {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, "'(a . b c)"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen, 1/y, " '(a . b c)                                           ", "F - test-run-multiple-expressions-after-dot/0"
  check-screen-row screen, 2/y, " ...                                                  ", "F - test-run-multiple-expressions-after-dot/1"
  check-screen-row screen, 3/y, " cannot have multiple expressions between '.' and ')' ", "F - test-run-multiple-expressions-after-dot/2"
  # further errors may occur
}

fn test-run-stream {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, "[a b]"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen, 1/y, " [a b]    ", "F - test-run-stream/0"
  check-screen-row screen, 2/y, " ...      ", "F - test-run-stream/1"
  check-screen-row screen, 3/y, " => [a b] ", "F - test-run-stream/2"
}

fn test-run-move-cursor-into-trace {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, "12"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen,                                  1/y, " 12    ", "F - test-run-move-cursor-into-trace/pre-0"
  check-background-color-in-screen-row screen, 7/bg=cursor, 1/y, "   |   ", "F - test-run-move-cursor-into-trace/pre-0/cursor"
  check-screen-row screen,                                  2/y, " ...   ", "F - test-run-move-cursor-into-trace/pre-1"
  check-background-color-in-screen-row screen, 7/bg=cursor, 2/y, "       ", "F - test-run-move-cursor-into-trace/pre-1/cursor"
  check-screen-row screen,                                  3/y, " => 12 ", "F - test-run-move-cursor-into-trace/pre-2"
  check-background-color-in-screen-row screen, 7/bg=cursor, 3/y, "       ", "F - test-run-move-cursor-into-trace/pre-2/cursor"
  # move cursor into trace
  edit-sandbox sandbox, 0xd/ctrl-m, 0/no-globals, 0/no-disk
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen,                                  1/y, " 12    ", "F - test-run-move-cursor-into-trace/trace-0"
  check-background-color-in-screen-row screen, 7/bg=cursor, 1/y, "       ", "F - test-run-move-cursor-into-trace/trace-0/cursor"
  check-screen-row screen,                                  2/y, " ...   ", "F - test-run-move-cursor-into-trace/trace-1"
  check-background-color-in-screen-row screen, 7/bg=cursor, 2/y, " |||   ", "F - test-run-move-cursor-into-trace/trace-1/cursor"
  check-screen-row screen,                                  3/y, " => 12 ", "F - test-run-move-cursor-into-trace/trace-2"
  check-background-color-in-screen-row screen, 7/bg=cursor, 3/y, "       ", "F - test-run-move-cursor-into-trace/trace-2/cursor"
  # move cursor into input
  edit-sandbox sandbox, 0xd/ctrl-m, 0/no-globals, 0/no-disk
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen,                                  1/y, " 12    ", "F - test-run-move-cursor-into-trace/input-0"
  check-background-color-in-screen-row screen, 7/bg=cursor, 1/y, "   |   ", "F - test-run-move-cursor-into-trace/input-0/cursor"
  check-screen-row screen,                                  2/y, " ...   ", "F - test-run-move-cursor-into-trace/input-1"
  check-background-color-in-screen-row screen, 7/bg=cursor, 2/y, "       ", "F - test-run-move-cursor-into-trace/input-1/cursor"
  check-screen-row screen,                                  3/y, " => 12 ", "F - test-run-move-cursor-into-trace/input-2"
  check-background-color-in-screen-row screen, 7/bg=cursor, 3/y, "       ", "F - test-run-move-cursor-into-trace/input-2/cursor"
}

fn has-trace? _self: (addr sandbox) -> _/eax: boolean {
  var self/esi: (addr sandbox) <- copy _self
  var trace-ah/eax: (addr handle trace) <- get self, trace
  var _trace/eax: (addr trace) <- lookup *trace-ah
  var trace/edx: (addr trace) <- copy _trace
  compare trace, 0
  {
    break-if-!=
    abort "null trace"
  }
  var first-free/ebx: (addr int) <- get trace, first-free
  compare *first-free, 0
  {
    break-if->
    return 0/false
  }
  return 1/true
}

fn test-run-expand-trace {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  initialize-sandbox-with sandbox, "12"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen,                                  1/y, " 12    ", "F - test-run-expand-trace/pre0-0"
