Doc/library/curses.rst

:mod:`curses` --- Terminal handling for character-cell displays
===============================================================

.. module:: curses
   :synopsis: An interface to the curses library, providing portable terminal
              handling.
   :platform: Unix
.. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il>
.. sectionauthor:: Eric Raymond <esr@thyrsus.com>

.. versionchanged:: 1.6
   Added support for the ``ncurses`` library and converted to a package.

The :mod:`curses` module provides an interface to the curses library, the
de-facto standard for portable advanced terminal handling.

While curses is most widely used in the Unix environment, versions are available
for DOS, OS/2, and possibly other systems as well.  This extension module is
designed to match the API of ncurses, an open-source curses library hosted on
Linux and the BSD variants of Unix.

.. note::

   Since version 5.4, the ncurses library decides how to interpret non-ASCII data
   using the ``nl_langinfo`` function.  That means that you have to call
   :func:`locale.setlocale` in the application and encode Unicode strings
   using one of the system's available encodings.  This example uses the
   system's default encoding::

      import locale
      locale.setlocale(locale.LC_ALL, '')
      code = locale.getpreferredencoding()

   Then use *code* as the encoding for :meth:`str.encode` calls.

.. seealso::

   Module :mod:`curses.ascii`
      Utilities for working with ASCII characters, regardless of your locale settings.

   Module :mod:`curses.panel`
      A panel stack extension that adds depth to  curses windows.

   Module :mod:`curses.textpad`
      Editable text widget for curses supporting  :program:`Emacs`\ -like bindings.

   :ref:`curses-howto`
      Tutorial material on using curses with Python, by Andrew Kuchling and Eric
      Raymond.

   The :source:`Demo/curses/` directory in the Python source distribution contains
   some example programs using the curses bindings provided by this module.


.. _curses-functions:

Functions
---------

The module :mod:`curses` defines the following exception:


.. exception:: error

   Exception raised when a curses library function returns an error.

.. note::

   Whenever *x* or *y* arguments to a function or a method are optional, they
   default to the current cursor location. Whenever *attr* is optional, it defaults
   to :const:`A_NORMAL`.

The module :mod:`curses` defines the following functions:


.. function:: baudrate()

   Return the output speed of the terminal in bits per second.  On software
   terminal emulators it will have a fixed high value. Included for historical
   reasons; in former times, it was used to  write output loops for time delays and
   occasionally to change interfaces depending on the line speed.


.. function:: beep()

   Emit a short attention sound.


.. function:: can_change_color()

   Return ``True`` or ``False``, depending on whether the programmer can change the colors
   displayed by the terminal.


.. function:: cbreak()

   Enter cbreak mode.  In cbreak mode (sometimes called "rare" mode) normal tty
   line buffering is turned off and characters are available to be read one by one.
   However, unlike raw mode, special characters (interrupt, quit, suspend, and flow
   control) retain their effects on the tty driver and calling program.  Calling
   first :func:`raw` then :func:`cbreak` leaves the terminal in cbreak mode.


.. function:: color_content(color_number)

   Return the intensity of the red, green, and blue (RGB) components in the color
   *color_number*, which must be between ``0`` and :const:`COLORS`.  A 3-tuple is
   returned, containing the R,G,B values for the given color, which will be between
   ``0`` (no component) and ``1000`` (maximum amount of component).


.. function:: color_pair(color_number)

   Return the attribute value for displaying text in the specified color.  This
   attribute value can be combined with :const:`A_STANDOUT`, :const:`A_REVERSE`,
   and the other :const:`A_\*` attributes.  :func:`pair_number` is the counterpart
   to this function.


.. function:: curs_set(visibility)

   Set the cursor state.  *visibility* can be set to 0, 1, or 2, for invisible,
   normal, or very visible.  If the terminal supports the visibility requested, the
   previous cursor state is returned; otherwise, an exception is raised.  On many
   terminals, the "visible" mode is an underline cursor and the "very visible" mode
   is a block cursor.


.. function:: def_prog_mode()

   Save the current terminal mode as the "program" mode, the mode when the running
   program is using curses.  (Its counterpart is the "shell" mode, for when the
   program is not in curses.)  Subsequent calls to :func:`reset_prog_mode` will
   restore this mode.


.. function:: def_shell_mode()

   Save the current terminal mode as the "shell" mode, the mode when the running
   program is not using curses.  (Its counterpart is the "program" mode, when the
   program is using curses capabilities.) Subsequent calls to
   :func:`reset_shell_mode` will restore this mode.


.. function:: delay_output(ms)

   Insert an *ms* millisecond pause in output.


.. function:: doupdate()

   Update the physical screen.  The curses library keeps two data structures, one
   representing the current physical screen contents and a virtual screen
   representing the desired next state.  The :func:`doupdate` ground updates the
   physical screen to match the virtual screen.

   The virtual screen may be updated by a :meth:`noutrefresh` call after write
   operations such as :meth:`addstr` have been performed on a window.  The normal
   :meth:`refresh` call is simply :meth:`noutrefresh` followed by :func:`doupdate`;
   if you have to update multiple windows, you can speed performance and perhaps
   reduce screen flicker by issuing :meth:`noutrefresh` calls on all windows,
   followed by a single :func:`doupdate`.


.. function:: echo()

   Enter echo mode.  In echo mode, each character input is echoed to the screen as
   it is entered.


.. function:: endwin()

   De-initialize the library, and return terminal to normal status.


.. function:: erasechar()

   Return the user's current erase character.  Under Unix operating systems this
   is a property of the controlling tty of the curses program, and is not set by
   the curses library itself.


.. function:: filter()

   The :func:`.filter` routine, if used, must be called before :func:`initscr` is
   called.  The effect is that, during those calls, :envvar:`LINES` is set to 1; the
   capabilities clear, cup, cud, cud1, cuu1, cuu, vpa are disabled; and the home
   string is set to the value of cr. The effect is that the cursor is confined to
   the current line, and so are screen updates.  This may be used for enabling
   character-at-a-time  line editing without touching the rest of the screen.


.. function:: flash()

   Flash the screen.  That is, change it to reverse-video and then change it back
   in a short interval.  Some people prefer such as 'visible bell' to the audible
   attention signal produced by :func:`beep`.


.. function:: flushinp()

   Flush all input buffers.  This throws away any  typeahead  that  has been typed
   by the user and has not yet been processed by the program.


.. function:: getmouse()

   After :meth:`getch` returns :const:`KEY_MOUSE` to signal a mouse event, this
   method should be call to retrieve the queued mouse event, represented as a
   5-tuple ``(id, x, y, z, bstate)``. *id* is an ID value used to distinguish
   multiple devices, and *x*, *y*, *z* are the event's coordinates.  (*z* is
   currently unused.)  *bstate* is an integer value whose bits will be set to
   indicate the type of event, and will be the bitwise OR of one or more of the
   following constants, where *n* is the button number from 1 to 4:
   :const:`BUTTONn_PRESSED`, :const:`BUTTONn_RELEASED`, :const:`BUTTONn_CLICKED`,
   :const:`BUTTONn_DOUBLE_CLICKED`, :const:`BUTTONn_TRIPLE_CLICKED`,
   :const:`BUTTON_SHIFT`, :const:`BUTTON_CTRL`, :const:`BUTTON_ALT`.


.. function:: getsyx()

   Return the current coordinates of the virtual screen cursor in y and x.  If
   leaveok is currently true, then -1,-1 is returned.


.. function:: getwin(file)

   Read window related data stored in the file by an earlier :func:`putwin` call.
   The routine then creates and initializes a new window using that data, returning
   the new window object.


.. function:: has_colors()

   Return ``True`` if the terminal can display colors; otherwise, return ``False``.


.. function:: has_ic()

   Return ``True`` if the terminal has insert- and delete-character capabilities.
   This function is included for historical reasons only, as all modern software
   terminal emulators have such capabilities.


