#!/usr/bin/python # # Urwid raw display module # Copyright (C) 2004-2009 Ian Ward # # This library is free software; you can redistribute it and/or # modify it under the terms of the GNU Lesser General Public # License as published by the Free Software Foundation; either # version 2.1 of the License, or (at your option) any later version. # # This library is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU # Lesser General Public License for more details. # # You should have received a copy of the GNU Lesser General Public # License along with this library; if not, write to the Free Software # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA # # Urwid web site: http://excess.org/urwid/ """ Direct terminal UI implementation """ import fcntl import termios import os import select import struct import sys import tty import signal from urwid import util from urwid import escape from urwid.display_common import BaseScreen, RealTerminal, \ UPDATE_PALETTE_ENTRY, AttrSpec, UNPRINTABLE_TRANS_TABLE, \ INPUT_DESCRIPTORS_CHANGED from urwid import signals from urwid.compat import PYTHON3, bytes, B from subprocess import Popen, PIPE class Screen(BaseScreen, RealTerminal): def __init__(self): """Initialize a screen that directly prints escape codes to an output terminal. """ super(Screen, self).__init__() self._pal_escape = {} self._pal_attrspec = {} signals.connect_signal(self, UPDATE_PALETTE_ENTRY, self._on_update_palette_entry) self.colors = 16 # FIXME: detect this self.has_underline = True # FIXME: detect this self.register_palette_entry( None, 'default','default') self._keyqueue = [] self.prev_input_resize = 0 self.set_input_timeouts() self.screen_buf = None self._screen_buf_canvas = None self._resized = False self.maxrow = None self.gpm_mev = None self.gpm_event_pending = False self._mouse_tracking_enabled = False self.last_bstate = 0 self._setup_G1_done = False self._rows_used = None self._cy = 0 term = os.environ.get('TERM', '') self.bright_is_bold = not term.startswith("xterm") self.back_color_erase = not term.startswith("screen") self._next_timeout = None self._term_output_file = sys.stdout self._term_input_file = sys.stdin # pipe for signalling external event loops about resize events self._resize_pipe_rd, self._resize_pipe_wr = os.pipe() fcntl.fcntl(self._resize_pipe_rd, fcntl.F_SETFL, os.O_NONBLOCK) def _on_update_palette_entry(self, name, *attrspecs): # copy the attribute to a dictionary containing the escape seqences a = attrspecs[{16:0,1:1,88:2,256:3}[self.colors]] self._pal_attrspec[name] = a self._pal_escape[name] = self._attrspec_to_escape(a) def set_input_timeouts(self, max_wait=None, complete_wait=0.125, resize_wait=0.125): """ Set the get_input timeout values. All values are in floating point numbers of seconds. max_wait -- amount of time in seconds to wait for input when there is no input pending, wait forever if None complete_wait -- amount of time in seconds to wait when get_input detects an incomplete escape sequence at the end of the available input resize_wait -- amount of time in seconds to wait for more input after receiving two screen resize requests in a row to stop Urwid from consuming 100% cpu during a gradual window resize operation """ self.max_wait = max_wait if max_wait is not None: if self._next_timeout is None: self._next_timeout = max_wait else: self._next_timeout = min(self._next_timeout, self.max_wait) self.complete_wait = complete_wait self.resize_wait = resize_wait def _sigwinch_handler(self, signum, frame): if not self._resized: os.write(self._resize_pipe_wr, B('R')) self._resized = True self.screen_buf = None def _sigcont_handler(self, signum, frame): self.stop() self.start() self._sigwinch_handler(None, None) def signal_init(self): """ Called in the startup of run wrapper to set the SIGWINCH and SIGCONT signal handlers. Override this function to call from main thread in threaded applications. """ signal.signal(signal.SIGWINCH, self._sigwinch_handler) signal.signal(signal.SIGCONT, self._sigcont_handler) def