path: root/apps/browse/paginated-screen.mu

# If a screen is too wide, split it up into a fixed size of pages.
# We take control of drawing and moving the cursor, and delegate everything else.
# Never scroll; use the 'done-drawing?' method instead.
#
# Example usage:
#   initialize-paginated-screen
#   on each frame
#     start-drawing
#     while !done-drawing
#       add-grapheme ...

type paginated-screen {
  screen: (handle screen)
  nrows: int  # const
  ncols: int  # const
  page-width: int
  top-margin: int
  left-margin: int
  # page bounds
  toprow: int
  botrow: int  # (inclusive)
  leftcol: int
  rightcol: int  # (exclusive)
  # current cursor position
  row: int
  col: int
}

fn initialize-paginated-screen _self: (addr paginated-screen), page-width: int, top-margin: int, left-margin: int {
  var self/esi: (addr paginated-screen) <- copy _self
  var screen-ah/eax: (addr handle screen) <- get self, screen
  var _screen-addr/eax: (addr screen) <- lookup *screen-ah
  var screen-addr/edi: (addr screen) <- copy _screen-addr
  var nrows/eax: int <- copy 0
  var ncols/ecx: int <- copy 0
  nrows, ncols <- screen-size screen-addr
  var dest/edx: (addr int) <- copy 0
  # self->nrows = nrows
  dest <- get self, nrows
  copy-to *dest, nrows
  # self->ncols = ncols
  dest <- get self, ncols
  copy-to *dest, ncols
  # self->page-width = page-width
  {
    var tmp/eax: int <- copy page-width
    dest <- get self, page-width
    copy-to *dest, tmp
  }
  # self->top-margin = top-margin
  {
    var tmp/eax: int <- copy top-margin
    dest <- get self, top-margin
    copy-to *dest, tmp
  }
  # self->left-margin = left-margin
  {
    var tmp/eax: int <- copy left-margin
    dest <- get self, left-margin
    copy-to *dest, tmp
  }
  # self->toprow = 1 + top-margin
  {
    var tmp/eax: int <- copy top-margin
    dest <- get self, toprow
    copy-to *dest, 1
    add-to *dest, tmp
  }
  # self->botrow = nrows
  {
    dest <- get self, botrow
    copy-to *dest, nrows
  }
  #
  start-drawing self
}

fn start-drawing _self: (addr paginated-screen) {
  var self/esi: (addr paginated-screen) <- copy _self
  clear-paginated-screen self
  var tmp/eax: (addr int) <- copy 0
  var tmp2/ecx: int <- copy 0
  # self->leftcol = 1 + left-margin
  tmp <- get self, left-margin
  tmp2 <- copy *tmp
  tmp <- get self, leftcol
  copy-to *tmp, 1
  add-to *tmp, tmp2
#?   print-string-to-real-screen "start: left column: "
#?   print-int32-hex-to-real-screen *tmp
  # self->rightcol = min(ncols+1, self->leftcol + page-width)
  # . tmp2 = self->leftcol + page-width
  tmp <- get self, page-width
  tmp2 <- copy *tmp
  tmp <- get self, leftcol
  tmp2 <- add *tmp
  # . if (tmp2 > ncols+1) tmp2 = ncols+1
  {
    tmp <- get self, ncols
    compare tmp2, *tmp
    break-if-<=
    tmp2 <- copy *tmp
    tmp2 <- increment
  }
  # . self->rightcol = tmp2
  tmp <- get self, rightcol
  copy-to *tmp, tmp2
#?   print-string-to-real-screen "; right column: "
#?   print-int32-hex-to-real-screen *tmp
#?   print-string-to-real-screen "\n"
  # self->row = self->toprow
  tmp <- get self, toprow
  tmp2 <- copy *tmp
  tmp <- get self, row
  copy-to *tmp, tmp2
  # self->col = self->leftcol
  tmp <- get self, leftcol
  tmp2 <- copy *tmp
  tmp <- get self, col
  copy-to *tmp, tmp2
  #
  reposition-cursor self
}

