[Python-Dev] Creating curses package: OK?
Eric S. Raymond
esr@thyrsus.com
Sat, 10 Jun 2000 13:24:18 -0400
Moshe Zadka <moshez@math.huji.ac.il>:
> I'm +1, except for some nagging doubt about the traceback wrapper.
> Why not put it in its own (small, granted) module?
I don't understand. Whuy do you want to do this?
> i'll-be-+1-on-the-text-pad-stuff-when-you-get-it-ready-eric-ly y'rs, Z.
You can try it out now:
#
# Curses extensions -- these are expected to be in the 1.6 Python library
#
import sys, curses, ascii
def wrapper(func, *rest):
"Wrapper function that restores normal keyboard/screen behavior on error."
res = None
try:
# Initialize curses
stdscr=curses.initscr()
# Turn off echoing of keys, and enter cbreak mode,
# where no buffering is performed on keyboard input
curses.noecho() ; curses.cbreak()
# In keypad mode, escape sequences for special keys
# (like the cursor keys) will be interpreted and
# a special value like curses.KEY_LEFT will be returned
stdscr.keypad(1)
res = apply(func, (stdscr,) + rest)
except:
# In the event of an error, restore the terminal
# to a sane state.
stdscr.keypad(0)
curses.echo() ; curses.nocbreak()
curses.endwin()
# Pass the exception upwards
(exc_type, exc_value, exc_traceback) = sys.exc_info()
raise exc_type, exc_value, exc_traceback
else:
# Set everything back to normal
stdscr.keypad(0)
curses.echo() ; curses.nocbreak()
curses.endwin() # Terminate curses
return res
def rectangle(win, uly, ulx, lry, lrx):
"Draw a rectangle."
win.vline(uly+1, ulx, curses.ACS_VLINE, lry - uly - 1)
win.hline(uly, ulx+1, curses.ACS_HLINE, lrx - ulx - 1)
win.hline(lry, ulx+1, curses.ACS_HLINE, lrx - ulx - 1)
win.vline(uly+1, lrx, curses.ACS_VLINE, lry - uly - 1)
win.addch(uly, ulx, curses.ACS_ULCORNER)
win.addch(uly, lrx, curses.ACS_URCORNER)
win.addch(lry, lrx, curses.ACS_LRCORNER)
win.addch(lry, ulx, curses.ACS_LLCORNER)
class textbox:
"""Editing widget using the interior of a window object.
Supports the following Emacs-like key bindings:
Ctrl-A Go to left edge of window.
Ctrl-B Cursor left, wrapping to previous line if appropriate.
Ctrl-D Delete character under cursor.
Ctrl-E Go to right edge (nospaces off) or end of line (nospaces on).
Ctrl-F Cursor right, wrapping to next line when appropriate.
Ctrl-G Terminate, returning the window contents.
Ctrl-J Terminate if the window is 1 line, otherwise insert newline.
Ctrl-K If line is blank, delete it, otherwise clear to end of line.
Ctrl-L Refresh screen
Ctrl-N Cursor down; move down one line.
Ctrl-O Insert a blank line at cursor location.
Ctrl-P Cursor up; move up one line.
Move operations do nothing if the cursor is at an edge where the movement
is not possible. The following synonyms are supported where possible:
KEY_LEFT = Ctrl-B, KEY_RIGHT = Ctrl-F, KEY_UP = Ctrl-P, KEY_DOWN = Ctrl-N
"""
def __init__(self, win):
self.win = win
(self.maxy, self.maxx) = win.getmaxyx()
self.maxy = self.maxy - 1
self.maxx = self.maxx - 1
self.stripspaces = 1
win.keypad(1)
def firstblank(self, y):
"Go to the location of the first blank on the given line."
(oldy, oldx) = self.win.getyx()
self.win.move(y, self.maxx-1)
last = self.maxx-1
while 1:
if last == 0:
break
if ascii.ascii(self.win.inch(y, last)) != ascii.SP:
last = last + 1
break
last = last - 1
self.win.move(oldy, oldx)
return last
def do_command(self, ch):
"Process a single editing command."
(y, x) = self.win.getyx()
if ascii.isprint(ch):
if y < self.maxy or x < self.maxx:
# The try-catch ignores the error we trigger from some curses
# versions by trying to write into the lowest-rightmost spot
# in the self.window.
try:
self.win.addch(ch)
except ERR:
pass
elif ch == ascii.SOH: # Ctrl-a
self.win.move(y, 0)
elif ch in (ascii.STX, curses.KEY_LEFT): # Ctrl-b
if x > 0:
self.win.move(y, x-1)
elif y == 0:
pass
elif self.stripspaces:
self.win.move(y-1, self.firstblank(y-1))
else:
self.win.move(y-1, self.maxx)
elif ch == ascii.EOT: # Ctrl-d
self.win.delch()
elif ch == ascii.ENQ: # Ctrl-e
if self.stripspaces:
self.win.move(y, self.firstblank(y, maxx))
else:
self.win.move(y, self.maxx)
elif ch in (ascii.ACK, curses.KEY_RIGHT): # Ctrl-f
if x < self.maxx:
self.win.move(y, x+1)
elif y == self.maxx:
pass
else:
self.win.move(y+1, 0)
elif ch == ascii.BEL: # Ctrl-g
return 0
elif ch == ascii.NL: # Ctrl-j
if self.maxy == 0:
return 0
elif y < self.maxy:
self.win.move(y+1, 0)
elif ch == ascii.VT: # Ctrl-k
if x == 0 and self.firstblank(y) == 0:
self.win.deleteln()
else:
self.win.clrtoeol()
elif ch == ascii.FF: # Ctrl-l
self.win.refresh()
elif ch in (ascii.SO, curses.KEY_DOWN): # Ctrl-n
if y < self.maxy:
self.win.move(y+1, x)
elif ch == ascii.SI: # Ctrl-o
self.win.insertln()
elif ch in (ascii.DLE, curses.KEY_UP): # Ctrl-p
if y > 0:
self.win.move(y-1, x)
self.win.refresh()
return 1
def gather(self):
"Collect and return the contents of the window."
result = ""
for y in range(self.maxy+1):
self.win.move(y, 0)
stop = self.firstblank(y)
if stop == 0 and self.stripspaces:
continue
for x in range(self.maxx+1):
if self.stripspaces and x == stop:
break
result = result + chr(ascii.ascii(self.win.inch(y, x)))
if self.maxy > 0:
result = result + "\n"
return result
def edit(self, validate=None):
"Edit in the widget window and collect the results."
while 1:
ch = self.win.getch()
if self.validate:
ch = validate(ch)
if not self.do_command(ch):
break
return self.gather()
if __name__ == '__main__':
def test_editbox(stdscr):
win = curses.newwin(4, 9, 15, 20)
rectangle(stdscr, 14, 19, 19, 29)
stdscr.refresh()
return textbox(win).edit()
str = wrapper(test_editbox)
print str
--
<a href="http://www.tuxedo.org/~esr">Eric S. Raymond</a>
The danger (where there is any) from armed citizens, is only to the
*government*, not to *society*; and as long as they have nothing to
revenge in the government (which they cannot have while it is in their
own hands) there are many advantages in their being accustomed to the
use of arms, and no possible disadvantage.
-- Joel Barlow, "Advice to the Privileged Orders", 1792-93