  check-background-color-in-screen-row screen, 7/bg=cursor, 1/y, "   |   ", "F - test-run-expand-trace/pre0-0/cursor"
  check-screen-row screen,                                  2/y, " ...   ", "F - test-run-expand-trace/pre0-1"
  check-background-color-in-screen-row screen, 7/bg=cursor, 2/y, "       ", "F - test-run-expand-trace/pre0-1/cursor"
  check-screen-row screen,                                  3/y, " => 12 ", "F - test-run-expand-trace/pre0-2"
  check-background-color-in-screen-row screen, 7/bg=cursor, 3/y, "       ", "F - test-run-expand-trace/pre0-2/cursor"
  # move cursor into trace
  edit-sandbox sandbox, 0xd/ctrl-m, 0/no-globals, 0/no-disk
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen,                                  1/y, " 12    ", "F - test-run-expand-trace/pre1-0"
  check-background-color-in-screen-row screen, 7/bg=cursor, 1/y, "       ", "F - test-run-expand-trace/pre1-0/cursor"
  check-screen-row screen,                                  2/y, " ...   ", "F - test-run-expand-trace/pre1-1"
  check-background-color-in-screen-row screen, 7/bg=cursor, 2/y, " |||   ", "F - test-run-expand-trace/pre1-1/cursor"
  check-screen-row screen,                                  3/y, " => 12 ", "F - test-run-expand-trace/pre1-2"
  check-background-color-in-screen-row screen, 7/bg=cursor, 3/y, "       ", "F - test-run-expand-trace/pre1-2/cursor"
  # expand
  edit-sandbox sandbox, 0xa/newline, 0/no-globals, 0/no-disk
  #
  clear-screen screen
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen,                                  1/y, " 12    ", "F - test-run-expand-trace/expand-0"
  check-background-color-in-screen-row screen, 7/bg=cursor, 1/y, "       ", "F - test-run-expand-trace/expand-0/cursor"
  check-screen-row screen,                                  2/y, " 1 toke", "F - test-run-expand-trace/expand-1"
  check-background-color-in-screen-row screen, 7/bg=cursor, 2/y, " ||||||", "F - test-run-expand-trace/expand-1/cursor"
  check-screen-row screen,                                  3/y, " ...   ", "F - test-run-expand-trace/expand-2"
  check-background-color-in-screen-row screen, 7/bg=cursor, 3/y, "       ", "F - test-run-expand-trace/expand-2/cursor"
  check-screen-row screen,                                  4/y, " 1 inse", "F - test-run-expand-trace/expand-3"
  check-background-color-in-screen-row screen, 7/bg=cursor, 4/y, "       ", "F - test-run-expand-trace/expand-3/cursor"
}

fn test-run-can-rerun-when-expanding-trace {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  # initialize sandbox with a max-depth of 3
  initialize-sandbox-with sandbox, "12"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen,                                  1/y, " 12    ", "F - test-run-can-rerun-when-expanding-trace/pre0-0"
  check-background-color-in-screen-row screen, 7/bg=cursor, 1/y, "   |   ", "F - test-run-can-rerun-when-expanding-trace/pre0-0/cursor"
  check-screen-row screen,                                  2/y, " ...   ", "F - test-run-can-rerun-when-expanding-trace/pre0-1"
  check-background-color-in-screen-row screen, 7/bg=cursor, 2/y, "       ", "F - test-run-can-rerun-when-expanding-trace/pre0-1/cursor"
  check-screen-row screen,                                  3/y, " => 12 ", "F - test-run-can-rerun-when-expanding-trace/pre0-2"
  check-background-color-in-screen-row screen, 7/bg=cursor, 3/y, "       ", "F - test-run-can-rerun-when-expanding-trace/pre0-2/cursor"
  # move cursor into trace
  edit-sandbox sandbox, 0xd/ctrl-m, 0/no-globals, 0/no-disk
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen,                                  1/y, " 12    ", "F - test-run-can-rerun-when-expanding-trace/pre1-0"
  check-background-color-in-screen-row screen, 7/bg=cursor, 1/y, "       ", "F - test-run-can-rerun-when-expanding-trace/pre1-0/cursor"
  check-screen-row screen,                                  2/y, " ...   ", "F - test-run-can-rerun-when-expanding-trace/pre1-1"
  check-background-color-in-screen-row screen, 7/bg=cursor, 2/y, " |||   ", "F - test-run-can-rerun-when-expanding-trace/pre1-1/cursor"
