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Text File  |  2005-09-12  |  7KB  |  174 lines
  1. """Simple textbox editing widget with Emacs-like keybindings."""
  2.  
  3. import curses, ascii
  4.  
  5. def rectangle(win, uly, ulx, lry, lrx):
  6.     """Draw a rectangle with corners at the provided upper-left
  7.     and lower-right coordinates.
  8.     """
  9.     win.vline(uly+1, ulx, curses.ACS_VLINE, lry - uly - 1)
  10.     win.hline(uly, ulx+1, curses.ACS_HLINE, lrx - ulx - 1)
  11.     win.hline(lry, ulx+1, curses.ACS_HLINE, lrx - ulx - 1)
  12.     win.vline(uly+1, lrx, curses.ACS_VLINE, lry - uly - 1)
  13.     win.addch(uly, ulx, curses.ACS_ULCORNER)
  14.     win.addch(uly, lrx, curses.ACS_URCORNER)
  15.     win.addch(lry, lrx, curses.ACS_LRCORNER)
  16.     win.addch(lry, ulx, curses.ACS_LLCORNER)
  17.  
  18. class Textbox:
  19.     """Editing widget using the interior of a window object.
  20.      Supports the following Emacs-like key bindings:
  21.  
  22.     Ctrl-A      Go to left edge of window.
  23.     Ctrl-B      Cursor left, wrapping to previous line if appropriate.
  24.     Ctrl-D      Delete character under cursor.
  25.     Ctrl-E      Go to right edge (stripspaces off) or end of line (stripspaces on).
  26.     Ctrl-F      Cursor right, wrapping to next line when appropriate.
  27.     Ctrl-G      Terminate, returning the window contents.
  28.     Ctrl-H      Delete character backward.
  29.     Ctrl-J      Terminate if the window is 1 line, otherwise insert newline.
  30.     Ctrl-K      If line is blank, delete it, otherwise clear to end of line.
  31.     Ctrl-L      Refresh screen.
  32.     Ctrl-N      Cursor down; move down one line.
  33.     Ctrl-O      Insert a blank line at cursor location.
  34.     Ctrl-P      Cursor up; move up one line.
  35.  
  36.     Move operations do nothing if the cursor is at an edge where the movement
  37.     is not possible.  The following synonyms are supported where possible:
  38.  
  39.     KEY_LEFT = Ctrl-B, KEY_RIGHT = Ctrl-F, KEY_UP = Ctrl-P, KEY_DOWN = Ctrl-N
  40.     KEY_BACKSPACE = Ctrl-h
  41.     """
  42.     def __init__(self, win):
  43.         self.win = win
  44.         (self.maxy, self.maxx) = win.getmaxyx()
  45.         self.maxy = self.maxy - 1
  46.         self.maxx = self.maxx - 1
  47.         self.stripspaces = 1
  48.         self.lastcmd = None
  49.         win.keypad(1)
  50.  
  51.     def _end_of_line(self, y):
  52.         "Go to the location of the first blank on the given line."
  53.         last = self.maxx
  54.         while 1:
  55.             if ascii.ascii(self.win.inch(y, last)) != ascii.SP:
  56.                 last = min(self.maxx, last+1)
  57.                 break
  58.             elif last == 0:
  59.                 break
  60.             last = last - 1
  61.         return last
  62.  
  63.     def do_command(self, ch):
  64.         "Process a single editing command."
  65.         (y, x) = self.win.getyx()
  66.         self.lastcmd = ch
  67.         if ascii.isprint(ch):
  68.             if y < self.maxy or x < self.maxx:
  69.                 # The try-catch ignores the error we trigger from some curses
  70.                 # versions by trying to write into the lowest-rightmost spot
  71.                 # in the window.
