|
HTML rendering created 2026-01-16 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | PORTABILITY | HISTORY | SEE ALSO | COLOPHON |
|
|
|
curs_pad(3X) Library calls curs_pad(3X)
newpad, subpad, prefresh, pnoutrefresh, pechochar, pecho_wchar -
create and display curses pads
#include <curses.h>
WINDOW *newpad(int nlines, int ncols);
WINDOW *subpad(WINDOW *parent, 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);
A curses 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, only part of which is to be visible on the
screen. Pads are not automatically refreshed by scrolling or
input-echoing operations.
Pads cannot be refreshed with wrefresh(3X); use prefresh or
pnoutrefresh instead.
newpad
newpad creates and returns a pointer to a new pad data structure
with the given number of lines, nlines, and columns, ncols.
subpad
subpad creates and returns a pointer to a subwindow within a pad
with the given number of lines, nlines, and columns, ncols.
Unlike subwin(3X), which uses screen coordinates, the new pad is
placed at position (begin_y, begin_x) relative to its parent.
Thus, changes made to one pad can affect both. When operating on
a subpad, it is often necessary to call touchwin(3X) or
touchline(3X) on parent before calling prefresh.
prefresh, pnoutrefresh
prefresh and pnoutrefresh are analogous to wrefresh(3X) and
wnoutrefresh(3X) except that they operate on pads rather than
windows. They require additional parameters are needed to
indicate what portions of the pad and screen are involved.
• pminrow and pmincol specify the upper left-hand corner of a
rectangular view of the pad.
• sminrow, smincol, smaxrow, and smaxcol specify the vertices 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. curses
treats negative values of any of these parameters as zero.
pechochar
pechochar is functionally equivalent to calling waddch(3X)
followed by prefresh. It suggests to the curses optimizer that
only a single character is being output; a considerable
performance benefit may be thus enjoyed. The location of the
character ch written to the pad is used to populate the arguments
to prefresh.
pecho_wchar
pecho_wchar is functionally equivalent to calling wadd_wch(3X)
followed by prefresh. It suggests to the curses optimizer that
only a single wide character is being output; a considerable
performance benefit may be thus enjoyed. The location of the
character wch written to the pad is used to populate the arguments
to prefresh.
Functions that return an integer return ERR upon failure and OK
upon successful completion.
Functions that return pointers return a null pointer on failure,
and set errno to ENOMEM.
In this implementation
prefresh and pnoutrefresh
return ERR 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 ERR if the window is not really a pad, and the
associated call to wechochar returns ERR.
pecho_wchar
returns ERR if the window is not really a pad, and the
associated call to wecho_wchar returns ERR.
pechochar may be implemented as a macro.
curses documentation is traditionally averse to motivating the
term “pad”. The Apollo Aegis workstation operating system (circa
1981) 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.
X/Open Curses Issue 4 describes these functions. It specifies no
error conditions for them.
SVr4 describes a successful return value only as “an integer value
other than ERR”.
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's newpad sets a flag in the WINDOW structure
indicating that 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);
its wrefresh does not check it to ensure that a pad is
properly updated.
• Solaris xcurses checks whether a window is a pad in its
wnoutrefresh, returning ERR in that case.
However, it sets the flag on subwindows only if the parent
window is a pad. Its newpad does not set this information.
Consequently, the check never fails.
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, aiding itself to distinguish between wnoutrefresh
and pnoutrefresh.
It does not check for the case where a subwindow is created in
a pad using subwin or derwin.
Its dupwin returns a regular window when duplicating a pad.
Likewise, its getwin always returns a window, even if the
saved data was from a pad.
ncurses:
• 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.
SVr2 (1984) introduced newpad, prefresh, and pnoutrefresh,
documenting them in a single line each.
SVr3 (1987) added subpad and pechochar, and provided more
extensive documentation.
The System V Interface Definition, Version 4 (1995), specified a
function named pechowchar. This was a later addition to SVr4.x,
not appearing in the first SVr4 (1989). It differs from X/Open's
later pecho_wchar in that its wstr parameter was a chtype instead
of a wchar_t, and was not const-qualified.
curses(3X), curs_addch(3X), curs_refresh(3X), curs_touch(3X)
This page is part of the ncurses (new curses) project.
Information about the project can be found at
⟨https://invisible-island.net/ncurses/ncurses.html⟩. If you have a
bug report for this manual page, send it to bug-ncurses@gnu.org.
This page was obtained from the tarball ncurses-6.6.tar.gz fetched
from ⟨https://ftp.gnu.org/gnu/ncurses/⟩ on 2026-01-16. If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for the
page, or you have corrections or improvements to the information
in this COLOPHON (which is not part of the original manual page),
send a mail to man-pages@man7.org
ncurses @NCURSES_MAJOR@.@NCU... 2025-08-23 curs_pad(3X)
|
HTML rendering created 2026-01-16 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|