fn done-drawing? _self: (addr paginated-screen) -> _/eax: boolean {
  # if (self->leftcol == left-margin + 1) return false
  var self/esi: (addr paginated-screen) <- copy _self
  var tmp/eax: (addr int) <- get self, left-margin
  var first-col/ecx: int <- copy *tmp
  first-col <- increment
  tmp <- get self, leftcol
  $done-drawing:first-page?: {
    compare first-col, *tmp
    break-if-!=
    return 0  # false
  }
  # return self->rightcol > self->ncols + 1
  tmp <- get self, ncols
  var max/ecx: int <- copy *tmp
  max <- increment
  tmp <- get self, rightcol
#?   print-string-to-real-screen "done-drawing? "
#?   print-int32-hex-to-real-screen *tmp
#?   print-string-to-real-screen " vs "
#?   print-int32-hex-to-real-screen max
#?   print-string-to-real-screen "\n"
  compare *tmp, max
  {
    break-if->
    return 0  # false
  }
  return 1  # true
}

fn add-grapheme _self: (addr paginated-screen), c: grapheme {
#?   print-string-to-real-screen "add-grapheme: "
#?   print-grapheme-to-real-screen c
#?   print-string-to-real-screen "\n"
$add-grapheme:body: {
  var self/esi: (addr paginated-screen) <- copy _self
  {
    compare c, 0xa  # newline
    break-if-!=
    next-line self
    reposition-cursor self
    break $add-grapheme:body
  }
  # print c
  var screen-ah/eax: (addr handle screen) <- get self, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  print-grapheme screen-addr, c
  # self->col++
  var tmp/eax: (addr int) <- get self, col
  increment *tmp
  # if (self->col > self->rightcol) next-line(self)
  var tmp2/ecx: int <- copy *tmp
  tmp <- get self, rightcol
  compare tmp2, *tmp
  {
    break-if-<
    next-line self
    reposition-cursor self
  }
}
}

## tests

fn test-print-grapheme-on-paginated-screen {
  var pg-on-stack: paginated-screen
  var pg/eax: (addr paginated-screen) <- address pg-on-stack
  initialize-fake-paginated-screen pg, 3, 0xa, 0xa, 0, 0
  start-drawing pg
  {
    var c/ecx: grapheme <- copy 0x61   # 'a'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-grapheme-on-paginated-screen/done"
  }
  var screen-ah/eax: (addr handle screen) <- get pg, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  check-screen-row screen-addr, 1, "a", "F - test-print-grapheme-on-paginated-screen"
}

fn test-print-single-page {
  var pg-on-stack: paginated-screen
  var pg/eax: (addr paginated-screen) <- address pg-on-stack
  initialize-fake-paginated-screen pg, 2, 4, 2, 0, 0  # 2 rows, 4 columns, 2 pages * 2 columns each
  start-drawing pg
  # pages at columns [1, 3), [3, 5)
  {
    var c/ecx: grapheme <- copy 0x61   # 'a'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page/done-1"
  }
  {
    var c/ecx: grapheme <- copy 0x62   # 'b'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page/done-2"
  }
  {
    var c/ecx: grapheme <- copy 0x63   # 'c'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page/done-3"
  }
  {
    var c/ecx: grapheme <- copy 0x64   # 'd'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page/done-4"
  }
  var screen-ah/eax: (addr handle screen) <- get pg, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  check-screen-row screen-addr, 1, "ab  ", "F - test-print-single-page/row1"
  check-screen-row screen-addr, 2, "cd  ", "F - test-print-single-page/row2"
  # currently it's hard-coded that we avoid printing to the bottom-most row of the screen
}