.. function:: has_il()

   Return ``True`` if the terminal has insert- and delete-line capabilities, or can
   simulate  them  using scrolling regions. This function is included for
   historical reasons only, as all modern software terminal emulators have such
   capabilities.


.. function:: has_key(ch)

   Take a key value *ch*, and return ``True`` if the current terminal type recognizes
   a key with that value.


.. function:: halfdelay(tenths)

   Used for half-delay mode, which is similar to cbreak mode in that characters
   typed by the user are immediately available to the program. However, after
   blocking for *tenths* tenths of seconds, an exception is raised if nothing has
   been typed.  The value of *tenths* must be a number between ``1`` and ``255``.  Use
   :func:`nocbreak` to leave half-delay mode.


.. function:: init_color(color_number, r, g, b)

   Change the definition of a color, taking the number of the color to be changed
   followed by three RGB values (for the amounts of red, green, and blue
   components).  The value of *color_number* must be between ``0`` and
   :const:`COLORS`.  Each of *r*, *g*, *b*, must be a value between ``0`` and
   ``1000``.  When :func:`init_color` is used, all occurrences of that color on the
   screen immediately change to the new definition.  This function is a no-op on
   most terminals; it is active only if :func:`can_change_color` returns ``1``.


.. function:: init_pair(pair_number, fg, bg)

   Change the definition of a color-pair.  It takes three arguments: the number of
   the color-pair to be changed, the foreground color number, and the background
   color number.  The value of *pair_number* must be between ``1`` and
   ``COLOR_PAIRS - 1`` (the ``0`` color pair is wired to white on black and cannot
   be changed).  The value of *fg* and *bg* arguments must be between ``0`` and
   :const:`COLORS`.  If the color-pair was previously initialized, the screen is
   refreshed and all occurrences of that color-pair are changed to the new
   definition.


.. function:: initscr()

   Initialize the library. Return a :class:`WindowObject` which represents the
   whole screen.

   .. note::

      If there is an error opening the terminal, the underlying curses library may
      cause the interpreter to exit.


.. function:: is_term_resized(nlines, ncols)

   Return ``True`` if :func:`resize_term` would modify the window structure,
   ``False`` otherwise.


.. function:: isendwin()

   Return ``True`` if :func:`endwin` has been called (that is, the  curses library has
   been deinitialized).


.. function:: keyname(k)

   Return the name of the key numbered *k*.  The name of a key generating printable
   ASCII character is the key's character.  The name of a control-key combination
   is a two-character string consisting of a caret followed by the corresponding
   printable ASCII character.  The name of an alt-key combination (128--255) is a
   string consisting of the prefix 'M-' followed by the name of the corresponding
   ASCII character.


.. function:: killchar()

   Return the user's current line kill character. Under Unix operating systems
   this is a property of the controlling tty of the curses program, and is not set
   by the curses library itself.


.. function:: longname()

   Return a string containing the terminfo long name field describing the current
   terminal.  The maximum length of a verbose description is 128 characters.  It is
   defined only after the call to :func:`initscr`.


.. function:: meta(yes)

   If *yes* is 1, allow 8-bit characters to be input. If *yes* is 0,  allow only
   7-bit chars.


.. function:: mouseinterval(interval)

   Set the maximum time in milliseconds that can elapse between press and release
   events in order for them to be recognized as a click, and return the previous
   interval value.  The default value is 200 msec, or one fifth of a second.


.. function:: mousemask(mousemask)

   Set the mouse events to be reported, and return a tuple ``(availmask,
   oldmask)``.   *availmask* indicates which of the specified mouse events can be
   reported; on complete failure it returns 0.  *oldmask* is the previous value of
   the given window's mouse event mask.  If this function is never called, no mouse
   events are ever reported.


.. function:: napms(ms)

   Sleep for *ms* milliseconds.


.. function:: newpad(nlines, ncols)

   Create and return a pointer to a new pad data structure with the given number
   of lines and columns.  A pad is returned as a window object.

   A pad is like a window, except that it is not restricted by the screen size, and
   is not necessarily associated with a particular part of the screen.  Pads can be
   used when a large window is needed, and only a part of the window will be on the
   screen at one time.  Automatic refreshes of pads (such as from scrolling or
   echoing of input) do not occur.  The :meth:`refresh` and :meth:`noutrefresh`
   methods of a pad require 6 arguments to specify the part of the pad to be
   displayed and the location on the screen to be used for the display. The
   arguments are *pminrow*, *pmincol*, *sminrow*, *smincol*, *smaxrow*, *smaxcol*; the *p*
   arguments refer to the upper left corner of the pad region to be displayed and
   the *s* arguments define a clipping box on the screen within which the pad region
   is to be displayed.


.. function:: newwin(nlines, ncols)
              newwin(nlines, ncols, begin_y, begin_x)

   Return a new window, whose left-upper corner is at  ``(begin_y, begin_x)``, and
   whose height/width is  *nlines*/*ncols*.

   By default, the window will extend from the  specified position to the lower
   right corner of the screen.


.. function:: nl()

   Enter newline mode.  This mode translates the return key into newline on input,
   and translates newline into return and line-feed on output. Newline mode is
   initially on.


.. function:: nocbreak()

   Leave cbreak mode.  Return to normal "cooked" mode with line buffering.


.. function:: noecho()

   Leave echo mode.  Echoing of input characters is turned off.


.. function:: nonl()

   Leave newline mode.  Disable translation of return into newline on input, and
   disable low-level translation of newline into newline/return on output (but this
   does not change the behavior of ``addch('\n')``, which always does the
   equivalent of return and line feed on the virtual screen).  With translation
   off, curses can sometimes speed up vertical motion a little; also, it will be
   able to detect the return key on input.


.. function:: noqiflush()

   When the :func:`noqiflush` routine is used, normal flush of input and output queues
   associated with the INTR, QUIT and SUSP characters will not be done.  You may
   want to call :func:`noqiflush` in a signal handler if you want output to
   continue as though the interrupt had not occurred, after the handler exits.


.. function:: noraw()

   Leave raw mode. Return to normal "cooked" mode with line buffering.


.. function:: pair_content(pair_number)

   Return a tuple ``(fg, bg)`` containing the colors for the requested color pair.
   The value of *pair_number* must be between ``1`` and ``COLOR_PAIRS - 1``.


.. function:: pair_number(attr)

   Return the number of the color-pair set by the attribute value *attr*.
   :func:`color_pair` is the counterpart to this function.


.. function:: putp(string)

   Equivalent to ``tputs(str, 1, putchar)``; emit the value of a specified
   terminfo capability for the current terminal.  Note that the output of :func:`putp`
   always goes to standard output.


.. function:: qiflush( [flag] )

   If *flag* is ``False``, the effect is the same as calling :func:`noqiflush`. If
   *flag* is ``True``, or no argument is provided, the queues will be flushed when
   these control characters are read.


.. function:: raw()

   Enter raw mode.  In raw mode, normal line buffering and  processing of
   interrupt, quit, suspend, and flow control keys are turned off; characters are
   presented to curses input functions one by one.


.. function:: reset_prog_mode()

   Restore the  terminal  to "program" mode, as previously saved  by
   :func:`def_prog_mode`.


.. function:: reset_shell_mode()

   Restore the  terminal  to "shell" mode, as previously saved  by
   :func:`def_shell_mode`.


.. function:: resetty()

   Restore the state of the terminal modes to what it was at the last call to
   :func:`savetty`.


.. function:: resize_term(nlines, ncols)

   Backend function used by :func:`resizeterm`, performing most of the work;
   when resizing the windows, :func:`resize_term` blank-fills the areas that are
   extended.  The calling application should fill in these areas with
   appropriate data.  The :func:`resize_term` function attempts to resize all
   windows.  However, due to the calling convention of pads, it is not possible
   to resize these without additional interaction with the application.


