scrolling resizable terminal draft

#! /usr/bin/env python
# -*- coding: utf-8 -*-

import sys
import signal
import os
import fcntl
import termios
import struct


class ExitException(Exception):
    pass


def exit(signum, frame):
    raise ExitException, "ESC key detected"

signal.signal(signal.SIGALRM, exit)

block = os.O_NONBLOCK if 'O_NONBLOCK' in dir(os) else (
    os.NOBLOCK if 'NONBLOCK' in dir(os) else None)

r = sys.stdin.fileno()
w = sys.stdout.fileno()

r_flags = fcntl.fcntl(r, fcntl.F_GETFL)

if r_flags & block:
    fcntl.fcntl(r, fcntl.F_SETFL, r_flags & ~block)
w_flags = fcntl.fcntl(w, fcntl.F_GETFL)
if w_flags & block:
    fcntl.fcntl(w, fcntl.F_SETFL, w_flags | block)

y = 0

width = 0
height = 0
data = []

for i in range(0, 201, 1):
    data.append(' line: {0}'.format(i + 1))


def render_scroll():
    w = globals()['width']
    h = globals()['height']

    y = globals()['y']
    data = globals()['data']

    workingHeight = h - 6

    start = max(0, min(
        len(data) - workingHeight, len(data) - (workingHeight / 2) - y))
    end = min(len(data), start + workingHeight)

    cursor = (len(data) - y - 1) - start

    view = []
    pointer = 0

    for i in range(start, end, 1):
        line = '\033[2K' + data[i] + (' ' * w)[:-len(data[i])]

        if pointer == cursor:
            view.append('\x1B[47m{0}\x1B[0m'.format(line))
        else:
            view.append(line)
        pointer += 1

    if len(view) < h:
        body = '\n'.join(view) + ((' ' * w) * (workingHeight - len(view)))
    else:
        body = '\n'.join(view)

    return body


def render():
    w = globals()['width']

    header = (u'┌' + (u'─' * (w - 2)) + u'┐') + '\n' \
        + (u'│' + (' ' * (w - 2)) + u'│') + '\n' \
        + (u'└' + (u'─' * (w - 2)) + u'┘')

    body = render_scroll()
    footer = (u'┌' + (u'─' * (w - 2)) + u'┐') + '\n' \
        + (u'│' + (' ' * (w - 2)) + u'│') + '\n' \
        + (u'└' + (u'─' * (w - 2)) + u'┘')

    screen = header + '\n' + body + '\n' + footer

    sys.stdout.write(u'\033[0;0H' + screen)


def resize(*args):
    h, w, hp, wp = struct.unpack('HHHH', fcntl.ioctl(0, termios.TIOCGWINSZ, struct.pack('HHHH', 0, 0, 0, 0)))  # noqa
    globals()['width'] = w
    globals()['height'] = h
    sys.stdout.write(u'\033[2J')
    render()


def scroll(direction):
    newY = min(len(globals()['data']) - 1, max(0, globals()['y'] + direction))  # noqa
    if newY != globals()['y']:
        globals()['y'] = newY
        render()


def main():
    signal.signal(signal.SIGWINCH, resize)

    try:
        sys.stdout.write('\033[?1049h\033[?25l')
        resize()
        r_old = termios.tcgetattr(r)
        r_new = termios.tcgetattr(r)
        r_new[3] = r_new[3] & ~termios.ICANON & ~termios.ECHO
        termios.tcsetattr(r, termios.TCSANOW, r_new)

        try:
            while 1:
                try:
                    a = sys.stdin.read(1)
                    if a == chr(27):
                        signal.setitimer(signal.ITIMER_REAL, 0.01, 0.01)
                        b = sys.stdin.read(1)
                        signal.setitimer(signal.ITIMER_REAL, 0)
                        if b == '[':
                            c = sys.stdin.read(1)
                            if c == 'A':
                                scroll(1)
                            elif c == 'B':
                                scroll(-1)
                        else:
                            break
                        continue
                except IOError:
                    pass
                except ExitException:
                    break
        finally:
            termios.tcsetattr(r, termios.TCSAFLUSH, r_old)
    except KeyboardInterrupt:
        pass
    finally:
        fcntl.fcntl(r, fcntl.F_SETFL, r_flags)
        fcntl.fcntl(w, fcntl.F_SETFL, w_flags)
        sys.stdout.write('\033[?1049l\033[?25h')

if __name__ == '__main__':
    main()