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Text File  |  2009-11-02  |  7KB  |  189 lines
  1. """Simple textbox editing widget with Emacs-like keybindings."""
  2.  
  3. import curses
  4. import curses.ascii
  5.  
  6. def rectangle(win, uly, ulx, lry, lrx):
  7.     """Draw a rectangle with corners at the provided upper-left
  8.     and lower-right coordinates.
  9.     """
  10.     win.vline(uly+1, ulx, curses.ACS_VLINE, lry - uly - 1)
  11.     win.hline(uly, ulx+1, curses.ACS_HLINE, lrx - ulx - 1)
  12.     win.hline(lry, ulx+1, curses.ACS_HLINE, lrx - ulx - 1)
  13.     win.vline(uly+1, lrx, curses.ACS_VLINE, lry - uly - 1)
  14.     win.addch(uly, ulx, curses.ACS_ULCORNER)
  15.     win.addch(uly, lrx, curses.ACS_URCORNER)
  16.     win.addch(lry, lrx, curses.ACS_LRCORNER)
  17.     win.addch(lry, ulx, curses.ACS_LLCORNER)
  18.  
  19. class Textbox:
  20.     """Editing widget using the interior of a window object.
  21.      Supports the following Emacs-like key bindings:
  22.  
  23.     Ctrl-A      Go to left edge of window.
  24.     Ctrl-B      Cursor left, wrapping to previous line if appropriate.
  25.     Ctrl-D      Delete character under cursor.
  26.     Ctrl-E      Go to right edge (stripspaces off) or end of line (stripspaces on).
  27.     Ctrl-F      Cursor right, wrapping to next line when appropriate.
  28.     Ctrl-G      Terminate, returning the window contents.
  29.     Ctrl-H      Delete character backward.
  30.     Ctrl-J      Terminate if the window is 1 line, otherwise insert newline.
  31.     Ctrl-K      If line is blank, delete it, otherwise clear to end of line.
  32.     Ctrl-L      Refresh screen.
  33.     Ctrl-N      Cursor down; move down one line.
  34.     Ctrl-O      Insert a blank line at cursor location.
  35.     Ctrl-P      Cursor up; move up one line.
  36.  
  37.     Move operations do nothing if the cursor is at an edge where the movement
  38.     is not possible.  The following synonyms are supported where possible:
  39.  
  40.     KEY_LEFT = Ctrl-B, KEY_RIGHT = Ctrl-F, KEY_UP = Ctrl-P, KEY_DOWN = Ctrl-N
  41.     KEY_BACKSPACE = Ctrl-h
  42.     """
  43.     def __init__(self, win, insert_mode=False):
  44.         self.win = win
  45.         self.insert_mode = insert_mode
  46.         (self.maxy, self.maxx) = win.getmaxyx()
  47.         self.maxy = self.maxy - 1
  48.         self.maxx = self.maxx - 1
  49.         self.stripspaces = 1
  50.         self.lastcmd = None
  51.         win.keypad(1)
  52.  
  53.     def _end_of_line(self, y):
  54.         """Go to the location of the first blank on the given line,
  55.         returning the index of the last non-blank character."""
  56.         last = self.maxx
  57.         while True:
  58.             if curses.ascii.ascii(self.win.inch(y, last)) != curses.ascii.SP:
  59.                 last = min(self.maxx, last+1)
  60.                 break
  61.             elif last == 0:
  62.                 break
  63.             last = last - 1
  64.         return last
  65.  
  66.     def _insert_printable_char(self, ch):
  67.         (y, x) = self.win.getyx()
  68.         if y < self.maxy or x < self.maxx:
  69.             if self.insert_mode:
  70.                 oldch = self.win.inch()
  71.             # The try-catch ignores the error we trigger from some curses
  72.             # versions by trying to write into the lowest-rightmost spot
  73.             # in the window.
  74.             try:
  75.                 self.win.addch(ch)
  76.             except curses.error:
  77.                 pass
  78.             if self.insert_mode:
  79.                 (backy, backx) = self.win.getyx()
  80.                 if curses.ascii.isprint(oldch):
  81.                     self._insert_printable_char(oldch)
  82.                     self.win.move(backy, backx)
  83.  
  84.     def do_command(self, ch):
  85.         "Process a single editing command."