.. function:: resizeterm(nlines, ncols)

   Resize the standard and current windows to the specified dimensions, and
   adjusts other bookkeeping data used by the curses library that record the
   window dimensions (in particular the SIGWINCH handler).


.. function:: savetty()

   Save the current state of the terminal modes in a buffer, usable by
   :func:`resetty`.


.. function:: setsyx(y, x)

   Set the virtual screen cursor to *y*, *x*. If *y* and *x* are both -1, then
   leaveok is set.


.. function:: setupterm([termstr, fd])

   Initialize the terminal.  *termstr* is a string giving the terminal name; if
   omitted, the value of the :envvar:`TERM` environment variable will be used.  *fd* is the
   file descriptor to which any initialization sequences will be sent; if not
   supplied, the file descriptor for ``sys.stdout`` will be used.


.. function:: start_color()

   Must be called if the programmer wants to use colors, and before any other color
   manipulation routine is called.  It is good practice to call this routine right
   after :func:`initscr`.

   :func:`start_color` initializes eight basic colors (black, red,  green, yellow,
   blue, magenta, cyan, and white), and two global variables in the :mod:`curses`
   module, :const:`COLORS` and :const:`COLOR_PAIRS`, containing the maximum number
   of colors and color-pairs the terminal can support.  It also restores the colors
   on the terminal to the values they had when the terminal was just turned on.


.. function:: termattrs()

   Return a logical OR of all video attributes supported by the terminal.  This
   information is useful when a curses program needs complete control over the
   appearance of the screen.


.. function:: termname()

   Return the value of the environment variable :envvar:`TERM`, truncated to 14 characters.


.. function:: tigetflag(capname)

   Return the value of the Boolean capability corresponding to the terminfo
   capability name *capname*.  The value ``-1`` is returned if *capname* is not a
   Boolean capability, or ``0`` if it is canceled or absent from the terminal
   description.


.. function:: tigetnum(capname)

   Return the value of the numeric capability corresponding to the terminfo
   capability name *capname*.  The value ``-2`` is returned if *capname* is not a
   numeric capability, or ``-1`` if it is canceled or absent from the terminal
   description.


.. function:: tigetstr(capname)

   Return the value of the string capability corresponding to the terminfo
   capability name *capname*.  ``None`` is returned if *capname* is not a string
   capability, or is canceled or absent from the terminal description.


.. function:: tparm(str[,...])

   Instantiate the string *str* with the supplied parameters, where *str* should
   be a parameterized string obtained from the terminfo database.  E.g.
   ``tparm(tigetstr("cup"), 5, 3)`` could result in ``'\033[6;4H'``, the exact
   result depending on terminal type.


.. function:: typeahead(fd)

   Specify that the file descriptor *fd* be used for typeahead checking.  If *fd*
   is ``-1``, then no typeahead checking is done.

   The curses library does "line-breakout optimization" by looking for typeahead
   periodically while updating the screen.  If input is found, and it is coming
   from a tty, the current update is postponed until refresh or doupdate is called
   again, allowing faster response to commands typed in advance. This function
   allows specifying a different file descriptor for typeahead checking.


.. function:: unctrl(ch)

   Return a string which is a printable representation of the character *ch*.
   Control characters are displayed as a caret followed by the character, for
   example as ``^C``. Printing characters are left as they are.


.. function:: ungetch(ch)

   Push *ch* so the next :meth:`getch` will return it.

   .. note::

      Only one *ch* can be pushed before :meth:`getch` is called.


.. function:: ungetmouse(id, x, y, z, bstate)

   Push a :const:`KEY_MOUSE` event onto the input queue, associating the given
   state data with it.


.. function:: use_env(flag)

   If used, this function should be called before :func:`initscr` or newterm are
   called.  When *flag* is ``False``, the values of lines and columns specified in the
   terminfo database will be used, even if environment variables :envvar:`LINES`
   and :envvar:`COLUMNS` (used by default) are set, or if curses is running in a
   window (in which case default behavior would be to use the window size if
   :envvar:`LINES` and :envvar:`COLUMNS` are not set).


.. function:: use_default_colors()

   Allow use of default values for colors on terminals supporting this feature. Use
   this to support transparency in your application.  The default color is assigned
   to the color number -1. After calling this function,  ``init_pair(x,
   curses.COLOR_RED, -1)`` initializes, for instance, color pair *x* to a red
   foreground color on the default background.


.. function:: wrapper(func, ...)

   Initialize curses and call another callable object, *func*, which should be the
   rest of your curses-using application.  If the application raises an exception,
   this function will restore the terminal to a sane state before re-raising the
   exception and generating a traceback.  The callable object *func* is then passed
   the main window 'stdscr' as its first argument, followed by any other arguments
   passed to :func:`wrapper`.  Before calling *func*, :func:`wrapper` turns on
   cbreak mode, turns off echo, enables the terminal keypad, and initializes colors
   if the terminal has color support.  On exit (whether normally or by exception)
   it restores cooked mode, turns on echo, and disables the terminal keypad.


.. _curses-window-objects:

Window Objects
--------------

Window objects, as returned by :func:`initscr` and :func:`newwin` above, have
the following methods:


.. method:: window.addch(ch[, attr])
            window.addch(y, x, ch[, attr])

   .. note::

      A *character* means a C character (an ASCII code), rather than a Python
      character (a string of length 1). (This note is true whenever the
      documentation mentions a character.) The built-in :func:`ord` is handy for
      conveying strings to codes.

   Paint character *ch* at ``(y, x)`` with attributes *attr*, overwriting any
   character previously painter at that location.  By default, the character
   position and attributes are the current settings for the window object.

   .. note::

      Writing outside the window, subwindow, or pad raises a :exc:`curses.error`.
      Attempting to write to the lower right corner of a window, subwindow,
      or pad will cause an exception to be raised after the character is printed.


.. method:: window.addnstr(str, n[, attr])
            window.addnstr(y, x, str, n[, attr])

   Paint at most *n* characters of the  string *str* at ``(y, x)`` with attributes
   *attr*, overwriting anything previously on the display.


.. method:: window.addstr(str[, attr])
            window.addstr(y, x, str[, attr])

   Paint the string *str* at ``(y, x)`` with attributes *attr*, overwriting
   anything previously on the display.

   .. note::

      Writing outside the window, subwindow, or pad raises :exc:`curses.error`.
      Attempting to write to the lower right corner of a window, subwindow,
      or pad will cause an exception to be raised after the string is printed.


.. method:: window.attroff(attr)

   Remove attribute *attr* from the "background" set applied to all writes to the
   current window.


.. method:: window.attron(attr)

   Add attribute *attr* from the "background" set applied to all writes to the
   current window.


.. method:: window.attrset(attr)

   Set the "background" set of attributes to *attr*.  This set is initially 0 (no
   attributes).


.. method:: window.bkgd(ch[, attr])

   Set the background property of the window to the character *ch*, with
   attributes *attr*.  The change is then applied to every character position in
   that window:

   * The attribute of every character in the window  is changed to the new
     background attribute.

   * Wherever  the  former background character appears, it is changed to the new
     background character.


.. method:: window.bkgdset(ch[, attr])

   Set the window's background.  A window's background consists of a character and
   any combination of attributes.  The attribute part of the background is combined
   (OR'ed) with all non-blank characters that are written into the window.  Both
   the character and attribute parts of the background are combined with the blank
   characters.  The background becomes a property of the character and moves with
   the character through any scrolling and insert/delete line/character operations.


.. method:: window.border([ls[, rs[, ts[, bs[, tl[, tr[, bl[, br]]]]]]]])

   Draw a border around the edges of the window. Each parameter specifies  the
   character to use for a specific part of the border; see the table below for more
   details.  The characters can be specified as integers or as one-character
   strings.