signal_restore(self): """ Called in the finally block of run wrapper to restore the SIGWINCH and SIGCONT signal handlers. Override this function to call from main thread in threaded applications. """ signal.signal(signal.SIGCONT, signal.SIG_DFL) signal.signal(signal.SIGWINCH, signal.SIG_DFL) def set_mouse_tracking(self, enable=True): """ Enable (or disable) mouse tracking. After calling this function get_input will include mouse click events along with keystrokes. """ enable = bool(enable) if enable == self._mouse_tracking_enabled: return self._mouse_tracking(enable) self._mouse_tracking_enabled = enable def _mouse_tracking(self, enable): if enable: self._term_output_file.write(escape.MOUSE_TRACKING_ON) self._start_gpm_tracking() else: self._term_output_file.write(escape.MOUSE_TRACKING_OFF) self._stop_gpm_tracking() def _start_gpm_tracking(self): if not os.path.isfile("/usr/bin/mev"): return if not os.environ.get('TERM',"").lower().startswith("linux"): return if not Popen: return m = Popen(["/usr/bin/mev","-e","158"], stdin=PIPE, stdout=PIPE, close_fds=True) fcntl.fcntl(m.stdout.fileno(), fcntl.F_SETFL, os.O_NONBLOCK) self.gpm_mev = m def _stop_gpm_tracking(self): if not self.gpm_mev: return os.kill(self.gpm_mev.pid, signal.SIGINT) os.waitpid(self.gpm_mev.pid, 0) self.gpm_mev = None def start(self, alternate_buffer=True): """ Initialize the screen and input mode. alternate_buffer -- use alternate screen buffer """ assert not self._started if alternate_buffer: self._term_output_file.write(escape.SWITCH_TO_ALTERNATE_BUFFER) self._rows_used = None else: self._rows_used = 0 fd = self._term_input_file.fileno() if os.isatty(fd): self._old_termios_settings = termios.tcgetattr(fd) tty.setcbreak(fd) self.signal_init() self._alternate_buffer = alternate_buffer self._input_iter = self._run_input_iter() self._next_timeout = self.max_wait if not self._signal_keys_set: self._old_signal_keys = self.tty_signal_keys(fileno=fd) super(Screen, self).start() signals.emit_signal(self, INPUT_DESCRIPTORS_CHANGED) # restore mouse tracking to previous state self._mouse_tracking(self._mouse_tracking_enabled) def stop(self): """ Restore the screen. """ self.clear() if not self._started: return signals.emit_signal(self, INPUT_DESCRIPTORS_CHANGED) self.signal_restore() fd = self._term_input_file.fileno() if os.isatty(fd): termios.tcsetattr(fd, termios.TCSADRAIN, self._old_termios_settings) self._mouse_tracking(False) move_cursor = "" if self._alternate_buffer: move_cursor = escape.RESTORE_NORMAL_BUFFER elif self.maxrow is not None: move_cursor = escape.set_cursor_position( 0, self.maxrow) self._term_output_file.write( self._attrspec_to_escape(AttrSpec('','')) + escape.SI + move_cursor + escape.SHOW_CURSOR) self._input_iter = self._fake_input_iter() if self._old_signal_keys: self.tty_signal_keys(*(self._old_signal_keys + (fd,))) super(Screen, self).stop() def run_wrapper(self, fn, alternate_buffer=True): """ Call start to initialize screen, then call fn. When fn exits call stop to restore the screen to normal. alternate_buffer -- use alternate screen buffer and restore normal screen buffer on exit """ try: self.start(alternate_buffer) return fn() finally: self.stop() def get_input(self, raw_keys=False): """Return pending input as a list. raw_keys -- return raw keycodes as well as translated versions This function will immediately return all the input since the last time it was called. If there is no input pending it will wait before returning an empty list. The wait time may be configured with the set_input_timeouts function. If raw_keys is False (default) this function will return a list of keys pressed. If raw_keys is True this function will return a ( keys pressed, raw keycodes ) tuple instead. Examples of keys returned: * ASCII printable characters: " ", "a", "0", "A", "-", "/" * ASCII control characters: "tab", "enter" * Escape sequences: "up", "page