# 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 2 Esc)
    (write 2 "[?1049h")
    #
    (clear-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 2 Esc)
    (write 2 "[?1049l")
$enable-screen-type-mode:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

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
$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-screen:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 2 Esc)
    (write 2 "[H")
    (write 2 Esc)
    (write 2 "[2J")
$clear-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:  # 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: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-screen:  # s: (addr array byte)
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 2 *(ebp+8))
$print-string-to-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

# just because Mu has no support for global variables yet
print-byte:  # 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 4/imm32/size
    89/<- %ecx 4/r32/esp
    (write 2 %ecx)
$print-byte: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

# just because Mu has no support for global variables yet
write-int32-hex-to-screen:  # n: int
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write-int32-hex-buffered Stdout *(ebp+8))
    (flush Stdout)
$write-int32-hex-to-screen:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

reset-formatting:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 2 Esc)
    (write 2 "(B")
    (write 2 Esc)
    (write 2 "[m")
$reset-formatting:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

start-color:  # 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: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:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 2 Esc)
    (write 2 "[1m")
$start-bold:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

start-underline:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 2 Esc)
    (write 2 "[4m")
$start-underline:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

start-reverse-video:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 2 Esc)
    (write 2 "[7m")
$start-reverse-video:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

# might require enabling blinking in your terminal program
start-blinking:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 2 Esc)
    (write 2 "[5m")
$start-blinking:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

hide-cursor:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 2 Esc)
    (write 2 "[?25l")
$hide-cursor:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

show-cursor:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (write 2 Esc)
    (write 2 "[?12l")
    (write 2 Esc)
    (write 2 "[?25h")
$show-cursor: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