   .. note::

      A ``0`` value for any parameter will cause the default character to be used for
      that parameter.  Keyword parameters can *not* be used.  The defaults are listed
      in this table:

   +-----------+---------------------+-----------------------+
   | Parameter | Description         | Default value         |
   +===========+=====================+=======================+
   | *ls*      | Left side           | :const:`ACS_VLINE`    |
   +-----------+---------------------+-----------------------+
   | *rs*      | Right side          | :const:`ACS_VLINE`    |
   +-----------+---------------------+-----------------------+
   | *ts*      | Top                 | :const:`ACS_HLINE`    |
   +-----------+---------------------+-----------------------+
   | *bs*      | Bottom              | :const:`ACS_HLINE`    |
   +-----------+---------------------+-----------------------+
   | *tl*      | Upper-left corner   | :const:`ACS_ULCORNER` |
   +-----------+---------------------+-----------------------+
   | *tr*      | Upper-right corner  | :const:`ACS_URCORNER` |
   +-----------+---------------------+-----------------------+
   | *bl*      | Bottom-left corner  | :const:`ACS_LLCORNER` |
   +-----------+---------------------+-----------------------+
   | *br*      | Bottom-right corner | :const:`ACS_LRCORNER` |
   +-----------+---------------------+-----------------------+


.. method:: window.box([vertch, horch])

   Similar to :meth:`border`, but both *ls* and *rs* are *vertch* and both *ts* and
   *bs* are *horch*.  The default corner characters are always used by this function.


.. method:: window.chgat(attr)
            window.chgat(num, attr)
            window.chgat(y, x, attr)
            window.chgat(y, x, num, attr)

   Set the attributes of *num* characters at the current cursor position, or at
   position ``(y, x)`` if supplied. If *num* is not given or is ``-1``,
   the attribute will be set on all the characters to the end of the line.  This
   function moves cursor to position ``(y, x)`` if supplied. The changed line
   will be touched using the :meth:`touchline` method so that the contents will
   be redisplayed by the next window refresh.


.. method:: window.clear()

   Like :meth:`erase`, but also cause the whole window to be repainted upon next
   call to :meth:`refresh`.


.. method:: window.clearok(yes)

   If *yes* is 1, the next call to :meth:`refresh` will clear the window
   completely.


.. method:: window.clrtobot()

   Erase from cursor to the end of the window: all lines below the cursor are
   deleted, and then the equivalent of :meth:`clrtoeol` is performed.


.. method:: window.clrtoeol()

   Erase from cursor to the end of the line.


.. method:: window.cursyncup()

   Update the current cursor position of all the ancestors of the window to
   reflect the current cursor position of the window.


.. method:: window.delch([y, x])

   Delete any character at ``(y, x)``.


.. method:: window.deleteln()

   Delete the line under the cursor. All following lines are moved up by one line.


.. method:: window.derwin(begin_y, begin_x)
            window.derwin(nlines, ncols, begin_y, begin_x)

   An abbreviation for "derive window", :meth:`derwin` is the same as calling
   :meth:`subwin`, except that *begin_y* and *begin_x* are relative to the origin
   of the window, rather than relative to the entire screen.  Return a window
   object for the derived window.


.. method:: window.echochar(ch[, attr])

   Add character *ch* with attribute *attr*, and immediately  call :meth:`refresh`
   on the window.


.. method:: window.enclose(y, x)

   Test whether the given pair of screen-relative character-cell coordinates are
   enclosed by the given window, returning ``True`` or ``False``.  It is useful for
   determining what subset of the screen windows enclose the location of a mouse
   event.


.. method:: window.erase()

   Clear the window.


.. method:: window.getbegyx()

   Return a tuple ``(y, x)`` of co-ordinates of upper-left corner.


.. method:: window.getbkgd()

   Return the given window's current background character/attribute pair.


.. method:: window.getch([y, x])

   Get a character. Note that the integer returned does *not* have to be in ASCII
   range: function keys, keypad keys and so on return numbers higher than 256. In
   no-delay mode, -1 is returned if there is no input, else :func:`getch` waits
   until a key is pressed.


.. method:: window.getkey([y, x])

   Get a character, returning a string instead of an integer, as :meth:`getch`
   does. Function keys, keypad keys and so on return a multibyte string containing
   the key name.  In no-delay mode, an exception is raised if there is no input.


.. method:: window.getmaxyx()

   Return a tuple ``(y, x)`` of the height and width of the window.


.. method:: window.getparyx()

   Return the beginning coordinates of this window relative to its parent window
   into two integer variables y and x.  Return ``-1, -1`` if this window has no
   parent.


.. method:: window.getstr([y, x])

   Read a string from the user, with primitive line editing capacity.


.. method:: window.getyx()

   Return a tuple ``(y, x)`` of current cursor position  relative to the window's
   upper-left corner.


.. method:: window.hline(ch, n)
            window.hline(y, x, ch, n)

   Display a horizontal line starting at ``(y, x)`` with length *n* consisting of
   the character *ch*.


.. method:: window.idcok(flag)

   If *flag* is ``False``, curses no longer considers using the hardware insert/delete
   character feature of the terminal; if *flag* is ``True``, use of character insertion
   and deletion is enabled.  When curses is first initialized, use of character
   insert/delete is enabled by default.


.. method:: window.idlok(yes)

   If called with *yes* equal to 1, :mod:`curses` will try and use hardware line
   editing facilities. Otherwise, line insertion/deletion are disabled.


.. method:: window.immedok(flag)

   If *flag* is ``True``, any change in the window image automatically causes the
   window to be refreshed; you no longer have to call :meth:`refresh` yourself.
   However, it may degrade performance considerably, due to repeated calls to
   wrefresh.  This option is disabled by default.


.. method:: window.inch([y, x])

   Return the character at the given position in the window. The bottom 8 bits are
   the character proper, and upper bits are the attributes.


.. method:: window.insch(ch[, attr])
            window.insch(y, x, ch[, attr])

   Paint character *ch* at ``(y, x)`` with attributes *attr*, moving the line from
   position *x* right by one character.


.. method:: window.insdelln(nlines)

   Insert *nlines* lines into the specified window above the current line.  The
   *nlines* bottom lines are lost.  For negative *nlines*, delete *nlines* lines
   starting with the one under the cursor, and move the remaining lines up.  The
   bottom *nlines* lines are cleared.  The current cursor position remains the
   same.


.. method:: window.insertln()

   Insert a blank line under the cursor. All following lines are moved down by one
   line.


.. method:: window.insnstr(str, n[, attr])
            window.insnstr(y, x, str, n[, attr])

   Insert a character string (as many characters as will fit on the line) before
   the character under the cursor, up to *n* characters.   If *n* is zero or
   negative, the entire string is inserted. All characters to the right of the
   cursor are shifted right, with the rightmost characters on the line being lost.
   The cursor position does not change (after moving to *y*, *x*, if specified).


.. method:: window.insstr(str[, attr])
            window.insstr(y, x, str[, attr])

   Insert a character string (as many characters as will fit on the line) before
   the character under the cursor.  All characters to the right of the cursor are
   shifted right, with the rightmost characters on the line being lost.  The cursor
   position does not change (after moving to *y*, *x*, if specified).


.. method:: window.instr([n])
            window.instr(y, x[, n])

   Return a string of characters, extracted from the window starting at the
   current cursor position, or at *y*, *x* if specified. Attributes are stripped
   from the characters.  If *n* is specified, :meth:`instr` returns a string
   at most *n* characters long (exclusive of the trailing NUL).


.. method:: window.is_linetouched(line)

   Return ``True`` if the specified line was modified since the last call to
   :meth:`refresh`; otherwise return ``False``.  Raise a :exc:`curses.error`
   exception if *line* is not valid for the given window.