up", "home", "insert", "f1" * Key combinations: "shift f1", "meta a", "ctrl b" * Window events: "window resize" When a narrow encoding is not enabled: * "Extended ASCII" characters: "\\xa1", "\\xb2", "\\xfe" When a wide encoding is enabled: * Double-byte characters: "\\xa1\\xea", "\\xb2\\xd4" When utf8 encoding is enabled: * Unicode characters: u"\\u00a5", u'\\u253c" Examples of mouse events returned: * Mouse button press: ('mouse press', 1, 15, 13), ('meta mouse press', 2, 17, 23) * Mouse drag: ('mouse drag', 1, 16, 13), ('mouse drag', 1, 17, 13), ('ctrl mouse drag', 1, 18, 13) * Mouse button release: ('mouse release', 0, 18, 13), ('ctrl mouse release', 0, 17, 23) """ assert self._started self._wait_for_input_ready(self._next_timeout) self._next_timeout, keys, raw = self._input_iter.next() # Avoid pegging CPU at 100% when slowly resizing if keys==['window resize'] and self.prev_input_resize: while True: self._wait_for_input_ready(self.resize_wait) self._next_timeout, keys, raw2 = \ self._input_iter.next() raw += raw2 #if not keys: # keys, raw2 = self._get_input( # self.resize_wait) # raw += raw2 if keys!=['window resize']: break if keys[-1:]!=['window resize']: keys.append('window resize') if keys==['window resize']: self.prev_input_resize = 2 elif self.prev_input_resize == 2 and not keys: self.prev_input_resize = 1 else: self.prev_input_resize = 0 if raw_keys: return keys, raw return keys def get_input_descriptors(self): """ Return a list of integer file descriptors that should be polled in external event loops to check for user input. Use this method if you are implementing your own event loop. """ if not self._started: return [] fd_list = [self._term_input_file.fileno(), self._resize_pipe_rd] if self.gpm_mev is not None: fd_list.append(self.gpm_mev.stdout.fileno()) return fd_list def get_input_nonblocking(self): """ Return a (next_input_timeout, keys_pressed, raw_keycodes) tuple. Use this method if you are implementing your own event loop. When there is input waiting on one of the descriptors returned by get_input_descriptors() this method should be called to read and process the input. This method expects to be called in next_input_timeout seconds (a floating point number) if there is no input waiting. """ return self._input_iter.next() def _run_input_iter(self): def empty_resize_pipe(): # clean out the pipe used to signal external event loops # that a resize has occurred try: while True: os.read(self._resize_pipe_rd, 1) except OSError: pass while True: processed = [] codes = self._get_gpm_codes() + \ self._get_keyboard_codes() original_codes = codes try: while codes: run, codes = escape.process_keyqueue( codes, True) processed.extend(run) except escape.MoreInputRequired: k = len(original_codes) - len(codes) yield (self.complete_wait, processed, original_codes[:k]) empty_resize_pipe() original_codes = codes processed = [] codes += self._get_keyboard_codes() + \ self._get_gpm_codes() while codes: run, codes = escape.process_keyqueue( codes, False) processed.extend(run) if self._resized: processed.append('window resize') self._resized = False yield (self.max_wait, processed, original_codes) empty_resize_pipe() def _fake_input_iter(self): """ This generator is a placeholder for when the screen is stopped to always return that no input is available. """ while True: yield (self.max_wait, [], []) def _get_keyboard_codes(self): codes = [] while True: code = self._getch_nodelay() if code < 0: break codes.append(code) return codes def _get_gpm_codes(self): codes = [] try: while self.gpm_mev is not None and self.gpm_event_pending: codes.extend(self._encode_gpm_event()) except IOError, e: if e.args[0] != 11: raise return codes def _wait_for_input_ready(self, timeout): ready = None fd_list = [self._term_input_file.fileno()] if self.gpm_mev is not None: fd_list.append(self.gpm_mev.stdout.fileno()) while True: try: if timeout is None: ready,w,err = select.select( fd_list, [], fd_list) else: ready,w,err = select.select( fd_list,[],fd_list, timeout) break except select.error, e: if e.args[0] != 4: raise if self._resized: ready = [] break return ready def _getch(self, timeout): ready = self._wait_for_input_ready(timeout) if self.gpm_mev is not None: if self.gpm_mev.stdout.fileno() in ready: self.gpm_event_pending = True if self._term_input_file.fileno() in ready: return ord(os.read(self._term_input_file.fileno(), 1)) return -1 def _encode_gpm_event( self ): self.gpm_event_pending = False s = self.gpm_mev.stdout.readline().decode('ascii') l = s.split(",") if len(l) != 6: # unexpected output, stop tracking self._stop_gpm_tracking() signals.emit_signal(self, INPUT_DESCRIPTORS_CHANGED) return [] ev, x, y, ign, b, m = s.split(",") ev = int( ev.split("x")[-1], 16) x = int( x.split(" ")[-1] ) y = int( y.lstrip().split(" ")[0] ) b = int( b.split(" ")[-1] ) m = int( m.split("x")[-1].rstrip(), 16 ) # convert to xterm-like escape sequence last = next = self.last_bstate l = [] mod = 0 if m & 1: mod |= 4 # shift if m & 10: mod |= 8 # alt if m & 4: mod |= 16 # ctrl def append_button( b ): b |= mod l.extend([ 27, ord('['), ord('M'), b+32, x+32, y+32 ]) def determine_button_release( flag ): if b & 4 and last & 1: append_button( 0 + flag ) next |= 1 if b & 2 and last & 2: append_button( 1 + flag ) next |= 2 if b & 1 and last & 4: append_button( 2 + flag ) next |= 4 if ev == 20 or ev == 36 or ev == 52: # press if b & 4 and last & 1 == 0: append_button( 0 ) next |= 1 if b & 2 and last & 2 == 0: append_button( 1 ) next |= 2 if b & 1 and last & 4 == 0: append_button( 2 ) next |= 4 elif ev == 146: # drag if b & 4: append_button( 0 + escape.MOUSE_DRAG_FLAG ) elif b & 2: append_button( 1 + escape.MOUSE_DRAG_FLAG ) elif b & 1: append_button( 2 + escape.MOUSE_DRAG_FLAG ) else: # release if b & 4 and last & 1: append_button( 0 + escape.MOUSE_RELEASE_FLAG ) next &= ~ 1 if b & 2 and last & 2: append_button( 1 + escape.MOUSE_RELEASE_FLAG ) next &= ~ 2 if b & 1 and last & 4: append_button( 2 + escape.MOUSE_RELEASE_FLAG ) next &= ~ 4 if ev == 40: # double click (release) if b & 4 and last & 1: append_button( 0 + escape.MOUSE_MULTIPLE_CLICK_FLAG ) if b & 2 and last & 2: append_button( 1 + escape.MOUSE_MULTIPLE_CLICK_FLAG ) if b & 1 and last & 4: append_button( 2 + escape.MOUSE_MULTIPLE_CLICK_FLAG ) elif ev == 52: if b & 4 and last & 1: append_button( 0 + escape.MOUSE_MULTIPLE_CLICK_FLAG*2 ) if b & 2 and last & 2: append_button( 1 + escape.MOUSE_MULTIPLE_CLICK_FLAG*2 ) if b & 1 and last & 4: append_button( 2 + escape.MOUSE_MULTIPLE_CLICK_FLAG*2 ) self.last_bstate = next return l def _getch_nodelay(self): return self._getch(0) def get_cols_rows(self): """Return the terminal dimensions (num columns, num rows).""" y, x = 80, 24 try: buf = fcntl.ioctl(self._term_output_file.fileno(), termios.TIOCGWINSZ, ' '*4) y, x = struct.unpack('hh', buf) except IOError: # Term size could not be determined pass self.maxrow = y return x, y def _setup_G1(self): """ Initialize the G1 character set to graphics mode if required. """ if self._setup_G1_done: return while True: try: self._term_output_file.write(escape.DESIGNATE_G1_SPECIAL) self._term_output_file.flush() break except IOError: pass self._setup_G1_done = True def draw_screen(self, (maxcol, maxrow), r ): """Paint screen with rendered canvas.""" assert self._started assert maxrow == r.rows() # quick return if nothing has changed if self.screen_buf and r is self._screen_buf_canvas: return self._setup_G1() if self._resized: # handle resize before trying to draw screen return o = [escape.HIDE_CURSOR, self._attrspec_to_escape(AttrSpec('',''))] def partial_display(): # returns True if the screen is in partial display mode # ie. only some rows belong to the display return self._rows_used is not None if not partial_display(): o.append(escape.CURSOR_HOME) if self.screen_buf: osb = self.screen_buf else: osb = [] sb = [] cy = self._cy y = -1 def set_cursor_home(): if not partial_display(): return escape.set_cursor_position(0, 