# Primitives for screen control.
# Require Linux and a modern terminal.

== code

enable-screen-grid-mode:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (flush Stdout)
    (flush Stderr)
    # switch to second screen buffer
    (write 1 Esc)
    (write 1 "[?1049h")
    #
    (clear-real-screen)
$enable-screen-grid-mode:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

enable-screen-type-mode:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    # switch to first screen buffer
    (write 1 Esc)
    (write 1 "[?1049l")
$enable-screen-type-mode:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

real-screen-size:  # -> nrows/eax: int, ncols/ecx: int
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    # . save registers
    52/push-edx
    53/push-ebx
    56/push-esi
    57/push-edi
    #
    (_maybe-open-terminal)
    # var window-size-info/esi: (addr winsize)
    # winsize is a type from the Linux kernel. We don't care how large it is.
    81 5/subop/subtract %esp 0x40/imm32
    89/<- %esi 4/r32/esp
    # ioctl(*Terminal-file-descriptor, TIOCGWINSZ, window-size-info)
    89/<- %edx 6/r32/esi
    b9/copy-to-ecx 0x5413/imm32/TIOCGWINSZ
    8b/-> *Terminal-file-descriptor 3/r32/ebx
    e8/call syscall_ioctl/disp32
    # some bitworking to extract 2 16-bit shorts
    8b/-> *esi 0/r32/eax
    81 4/subop/and %eax 0xffff/imm32
    8b/-> *esi 1/r32/ecx
    c1/shift 5/subop/logical-right %ecx 0x10/imm8
$real-screen-size:end:
    # . reclaim locals
    81 0/subop/add %esp 0x40/imm32
    # . restore registers
    5f/pop-to-edi
    5e/pop-to-esi
    5b/pop-to-ebx
    5a/pop-to-edx
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

clear-real-screen:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 1 Esc)
    (write 1 "[H")
    (write 1 Esc)
    (write 1 "[2J")
$clear-real-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

# row and col count from the top-left as (1, 1)
move-cursor-on-real-screen:  # row: int, column: int
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    # . save registers
    51/push-ecx
    # var buf/ecx: (stream byte 32)
    81 5/subop/subtract %esp 0x20/imm32
    68/push 0x20/imm32/size
    68/push 0/imm32/read
    68/push 0/imm32/write
    89/<- %ecx 4/r32/esp
    # construct directive in buf
    (write %ecx Esc)
    (write %ecx "[")
    (write-int32-decimal %ecx *(ebp+8))
    (write %ecx ";")
    (write-int32-decimal %ecx *(ebp+0xc))
    (write %ecx "H")
    # flush
    (write-stream 2 %ecx)
$move-cursor-on-real-screen:end:
    # . reclaim locals
    81 0/subop/add %esp 0x2c/imm32
    # . restore registers
    59/pop-to-ecx
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

print-string-to-real-screen:  # s: (addr array byte)
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 1 *(ebp+8))
$print-string-to-real-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

print-slice-to-real-screen:  # s: (addr slice)
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write-slice-buffered Stdout *(ebp+8))
    (flush Stdout)
$print-slice-to-real-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

print-stream-to-real-screen:  # s: (addr stream byte)
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write-stream-data Stdout *(ebp+8))
    (flush Stdout)
$print-stream-to-real-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

# print a grapheme in utf-8 (only up to 4 bytes so far)
print-grapheme-to-real-screen:  # c: grapheme
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    # . save registers
    50/push-eax
    # var curr/eax: byte = 0
    b8/copy-to-eax 0/imm32
    # curr = *(ebp+8)
    8a/byte-> *(ebp+8) 0/r32/al
    # if (curr == 0) return
    3d/compare-eax-and 0/imm32
    74/jump-if-= $print-grapheme-to-real-screen:end/disp8
    #
    (print-byte-to-real-screen %eax)
    # curr = *(ebp+9)
    8a/byte-> *(ebp+9) 0/r32/al
    # if (curr == 0) return
    3d/compare-eax-and 0/imm32
    74/jump-if-= $print-grapheme-to-real-screen:end/disp8
    #
    (print-byte-to-real-screen %eax)
    # curr = *(ebp+10)
    8a/byte-> *(ebp+0xa) 0/r32/al
    # if (curr == 0) return
    3d/compare-eax-and 0/imm32
    74/jump-if-= $print-grapheme-to-real-screen:end/disp8
    #
    (print-byte-to-real-screen %eax)
    # curr = *(ebp+11)
    8a/byte-> *(ebp+0xb) 0/r32/al
    # if (curr == 0) return
    3d/compare-eax-and 0/imm32
    74/jump-if-= $print-grapheme-to-real-screen:end/disp8
    #
    (print-byte-to-real-screen %eax)
$print-grapheme-to-real-screen:end:
    # . restore registers
    58/pop-to-eax
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