.. method:: window.is_wintouched()

   Return ``True`` if the specified window was modified since the last call to
   :meth:`refresh`; otherwise return ``False``.


.. method:: window.keypad(yes)

   If *yes* is 1, escape sequences generated by some keys (keypad,  function keys)
   will be interpreted by :mod:`curses`. If *yes* is 0, escape sequences will be
   left as is in the input stream.


.. method:: window.leaveok(yes)

   If *yes* is 1, cursor is left where it is on update, instead of being at "cursor
   position."  This reduces cursor movement where possible. If possible the cursor
   will be made invisible.

   If *yes* is 0, cursor will always be at "cursor position" after an update.


.. method:: window.move(new_y, new_x)

   Move cursor to ``(new_y, new_x)``.


.. method:: window.mvderwin(y, x)

   Move the window inside its parent window.  The screen-relative parameters of
   the window are not changed.  This routine is used to display different parts of
   the parent window at the same physical position on the screen.


.. method:: window.mvwin(new_y, new_x)

   Move the window so its upper-left corner is at ``(new_y, new_x)``.


.. method:: window.nodelay(yes)

   If *yes* is ``1``, :meth:`getch` will be non-blocking.


.. method:: window.notimeout(yes)

   If *yes* is ``1``, escape sequences will not be timed out.

   If *yes* is ``0``, after a few milliseconds, an escape sequence will not be
   interpreted, and will be left in the input stream as is.


.. method:: window.noutrefresh()

   Mark for refresh but wait.  This function updates the data structure
   representing the desired state of the window, but does not force an update of
   the physical screen.  To accomplish that, call  :func:`doupdate`.


.. method:: window.overlay(destwin[, sminrow, smincol, dminrow, dmincol, dmaxrow, dmaxcol])

   Overlay the window on top of *destwin*. The windows need not be the same size,
   only the overlapping region is copied. This copy is non-destructive, which means
   that the current background character does not overwrite the old contents of
   *destwin*.

   To get fine-grained control over the copied region, the second form of
   :meth:`overlay` can be used. *sminrow* and *smincol* are the upper-left
   coordinates of the source window, and the other variables mark a rectangle in
   the destination window.


.. method:: window.overwrite(destwin[, sminrow, smincol, dminrow, dmincol, dmaxrow, dmaxcol])

   Overwrite the window on top of *destwin*. The windows need not be the same size,
   in which case only the overlapping region is copied. This copy is destructive,
   which means that the current background character overwrites the old contents of
   *destwin*.

   To get fine-grained control over the copied region, the second form of
   :meth:`overwrite` can be used. *sminrow* and *smincol* are the upper-left
   coordinates of the source window, the other variables mark a rectangle in the
   destination window.


.. method:: window.putwin(file)

   Write all data associated with the window into the provided file object.  This
   information can be later retrieved using the :func:`getwin` function.


.. method:: window.redrawln(beg, num)

   Indicate that the *num* screen lines, starting at line *beg*, are corrupted and
   should be completely redrawn on the next :meth:`refresh` call.


.. method:: window.redrawwin()

   Touch the entire window, causing it to be completely redrawn on the next
   :meth:`refresh` call.


.. method:: window.refresh([pminrow, pmincol, sminrow, smincol, smaxrow, smaxcol])

   Update the display immediately (sync actual screen with previous
   drawing/deleting methods).

   The 6 optional arguments can only be specified when the window is a pad created
   with :func:`newpad`.  The additional parameters are needed to indicate what part
   of the pad and screen are involved. *pminrow* and *pmincol* specify the upper
   left-hand corner of the rectangle to be displayed in the pad.  *sminrow*,
   *smincol*, *smaxrow*, and *smaxcol* specify the edges of the rectangle to be
   displayed on the screen.  The lower right-hand corner of the rectangle to be
   displayed in the pad is calculated from the screen coordinates, since the
   rectangles must be the same size.  Both rectangles must be entirely contained
   within their respective structures.  Negative values of *pminrow*, *pmincol*,
   *sminrow*, or *smincol* are treated as if they were zero.


.. method:: window.resize(nlines, ncols)

   Reallocate storage for a curses window to adjust its dimensions to the
   specified values.  If either dimension is larger than the current values, the
   window's data is filled with blanks that have the current background
   rendition (as set by :meth:`bkgdset`) merged into them.


.. method:: window.scroll([lines=1])

   Scroll the screen or scrolling region upward by *lines* lines.


.. method:: window.scrollok(flag)

   Control what happens when the cursor of a window is moved off the edge of the
   window or scrolling region, either as a result of a newline action on the bottom
   line, or typing the last character of the last line.  If *flag* is false, the
   cursor is left on the bottom line.  If *flag* is true, the window is scrolled up
   one line.  Note that in order to get the physical scrolling effect on the
   terminal, it is also necessary to call :meth:`idlok`.


.. method:: window.setscrreg(top, bottom)

   Set the scrolling region from line *top* to line *bottom*. All scrolling actions
   will take place in this region.


.. method:: window.standend()

   Turn off the standout attribute.  On some terminals this has the side effect of
   turning off all attributes.


.. method:: window.standout()

   Turn on attribute *A_STANDOUT*.


.. method:: window.subpad(begin_y, begin_x)
            window.subpad(nlines, ncols, begin_y, begin_x)

   Return a sub-window, whose upper-left corner is at ``(begin_y, begin_x)``, and
   whose width/height is *ncols*/*nlines*.


.. method:: window.subwin(begin_y, begin_x)
            window.subwin(nlines, ncols, begin_y, begin_x)

   Return a sub-window, whose upper-left corner is at ``(begin_y, begin_x)``, and
   whose width/height is *ncols*/*nlines*.

   By default, the sub-window will extend from the specified position to the lower
   right corner of the window.


.. method:: window.syncdown()

   Touch each location in the window that has been touched in any of its ancestor
   windows.  This routine is called by :meth:`refresh`, so it should almost never
   be necessary to call it manually.


.. method:: window.syncok(flag)

   If called with *flag* set to ``True``, then :meth:`syncup` is called automatically
   whenever there is a change in the window.


.. method:: window.syncup()

   Touch all locations in ancestors of the window that have been changed in  the
   window.


.. method:: window.timeout(delay)

   Set blocking or non-blocking read behavior for the window.  If *delay* is
   negative, blocking read is used (which will wait indefinitely for input).  If
   *delay* is zero, then non-blocking read is used, and -1 will be returned by
   :meth:`getch` if no input is waiting.  If *delay* is positive, then
   :meth:`getch` will block for *delay* milliseconds, and return -1 if there is
   still no input at the end of that time.


.. method:: window.touchline(start, count[, changed])

   Pretend *count* lines have been changed, starting with line *start*.  If
   *changed* is supplied, it specifies whether the affected lines are marked as
   having been changed (*changed*\ =1) or unchanged (*changed*\ =0).


.. method:: window.touchwin()

   Pretend the whole window has been changed, for purposes of drawing
   optimizations.


.. method:: window.untouchwin()

   Mark all lines in  the  window  as unchanged since the last call to
   :meth:`refresh`.


.. method:: window.vline(ch, n)
            window.vline(y, x, ch, n)

   Display a vertical line starting at ``(y, x)`` with length *n* consisting of the
   character *ch*.


Constants
---------

The :mod:`curses` module defines the following data members:


.. data:: ERR

   Some curses routines  that  return  an integer, such as  :func:`getch`, return
   :const:`ERR` upon failure.


.. data:: OK

   Some curses routines  that  return  an integer, such as  :func:`napms`, return
   :const:`OK` upon success.


.. data:: version

   A string representing the current version of the module.  Also available as
   :const:`__version__`.

Some constants are available to specify character cell attributes.
The exact constants available are system dependent.