  check-screen-row screen,                                  3/y, " => 12 ", "F - test-run-can-rerun-when-expanding-trace/pre1-2"
  check-background-color-in-screen-row screen, 7/bg=cursor, 3/y, "       ", "F - test-run-can-rerun-when-expanding-trace/pre1-2/cursor"
  # expand
  edit-sandbox sandbox, 0xa/newline, 0/no-globals, 0/no-disk
  #
  clear-screen screen
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen,                                  1/y, " 12    ", "F - test-run-can-rerun-when-expanding-trace/pre2-0"
  check-background-color-in-screen-row screen, 7/bg=cursor, 1/y, "       ", "F - test-run-can-rerun-when-expanding-trace/pre2-0/cursor"
  check-screen-row screen,                                  2/y, " 1 toke", "F - test-run-can-rerun-when-expanding-trace/pre2-1"
  check-background-color-in-screen-row screen, 7/bg=cursor, 2/y, " ||||||", "F - test-run-can-rerun-when-expanding-trace/pre2-1/cursor"
  check-screen-row screen,                                  3/y, " ...   ", "F - test-run-can-rerun-when-expanding-trace/pre2-2"
  check-background-color-in-screen-row screen, 7/bg=cursor, 3/y, "       ", "F - test-run-can-rerun-when-expanding-trace/pre2-2/cursor"
  check-screen-row screen,                                  4/y, " 1 inse", "F - test-run-can-rerun-when-expanding-trace/pre2-2"
  check-background-color-in-screen-row screen, 7/bg=cursor, 4/y, "       ", "F - test-run-can-rerun-when-expanding-trace/pre2-2/cursor"
  # move cursor down and expand
  edit-sandbox sandbox, 0x6a/j, 0/no-globals, 0/no-disk
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  edit-sandbox sandbox, 0xa/newline, 0/no-globals, 0/no-disk
  #
  clear-screen screen
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # screen looks same as if trace max-depth was really high
  check-screen-row screen,                                  1/y, " 12    ", "F - test-run-can-rerun-when-expanding-trace/expand-0"
  check-background-color-in-screen-row screen, 7/bg=cursor, 1/y, "       ", "F - test-run-can-rerun-when-expanding-trace/expand-0/cursor"
  check-screen-row screen,                                  2/y, " 1 toke", "F - test-run-can-rerun-when-expanding-trace/expand-1"
  check-background-color-in-screen-row screen, 7/bg=cursor, 2/y, "       ", "F - test-run-can-rerun-when-expanding-trace/expand-1/cursor"
  check-screen-row screen,                                  3/y, " 2 next", "F - test-run-can-rerun-when-expanding-trace/expand-2"
  check-background-color-in-screen-row screen, 7/bg=cursor, 3/y, " ||||||", "F - test-run-can-rerun-when-expanding-trace/expand-2/cursor"
  check-screen-row screen,                                  4/y, " ...   ", "F - test-run-can-rerun-when-expanding-trace/expand-3"
  check-background-color-in-screen-row screen, 7/bg=cursor, 4/y, "       ", "F - test-run-can-rerun-when-expanding-trace/expand-3/cursor"
  check-screen-row screen,                                  5/y, " 2 next", "F - test-run-can-rerun-when-expanding-trace/expand-4"
  check-background-color-in-screen-row screen, 7/bg=cursor, 5/y, "       ", "F - test-run-can-rerun-when-expanding-trace/expand-4/cursor"
  check-screen-row screen,                                  6/y, " ...   ", "F - test-run-can-rerun-when-expanding-trace/expand-5"
  check-background-color-in-screen-row screen, 7/bg=cursor, 6/y, "       ", "F - test-run-can-rerun-when-expanding-trace/expand-5/cursor"
  check-screen-row screen,                                  7/y, " 2 => 1", "F - test-run-can-rerun-when-expanding-trace/expand-6"
  check-background-color-in-screen-row screen, 7/bg=cursor, 7/y, "       ", "F - test-run-can-rerun-when-expanding-trace/expand-6/cursor"
}

fn test-run-preserves-trace-view-on-rerun {
  var sandbox-storage: sandbox
  var sandbox/esi: (addr sandbox) <- address sandbox-storage
  # initialize sandbox with a max-depth of 3
  initialize-sandbox-with sandbox, "7"
  # eval
  edit-sandbox sandbox, 0x13/ctrl-s, 0/no-globals, 0/no-disk
  # setup: screen
  var screen-on-stack: screen
  var screen/edi: (addr screen) <- address screen-on-stack
