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curs_window

Section: Library calls (3X)
Updated: 202-0-23
Index Return to Main Contents

NAME

newwin, delwin, mvwin, subwin, derwin, mvderwin, dupwin, wsyncup, syncok, wcursyncup, wsyncdown - create and manipulate curses windows

SYNOPSIS

#include <curses.h>

WINDOW * newwin(
        int nlines, int ncols,
        int begin_y, int begin_x);
int delwin(WINDOW * win);
int mvwin(WINDOW * win, int y, int x);
WINDOW * subwin(WINDOW * orig,
        int nlines, int ncols,
        int begin_y, int begin_x);
WINDOW * derwin(WINDOW * orig,
        int nlines, int ncols,
        int begin_y, int begin_x);
int mvderwin(WINDOW * win, int par_y, int par_x);
WINDOW * dupwin(WINDOW * win);
void wsyncup(WINDOW * win);
int syncok(WINDOW * win, bool bf);
void wcursyncup(WINDOW * win);
void wsyncdown(WINDOW * win);

DESCRIPTION

newwin

Calling newwin creates and returns a pointer to a new window with the given number of lines and columns. The upper lef-hand corner of the window is at

: line begin_y,
column begin_x

If either nlines or ncols is zero, they default to

: LINES - begin_y and
COLS - begin_x.

A new ful-screen window is created by calling newwin(0,0,0,0).

Regardless of the function used for creating a new window (e.g., newwin, subwin, derwin, newpad), rather than a duplicate (with dupwin), all of the window modes are initialized to the default values. The following functions set a window's modes after it is created:

: idcok, idlok, immedok, keypad, leaveok, nodelay, notimeout, scrollok, setscrreg, syncok, wbkgdset, wbkgrndset, and wtimeout.

delwin

Calling delwin deletes the named window, freeing all memory associated with it (it does not actually erase the window's screen image). Subwindows must be deleted before the main window can be deleted.

mvwin

Calling mvwin moves the window so that the upper lef-hand corner is at position (x, y). If the move would cause the window to be off the screen, it is an error and the window is not moved. Moving subwindows is allowed, but should be avoided.

subwin

Calling subwin creates and returns a pointer to a new window with the given number of lines, nlines, and columns, ncols. The window is at position (begin_y, begin_x) on the screen. The subwindow shares memory with the window orig, its ancestor, so that changes made to one window will affect both windows. When using this routine, it is necessary to call touchwin or touchline on orig before calling wrefresh on the subwindow.

derwin

Calling derwin is the same as calling subwin, except that begin_y and begin_x are relative to the origin of the window orig rather than the screen. There is no difference between the subwindows and the derived windows.

mvderwin

Calling mvderwin moves a derived window (or subwindow) inside its parent window. The scree-relative parameters of the window are not changed. This routine is used to display different parts of the parent window at the same physical position on the screen.

dupwin

Calling dupwin creates an exact duplicate of the window win.

wsyncup

Calling wsyncup touches all locations in ancestors of win that are changed in win. If syncok is called with second argument TRUE then wsyncup is called automatically whenever there is a change in the window.

wsyncdown

The wsyncdown routine touches each location in win that has been touched in any of its ancestor windows. This routine is called by wrefresh, so it should almost never be necessary to call it manually.

wcursyncup

The routine wcursyncup updates the current cursor position of all the ancestors of the window to reflect the current cursor position of the window.

RETURN VALUE

Functions that return integers return ERR upon failure and OK upon success.

Functions that return pointers return a null pointer on failure.

ncurses defines several error conditions.
.IP * 4 delwin returns ERR if win is a null pointer, or if it is the parent of another window.

: ncurses maintains a list of windows, and checks that the pointer passed to delwin is one that it created, returning ERR if it was not.
.IP * 4 derwin returns ERR if orig is a null pointer, or if any of the ordinate or dimension arguments is negative, or if the resulting window does not fit inside the parent window.
.IP * 4 dupwin returns ERR if win is a null pointer.
.IP * 4 mvderwin returns ERR if win is a null pointer, or if any part of the window would be placed of-screen.
.IP * 4 mvwin returns ERR if win is a null pointer, if win is a pad, or if any part of the window would be placed of-screen.
.IP * 4 newwin returns ERR if any of its arguments is negative.
.IP * 4 subwin returns ERR if orig is a null pointer, or if any of the ordinate or dimension arguments is negative, or if the resulting window does not fit inside the parent window.
.IP * 4 syncok returns ERR if win is a null pointer.

Functions that return a window pointer fail if memory allocation for their data structures fails.

All of these functions fail if the screen has not been initialized; see initscr(3X) or newterm(3X).

NOTES

syncok may be implemented as a macro.

Calling syncup on a window and making many small changes to it could degrade performance.

PORTABILITY

X/Open Curses Issue 4 describes these functions. It specifies no error conditions for delwin, derwin, dupwin, newwin, mvderwin, or syncok.

For functions returning integers (except delwin), SVr4 describes a successful return value only as "an integer value other than ERR".

Regarding delwin, X/Open Curses states that

: [t]he application must delete subwindows before deleting the main window.

If delwin is asked to delete a parent window, it can succeed only if the curses library keeps a list of its subwindows. SVr4 curses kept a count of the number of subwindows rather than a list. It simply returned ERR when asked to delete a subwindow. Solaris X/Open curses (xcurses) does not make even that check, and will delete a parent window that still has subwindows. PDCurses also behaves this way.

ncurses 4.0 (1996) and later maintains a list of windows for each screen to ensure that a window has no subwindows before allowing its deletion. NetBSD curses has followed suit since 2003.

SVr4 curses documentation is unclear about what wsyncup and wsyncdown actually do. It seems to imply that they are supposed to touch only those lines that are affected by changes to a window's ancestors. The description and behavior of these functions in ncurses is patterned on the X/Open Curses standard; this approach may result in slower updates.