fn test-print-single-page-narrower-than-page-width {
  var pg-on-stack: paginated-screen
  var pg/eax: (addr paginated-screen) <- address pg-on-stack
  initialize-fake-paginated-screen pg, 2, 4, 5, 0, 0  # 2 rows, 4 columns, 5-column pages
  start-drawing pg
  {
    var c/ecx: grapheme <- copy 0x61   # 'a'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page-narrower-than-page-width/done-1"
  }
  {
    var c/ecx: grapheme <- copy 0x62   # 'b'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page-narrower-than-page-width/done-2"
  }
  {
    var c/ecx: grapheme <- copy 0x63   # 'c'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page-narrower-than-page-width/done-3"
  }
  {
    var c/ecx: grapheme <- copy 0x64   # 'd'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page-narrower-than-page-width/done-4"
  }
  {
    var c/ecx: grapheme <- copy 0x65   # 'e'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page-narrower-than-page-width/done-5"
  }
  var screen-ah/eax: (addr handle screen) <- get pg, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  check-screen-row screen-addr, 1, "abcd", "F - test-print-single-page-narrower-than-page-width/row1"
  check-screen-row screen-addr, 2, "e   ", "F - test-print-single-page-narrower-than-page-width/row2"
  # currently it's hard-coded that we avoid printing to the bottom-most row of the screen
}

fn test-print-single-page-narrower-than-page-width-with-margin {
  var pg-on-stack: paginated-screen
  var pg/eax: (addr paginated-screen) <- address pg-on-stack
  initialize-fake-paginated-screen pg, 2, 4, 5, 0, 1  # 2 rows, 4 columns, 5-column pages, left margin
  start-drawing pg
  {
    var c/ecx: grapheme <- copy 0x61   # 'a'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page-narrower-than-page-width-with-margin/done-1"
  }
  {
    var c/ecx: grapheme <- copy 0x62   # 'b'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page-narrower-than-page-width-with-margin/done-2"
  }
  {
    var c/ecx: grapheme <- copy 0x63   # 'c'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page-narrower-than-page-width-with-margin/done-3"
  }
  {
    var c/ecx: grapheme <- copy 0x64   # 'd'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page-narrower-than-page-width-with-margin/done-4"
  }
  {
    var c/ecx: grapheme <- copy 0x65   # 'e'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-single-page-narrower-than-page-width-with-margin/done-5"
  }
  var screen-ah/eax: (addr handle screen) <- get pg, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  check-screen-row screen-addr, 1, " abc", "F - test-print-single-page-narrower-than-page-width-with-margin/row1"
  check-screen-row screen-addr, 2, " de ", "F - test-print-single-page-narrower-than-page-width-with-margin/row2"
  # currently it's hard-coded that we avoid printing to the bottom-most row of the screen
}

fn test-print-multiple-pages {
  var pg-on-stack: paginated-screen
  var pg/eax: (addr paginated-screen) <- address pg-on-stack
  initialize-fake-paginated-screen pg, 2, 2, 1, 0, 0  # 2 rows, 2 columns, 2 pages * 1 column each
  start-drawing pg
  {
    var c/ecx: grapheme <- copy 0x61   # 'a'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages/done-1"
  }
  {
    var c/ecx: grapheme <- copy 0x62   # 'b'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages/done-2"
  }
  {
    var c/ecx: grapheme <- copy 0x63   # 'c'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages/done-3"
  }
  {
    var c/ecx: grapheme <- copy 0x64   # 'd'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 1, "F - test-print-multiple-pages/done-4"
  }
  var screen-ah/eax: (addr handle screen) <- get pg, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  check-screen-row screen-addr, 1, "ac", "F - test-print-multiple-pages/row1"
  check-screen-row screen-addr, 2, "bd", "F - test-print-multiple-pages/row2"
  # currently it's hard-coded that we avoid printing to the bottom-most row of the screen
}

