curs_window(3X)

Library calls

curs_window(3X)

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 left-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 full-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. These functions set window modes after a window is created:

idcok idlok immedok keypad leaveok nodelay 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 left-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 screen-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

Routines that return an integer return the integer 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.

X/Open defines no error conditions. In this implementation

delwin: returns an error if the window pointer is null, or if the window is the parent of another window.
derwin: returns an error if the parent window pointer is null, or if any of its ordinates or dimensions is negative, or if the resulting window does not fit inside the parent window.
dupwin: returns an error if the window pointer is null.

: This implementation also maintains a list of windows, and checks that the pointer passed to delwin is one that it created, returning an error if it was not..

mvderwin: returns an error if the window pointer is null, or if some part of the window would be placed off-screen.
mvwin: returns an error if the window pointer is null, or if the window is really a pad, or if some part of the window would be placed off-screen.
newwin: will fail if either of its beginning ordinates is negative, or if either the number of lines or columns is negative.
syncok: returns an error if the window pointer is null.
subwin: returns an error if the parent window pointer is null, or if any of its ordinates or dimensions is negative, or if the resulting window does not fit inside the parent window.

The functions which return a window pointer may also fail if there is insufficient memory for its data structures. Any of these functions will fail if the screen has not been initialized, i.e., with initscr or newterm.

NOTES

If many small changes are made to the window, the wsyncup option could degrade performance.

Note that syncok may be a macro.

PORTABILITY

X/Open Curses, Issue 4 describes these functions.

X/Open Curses states regarding delwin:

It must delete subwindows before deleting their parent.
If delwin is asked to delete a parent window, it can only succeed if the curses library keeps a list of the 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 does not even make that check, and will delete a parent window which still has subwindows.
Since release 4.0 (1996), ncurses maintains a list of windows for each screen, to ensure that a window has no subwindows before allowing deletion.
NetBSD copied this feature of ncurses in 2003.
PDCurses follows the scheme used in Solaris X/Open curses.

BUGS

The subwindow functions subwin, derwin, mvderwin, wsyncup, wsyncdown, wcursyncup, and syncok are flaky, incompletely implemented, and not well tested.

System V's 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 language here, and behavior of ncurses, is patterned on the X/Open Curses standard; this approach may result in slower updates.