+------------------+-------------------------------+
| Attribute        | Meaning                       |
+==================+===============================+
| ``A_ALTCHARSET`` | Alternate character set mode  |
+------------------+-------------------------------+
| ``A_BLINK``      | Blink mode                    |
+------------------+-------------------------------+
| ``A_BOLD``       | Bold mode                     |
+------------------+-------------------------------+
| ``A_DIM``        | Dim mode                      |
+------------------+-------------------------------+
| ``A_INVIS``      | Invisible or blank mode       |
+------------------+-------------------------------+
| ``A_NORMAL``     | Normal attribute              |
+------------------+-------------------------------+
| ``A_PROTECT``    | Protected mode                |
+------------------+-------------------------------+
| ``A_REVERSE``    | Reverse background and        |
|                  | foreground colors             |
+------------------+-------------------------------+
| ``A_STANDOUT``   | Standout mode                 |
+------------------+-------------------------------+
| ``A_UNDERLINE``  | Underline mode                |
+------------------+-------------------------------+
| ``A_HORIZONTAL`` | Horizontal highlight          |
+------------------+-------------------------------+
| ``A_LEFT``       | Left highlight                |
+------------------+-------------------------------+
| ``A_LOW``        | Low highlight                 |
+------------------+-------------------------------+
| ``A_RIGHT``      | Right highlight               |
+------------------+-------------------------------+
| ``A_TOP``        | Top highlight                 |
+------------------+-------------------------------+
| ``A_VERTICAL``   | Vertical highlight            |
+------------------+-------------------------------+
| ``A_CHARTEXT``   | Bit-mask to extract a         |
|                  | character                     |
+------------------+-------------------------------+

Several constants are available to extract corresponding attributes returned
by some methods.

+------------------+-------------------------------+
| Bit-mask         | Meaning                       |
+==================+===============================+
| ``A_ATTRIBUTES`` | Bit-mask to extract           |
|                  | attributes                    |
+------------------+-------------------------------+
| ``A_CHARTEXT``   | Bit-mask to extract a         |
|                  | character                     |
+------------------+-------------------------------+
| ``A_COLOR``      | Bit-mask to extract           |
|                  | color-pair field information  |
+------------------+-------------------------------+

Keys are referred to by integer constants with names starting with  ``KEY_``.
The exact keycaps available are system dependent.

.. XXX this table is far too large! should it be alphabetized?

+-------------------+--------------------------------------------+
| Key constant      | Key                                        |
+===================+============================================+
| ``KEY_MIN``       | Minimum key value                          |
+-------------------+--------------------------------------------+
| ``KEY_BREAK``     | Break key (unreliable)                     |
+-------------------+--------------------------------------------+
| ``KEY_DOWN``      | Down-arrow                                 |
+-------------------+--------------------------------------------+
| ``KEY_UP``        | Up-arrow                                   |
+-------------------+--------------------------------------------+
| ``KEY_LEFT``      | Left-arrow                                 |
+-------------------+--------------------------------------------+
| ``KEY_RIGHT``     | Right-arrow                                |
+-------------------+--------------------------------------------+
| ``KEY_HOME``      | Home key (upward+left arrow)               |
+-------------------+--------------------------------------------+
| ``KEY_BACKSPACE`` | Backspace (unreliable)                     |
+-------------------+--------------------------------------------+
| ``KEY_F0``        | Function keys.  Up to 64 function keys are |
|                   | supported.                                 |
+-------------------+--------------------------------------------+
| ``KEY_Fn``        | Value of function key *n*                  |
+-------------------+--------------------------------------------+
| ``KEY_DL``        | Delete line                                |
+-------------------+--------------------------------------------+
| ``KEY_IL``        | Insert line                                |
+-------------------+--------------------------------------------+
| ``KEY_DC``        | Delete character                           |
+-------------------+--------------------------------------------+
| ``KEY_IC``        | Insert char or enter insert mode           |
+-------------------+--------------------------------------------+
| ``KEY_EIC``       | Exit insert char mode                      |
+-------------------+--------------------------------------------+
| ``KEY_CLEAR``     | Clear screen                               |
+-------------------+--------------------------------------------+
| ``KEY_EOS``       | Clear to end of screen                     |
+-------------------+--------------------------------------------+
| ``KEY_EOL``       | Clear to end of line                       |
+-------------------+--------------------------------------------+
| ``KEY_SF``        | Scroll 1 line forward                      |
+-------------------+--------------------------------------------+
| ``KEY_SR``        | Scroll 1 line backward (reverse)           |
+-------------------+--------------------------------------------+
| ``KEY_NPAGE``     | Next page                                  |
+-------------------+--------------------------------------------+
| ``KEY_PPAGE``     | Previous page                              |
+-------------------+--------------------------------------------+
| ``KEY_STAB``      | Set tab                                    |
+-------------------+--------------------------------------------+
| ``KEY_CTAB``      | Clear tab                                  |
+-------------------+--------------------------------------------+
| ``KEY_CATAB``     | Clear all tabs                             |
+-------------------+--------------------------------------------+
| ``KEY_ENTER``     | Enter or send (unreliable)                 |
+-------------------+--------------------------------------------+
| ``KEY_SRESET``    | Soft (partial) reset (unreliable)          |
+-------------------+--------------------------------------------+
| ``KEY_RESET``     | Reset or hard reset (unreliable)           |
+-------------------+--------------------------------------------+
| ``KEY_PRINT``     | Print                                      |
+-------------------+--------------------------------------------+
| ``KEY_LL``        | Home down or bottom (lower left)           |
+-------------------+--------------------------------------------+
| ``KEY_A1``        | Upper left of keypad                       |
+-------------------+--------------------------------------------+
| ``KEY_A3``        | Upper right of keypad                      |
+-------------------+--------------------------------------------+
| ``KEY_B2``        | Center of keypad                           |
+-------------------+--------------------------------------------+
| ``KEY_C1``        | Lower left of keypad                       |
+-------------------+--------------------------------------------+
| ``KEY_C3``        | Lower right of keypad                      |
+-------------------+--------------------------------------------+
| ``KEY_BTAB``      | Back tab                                   |
+-------------------+--------------------------------------------+
| ``KEY_BEG``       | Beg (beginning)                            |
+-------------------+--------------------------------------------+
| ``KEY_CANCEL``    | Cancel                                     |
+-------------------+--------------------------------------------+
| ``KEY_CLOSE``     | Close                                      |
+-------------------+--------------------------------------------+
| ``KEY_COMMAND``   | Cmd (command)                              |
+-------------------+--------------------------------------------+
| ``KEY_COPY``      | Copy                                       |
+-------------------+--------------------------------------------+
| ``KEY_CREATE``    | Create                                     |
+-------------------+--------------------------------------------+
| ``KEY_END``       | End                                        |
+-------------------+--------------------------------------------+
| ``KEY_EXIT``      | Exit                                       |
+-------------------+--------------------------------------------+
| ``KEY_FIND``      | Find                                       |
+-------------------+--------------------------------------------+
| ``KEY_HELP``      | Help                                       |
+-------------------+--------------------------------------------+
| ``KEY_MARK``      | Mark                                       |
+-------------------+--------------------------------------------+
| ``KEY_MESSAGE``   | Message                                    |
+-------------------+--------------------------------------------+
| ``KEY_MOVE``      | Move                                       |
+-------------------+--------------------------------------------+
| ``KEY_NEXT``      | Next                                       |
+-------------------+--------------------------------------------+
| ``KEY_OPEN``      | Open                                       |
+-------------------+--------------------------------------------+
| ``KEY_OPTIONS``   | Options                                    |
+-------------------+--------------------------------------------+
| ``KEY_PREVIOUS``  | Prev (previous)                            |
+-------------------+--------------------------------------------+
| ``KEY_REDO``      | Redo                                       |
+-------------------+--------------------------------------------+
| ``KEY_REFERENCE`` | Ref (reference)                            |
+-------------------+--------------------------------------------+
| ``KEY_REFRESH``   | Refresh                                    |
+-------------------+--------------------------------------------+
| ``KEY_REPLACE``   | Replace                                    |
+-------------------+--------------------------------------------+
| ``KEY_RESTART``   | Restart                                    |
+-------------------+--------------------------------------------+
| ``KEY_RESUME``    | Resume                                     |
+-------------------+--------------------------------------------+
| ``KEY_SAVE``      | Save                                       |
+-------------------+--------------------------------------------+
| ``KEY_SBEG``      | Shifted Beg (beginning)                    |
+-------------------+--------------------------------------------+
| ``KEY_SCANCEL``   | Shifted Cancel                             |
+-------------------+--------------------------------------------+
| ``KEY_SCOMMAND``  | Shifted Command                            |
+-------------------+--------------------------------------------+
| ``KEY_SCOPY``     | Shifted Copy                               |
+-------------------+--------------------------------------------+
| ``KEY_SCREATE``   | Shifted Create                             |
+-------------------+--------------------------------------------+
| ``KEY_SDC``       | Shifted Delete char                        |
+-------------------+--------------------------------------------+
| ``KEY_SDL``       | Shifted Delete line                        |
+-------------------+--------------------------------------------+
| ``KEY_SELECT``    | Select                                     |
+-------------------+--------------------------------------------+
| ``KEY_SEND``      | Shifted End                                |
+-------------------+--------------------------------------------+
| ``KEY_SEOL``      | Shifted Clear line                         |
+-------------------+--------------------------------------------+
| ``KEY_SEXIT``     | Shifted Exit                               |
+-------------------+--------------------------------------------+
| ``KEY_SFIND``     | Shifted Find                               |
+-------------------+--------------------------------------------+
| ``KEY_SHELP``     | Shifted Help                               |
+-------------------+--------------------------------------------+
| ``KEY_SHOME``     | Shifted Home                               |
+-------------------+--------------------------------------------+
| ``KEY_SIC``       | Shifted Input                              |
+-------------------+--------------------------------------------+
| ``KEY_SLEFT``     | Shifted Left arrow                         |
+-------------------+--------------------------------------------+
| ``KEY_SMESSAGE``  | Shifted Message                            |
+-------------------+--------------------------------------------+
| ``KEY_SMOVE``     | Shifted Move                               |
+-------------------+--------------------------------------------+
| ``KEY_SNEXT``     | Shifted Next                               |
+-------------------+--------------------------------------------+
| ``KEY_SOPTIONS``  | Shifted Options                            |
+-------------------+--------------------------------------------+
| ``KEY_SPREVIOUS`` | Shifted Prev                               |
+-------------------+--------------------------------------------+
| ``KEY_SPRINT``    | Shifted Print                              |
+-------------------+--------------------------------------------+
| ``KEY_SREDO``     | Shifted Redo                               |
+-------------------+--------------------------------------------+
| ``KEY_SREPLACE``  | Shifted Replace                            |
+-------------------+--------------------------------------------+
| ``KEY_SRIGHT``    | Shifted Right arrow                        |
+-------------------+--------------------------------------------+
| ``KEY_SRSUME``    | Shifted Resume                             |
+-------------------+--------------------------------------------+
| ``KEY_SSAVE``     | Shifted Save                               |
+-------------------+--------------------------------------------+
| ``KEY_SSUSPEND``  | Shifted Suspend                            |
+-------------------+--------------------------------------------+
| ``KEY_SUNDO``     | Shifted Undo                               |
+-------------------+--------------------------------------------+
| ``KEY_SUSPEND``   | Suspend                                    |
+-------------------+--------------------------------------------+
| ``KEY_UNDO``      | Undo                                       |
+-------------------+--------------------------------------------+
| ``KEY_MOUSE``     | Mouse event has occurred                   |
+-------------------+--------------------------------------------+
| ``KEY_RESIZE``    | Terminal resize event                      |
+-------------------+--------------------------------------------+
| ``KEY_MAX``       | Maximum key value                          |
+-------------------+--------------------------------------------+