print-byte-to-real-screen:  # c: byte
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    # . save registers
    51/push-ecx
    # var s/ecx: (addr array byte)
    ff 6/subop/push *(ebp+8)
    68/push 1/imm32/size
    89/<- %ecx 4/r32/esp
    (write 1 %ecx)
$print-byte-to-real-screen:end:
    # . reclaim locals
    81 0/subop/add %esp 8/imm32
    # . restore registers
    59/pop-to-ecx
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

print-int32-hex-to-real-screen:  # n: int
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write-int32-hex-buffered Stdout *(ebp+8))
    (flush Stdout)
$print-int32-hex-to-real-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

print-int32-decimal-to-real-screen:  # n: int
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write-int32-decimal-buffered Stdout *(ebp+8))
    (flush Stdout)
$print-int32-decimal-to-real-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

write-int32-decimal-buffered:  # f: (addr buffered-file), n: int
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    # . save registers
    51/push-ecx
    # var ecx: (stream byte 16)
    81 5/subop/subtract %esp 0x10/imm32
    68/push 0x10/imm32/size
    68/push 0/imm32/read
    68/push 0/imm32/write
    89/<- %ecx 4/r32/esp
    (write-int32-decimal %ecx *(ebp+0xc))
    (write-stream-data *(ebp+8) %ecx)
$write-int32-decimal-buffered:end:
    # . reclaim locals
    81 0/subop/add %esp 0x1c/imm32
    # . restore registers
    59/pop-to-ecx
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

reset-formatting-on-real-screen:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 1 Esc)
    (write 1 "(B")
    (write 1 Esc)
    (write 1 "[m")
$reset-formatting-on-real-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

start-color-on-real-screen:  # fg: int, bg: int
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    # . save registers
    51/push-ecx
    # var buf/ecx: (stream byte 32)
    81 5/subop/subtract %esp 0x20/imm32
    68/push 0x20/imm32/size
    68/push 0/imm32/read
    68/push 0/imm32/write
    89/<- %ecx 4/r32/esp
    # construct directive in buf
    # . set fg
    (write %ecx Esc)
    (write %ecx "[38;5;")
    (write-int32-decimal %ecx *(ebp+8))
    (write %ecx "m")
    # . set bg
    (write %ecx Esc)
    (write %ecx "[48;5;")
    (write-int32-decimal %ecx *(ebp+0xc))
    (write %ecx "m")
    # flush
    (write-stream 2 %ecx)
$start-color-on-real-screen:end:
    # . reclaim locals
    81 0/subop/add %esp 0x2c/imm32
    # . restore registers
    59/pop-to-ecx
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

start-bold-on-real-screen:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 1 Esc)
    (write 1 "[1m")
$start-bold-on-real-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

start-underline-on-real-screen:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 1 Esc)
    (write 1 "[4m")
$start-underline-on-real-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

start-reverse-video-on-real-screen:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 1 Esc)
    (write 1 "[7m")
$start-reverse-video-on-real-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

# might require enabling blinking in your terminal program
start-blinking-on-real-screen:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 1 Esc)
    (write 1 "[5m")
$start-blinking-on-real-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

hide-cursor-on-real-screen:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 1 Esc)
    (write 1 "[?25l")
$hide-cursor-on-real-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

show-cursor-on-real-screen:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 1 Esc)
    (write 1 "[?12l")
    (write 1 Esc)
    (write 1 "[?25h")
$show-cursor-on-real-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

# This is a low-level detail; I don't think everything should be a file.
#
# Open "/dev/tty" if necessary and cache its file descriptor in Terminal-file-descriptor
# where later primitives can use it.
_maybe-open-terminal:
    81 7/subop/compare *Terminal-file-descriptor -1/imm32
    75/jump-if-!= $_maybe-open-terminal:epilogue/disp8
    # . save registers
    50/push-eax
    51/push-ecx
    53/push-ebx
    # open("/dev/tty", O_RDWR)
    bb/copy-to-ebx Terminal-filename/imm32
    b9/copy-to-ecx 2/imm32/O_RDWR
    e8/call syscall_open/disp32
    89/<- *Terminal-file-descriptor 0/r32/eax
$_maybe-open-terminal:end:
    # . restore registers
    5b/pop-to-ebx
    59/pop-to-ecx
    58/pop-to-eax
$_maybe-open-terminal:epilogue:
    c3/return

== data

Terminal-file-descriptor:  # (addr int)
  -1/imm32

Esc:  # (addr array byte)
  # size
  1/imm32
  # data
  0x1b

Terminal-filename:  # (addr kernel-string)
  # "/dev/null"
  2f/slash 64/d 65/e 76/v 2f/slash 74/t 74/t 79/y 0/nul