# curs_pad 3x

    curs_pad(3x)                                                      curs_pad(3x)

## NAME

           newpad, subpad, prefresh, pnoutrefresh, pechochar, pecho_wchar - create
           and display curses pads

## SYNOPSIS

           #include <curses.h>

           WINDOW *newpad(int nlines, int ncols);
           WINDOW *subpad(WINDOW *orig, int nlines, int ncols,
                 int begin_y, int begin_x);
           int prefresh(WINDOW *pad, int pminrow, int pmincol,
                 int sminrow, int smincol, int smaxrow, int smaxcol);
           int pnoutrefresh(WINDOW *pad, int pminrow, int pmincol,
                 int sminrow, int smincol, int smaxrow, int smaxcol);
           int pechochar(WINDOW *pad, chtype ch);
           int pecho_wchar(WINDOW *pad, const cchar_t *wch);

## DESCRIPTION

### newpad

           The newpad routine creates and returns a pointer  to  a  new  pad  data
           structure  with  the given number of lines, nlines, and columns, ncols.
           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 re-
           freshes of pads (e.g., from scrolling or echoing of input) do  not  oc-
           cur.

           It  is  not  legal to call wrefresh with a pad as an argument; the rou-
           tines prefresh or pnoutrefresh should be  called  instead.   Note  that
           these routines require additional parameters to specify the part of the
           pad to be displayed and the location on the screen to be used  for  the
           display.

### subpad

           The  subpad routine creates and returns a pointer to a subwindow within
           a pad with the given number of lines, nlines, and columns, ncols.   Un-
           like  subwin,  which uses screen coordinates, the window is at position
           (begin_x, begin_y) on the pad.  The window is made in the middle of the
           window  orig,  so  that changes made to one window affect both windows.
           During the use of this routine, it will  often  be  necessary  to  call
           touchwin or touchline on orig before calling prefresh.

### prefresh, pnoutrefresh

           The  prefresh  and  pnoutrefresh routines are analogous to wrefresh and
           wnoutrefresh except that they relate to pads instead of  windows.   The
           additional  parameters  are needed to indicate what part of the pad and
           screen are involved.

           o   The pminrow and pmincol parameters specify the upper left-hand cor-
               ner of the rectangle to be displayed in the pad.

           o   The  sminrow,  smincol, smaxrow, and smaxcol parameters 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.

### pechochar

           The pechochar routine is functionally equivalent to  a  call  to  addch
           followed  by a call to refresh(3x), a call to waddch followed by a call
           to wrefresh, or a call to waddch followed by a call to  prefresh.   The
           knowledge  that  only  a single character is being output is taken into
           consideration and, for non-control characters, a  considerable  perfor-
           mance  gain  might  be  seen  by  using these routines instead of their
           equivalents.  In the case of pechochar, the last location of the pad on
           the screen is reused for the arguments to prefresh.

### pecho_wchar

           The  pecho_wchar  function  is the analogous wide-character form of pe-
           chochar.  It outputs one character to a pad and  immediately  refreshes
           the pad.  It does this by a call to wadd_wch followed by a call to pre-
           fresh.

## RETURN VALUE

           Routines that return an integer return ERR upon failure  and  OK  (SVr4
           only  specifies "an integer value other than ERR") upon successful com-
           pletion.

           Routines that return pointers return NULL on error, and  set  errno  to
           ENOMEM.

           X/Open does not define any error conditions.  In this implementation

              prefresh and pnoutrefresh
                   return an error if the window pointer is null, or if the window
                   is not really a pad or if the  area  to  refresh  extends  off-
                   screen or if the minimum coordinates are greater than the maxi-
                   mum.

              pechochar
                   returns an error if the window is not really a pad, and the as-
                   sociated call to wechochar returns an error.

              pecho_wchar
                   returns an error if the window is not really a pad, and the as-
                   sociated call to wecho_wchar returns an error.

## NOTES

           Note that pechochar may be a macro.

## PORTABILITY

           BSD curses has no pad feature.

           SVr2 curses (1986) provided the newpad and related functions, document-
           ing  them  in  a single line each.  SVr3 (1987) provided more extensive
           documentation.

           The documentation does not explain the term pad.  However,  the  Apollo
           Aegis workstation operating system supported a graphical pad feature:

           o   These  graphical pads could be much larger than the computer's dis-
               play.

           o   The read-only output from a command could be scrolled back  to  in-
               spect, and select text from the pad.

           The two uses may be related.

           The  XSI  Curses  standard,  Issue 4 describes these functions, without
           significant change from the SVr3 documentation.  It describes no  error
           conditions.   The  behavior of subpad if the parent window is not a pad
           is undocumented, and is not checked by the vendor Unix implementations:

           o   SVr4 curses sets a flag in the WINDOW  structure  in  newpad  which
               tells if the window is a pad.

               However,  it  uses this information only in waddch (to decide if it
               should call wrefresh) and wscrl (to avoid  scrolling  a  pad),  and
               does  not  check  in  wrefresh  to ensure that the pad is refreshed
               properly.

           o   Solaris X/Open Curses checks if a window is a pad in  wnoutrefresh,
               returning ERR in that case.

               However,  it only sets the flag for subwindows if the parent window
               is a pad.  Its newpad function does not set this information.  Con-
               sequently, the check will never fail.

               It  makes no comparable check in pnoutrefresh, though interestingly
               enough, a comment in the source code states  that  the  lack  of  a
               check was an MKS extension.

           o   NetBSD  7 curses sets a flag in the WINDOW structure for newpad and
               subpad, using this to help with the  distinction  between  wnoutre-
               fresh and pnoutrefresh.

               It  does  not  check for the case where a subwindow is created in a
               pad using subwin or derwin.

               The dupwin function returns a regular  window  when  duplicating  a
               pad.   Likewise,  getwin always returns a window, even if the saved
               data was from a pad.

           This implementation

           o   sets a flag in the WINDOW structure for newpad and subpad,

           o   allows a subwin or derwin call to succeed having a  pad  parent  by
               forcing the subwindow to be a pad,

           o   checks  in  both  wnoutrefresh and pnoutrefresh to ensure that pads
               and windows are handled distinctly, and

           o   ensures that dupwin and getwin treat pads  versus  windows  consis-
               tently.

## SEE ALSO

           curses(3x), curs_refresh(3x), curs_touch(3x), curs_addch(3x).

                                                                      curs_pad(3x)