On VT100s and their software emulations, such as X terminal emulators, there are
normally at least four function keys (:const:`KEY_F1`, :const:`KEY_F2`,
:const:`KEY_F3`, :const:`KEY_F4`) available, and the arrow keys mapped to
:const:`KEY_UP`, :const:`KEY_DOWN`, :const:`KEY_LEFT` and :const:`KEY_RIGHT` in
the obvious way.  If your machine has a PC keyboard, it is safe to expect arrow
keys and twelve function keys (older PC keyboards may have only ten function
keys); also, the following keypad mappings are standard:

+------------------+-----------+
| Keycap           | Constant  |
+==================+===========+
| :kbd:`Insert`    | KEY_IC    |
+------------------+-----------+
| :kbd:`Delete`    | KEY_DC    |
+------------------+-----------+
| :kbd:`Home`      | KEY_HOME  |
+------------------+-----------+
| :kbd:`End`       | KEY_END   |
+------------------+-----------+
| :kbd:`Page Up`   | KEY_PPAGE |
+------------------+-----------+
| :kbd:`Page Down` | KEY_NPAGE |
+------------------+-----------+

The following table lists characters from the alternate character set. These are
inherited from the VT100 terminal, and will generally be  available on software
emulations such as X terminals.  When there is no graphic available, curses
falls back on a crude printable ASCII approximation.

.. note::

   These are available only after :func:`initscr` has  been called.

+------------------+------------------------------------------+
| ACS code         | Meaning                                  |
+==================+==========================================+
| ``ACS_BBSS``     | alternate name for upper right corner    |
+------------------+------------------------------------------+
| ``ACS_BLOCK``    | solid square block                       |
+------------------+------------------------------------------+
| ``ACS_BOARD``    | board of squares                         |
+------------------+------------------------------------------+
| ``ACS_BSBS``     | alternate name for horizontal line       |
+------------------+------------------------------------------+
| ``ACS_BSSB``     | alternate name for upper left corner     |
+------------------+------------------------------------------+
| ``ACS_BSSS``     | alternate name for top tee               |
+------------------+------------------------------------------+
| ``ACS_BTEE``     | bottom tee                               |
+------------------+------------------------------------------+
| ``ACS_BULLET``   | bullet                                   |
+------------------+------------------------------------------+
| ``ACS_CKBOARD``  | checker board (stipple)                  |
+------------------+------------------------------------------+
| ``ACS_DARROW``   | arrow pointing down                      |
+------------------+------------------------------------------+
| ``ACS_DEGREE``   | degree symbol                            |
+------------------+------------------------------------------+
| ``ACS_DIAMOND``  | diamond                                  |
+------------------+------------------------------------------+
| ``ACS_GEQUAL``   | greater-than-or-equal-to                 |
+------------------+------------------------------------------+
| ``ACS_HLINE``    | horizontal line                          |
+------------------+------------------------------------------+
| ``ACS_LANTERN``  | lantern symbol                           |
+------------------+------------------------------------------+
| ``ACS_LARROW``   | left arrow                               |
+------------------+------------------------------------------+
| ``ACS_LEQUAL``   | less-than-or-equal-to                    |
+------------------+------------------------------------------+
| ``ACS_LLCORNER`` | lower left-hand corner                   |
+------------------+------------------------------------------+
| ``ACS_LRCORNER`` | lower right-hand corner                  |
+------------------+------------------------------------------+
| ``ACS_LTEE``     | left tee                                 |
+------------------+------------------------------------------+
| ``ACS_NEQUAL``   | not-equal sign                           |
+------------------+------------------------------------------+
| ``ACS_PI``       | letter pi                                |
+------------------+------------------------------------------+
| ``ACS_PLMINUS``  | plus-or-minus sign                       |
+------------------+------------------------------------------+
| ``ACS_PLUS``     | big plus sign                            |
+------------------+------------------------------------------+
| ``ACS_RARROW``   | right arrow                              |
+------------------+------------------------------------------+
| ``ACS_RTEE``     | right tee                                |
+------------------+------------------------------------------+
| ``ACS_S1``       | scan line 1                              |
+------------------+------------------------------------------+
| ``ACS_S3``       | scan line 3                              |
+------------------+------------------------------------------+
| ``ACS_S7``       | scan line 7                              |
+------------------+------------------------------------------+
| ``ACS_S9``       | scan line 9                              |
+------------------+------------------------------------------+
| ``ACS_SBBS``     | alternate name for lower right corner    |
+------------------+------------------------------------------+
| ``ACS_SBSB``     | alternate name for vertical line         |
+------------------+------------------------------------------+
| ``ACS_SBSS``     | alternate name for right tee             |
+------------------+------------------------------------------+
| ``ACS_SSBB``     | alternate name for lower left corner     |
+------------------+------------------------------------------+
| ``ACS_SSBS``     | alternate name for bottom tee            |
+------------------+------------------------------------------+
| ``ACS_SSSB``     | alternate name for left tee              |
+------------------+------------------------------------------+
| ``ACS_SSSS``     | alternate name for crossover or big plus |
+------------------+------------------------------------------+
| ``ACS_STERLING`` | pound sterling                           |
+------------------+------------------------------------------+
| ``ACS_TTEE``     | top tee                                  |
+------------------+------------------------------------------+
| ``ACS_UARROW``   | up arrow                                 |
+------------------+------------------------------------------+
| ``ACS_ULCORNER`` | upper left corner                        |
+------------------+------------------------------------------+
| ``ACS_URCORNER`` | upper right corner                       |
+------------------+------------------------------------------+
| ``ACS_VLINE``    | vertical line                            |
+------------------+------------------------------------------+