0) return (escape.CURSOR_HOME_COL + escape.move_cursor_up(cy)) def set_cursor_row(y): if not partial_display(): return escape.set_cursor_position(0, y) return escape.move_cursor_down(y - cy) def set_cursor_position(x, y): if not partial_display(): return escape.set_cursor_position(x, y) if cy > y: return ('\b' + escape.CURSOR_HOME_COL + escape.move_cursor_up(cy - y) + escape.move_cursor_right(x)) return ('\b' + escape.CURSOR_HOME_COL + escape.move_cursor_down(y - cy) + escape.move_cursor_right(x)) def is_blank_row(row): if len(row) > 1: return False if row[0][2].strip(): return False return True def attr_to_escape(a): if a in self._pal_escape: return self._pal_escape[a] elif isinstance(a, AttrSpec): return self._attrspec_to_escape(a) # undefined attributes use default/default # TODO: track and report these return self._attrspec_to_escape( AttrSpec('default','default')) def using_standout(a): a = self._pal_attrspec.get(a, a) return isinstance(a, AttrSpec) and a.standout ins = None o.append(set_cursor_home()) cy = 0 for row in r.content(): y += 1 if False and osb and osb[y] == row: # this row of the screen buffer matches what is # currently displayed, so we can skip this line sb.append( osb[y] ) continue sb.append(row) # leave blank lines off display when we are using # the default screen buffer (allows partial screen) if partial_display() and y > self._rows_used: if is_blank_row(row): continue self._rows_used = y if y or partial_display(): o.append(set_cursor_position(0, y)) # after updating the line we will be just over the # edge, but terminals still treat this as being # on the same line cy = y whitespace_at_end = False if row: a, cs, run = row[-1] if (run[-1:] == B(' ') and self.back_color_erase and not using_standout(a)): whitespace_at_end = True row = row[:-1] + [(a, cs, run.rstrip(B(' ')))] elif y == maxrow-1 and maxcol > 1: row, back, ins = self._last_row(row) first = True lasta = lastcs = None for (a,cs, run) in row: assert isinstance(run, bytes) # canvases should render with bytes if cs != 'U': run = run.translate(UNPRINTABLE_TRANS_TABLE) if first or lasta != a: o.append(attr_to_escape(a)) lasta = a if first or lastcs != cs: assert cs in [None, "0", "U"], repr(cs) if lastcs == "U": o.append( escape.IBMPC_OFF ) if cs is None: o.append( escape.SI ) elif cs == "U": o.append( escape.IBMPC_ON ) else: o.append( escape.SO ) lastcs = cs o.append( run ) first = False if ins: (inserta, insertcs, inserttext) = ins ias = attr_to_escape(inserta) assert insertcs in [None, "0", "U"], repr(insertcs) if cs is None: icss = escape.SI elif cs == "U": icss = escape.IBMPC_ON else: icss = escape.SO o += [ "\x08"*back, ias, icss, escape.INSERT_ON, inserttext, escape.INSERT_OFF ] if cs == "U": o.append(escape.IBMPC_OFF) if whitespace_at_end: o.append(escape.ERASE_IN_LINE_RIGHT) if r.cursor is not None: x,y = r.cursor o += [set_cursor_position(x, y), escape.SHOW_CURSOR ] self._cy = y if self._resized: # handle resize before trying to draw screen return try: for l in o: if isinstance(l, bytes) and PYTHON3: l = l.decode('utf-8') self._term_output_file.write(l) self._term_output_file.flush() except IOError, e: # ignore interrupted syscall if e.args[0] != 4: raise self.screen_buf = sb self._screen_buf_canvas = r def _last_row(self, row): """On the last row we need to slide the bottom right character into place. Calculate the new line, attr and an insert sequence to do that. eg. last row: XXXXXXXXXXXXXXXXXXXXYZ Y will be drawn after Z, shifting Z into position. """ new_row = row[:-1] z_attr, z_cs, last_text = row[-1] last_cols = util.calc_width(last_text, 0, len(last_text)) last_offs, z_col = util.calc_text_pos(last_text, 0, len(last_text), last_cols-1) if last_offs == 0: z_text = last_text del new_row[-1] # we need another segment y_attr, y_cs, nlast_text = row[-2] nlast_cols = util.calc_width(nlast_text, 0, len(nlast_text)) z_col += nlast_cols nlast_offs, y_col = util.calc_text_pos(nlast_text, 