curs_pad(3x) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | PORTABILITY | SEE ALSO | COLOPHON

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

   newpad
       The newpad routine creates and returns a pointer to a new pad da‐
       ta 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 par‐
       ticular 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 be‐
       fore calling prefresh.

   prefresh, pnoutrefresh
       The  prefresh and pnoutrefresh routines are analogous to wrefresh
       and wnoutrefresh except that they relate to pads instead of  win‐
       dows.  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 rec‐
       tangles 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 ad‐
       dch 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 charac‐
       ters, a considerable performance gain might be seen by using
       these routines instead of their equivalents.  In the case of pe‐
       chochar, 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 re‐
       freshes 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 suc‐
       cessful completion.

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

       X/Open does not define any error conditions.  In this implementa‐
       tion

          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 ex‐
               tends 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         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
           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, with‐
       out 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 wnoutre‐
           fresh, 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 in‐
           formation.  Consequently, the check will never fail.

           It makes no comparable check in pnoutrefresh, though inter‐
           estingly 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 new‐
           pad and subpad, using this to help with the distinction be‐
           tween 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 con‐
           sistently.

SEE ALSO         top

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

COLOPHON         top

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                                                            curs_pad(3X)