  72.                 try:
  73.                     self.win.addch(ch)
  74.                 except curses.error:
  75.                     pass
  76.         elif ch == ascii.SOH:                           # ^a
  77.             self.win.move(y, 0)
  78.         elif ch in (ascii.STX,curses.KEY_LEFT, ascii.BS,curses.KEY_BACKSPACE):
  79.             if x > 0:
  80.                 self.win.move(y, x-1)
  81.             elif y == 0:
  82.                 pass
  83.             elif self.stripspaces:
  84.                 self.win.move(y-1, self._end_of_line(y-1))
  85.             else:
  86.                 self.win.move(y-1, self.maxx)
  87.             if ch in (ascii.BS, curses.KEY_BACKSPACE):
  88.                 self.win.delch()
  89.         elif ch == ascii.EOT:                           # ^d
  90.             self.win.delch()
  91.         elif ch == ascii.ENQ:                           # ^e
  92.             if self.stripspaces:
  93.                 self.win.move(y, self._end_of_line(y))
  94.             else:
  95.                 self.win.move(y, self.maxx)
  96.         elif ch in (ascii.ACK, curses.KEY_RIGHT):       # ^f
  97.             if x < self.maxx:
  98.                 self.win.move(y, x+1)
  99.             elif y == self.maxy:
  100.                 pass
  101.             else:
  102.                 self.win.move(y+1, 0)
  103.         elif ch == ascii.BEL:                           # ^g
  104.             return 0
  105.         elif ch == ascii.NL:                            # ^j
  106.             if self.maxy == 0:
  107.                 return 0
  108.             elif y < self.maxy:
  109.                 self.win.move(y+1, 0)
  110.         elif ch == ascii.VT:                            # ^k
  111.             if x == 0 and self._end_of_line(y) == 0:
  112.                 self.win.deleteln()
  113.             else:
  114.                 # first undo the effect of self._end_of_line
  115.                 self.win.move(y, x)
  116.                 self.win.clrtoeol()
  117.         elif ch == ascii.FF:                            # ^l
  118.             self.win.refresh()
  119.         elif ch in (ascii.SO, curses.KEY_DOWN):         # ^n
  120.             if y < self.maxy:
  121.                 self.win.move(y+1, x)
  122.                 if x > self._end_of_line(y+1):
  123.                     self.win.move(y+1, self._end_of_line(y+1))
  124.         elif ch == ascii.SI:                            # ^o
  125.             self.win.insertln()
  126.         elif ch in (ascii.DLE, curses.KEY_UP):          # ^p
  127.             if y > 0:
  128.                 self.win.move(y-1, x)
  129.                 if x > self._end_of_line(y-1):
  130.                     self.win.move(y-1, self._end_of_line(y-1))
  131.         return 1
  132.  
  133.     def gather(self):
  134.         "Collect and return the contents of the window."
  135.         result = ""
  136.         for y in range(self.maxy+1):
  137.             self.win.move(y, 0)
  138.             stop = self._end_of_line(y)
  139.             if stop == 0 and self.stripspaces:
  140.                 continue
  141.             for x in range(self.maxx+1):
  142.                 if self.stripspaces and x == stop:
  143.                     break
  144.                 result = result + chr(ascii.ascii(self.win.inch(y, x)))
  145.             if self.maxy > 0:
  146.                 result = result + "\n"
  147.         return result
  148.  
  149.     def edit(self, validate=None):
  150.         "Edit in the widget window and collect the results."
  151.         while 1:
  152.             ch = self.win.getch()
  153.             if validate:
  154.                 ch = validate(ch)
  155.             if not ch:
  156.                 continue
  157.             if not self.do_command(ch):
  158.                 break
  159.             self.win.refresh()
  160.         return self.gather()
  161.  
  162. if __name__ == '__main__':
  163.     def test_editbox(stdscr):
  164.         ncols, nlines = 9, 4
  165.         uly, ulx = 15, 20
  166.         stdscr.addstr(uly-2, ulx, "Use Ctrl-G to end editing.")
  167.         win = curses.newwin(nlines, ncols, uly, ulx)
  168.         rectangle(stdscr, uly-1, ulx-1, uly + nlines, ulx + ncols)
  169.         stdscr.refresh()
  170.         return Textbox(win).edit()
  171.  
  172.     str = curses.wrapper(test_editbox)
  173.     print 'Contents of text box:', repr(str)
  174.