0, len(nlast_text), nlast_cols-1) y_text = nlast_text[nlast_offs:] if nlast_offs: new_row.append((y_attr, y_cs, nlast_text[:nlast_offs])) else: z_text = last_text[last_offs:] y_attr, y_cs = z_attr, z_cs nlast_cols = util.calc_width(last_text, 0, last_offs) nlast_offs, y_col = util.calc_text_pos(last_text, 0, last_offs, nlast_cols-1) y_text = last_text[nlast_offs:last_offs] if nlast_offs: new_row.append((y_attr, y_cs, last_text[:nlast_offs])) new_row.append((z_attr, z_cs, z_text)) return new_row, z_col-y_col, (y_attr, y_cs, y_text) def clear(self): """ Force the screen to be completely repainted on the next call to draw_screen(). """ self.screen_buf = None self.setup_G1 = True def _attrspec_to_escape(self, a): """ Convert AttrSpec instance a to an escape sequence for the terminal >>> s = Screen() >>> s.set_terminal_properties(colors=256) >>> a2e = s._attrspec_to_escape >>> a2e(s.AttrSpec('brown', 'dark green')) '\\x1b[0;33;42m' >>> a2e(s.AttrSpec('#fea,underline', '#d0d')) '\\x1b[0;38;5;229;4;48;5;164m' """ if a.foreground_high: fg = "38;5;%d" % a.foreground_number elif a.foreground_basic: if a.foreground_number > 7: if self.bright_is_bold: fg = "1;%d" % (a.foreground_number - 8 + 30) else: fg = "%d" % (a.foreground_number - 8 + 90) else: fg = "%d" % (a.foreground_number + 30) else: fg = "39" st = ("1;" * a.bold + "4;" * a.underline + "5;" * a.blink + "7;" * a.standout) if a.background_high: bg = "48;5;%d" % a.background_number elif a.background_basic: if a.background_number > 7: # this doesn't work on most terminals bg = "%d" % (a.background_number - 8 + 100) else: bg = "%d" % (a.background_number + 40) else: bg = "49" return escape.ESC + "[0;%s;%s%sm" % (fg, st, bg) def set_terminal_properties(self, colors=None, bright_is_bold=None, has_underline=None): """ colors -- number of colors terminal supports (1, 16, 88 or 256) or None to leave unchanged bright_is_bold -- set to True if this terminal uses the bold setting to create bright colors (numbers 8-15), set to False if this Terminal can create bright colors without bold or None to leave unchanged has_underline -- set to True if this terminal can use the underline setting, False if it cannot or None to leave unchanged """ if colors is None: colors = self.colors if bright_is_bold is None: bright_is_bold = self.bright_is_bold if has_underline is None: has_underline = self.has_underline if colors == self.colors and bright_is_bold == self.bright_is_bold \ and has_underline == self.has_underline: return self.colors = colors self.bright_is_bold = bright_is_bold self.has_underline = has_underline self.clear() self._pal_escape = {} for p,v in self._palette.items(): self._on_update_palette_entry(p, *v) def reset_default_terminal_palette(self): """ Attempt to set the terminal palette to default values as taken from xterm. Uses number of colors from current set_terminal_properties() screen setting. """ if self.colors == 1: return def rgb_values(n): if self.colors == 16: aspec = AttrSpec("h%d"%n, "", 256) else: aspec = AttrSpec("h%d"%n, "", self.colors) return aspec.get_rgb_values()[:3] entries = [(n,) + rgb_values(n) for n in range(self.colors)] self.modify_terminal_palette(entries) def modify_terminal_palette(self, entries): """ entries - list of (index, red, green, blue) tuples. Attempt to set part of the terminal palette (this does not work on all terminals.) The changes are sent as a single escape sequence so they should all take effect at the same time. 0 <= index < 256 (some terminals will only have 16 or 88 colors) 0 <= red, green, blue < 256 """ modify = ["%d;rgb:%02x/%02x/%02x" % (index, red, green, blue) for index, red, green, blue in entries] self._term_output_file.write("\x1b]4;"+";".join(modify)+"\x1b\\") self._term_output_file.flush() # shortcut for creating an AttrSpec with this screen object's # number of colors AttrSpec = lambda self, fg, bg: AttrSpec(fg, bg, self.colors) def _test(): import doctest doctest.testmod() if __name__=='__main__': _test()