  initialize-screen screen, 0x80/width, 0x10/height, 0/no-pixel-graphics
  #
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # skip one line of padding
  check-screen-row screen,                                    1/y, " 7                     ", "F - test-run-preserves-trace-view-on-rerun/pre0-0"
  check-background-color-in-screen-row screen, 7/bg=cursor,   1/y, "  |                    ", "F - test-run-preserves-trace-view-on-rerun/pre0-0/cursor"
  check-screen-row screen,                                    2/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/pre0-1"
  check-background-color-in-screen-row screen, 7/bg=cursor,   2/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre0-1/cursor"
  check-screen-row screen,                                    3/y, " => 7                  ", "F - test-run-preserves-trace-view-on-rerun/pre0-2"
  check-background-color-in-screen-row screen, 7/bg=cursor,   3/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre0-2/cursor"
  # move cursor into trace
  edit-sandbox sandbox, 0xd/ctrl-m, 0/no-globals, 0/no-disk
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  #
  check-screen-row screen,                                    1/y, " 7                     ", "F - test-run-preserves-trace-view-on-rerun/pre1-0"
  check-background-color-in-screen-row screen, 7/bg=cursor,   1/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre1-0/cursor"
  check-screen-row screen,                                    2/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/pre1-1"
  check-background-color-in-screen-row screen, 7/bg=cursor,   2/y, " |||                   ", "F - test-run-preserves-trace-view-on-rerun/pre1-1/cursor"
  check-screen-row screen,                                    3/y, " => 7                  ", "F - test-run-preserves-trace-view-on-rerun/pre1-2"
  check-background-color-in-screen-row screen, 7/bg=cursor,   3/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre1-2/cursor"
  # expand
  edit-sandbox sandbox, 0xa/newline, 0/no-globals, 0/no-disk
  clear-screen screen
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  #
  check-screen-row screen,                                    1/y, " 7                     ", "F - test-run-preserves-trace-view-on-rerun/pre2-0"
  check-background-color-in-screen-row screen, 7/bg=cursor,   1/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre2-0/cursor"
  check-screen-row screen,                                    2/y, " 1 tokenize            ", "F - test-run-preserves-trace-view-on-rerun/pre2-1"
  check-background-color-in-screen-row screen, 7/bg=cursor,   2/y, " ||||||||||            ", "F - test-run-preserves-trace-view-on-rerun/pre2-1/cursor"
  check-screen-row screen,                                    3/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/pre2-2"
  check-background-color-in-screen-row screen, 7/bg=cursor,   3/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre2-2/cursor"
  check-screen-row screen,                                    4/y, " 1 insert parens       ", "F - test-run-preserves-trace-view-on-rerun/pre2-3"
  check-background-color-in-screen-row screen, 7/bg=cursor,   4/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre2-3/cursor"
  check-screen-row screen,                                    5/y, " 1 parse               ", "F - test-run-preserves-trace-view-on-rerun/pre2-4"
  check-background-color-in-screen-row screen, 7/bg=cursor,   5/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre2-4/cursor"
  check-screen-row screen,                                    6/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/pre2-5"
  check-background-color-in-screen-row screen, 7/bg=cursor,   6/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre2-5/cursor"
  check-screen-row screen,                                    7/y, " 1 transform infix     ", "F - test-run-preserves-trace-view-on-rerun/pre2-6"
  check-background-color-in-screen-row screen, 7/bg=cursor,   7/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre2-6/cursor"
