Provided by: ncurses-doc_6.1+20181013-2ubuntu2_all bug

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 refreshes  of  pads  (e.g.,  from
       scrolling or echoing of input) do not occur.

       It  is  not  legal  to  call  wrefresh with a pad as an argument; the routines 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.  Unlike 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.

       ·   The pminrow and pmincol parameters specify the upper left-hand corner of the rectangle
           to be displayed in the pad.

       ·   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 performance 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  pechochar.   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 prefresh.

RETURN VALUE

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

       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 maximum.

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

          pecho_wchar
               returns an error if the window is not really a pad, and  the  associated  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, documenting 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:

       ·   These graphical pads could be much larger than the computer's display.

       ·   The read-only output from a command could be scrolled back to inspect, 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:

       ·   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.

       ·   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.  Consequently,  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.

       ·   NetBSD 7 curses sets a flag in the WINDOW structure for newpad and subpad, using  this
           to help with the distinction between wnoutrefresh 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

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

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

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

       ·   ensures that dupwin and getwin treat pads versus windows consistently.

SEE ALSO

       ncurses(3NCURSES), refresh(3NCURSES), touch(3NCURSES), addch(3NCURSES).

                                                                                    pad(3NCURSES)