pechochar(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, 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

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

       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

               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

       ·   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

       ·   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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