terminal-eyes.rb

terminal-eyes.rb

at_exit { stop! }
require "io/console"

$last_click_pos = nil

LEFT_EYE_OFFSET = -3
RIGHT_EYE_OFFSET = 3
EYE_CENTER_OFFSET = 2

# Xterm control sequences
CTL_START_TRACKING = "\e[?1003h".freeze
CTL_STOP_TRACKING = "\e[?1003l".freeze
CTL_CLEAR_CANVAS = "\e[2J".freeze
CTL_MOVE_CURSOR = "\e[%d;%dH".freeze
# CTL_HIDE_CURSOR = "\e[?25l".freeze
# CTL_SHOW_CURSOR = "\e[?25h".freeze

def set_cursor_position(x, y)
  printf CTL_MOVE_CURSOR, y, x
end

def start!
  # print CTL_HIDE_CURSOR
  print CTL_CLEAR_CANVAS
  print CTL_START_TRACKING
end

def stop!
  print CTL_STOP_TRACKING
  # print CTL_SHOW_CURSOR
end

# Parse Xterm control sequences
MATCH_SEQUENCE = /\e\[M(?<event>[C#])(?<x>.)(?<y>.)/
EVENT_CODE_RELEASE = "#".freeze

def decode_sequence(str)
  return unless MATCH_SEQUENCE =~ str
  { event_code: $~["event"],
    x: $~["x"].ord - 32,
    y: $~["y"].ord - 32,
  }
end

# \e[5D = move cursor 5 left
# \e[1B = move cursor 1 down
EYE =
  ".---.\e[5D\e[1B" \
  "|cde|\e[5D\e[1B" \
  "|bf7|\e[5D\e[1B" \
  "|a98|\e[5D\e[1B" \
  "'---'"

def eye(target_x, target_y)
  # Calculate angle w/ x-axis
  hyp = Math.sqrt(target_y**2 + target_x**2)
  theta = Math.asin(target_y / hyp)

  # Convert to eighths of a turn
  eighths = 4 * theta / Math::PI
  octant_num =
    if target_x < 0
      4 - eighths
    elsif target_y < 0
      8 + eighths
    else
      eighths
    end

  # Convert octant 0–7 to 7–e (avoids conflict w/ nums in control seqs), or f for center
  octant_code = octant_num.nan? ? 15 : octant_num.round % 8 + 7
  EYE.tr(octant_code.to_s(16), "0").tr("789a-f", " ")
end

def draw_eyes(mouse_x, mouse_y)
  base_x, y = $last_click_pos
  [ base_x - LEFT_EYE_OFFSET, base_x - RIGHT_EYE_OFFSET ].each do |x|
    set_cursor_position(x - EYE_CENTER_OFFSET, y - EYE_CENTER_OFFSET)
    print eye(mouse_x - x, mouse_y - y)
  end
end

def handle_event(event_code:, x:, y:)
  print CTL_CLEAR_CANVAS
  $last_click_pos = [ x, y ] if event_code == EVENT_CODE_RELEASE
  draw_eyes(x, y) unless $last_click_pos.nil?
end

start!

input = ""
while char = STDIN.getch
  exit 130 if char == "\003" # Ctrl+C

  input << char
  if info = decode_sequence(input)
    handle_event(info)
    input = ""
  end
end