"""Simple textbox editing widget with Emacs-like keybindings."""

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import curses

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import curses.ascii

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def rectangle(win, uly, ulx, lry, lrx):

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"""Draw a rectangle with corners at the provided upper-left

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and lower-right coordinates.

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"""

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win.vline(uly+1, ulx, curses.ACS_VLINE, lry - uly - 1)

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win.hline(uly, ulx+1, curses.ACS_HLINE, lrx - ulx - 1)

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win.hline(lry, ulx+1, curses.ACS_HLINE, lrx - ulx - 1)

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win.vline(uly+1, lrx, curses.ACS_VLINE, lry - uly - 1)

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win.addch(uly, ulx, curses.ACS_ULCORNER)

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win.addch(uly, lrx, curses.ACS_URCORNER)

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win.addch(lry, lrx, curses.ACS_LRCORNER)

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win.addch(lry, ulx, curses.ACS_LLCORNER)

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class Textbox:

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"""Editing widget using the interior of a window object.

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Supports the following Emacs-like key bindings:

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Ctrl-A Go to left edge of window.

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Ctrl-B Cursor left, wrapping to previous line if appropriate.

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Ctrl-D Delete character under cursor.

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Ctrl-E Go to right edge (stripspaces off) or end of line (stripspaces on).

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Ctrl-F Cursor right, wrapping to next line when appropriate.

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Ctrl-G Terminate, returning the window contents.

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Ctrl-H Delete character backward.

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Ctrl-J Terminate if the window is 1 line, otherwise insert newline.

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Ctrl-K If line is blank, delete it, otherwise clear to end of line.

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Ctrl-L Refresh screen.

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Ctrl-N Cursor down; move down one line.

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Ctrl-O Insert a blank line at cursor location.

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Ctrl-P Cursor up; move up one line.

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Move operations do nothing if the cursor is at an edge where the movement

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is not possible. The following synonyms are supported where possible:

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KEY_LEFT = Ctrl-B, KEY_RIGHT = Ctrl-F, KEY_UP = Ctrl-P, KEY_DOWN = Ctrl-N

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KEY_BACKSPACE = Ctrl-h

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"""

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def __init__(self, win, insert_mode=False):

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self.win = win

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self.insert_mode = insert_mode

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self._update_max_yx()

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self.stripspaces = 1

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self.lastcmd = None

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win.keypad(1)

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def _update_max_yx(self):

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maxy, maxx = self.win.getmaxyx()

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self.maxy = maxy - 1

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self.maxx = maxx - 1

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def _end_of_line(self, y):

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"""Go to the location of the first blank on the given line,

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returning the index of the last non-blank character."""

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self._update_max_yx()

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last = self.maxx

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while True:

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if curses.ascii.ascii(self.win.inch(y, last)) != curses.ascii.SP:

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last = min(self.maxx, last+1)

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break

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elif last == 0:

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break

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last = last - 1

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return last

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def _insert_printable_char(self, ch):

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self._update_max_yx()

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(y, x) = self.win.getyx()

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backyx = None

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while y < self.maxy or x < self.maxx:

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if self.insert_mode:

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oldch = self.win.inch()

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# The try-catch ignores the error we trigger from some curses

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# versions by trying to write into the lowest-rightmost spot

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# in the window.

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try:

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self.win.addch(ch)

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except curses.error:

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pass

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if not self.insert_mode or not curses.ascii.isprint(oldch):

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break

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ch = oldch

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(y, x) = self.win.getyx()

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# Remember where to put the cursor back since we are in insert_mode

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if backyx is None:

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backyx = y, x

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if backyx is not None:

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self.win.move(*backyx)

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def do_command(self, ch):

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"Process a single editing command."

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self._update_max_yx()

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(y, x) = self.win.getyx()

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self.lastcmd = ch

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if curses.ascii.isprint(ch):

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if y < self.maxy or x < self.maxx:

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self._insert_printable_char(ch)

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elif ch == curses.ascii.SOH: # ^a

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self.win.move(y, 0)

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elif ch in (curses.ascii.STX,curses.KEY_LEFT, curses.ascii.BS,curses.KEY_BACKSPACE):

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if x > 0:

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self.win.move(y, x-1)

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elif y == 0:

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pass

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elif self.stripspaces:

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self.win.move(y-1, self._end_of_line(y-1))

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else:

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self.win.move(y-1, self.maxx)

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if ch in (curses.ascii.BS, curses.KEY_BACKSPACE):

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self.win.delch()

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elif ch == curses.ascii.EOT: # ^d

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self.win.delch()

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elif ch == curses.ascii.ENQ: # ^e

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if self.stripspaces:

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self.win.move(y, self._end_of_line(y))

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else:

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self.win.move(y, self.maxx)

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elif ch in (curses.ascii.ACK, curses.KEY_RIGHT): # ^f

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if x < self.maxx:

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self.win.move(y, x+1)

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elif y == self.maxy:

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pass

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else:

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self.win.move(y+1, 0)

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elif ch == curses.ascii.BEL: # ^g

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return 0

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elif ch == curses.ascii.NL: # ^j

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if self.maxy == 0:

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return 0

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elif y < self.maxy:

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self.win.move(y+1, 0)

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elif ch == curses.ascii.VT: # ^k

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if x == 0 and self._end_of_line(y) == 0:

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self.win.deleteln()

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else:

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# first undo the effect of self._end_of_line

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self.win.move(y, x)

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self.win.clrtoeol()

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elif ch == curses.ascii.FF: # ^l

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self.win.refresh()

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elif ch in (curses.ascii.SO, curses.KEY_DOWN): # ^n

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if y < self.maxy:

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self.win.move(y+1, x)

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if x > self._end_of_line(y+1):

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self.win.move(y+1, self._end_of_line(y+1))

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elif ch == curses.ascii.SI: # ^o

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self.win.insertln()

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elif ch in (curses.ascii.DLE, curses.KEY_UP): # ^p

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if y > 0:

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self.win.move(y-1, x)

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if x > self._end_of_line(y-1):

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self.win.move(y-1, self._end_of_line(y-1))

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return 1

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def gather(self):

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"Collect and return the contents of the window."

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result = ""

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self._update_max_yx()

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for y in range(self.maxy+1):

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self.win.move(y, 0)

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stop = self._end_of_line(y)

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if stop == 0 and self.stripspaces:

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continue

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for x in range(self.maxx+1):

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if self.stripspaces and x > stop:

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break

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result = result + chr(curses.ascii.ascii(self.win.inch(y, x)))

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if self.maxy > 0:

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result = result + "\n"

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return result

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def edit(self, validate=None):

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"Edit in the widget window and collect the results."

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while 1:

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ch = self.win.getch()

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if validate:

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ch = validate(ch)

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if not ch:

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continue

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if not self.do_command(ch):

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break

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self.win.refresh()

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return self.gather()

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if __name__ == '__main__':

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def test_editbox(stdscr):

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ncols, nlines = 9, 4

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uly, ulx = 15, 20

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stdscr.addstr(uly-2, ulx, "Use Ctrl-G to end editing.")

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win = curses.newwin(nlines, ncols, uly, ulx)

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rectangle(stdscr, uly-1, ulx-1, uly + nlines, ulx + ncols)

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stdscr.refresh()

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return Textbox(win).edit()

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str = curses.wrapper(test_editbox)

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print('Contents of text box:', repr(str))

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