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curs_pad(3)                                                        curs_pad(3)




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.

       o   The pminrow and pmincol parameters specify the upper left-hand corner
           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 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:

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

       o   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:

       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.
           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.

       o   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

       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
           consistently.


SEE ALSO

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



                                                                    curs_pad(3)

ncurses 6.4 - Generated Thu Jan 5 18:59:40 CST 2023
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