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textpad.py
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"""Simple textbox editing widget with Emacs-like keybindings.""" import curses import curses.ascii def rectangle(win, uly, ulx, lry, lrx): """Draw a rectangle with corners at the provided upper-left and lower-right coordinates. """ 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 (stripspaces off) or end of line (stripspaces on). Ctrl-F Cursor right, wrapping to next line when appropriate. Ctrl-G Terminate, returning the window contents. Ctrl-H Delete character backward. 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 KEY_BACKSPACE = Ctrl-h """ def __init__(self, win, insert_mode=False): self.win = win self.insert_mode = insert_mode self._update_max_yx() self.stripspaces = 1 self.lastcmd = None win.keypad(1) def _update_max_yx(self): maxy, maxx = self.win.getmaxyx() self.maxy = maxy - 1 self.maxx = maxx - 1 def _end_of_line(self, y): """Go to the location of the first blank on the given line, returning the index of the last non-blank character.""" self._update_max_yx() last = self.maxx while True: if curses.ascii.ascii(self.win.inch(y, last)) != curses.ascii.SP: last = min(self.maxx, last+1) break elif last == 0: break last = last - 1 return last def _insert_printable_char(self, ch): self._update_max_yx() (y, x) = self.win.getyx() backyx = None while y < self.maxy or x < self.maxx: if self.insert_mode: oldch = self.win.inch() # The try-catch ignores the error we trigger from some curses # versions by trying to write into the lowest-rightmost spot # in the window. try: self.win.addch(ch) except curses.error: pass if not self.insert_mode or not curses.ascii.isprint(oldch): break ch = oldch (y, x) = self.win.getyx() # Remember where to put the cursor back since we are in insert_mode if backyx is None: backyx = y, x if backyx is not None: self.win.move(*backyx) def do_command(self, ch): "Process a single editing command." self._update_max_yx() (y, x) = self.win.getyx() self.lastcmd = ch if curses.ascii.isprint(ch): if y < self.maxy or x < self.maxx: self._insert_printable_char(ch) elif ch == curses.ascii.SOH: # ^a self.win.move(y, 0) elif ch in (curses.ascii.STX,curses.KEY_LEFT, curses.ascii.BS,curses.KEY_BACKSPACE): if x > 0: self.win.move(y, x-1) elif y == 0: pass elif self.stripspaces: self.win.move(y-1, self._end_of_line(y-1)) else: self.win.move(y-1, self.maxx) if ch in (curses.ascii.BS, curses.KEY_BACKSPACE): self.win.delch() elif ch == curses.ascii.EOT: # ^d self.win.delch() elif ch == curses.ascii.ENQ: # ^e if self.stripspaces: self.win.move(y, self._end_of_line(y)) else: self.win.move(y, self.maxx) elif ch in (curses.ascii.ACK, curses.KEY_RIGHT): # ^f if x < self.maxx: self.win.move(y, x+1) elif y == self.maxy: pass else: self.win.move(y+1, 0) elif ch == curses.ascii.BEL: # ^g return 0 elif ch == curses.ascii.NL: # ^j if self.maxy == 0: return 0 elif y < self.maxy: self.win.move(y+1, 0) elif ch == curses.ascii.VT: # ^k if x == 0 and self._end_of_line(y) == 0: self.win.deleteln() else: # first undo the effect of self._end_of_line self.win.move(y, x) self.win.clrtoeol() elif ch == curses.ascii.FF: # ^l self.win.refresh() elif ch in (curses.ascii.SO, curses.KEY_DOWN): # ^n if y < self.maxy: self.win.move(y+1, x) if x > self._end_of_line(y+1): self.win.move(y+1, self._end_of_line(y+1)) elif ch == curses.ascii.SI: # ^o self.win.insertln() elif ch in (curses.ascii.DLE, curses.KEY_UP): # ^p if y > 0: self.win.move(y-1, x) if x > self._end_of_line(y-1): self.win.move(y-1, self._end_of_line(y-1)) return 1 def gather(self): "Collect and return the contents of the window." result = "" self._update_max_yx() for y in range(self.maxy+1): self.win.move(y, 0) stop = self._end_of_line(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(curses.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 validate: ch = validate(ch) if not ch: continue if not self.do_command(ch): break self.win.refresh() return self.gather() if __name__ == '__main__': def test_editbox(stdscr): ncols, nlines = 9, 4 uly, ulx = 15, 20 stdscr.addstr(uly-2, ulx, "Use Ctrl-G to end editing.") win = curses.newwin(nlines, ncols, uly, ulx) rectangle(stdscr, uly-1, ulx-1, uly + nlines, ulx + ncols) stdscr.refresh() return Textbox(win).edit() str = curses.wrapper(test_editbox) print('Contents of text box:', repr(str))