端末が落ちます (下方向に)

fall.rb

#!/usr/bin/env ruby
#
# fall.rb -- 端末が落ちます (下方向に)
#
# 対応端末:
#   dttermのウィンドウ制御シーケンスに一通り対応していれば動くはず……だけど意外と少ないんだ、これが
#   手元で動作するのを確認したのは xterm, Tera Term, mintty の三つ
#
# License: CC0

#$gravity = 2.4
$gravity = 3

require 'timeout'
include Math

$stdout.sync = 1

def getCSIstr(t = 1)
  resp = ""
  Timeout.timeout(t) {
    while c = $stdin.getc
      case c.ord
      when 0x1b
	c = $stdin.getc
	break if c.chr == "["
	$stdin.ungetc c
      when 0x9c
	break
      when 3, 4
	return ""
      when 0..0x1f
	raise
      end
    end

    while c = $stdin.getc
      case c.ord
      when 0x20..0x3f
	resp << c.chr
      when 0x40..0x7e
	resp << c.chr
	break
      else
	raise
      end
    end
  }
  resp
end

def moveTo(x, y)
  print "\e[3;#{x.to_i};#{y.to_i}t"
end

def resizeTerm(h, w)
  print "\e[8;#{h};#{w}t"
end

def getCurrentPosition
  begin
    system("stty raw -echo")
    print "\e[13t"
    case getCSIstr(0)
    when ""
      return [-1, -1]
    when /(\d+)\;(\d+);(\d+)t/
      raise unless $1 == "3"
    else
      raise
    end
    [$2.to_i, $3.to_i]
  ensure
    system("stty #{$saved_mode}")
  end
end

def do_fall(x, y, maxY)
  dirV = 0
  begin
    while true
      y += dirV
      if y > maxY
	y = maxY
	dirV /= 2
	break if dirV <= 1
	dirV = -dirV
      elsif y < 0
	y = 0
      end

      dirV += $gravity

      moveTo x, y

      sleep 0.02
    end
  end
end

maxX = 0
maxY = 0
termWidth = -1
termHeight = -1
origX = -1
origY = -1

$saved_mode = `stty -g`
begin
  system("stty raw -echo")

  print "\e[18t"
  raise unless /(\d+)\;(\d+);(\d+)t/ =~ getCSIstr && $1 == "8"
  termHeight = $2.to_i
  termWidth = $3.to_i

  print "\e[13t"
  raise unless /(\d+)\;(\d+);(\d+)t/ =~ getCSIstr && $1 == "3"
  origX = $2.to_i
  origY = $3.to_i

  resizeTerm 25, 81
  print "\e[14t"
  raise unless /(\d+)\;(\d+);(\d+)t/ =~ getCSIstr && $1 == "4"
  tmpHeight = $2.to_i
  tmpWidth = $3.to_i

  resizeTerm 24, 80
  print "\e[14t"
  raise unless /(\d+)\;(\d+);(\d+)t/ =~ getCSIstr && $1 == "4"
  winHeight = $2.to_i
  winWidth = $3.to_i

  cellHeight = tmpHeight - winHeight
  cellWidth = tmpWidth - winWidth

  print "\e[19t"
  raise unless /(\d+)\;(\d+);(\d+)t/ =~ getCSIstr && $1 == "9"
  rootHeight = $2.to_i * cellHeight
  rootWidth = $3.to_i * cellWidth

  maxY = rootHeight - winHeight
  maxX = rootWidth - winWidth

rescue Timeout::Error, RuntimeError
  puts "not supported terminal"
  resizeTerm(termHeight, termWidth) if termHeight > 0 && termWidth > 0
  moveTo(origX, origY) if origX >= 0 && origY >= 0
  exit 1
ensure
  system("stty #{$saved_mode}")
end

begin
  do_fall(origX, origY, maxY)

  while true
    sleep 1
    x, y = getCurrentPosition
    break if x < 0
    do_fall(x, y, maxY) if y != maxY
  end
rescue Interrupt
  exit 0
ensure
  resizeTerm(termHeight, termWidth)
  moveTo(origX, origY)
end