  86.         (y, x) = self.win.getyx()
  87.         self.lastcmd = ch
  88.         if curses.ascii.isprint(ch):
  89.             if y < self.maxy or x < self.maxx:
  90.                 self._insert_printable_char(ch)
  91.         elif ch == curses.ascii.SOH:                           # ^a
  92.             self.win.move(y, 0)
  93.         elif ch in (curses.ascii.STX,curses.KEY_LEFT, curses.ascii.BS,curses.KEY_BACKSPACE):
  94.             if x > 0:
  95.                 self.win.move(y, x-1)
  96.             elif y == 0:
  97.                 pass
  98.             elif self.stripspaces:
  99.                 self.win.move(y-1, self._end_of_line(y-1))
  100.             else:
  101.                 self.win.move(y-1, self.maxx)
  102.             if ch in (curses.ascii.BS, curses.KEY_BACKSPACE):
  103.                 self.win.delch()
  104.         elif ch == curses.ascii.EOT:                           # ^d
  105.             self.win.delch()
  106.         elif ch == curses.ascii.ENQ:                           # ^e
  107.             if self.stripspaces:
  108.                 self.win.move(y, self._end_of_line(y))
  109.             else:
  110.                 self.win.move(y, self.maxx)
  111.         elif ch in (curses.ascii.ACK, curses.KEY_RIGHT):       # ^f
  112.             if x < self.maxx:
  113.                 self.win.move(y, x+1)
  114.             elif y == self.maxy:
  115.                 pass
  116.             else:
  117.                 self.win.move(y+1, 0)
  118.         elif ch == curses.ascii.BEL:                           # ^g
  119.             return 0
  120.         elif ch == curses.ascii.NL:                            # ^j
  121.             if self.maxy == 0:
  122.                 return 0
  123.             elif y < self.maxy:
  124.                 self.win.move(y+1, 0)
  125.         elif ch == curses.ascii.VT:                            # ^k
  126.             if x == 0 and self._end_of_line(y) == 0:
  127.                 self.win.deleteln()
  128.             else:
  129.                 # first undo the effect of self._end_of_line
  130.                 self.win.move(y, x)
  131.                 self.win.clrtoeol()
  132.         elif ch == curses.ascii.FF:                            # ^l
  133.             self.win.refresh()
  134.         elif ch in (curses.ascii.SO, curses.KEY_DOWN):         # ^n
  135.             if y < self.maxy:
  136.                 self.win.move(y+1, x)
  137.                 if x > self._end_of_line(y+1):
  138.                     self.win.move(y+1, self._end_of_line(y+1))
  139.         elif ch == curses.ascii.SI:                            # ^o
  140.             self.win.insertln()
  141.         elif ch in (curses.ascii.DLE, curses.KEY_UP):          # ^p
  142.             if y > 0:
  143.                 self.win.move(y-1, x)
  144.                 if x > self._end_of_line(y-1):
  145.                     self.win.move(y-1, self._end_of_line(y-1))
  146.         return 1
  147.  
  148.     def gather(self):
  149.         "Collect and return the contents of the window."
  150.         result = ""
  151.         for y in range(self.maxy+1):
  152.             self.win.move(y, 0)
  153.             stop = self._end_of_line(y)
  154.             if stop == 0 and self.stripspaces:
  155.                 continue
  156.             for x in range(self.maxx+1):
  157.                 if self.stripspaces and x > stop:
  158.                     break
  159.                 result = result + chr(curses.ascii.ascii(self.win.inch(y, x)))
  160.             if self.maxy > 0:
  161.                 result = result + "\n"
  162.         return result
  163.  
  164.     def edit(self, validate=None):
  165.         "Edit in the widget window and collect the results."
  166.         while 1:
  167.             ch = self.win.getch()
  168.             if validate:
  169.                 ch = validate(ch)
  170.             if not ch:
  171.                 continue
  172.             if not self.do_command(ch):
  173.                 break
  174.             self.win.refresh()
  175.         return self.gather()
  176.  
  177. if __name__ == '__main__':
  178.     def test_editbox(stdscr):
  179.         ncols, nlines = 9, 4
  180.         uly, ulx = 15, 20
  181.         stdscr.addstr(uly-2, ulx, "Use Ctrl-G to end editing.")
  182.         win = curses.newwin(nlines, ncols, uly, ulx)
  183.         rectangle(stdscr, uly-1, ulx-1, uly + nlines, ulx + ncols)
  184.         stdscr.refresh()
  185.         return Textbox(win).edit()
  186.  
  187.     str = curses.wrapper(test_editbox)
  188.     print 'Contents of text box:', repr(str)
  189.