clearok, idlok, idcok, immedok, leaveok, setscrreg, wsetscrreg,
   scrollok, nl, nonl - curses output options


   #include <curses.h>

   int clearok(WINDOW *win, bool bf);
   int idlok(WINDOW *win, bool bf);
   void idcok(WINDOW *win, bool bf);
   void immedok(WINDOW *win, bool bf);
   int leaveok(WINDOW *win, bool bf);
   int setscrreg(int top, int bot);
   int wsetscrreg(WINDOW *win, int top, int bot);
   int scrollok(WINDOW *win, bool bf);
   int nl(void);
   int nonl(void);


   These routines set options that  change  the  style  of  output  within
   curses.   All options are initially FALSE, unless otherwise stated.  It
   is not necessary to turn these options off before calling endwin.

   If clearok is called with TRUE as argument, the next call  to  wrefresh
   with this window will clear the screen completely and redraw the entire
   screen from scratch.  This is useful when the contents  of  the  screen
   are  uncertain, or in some cases for a more pleasing visual effect.  If
   the win argument to clearok is the global  variable  curscr,  the  next
   call  to  wrefresh  with any window causes the screen to be cleared and
   repainted from scratch.

   If idlok is called with TRUE as second argument, curses considers using
   the  hardware  insert/delete  line  feature  of  terminals so equipped.
   Calling idlok with FALSE  as  second  argument  disables  use  of  line
   insertion  and  deletion.   This  option  should be enabled only if the
   application needs insert/delete line, for example, for a screen editor.
   It  is  disabled  by  default  because  insert/delete  line tends to be
   visually annoying when used in applications  where  it  is  not  really
   needed.   If  insert/delete  line  cannot  be  used, curses redraws the
   changed portions of all lines.

   If idcok is called with FALSE as  second  argument,  curses  no  longer
   considers   using  the  hardware  insert/delete  character  feature  of
   terminals so equipped.  Use of character insert/delete  is  enabled  by
   default.   Calling idcok with TRUE as second argument re-enables use of
   character insertion and deletion.

   If immedok is called with TRUE as argument, any change  in  the  window
   image,  such  as  the  ones  caused  by waddch, wclrtobot, wscrl, etc.,
   automatically cause a  call  to  wrefresh.   However,  it  may  degrade
   performance  considerably,  due  to  repeated calls to wrefresh.  It is
   disabled by default.

   Normally, the hardware cursor is left at the  location  of  the  window
   cursor  being  refreshed.   The  leaveok option allows the cursor to be
   left wherever the update  happens  to  leave  it.   It  is  useful  for
   applications  where  the  cursor is not used, since it reduces the need
   for cursor motions.

   The setscrreg and wsetscrreg routines allow the application  programmer
   to  set  a  software  scrolling  region  in  a window.  The top and bot
   parameters are the line numbers of the top and  bottom  margin  of  the
   scrolling  region.   (Line  0  is the top line of the window.)  If this
   option and scrollok are enabled, an attempt  to  move  off  the  bottom
   margin line causes all lines in the scrolling region to scroll one line
   in the direction of the first line.  Only the text  of  the  window  is
   scrolled.  (Note that this has nothing to do with the use of a physical
   scrolling region capability in the terminal, like that  in  the  VT100.
   If  idlok  is enabled and the terminal has either a scrolling region or
   insert/delete line capability, they will probably be used by the output

   The  scrollok  option controls 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 disabled, (bf is FALSE), the cursor  is
   left  on  the  bottom  line.   If  enabled, (bf is TRUE), the window is
   scrolled up one line (Note that to get the physical scrolling effect on
   the terminal, it is also necessary to call idlok).

   nl, nonl
   The  nl and nonl routines control whether the underlying display device
   translates the return  key  into  newline  on  input,  and  whether  it
   translates newline into return and line-feed on output (in either case,
   the call addch('\n') does the equivalent of return and line feed on the
   virtual  screen).   Initially,  these  translations  do  occur.  If you
   disable them using nonl, curses will be able to make better use of  the
   line-feed  capability, resulting in faster cursor motion.  Also, curses
   will then be able to detect the return key.


   The functions setscrreg and wsetscrreg return OK upon success  and  ERR
   upon  failure.  All other routines that return an integer always return

   X/Open Curses does not define any error conditions.

   In this implementation, those functions that have a window pointer will
   return an error if the window pointer is null.

               returns an error if the cursor position is about to wrap.

               returns  an  error  if  the  scrolling region limits extend
               outside the window.

   X/Open does not  define  any  error  conditions.   This  implementation
   returns an error if the window pointer is null.


   These functions are described in the XSI Curses standard, Issue 4.

   The  XSI  Curses standard is ambiguous on the question of whether raw()
   should disable the CRLF translations controlled  by  nl()  and  nonl().
   BSD  curses  did  turn off these translations; AT&T curses (at least as
   late as SVr1) did not.  We choose to  do  so,  on  the  theory  that  a
   programmer  requesting  raw  input  wants a clean (ideally 8-bit clean)
   connection that the operating system will not alter.

   Some historic curses implementations had, as an  undocumented  feature,
   the  ability  to  do  the  equivalent  of  clearok(...,  1)  by  saying
   touchwin(stdscr) or clear(stdscr).  This will not work under ncurses.

   Earlier System V curses implementations specified  that  with  scrollok
   enabled,  any  window  modification  triggering  a scroll also forced a
   physical refresh.  XSI Curses does not require this, and ncurses avoids
   doing  it  to  perform  better vertical-motion optimization at wrefresh

   The XSI Curses standard does not mention that the cursor should be made
   invisible  as a side-effect of leaveok.  SVr4 curses documentation does
   this, but  the  code  does  not.   Use  curs_set  to  make  the  cursor


   Note that clearok, leaveok, scrollok, idcok, nl, nonl and setscrreg may
   be macros.

   The immedok routine is useful for windows that  are  used  as  terminal


   ncurses(3NCURSES), addch(3NCURSES), clear(3NCURSES), initscr(3NCURSES),
   scroll(3NCURSES), refresh(3NCURSES), curses_variables(3NCURSES).



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