Manual Pages  — curs_pad

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

SYNOPSIS DESCRIPTION newpad subpad prefresh, pnoutrefresh pechochar pecho_wchar RETURN VALUE NOTES PORTABILITY SEE ALSO

#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 creates and returns a pointer to a new pad data structure with the given number of lines, nlines, and columns, ncols.

 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 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 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 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 (SVr4 specifies only an integer value other than ERR) upon successful completion.

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

X/Open Curses does not specify 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.

 pechochar may be a macro.

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.

X/Open Curses, 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  xcurses checks whether 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 consistently.

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