curs_pad(3x) — Linux manual page


curs_pad(3X)                                                curs_pad(3X)

NAME         top

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

SYNOPSIS         top

       #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         top

       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.

       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.

       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.

       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         top

       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

          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.

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

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

NOTES         top

       Note that pechochar may be a macro.

PORTABILITY         top

       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

       •   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

SEE ALSO         top

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

COLOPHON         top

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