  check-screen-row screen,                                    8/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/pre2-7"
  check-background-color-in-screen-row screen, 7/bg=cursor,   8/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre2-7/cursor"
  check-screen-row screen,                                    9/y, " 1 macroexpand 7       ", "F - test-run-preserves-trace-view-on-rerun/pre2-8"
  check-background-color-in-screen-row screen, 7/bg=cursor,   9/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre2-8/cursor"
  check-screen-row screen,                                  0xa/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/pre2-9"
  check-background-color-in-screen-row screen, 7/bg=cursor, 0xa/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre2-9/cursor"
  check-screen-row screen,                                  0xb/y, " 1 => 7                ", "F - test-run-preserves-trace-view-on-rerun/pre2-10"
  check-background-color-in-screen-row screen, 7/bg=cursor, 0xb/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre2-10/cursor"
  # move cursor down below the macroexpand line and expand
  edit-sandbox sandbox, 0x6a/j, 0/no-globals, 0/no-disk
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  edit-sandbox sandbox, 0x6a/j, 0/no-globals, 0/no-disk
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  edit-sandbox sandbox, 0x6a/j, 0/no-globals, 0/no-disk
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  edit-sandbox sandbox, 0x6a/j, 0/no-globals, 0/no-disk
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  edit-sandbox sandbox, 0x6a/j, 0/no-globals, 0/no-disk
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  edit-sandbox sandbox, 0x6a/j, 0/no-globals, 0/no-disk
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  edit-sandbox sandbox, 0x6a/j, 0/no-globals, 0/no-disk
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  edit-sandbox sandbox, 0x6a/j, 0/no-globals, 0/no-disk
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  #
  check-screen-row screen,                                    1/y, " 7                     ", "F - test-run-preserves-trace-view-on-rerun/pre3-0"
  check-background-color-in-screen-row screen, 7/bg=cursor,   1/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre3-0/cursor"
  check-screen-row screen,                                    2/y, " 1 tokenize            ", "F - test-run-preserves-trace-view-on-rerun/pre3-1"
  check-background-color-in-screen-row screen, 7/bg=cursor,   2/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre3-1/cursor"
  check-screen-row screen,                                    3/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/pre3-2"
  check-background-color-in-screen-row screen, 7/bg=cursor,   3/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre3-2/cursor"
  check-screen-row screen,                                    4/y, " 1 insert parens       ", "F - test-run-preserves-trace-view-on-rerun/pre3-3"
  check-background-color-in-screen-row screen, 7/bg=cursor,   4/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre3-3/cursor"
  check-screen-row screen,                                    5/y, " 1 parse               ", "F - test-run-preserves-trace-view-on-rerun/pre3-4"
  check-background-color-in-screen-row screen, 7/bg=cursor,   5/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre3-4/cursor"
  check-screen-row screen,                                    6/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/pre3-5"
  check-background-color-in-screen-row screen, 7/bg=cursor,   6/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre3-5/cursor"
  check-screen-row screen,                                    7/y, " 1 transform infix     ", "F - test-run-preserves-trace-view-on-rerun/pre3-6"
  check-background-color-in-screen-row screen, 7/bg=cursor,   7/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre3-6/cursor"
  check-screen-row screen,                                    8/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/pre3-7"
  check-background-color-in-screen-row screen, 7/bg=cursor,   8/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre3-7/cursor"