fn test-print-multiple-pages-2 {
  var pg-on-stack: paginated-screen
  var pg/eax: (addr paginated-screen) <- address pg-on-stack
  initialize-fake-paginated-screen pg, 2, 4, 2, 0, 0  # 2 rows, 4 columns, 2 pages * 2 columns each
  start-drawing pg
  {
    var c/ecx: grapheme <- copy 0x61   # 'a'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-2/done-1"
  }
  {
    var c/ecx: grapheme <- copy 0x62   # 'b'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-2/done-2"
  }
  {
    var c/ecx: grapheme <- copy 0x63   # 'c'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-2/done-3"
  }
  {
    var c/ecx: grapheme <- copy 0x64   # 'd'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-2/done-4"
  }
  {
    var c/ecx: grapheme <- copy 0x65   # 'e'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-2/done-5"
  }
  {
    var c/ecx: grapheme <- copy 0x66   # 'f'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-2/done-6"
  }
  {
    var c/ecx: grapheme <- copy 0x67   # 'g'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-2/done-7"
  }
  {
    var c/ecx: grapheme <- copy 0x68   # 'h'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 1, "F - test-print-multiple-pages-2/done-8"
  }
  var screen-ah/eax: (addr handle screen) <- get pg, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  check-screen-row screen-addr, 1, "abef", "F - test-print-multiple-pages-2/row1"
  check-screen-row screen-addr, 2, "cdgh", "F - test-print-multiple-pages-2/row2"
  # currently it's hard-coded that we avoid printing to the bottom-most row of the screen
}

fn test-print-multiple-pages-with-margins {
  var pg-on-stack: paginated-screen
  var pg/eax: (addr paginated-screen) <- address pg-on-stack
  initialize-fake-paginated-screen pg, 3, 6, 2, 1, 1  # 3 rows, 5 columns, 2 pages * 2 columns each
  start-drawing pg
  {
    var c/ecx: grapheme <- copy 0x61   # 'a'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-with-margins/grapheme-1"
  }
  {
    var c/ecx: grapheme <- copy 0x62   # 'b'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-with-margins/grapheme-2"
  }
  {
    var c/ecx: grapheme <- copy 0x63   # 'c'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-with-margins/grapheme-3"
  }
  {
    var c/ecx: grapheme <- copy 0x64   # 'd'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-with-margins/grapheme-4"
  }
  {
    var c/ecx: grapheme <- copy 0x65   # 'e'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-with-margins/grapheme-5"
  }
  {
    var c/ecx: grapheme <- copy 0x66   # 'f'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-with-margins/grapheme-6"
  }
  {
    var c/ecx: grapheme <- copy 0x67   # 'g'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 0, "F - test-print-multiple-pages-with-margins/grapheme-7"
  }
  {
    var c/ecx: grapheme <- copy 0x68   # 'h'
    add-grapheme pg, c
    var done?/eax: boolean <- done-drawing? pg
    var done/eax: int <- copy done?
    check-ints-equal done, 1, "F - test-print-multiple-pages-with-margins/grapheme-8"
  }
  var screen-ah/eax: (addr handle screen) <- get pg, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  check-screen-row screen-addr, 1, "      ", "F - test-print-multiple-pages-with-margins/row1"
  check-screen-row screen-addr, 2, " ab ef", "F - test-print-multiple-pages-with-margins/row2"
  check-screen-row screen-addr, 3, " cd gh", "F - test-print-multiple-pages-with-margins/row3"
  # currently it's hard-coded that we avoid printing to the bottom-most row of the screen
}

fn initialize-fake-paginated-screen _self: (addr paginated-screen), nrows: int, ncols: int, page-width: int, top-margin: int, left-margin: int {
  var self/esi: (addr paginated-screen) <- copy _self
  var screen-ah/eax: (addr handle screen) <- get self, screen
  allocate screen-ah
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  initialize-screen screen-addr, nrows, ncols
  initialize-paginated-screen self, page-width, top-margin, left-margin
}

## simple delegates

fn reposition-cursor _self: (addr paginated-screen) {
  var self/esi: (addr paginated-screen) <- copy _self
  var r/ecx: (addr int) <- get self, row
  var c/edx: (addr int) <- get self, col
#?   print-string-to-real-screen "reposition cursor: "
#?   print-int32-hex-to-real-screen *r
#?   print-string-to-real-screen ", "
#?   print-int32-hex-to-real-screen *c
#?   print-string-to-real-screen "\n"
  var screen-ah/eax: (addr handle screen) <- get self, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  move-cursor screen-addr, *r *c
}

fn clear-paginated-screen _self: (addr paginated-screen) {
  var self/esi: (addr paginated-screen) <- copy _self
  var screen-ah/eax: (addr handle screen) <- get self, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  clear-screen screen-addr
}

