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#!/usr/bin/env python
"""
A Dumb full-screen editor.
This example program makes use of many context manager methods:
:meth:`~.Terminal.hidden_cursor`, :meth:`~.Terminal.raw`,
:meth:`~.Terminal.location`, :meth:`~.Terminal.fullscreen`, and
:meth:`~.Terminal.keypad`.
Early curses work focused namely around writing screen editors, naturally
any serious editor would make liberal use of special modes.
Actions:
- ``Ctrl - L`` refresh
- ``F2`` quit
- ``F1`` save
- ``LEFT MOUSE BUTTON`` move cursor
"""
# std imports
import collections
# local
from blessed import Terminal
def echo(text):
"""Display ``text`` and flush output."""
print(text, end='', flush=True)
def input_filter(keystroke):
"""
For given keystroke, return whether it should be allowed as input.
This somewhat requires that the interface use special application keys to perform functions, as
alphanumeric input intended for persisting could otherwise be interpreted as a command sequence.
"""
if keystroke.is_sequence:
# Namely, deny multi-byte sequences (such as '\x1b[A'),
return False
if ord(keystroke) < ord(' '):
# or control characters (such as ^L),
return False
return True
def echo_yx(cursor, text):
"""Move to ``cursor`` and display ``text``."""
echo(cursor.term.move_yx(cursor.y, cursor.x) + text)
Cursor = collections.namedtuple('Cursor', ('y', 'x', 'term'))
def readline(term, width=20):
"""A rudimentary readline implementation."""
text = ''
while True:
inp = term.inkey()
if inp.code == term.KEY_ENTER:
break
elif inp.code == term.KEY_ESCAPE or inp == chr(3):
text = None
break
elif not inp.is_sequence and len(text) < width:
text += inp
echo(inp)
elif inp.code in (term.KEY_BACKSPACE, term.KEY_DELETE):
text = text[:-1]
# https://utcc.utoronto.ca/~cks/space/blog/unix/HowUnixBackspaces
#
# "When you hit backspace, the kernel tty line discipline rubs out
# your previous character by printing (in the simple case)
# Ctrl-H, a space, and then another Ctrl-H."
echo('\b \b')
return text
def save(screen, fname):
"""Save screen contents to file."""
if not fname:
return
with open(fname, 'w') as fout:
cur_row = cur_col = 0
for (row, col) in sorted(screen):
char = screen[(row, col)]
while row != cur_row:
cur_row += 1
cur_col = 0
fout.write('\n')
while col > cur_col:
cur_col += 1
fout.write(' ')
fout.write(char)
cur_col += 1
fout.write('\n')
def redraw(term, screen, start=None, end=None):
"""Redraw the screen."""
if start is None and end is None:
echo(term.clear)
start, end = (Cursor(y=min(y for (y, x) in screen or [(0, 0)]),
x=min(x for (y, x) in screen or [(0, 0)]),
term=term),
Cursor(y=max(y for (y, x) in screen or [(0, 0)]),
x=max(x for (y, x) in screen or [(0, 0)]),
term=term))
lastcol, lastrow = -1, -1
for row, col in sorted(screen):
if start.y <= row <= end.y and start.x <= col <= end.x:
if col >= term.width or row >= term.height:
# out of bounds
continue
if row != lastrow or col != lastcol + 1:
# use cursor movement
echo_yx(Cursor(row, col, term), screen[row, col])
else:
# just write past last one
echo(screen[row, col])
def main():
"""Program entry point."""
def above(csr, offset):
return Cursor(y=max(0, csr.y - offset),
x=csr.x,
term=csr.term)
def below(csr, offset):
return Cursor(y=min(csr.term.height - 1, csr.y + offset),
x=csr.x,
term=csr.term)
def right_of(csr, offset):
return Cursor(y=csr.y,
x=min(csr.term.width - 1, csr.x + offset),
term=csr.term)
def left_of(csr, offset):
return Cursor(y=csr.y,
x=max(0, csr.x - offset),
term=csr.term)
def home(csr):
return Cursor(y=csr.y,
x=0,
term=csr.term)
def end(csr):
return Cursor(y=csr.y,
x=csr.term.width - 1,
term=csr.term)
def bottom(csr):
return Cursor(y=csr.term.height - 1,
x=csr.x,
term=csr.term)
def center(csr):
return Cursor(csr.term.height // 2,
csr.term.width // 2,
csr.term)
def lookup_move(inp_code, csr):
return {
# arrows, including angled directionals
csr.term.KEY_END: below(left_of(csr, 1), 1),
csr.term.KEY_KP_1: below(left_of(csr, 1), 1),
csr.term.KEY_DOWN: below(csr, 1),
csr.term.KEY_KP_2: below(csr, 1),
csr.term.KEY_PGDOWN: below(right_of(csr, 1), 1),
csr.term.KEY_LR: below(right_of(csr, 1), 1),
csr.term.KEY_KP_3: below(right_of(csr, 1), 1),
csr.term.KEY_LEFT: left_of(csr, 1),
csr.term.KEY_KP_4: left_of(csr, 1),
csr.term.KEY_CENTER: center(csr),
csr.term.KEY_KP_5: center(csr),
csr.term.KEY_RIGHT: right_of(csr, 1),
csr.term.KEY_KP_6: right_of(csr, 1),
csr.term.KEY_HOME: above(left_of(csr, 1), 1),
csr.term.KEY_KP_7: above(left_of(csr, 1), 1),
csr.term.KEY_UP: above(csr, 1),
csr.term.KEY_KP_8: above(csr, 1),
csr.term.KEY_PGUP: above(right_of(csr, 1), 1),
csr.term.KEY_KP_9: above(right_of(csr, 1), 1),
# shift + arrows
csr.term.KEY_SLEFT: left_of(csr, 10),
csr.term.KEY_SRIGHT: right_of(csr, 10),
csr.term.KEY_SDOWN: below(csr, 10),
csr.term.KEY_SUP: above(csr, 10),
# carriage return
csr.term.KEY_ENTER: home(below(csr, 1)),
}.get(inp_code, csr)
term = Terminal()
csr = Cursor(0, 0, term)
screen = {}
with term.hidden_cursor(), \
term.raw(), \
term.location(), \
term.fullscreen(), \
term.keypad(), \
term.mouse_enabled():
inp = None
while True:
echo_yx(csr, term.reverse(screen.get((csr.y, csr.x), ' ')))
inp = term.inkey()
if inp.name == 'KEY_F2':
break
elif inp.name == 'KEY_F1':
# ^s saves
echo_yx(home(bottom(csr)),
term.ljust(term.bold_white('Filename: ')))
echo_yx(right_of(home(bottom(csr)), len('Filename: ')), '')
save(screen, readline(term))
echo_yx(home(bottom(csr)), term.clear_eol)
redraw(term=term, screen=screen,
start=home(bottom(csr)),
end=end(bottom(csr)))
continue
elif inp == chr(12):
# ^l refreshes
redraw(term=term, screen=screen)
elif inp.is_mouse_left():
# Handle left mouse button press
csr = Cursor(inp.y - 1, inp.x - 1, term)
continue
else:
n_csr = lookup_move(inp.code, csr)
if n_csr != csr:
# erase old cursor,
echo_yx(csr, screen.get((csr.y, csr.x), ' '))
csr = n_csr
elif input_filter(inp):
echo_yx(csr, inp)
screen[(csr.y, csr.x)] = inp.__str__()
n_csr = right_of(csr, 1)
if n_csr == csr:
# wrap around margin
n_csr = home(below(csr, 1))
csr = n_csr
if __name__ == '__main__':
main()
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