  check-screen-row screen,                                    9/y, " 1 macroexpand 7       ", "F - test-run-preserves-trace-view-on-rerun/pre3-8"
  check-background-color-in-screen-row screen, 7/bg=cursor,   9/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre3-8/cursor"
  check-screen-row screen,                                  0xa/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/pre3-9"
  check-background-color-in-screen-row screen, 7/bg=cursor, 0xa/y, " |||                   ", "F - test-run-preserves-trace-view-on-rerun/pre3-9/cursor"
  check-screen-row screen,                                  0xb/y, " 1 => 7                ", "F - test-run-preserves-trace-view-on-rerun/pre3-10"
  check-background-color-in-screen-row screen, 7/bg=cursor, 0xb/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/pre3-10/cursor"
  # expand
  edit-sandbox sandbox, 0xa/newline, 0/no-globals, 0/no-disk
  clear-screen screen
  render-sandbox screen, sandbox, 0/x, 0/y, 0x80/width, 0x10/height, 1/show-cursor
  # cursor line is expanded
  check-screen-row screen,                                    1/y, " 7                     ", "F - test-run-preserves-trace-view-on-rerun/expand-0"
  check-background-color-in-screen-row screen, 7/bg=cursor,   1/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/expand-0/cursor"
  check-screen-row screen,                                    2/y, " 1 tokenize            ", "F - test-run-preserves-trace-view-on-rerun/expand-1"
  check-background-color-in-screen-row screen, 7/bg=cursor,   2/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/expand-1/cursor"
  check-screen-row screen,                                    3/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/expand-2"
  check-background-color-in-screen-row screen, 7/bg=cursor,   3/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/expand-2/cursor"
  check-screen-row screen,                                    4/y, " 1 insert parens       ", "F - test-run-preserves-trace-view-on-rerun/expand-3"
  check-background-color-in-screen-row screen, 7/bg=cursor,   4/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/expand-3/cursor"
  check-screen-row screen,                                    5/y, " 1 parse               ", "F - test-run-preserves-trace-view-on-rerun/expand-4"
  check-background-color-in-screen-row screen, 7/bg=cursor,   5/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/expand-4/cursor"
  check-screen-row screen,                                    6/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/expand-5"
  check-background-color-in-screen-row screen, 7/bg=cursor,   6/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/expand-5/cursor"
  check-screen-row screen,                                    7/y, " 1 transform infix     ", "F - test-run-preserves-trace-view-on-rerun/expand-6"
  check-background-color-in-screen-row screen, 7/bg=cursor,   7/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/expand-6/cursor"
  check-screen-row screen,                                    8/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/expand-7"
  check-background-color-in-screen-row screen, 7/bg=cursor,   8/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/expand-7/cursor"
  check-screen-row screen,                                    9/y, " 1 macroexpand 7       ", "F - test-run-preserves-trace-view-on-rerun/expand-8"
  check-background-color-in-screen-row screen, 7/bg=cursor,   9/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/expand-8/cursor"
  check-screen-row screen,                                  0xa/y, " 2 macroexpand-iter 7  ", "F - test-run-preserves-trace-view-on-rerun/expand-9"
  check-background-color-in-screen-row screen, 7/bg=cursor, 0xa/y, " ||||||||||||||||||||  ", "F - test-run-preserves-trace-view-on-rerun/expand-9/cursor"
  check-screen-row screen,                                  0xb/y, " ...                   ", "F - test-run-preserves-trace-view-on-rerun/expand-10"
  check-background-color-in-screen-row screen, 7/bg=cursor, 0xb/y, "                       ", "F - test-run-preserves-trace-view-on-rerun/expand-10/cursor"
}