fn start-color-on-paginated-screen _self: (addr paginated-screen), fg: int, bg: int {
  var self/esi: (addr paginated-screen) <- copy _self
  var screen-ah/eax: (addr handle screen) <- get self, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  start-color screen-addr, fg, bg
}

fn start-bold-on-paginated-screen _self: (addr paginated-screen) {
  var self/esi: (addr paginated-screen) <- copy _self
  var screen-ah/eax: (addr handle screen) <- get self, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  start-bold screen-addr
}

fn start-underline-on-paginated-screen _self: (addr paginated-screen) {
  var self/esi: (addr paginated-screen) <- copy _self
  var screen-ah/eax: (addr handle screen) <- get self, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  start-underline screen-addr
}

fn start-reverse-video-on-paginated-screen _self: (addr paginated-screen) {
  var self/esi: (addr paginated-screen) <- copy _self
  var screen-ah/eax: (addr handle screen) <- get self, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  start-reverse-video screen-addr
}

fn start-blinking-on-paginated-screen _self: (addr paginated-screen) {
  var self/esi: (addr paginated-screen) <- copy _self
  var screen-ah/eax: (addr handle screen) <- get self, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  start-blinking screen-addr
}

fn reset-formatting-on-paginated-screen _self: (addr paginated-screen) {
  var self/esi: (addr paginated-screen) <- copy _self
  var screen-ah/eax: (addr handle screen) <- get self, screen
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  reset-formatting screen-addr
}

## helpers

fn next-line _self: (addr paginated-screen) {
#?   print-string-to-real-screen "next-line\n"
  var self/esi: (addr paginated-screen) <- copy _self
  var tmp/eax: (addr int) <- copy 0
  var tmp2/ecx: int <- copy 0
  # self->col = self->leftcol
  tmp <- get self, leftcol
  tmp2 <- copy *tmp
  tmp <- get self, col
  copy-to *tmp, tmp2
  # self->row++
  tmp <- get self, row
  increment *tmp
#?   print-string-to-real-screen "next-line: row: "
#?   print-int32-hex-to-real-screen *tmp
#?   print-string-to-real-screen "\n"
  # if (self->row > self->botrow) next-page(self)
  tmp2 <- copy *tmp
  tmp <- get self, botrow
  compare tmp2, *tmp
  {
    break-if-<=
    next-page self
  }
}

fn next-page _self: (addr paginated-screen) {
#?   print-string-to-real-screen "next-page\n"
  var self/esi: (addr paginated-screen) <- copy _self
  var tmp/eax: (addr int) <- copy 0
  var tmp2/ecx: int <- copy 0
#?   # temporary: stop
#?   tmp <- get self, ncols
#?   tmp2 <- copy *tmp
#?   tmp <- get self, rightcol
#?   copy-to *tmp, tmp2
  # real: multiple pages
  # self->leftcol = self->rightcol + left-margin
  tmp <- get self, rightcol
  tmp2 <- copy *tmp
  tmp <- get self, left-margin
  tmp2 <- add *tmp
  tmp <- get self, leftcol
  copy-to *tmp, tmp2
#?   print-string-to-real-screen "left: "
#?   print-int32-hex-to-real-screen tmp2
#?   print-string-to-real-screen "\n"
  # self->rightcol = self->leftcol + page-width
  tmp <- get self, page-width
  tmp2 <- copy *tmp
  tmp <- get self, leftcol
  tmp2 <- add *tmp
  tmp <- get self, rightcol
  copy-to *tmp, tmp2
#?   print-string-to-real-screen "right: "
#?   print-int32-hex-to-real-screen tmp2
#?   print-string-to-real-screen "\n"
  # self->row = self->toprow
  tmp <- get self, toprow
  tmp2 <- copy *tmp
  tmp <- get self, row
  copy-to *tmp, tmp2
  # self->col = self->leftcol
  tmp <- get self, leftcol
  tmp2 <- copy *tmp
  tmp <- get self, col
  copy-to *tmp, tmp2
}