The following table lists the predefined colors:

+-------------------+----------------------------+
| Constant          | Color                      |
+===================+============================+
| ``COLOR_BLACK``   | Black                      |
+-------------------+----------------------------+
| ``COLOR_BLUE``    | Blue                       |
+-------------------+----------------------------+
| ``COLOR_CYAN``    | Cyan (light greenish blue) |
+-------------------+----------------------------+
| ``COLOR_GREEN``   | Green                      |
+-------------------+----------------------------+
| ``COLOR_MAGENTA`` | Magenta (purplish red)     |
+-------------------+----------------------------+
| ``COLOR_RED``     | Red                        |
+-------------------+----------------------------+
| ``COLOR_WHITE``   | White                      |
+-------------------+----------------------------+
| ``COLOR_YELLOW``  | Yellow                     |
+-------------------+----------------------------+


:mod:`curses.textpad` --- Text input widget for curses programs
===============================================================

.. module:: curses.textpad
   :synopsis: Emacs-like input editing in a curses window.
.. moduleauthor:: Eric Raymond <esr@thyrsus.com>
.. sectionauthor:: Eric Raymond <esr@thyrsus.com>


.. versionadded:: 1.6

The :mod:`curses.textpad` module provides a :class:`Textbox` class that handles
elementary text editing in a curses window, supporting a set of keybindings
resembling those of Emacs (thus, also of Netscape Navigator, BBedit 6.x,
FrameMaker, and many other programs).  The module also provides a
rectangle-drawing function useful for framing text boxes or for other purposes.

The module :mod:`curses.textpad` defines the following function:


.. function:: rectangle(win, uly, ulx, lry, lrx)

   Draw a rectangle.  The first argument must be a window object; the remaining
   arguments are coordinates relative to that window.  The second and third
   arguments are the y and x coordinates of the upper left hand corner of the
   rectangle to be drawn; the fourth and fifth arguments are the y and x
   coordinates of the lower right hand corner. The rectangle will be drawn using
   VT100/IBM PC forms characters on terminals that make this possible (including
   xterm and most other software terminal emulators).  Otherwise it will be drawn
   with ASCII  dashes, vertical bars, and plus signs.


.. _curses-textpad-objects:

Textbox objects
---------------

You can instantiate a :class:`Textbox` object as follows:


.. class:: Textbox(win)

   Return a textbox widget object.  The *win* argument should be a curses
   :class:`WindowObject` in which the textbox is to be contained. The edit cursor
   of the textbox is initially located at the upper left hand corner of the
   containing window, with coordinates ``(0, 0)``. The instance's
   :attr:`stripspaces` flag is initially on.

   :class:`Textbox` objects have the following methods:


   .. method:: edit([validator])

      This is the entry point you will normally use.  It accepts editing
      keystrokes until one of the termination keystrokes is entered.  If
      *validator* is supplied, it must be a function.  It will be called for
      each keystroke entered with the keystroke as a parameter; command dispatch
      is done on the result. This method returns the window contents as a
      string; whether blanks in the window are included is affected by the
      :attr:`stripspaces` attribute.


   .. method:: do_command(ch)

      Process a single command keystroke.  Here are the supported special
      keystrokes:

      +------------------+-------------------------------------------+
      | Keystroke        | Action                                    |
      +==================+===========================================+
      | :kbd:`Control-A` | Go to left edge of window.                |
      +------------------+-------------------------------------------+
      | :kbd:`Control-B` | Cursor left, wrapping to previous line if |
      |                  | appropriate.                              |
      +------------------+-------------------------------------------+
      | :kbd:`Control-D` | Delete character under cursor.            |
      +------------------+-------------------------------------------+
      | :kbd:`Control-E` | Go to right edge (stripspaces off) or end |
      |                  | of line (stripspaces on).                 |
      +------------------+-------------------------------------------+
      | :kbd:`Control-F` | Cursor right, wrapping to next line when  |
      |                  | appropriate.                              |
      +------------------+-------------------------------------------+
      | :kbd:`Control-G` | Terminate, returning the window contents. |
      +------------------+-------------------------------------------+
      | :kbd:`Control-H` | Delete character backward.                |
      +------------------+-------------------------------------------+
      | :kbd:`Control-J` | Terminate if the window is 1 line,        |
      |                  | otherwise insert newline.                 |
      +------------------+-------------------------------------------+
      | :kbd:`Control-K` | If line is blank, delete it, otherwise    |
      |                  | clear to end of line.                     |
      +------------------+-------------------------------------------+
      | :kbd:`Control-L` | Refresh screen.                           |
      +------------------+-------------------------------------------+
      | :kbd:`Control-N` | Cursor down; move down one line.          |
      +------------------+-------------------------------------------+
      | :kbd:`Control-O` | Insert a blank line at cursor location.   |
      +------------------+-------------------------------------------+
      | :kbd:`Control-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:

      +------------------------+------------------+
      | Constant               | Keystroke        |
      +========================+==================+
      | :const:`KEY_LEFT`      | :kbd:`Control-B` |
      +------------------------+------------------+
      | :const:`KEY_RIGHT`     | :kbd:`Control-F` |
      +------------------------+------------------+
      | :const:`KEY_UP`        | :kbd:`Control-P` |
      +------------------------+------------------+
      | :const:`KEY_DOWN`      | :kbd:`Control-N` |
      +------------------------+------------------+
      | :const:`KEY_BACKSPACE` | :kbd:`Control-h` |
      +------------------------+------------------+

      All other keystrokes are treated as a command to insert the given
      character and move right (with line wrapping).


   .. method:: gather()

      Return the window contents as a string; whether blanks in the
      window are included is affected by the :attr:`stripspaces` member.


   .. attribute:: stripspaces

      This attribute is a flag which controls the interpretation of blanks in
      the window.  When it is on, trailing blanks on each line are ignored; any
      cursor motion that would land the cursor on a trailing blank goes to the
      end of that line instead, and trailing blanks are stripped when the window
      contents are gathered.