.\" $OpenBSD: curs_window.3,v 1.11 2023/10/17 09:52:08 nicm Exp $
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.\" $Id: curs_window.3,v 1.11 2023/10/17 09:52:08 nicm Exp $
.TH curs_window 3 2023-07-01 "ncurses 6.4" "Library calls"
.de bP
.ie n  .IP \(bu 4
.el    .IP \(bu 2
..
.na
.hy 0
.SH NAME
\fBnewwin\fP,
\fBdelwin\fP,
\fBmvwin\fP,
\fBsubwin\fP,
\fBderwin\fP,
\fBmvderwin\fP,
\fBdupwin\fP,
\fBwsyncup\fP,
\fBsyncok\fP,
\fBwcursyncup\fP,
\fBwsyncdown\fP \- create \fBcurses\fP windows
.ad
.hy
.SH SYNOPSIS
\fB#include <curses.h>\fP
.sp
\fBWINDOW *newwin(\fP
      \fBint \fInlines\fB, int \fIncols\fB,\fR
      \fBint \fIbegin_y\fB, int \fIbegin_x\fB);\fR
.br
\fBint delwin(WINDOW *\fIwin\fB);\fR
.br
\fBint mvwin(WINDOW *\fIwin\fB, int \fIy\fB, int \fIx\fB);\fR
.br
\fBWINDOW *subwin(WINDOW *\fIorig\fB,\fR
      \fBint \fInlines\fB, int \fIncols\fB,\fR
      \fBint \fIbegin_y\fB, int \fIbegin_x\fB);\fR
.br
\fBWINDOW *derwin(WINDOW *\fIorig\fB,\fR
      \fBint \fInlines\fB, int \fIncols\fB,\fR
      \fBint \fIbegin_y\fB, int \fIbegin_x\fB);\fR
.br
\fBint mvderwin(WINDOW *\fIwin\fB, int \fIpar_y\fB, int \fIpar_x\fB);\fR
.br
\fBWINDOW *dupwin(WINDOW *\fIwin\fB);\fR
.br
\fBvoid wsyncup(WINDOW *\fIwin\fB);\fR
.br
\fBint syncok(WINDOW *\fIwin\fB, bool \fIbf\fB);\fR
.br
\fBvoid wcursyncup(WINDOW *\fIwin\fB);\fR
.br
\fBvoid wsyncdown(WINDOW *\fIwin\fB);\fR
.SH DESCRIPTION
.SS newwin
Calling \fBnewwin\fP 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
.RS
line \fIbegin\fR_\fIy\fP,
.br
column \fIbegin\fR_\fIx\fP
.RE
.PP
If either
\fInlines\fP or \fIncols\fP is zero, they default to
.RS
\fBLINES \-\fP \fIbegin\fR_\fIy\fP and
.br
\fBCOLS \-\fP \fIbegin\fR_\fIx\fP.
.RE
.PP
A new full-screen window is created by calling \fBnewwin(0,0,0,0)\fP.
.PP
Regardless of the function used for creating a new window
(e.g., \fBnewwin\fP, \fBsubwin\fP, \fBderwin\fP, \fBnewpad\fP),
rather than a duplicate (with \fBdupwin\fP),
all of the window modes are initialized to the default values.
These functions set window modes after a window is created:
.RS
.na
.PP
idcok,
idlok,
immedok,
keypad,
leaveok,
nodelay,
scrollok,
setscrreg,
syncok,
wbkgdset,
wbkgrndset, and
wtimeout
.RE
.ad
.SS delwin
Calling \fBdelwin\fP 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.
.SS mvwin
Calling \fBmvwin\fP moves the window so that the upper left-hand
corner is at position (\fIx\fP, \fIy\fP).
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.
.SS subwin
Calling \fBsubwin\fP creates and returns a pointer to a new window
with the given number of lines, \fInlines\fP, and columns, \fIncols\fP.
The window is at position (\fIbegin\fR_\fIy\fP,
\fIbegin\fR_\fIx\fP) on the screen.
The subwindow shares memory with the window \fIorig\fP,
so that changes made to one window
will affect both windows.
When using this routine, it is necessary to call
\fBtouchwin\fP or \fBtouchline\fP on \fIorig\fP before calling
\fBwrefresh\fP on the subwindow.
.SS derwin
Calling \fBderwin\fP is the same as calling \fBsubwin,\fP except that
\fIbegin\fR_\fIy\fP and \fIbegin\fR_\fIx\fP are relative to the origin
of the window \fIorig\fP rather than the screen.
There is no difference between the subwindows and the derived windows.
.PP
Calling \fBmvderwin\fP 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.
.SS dupwin
Calling \fBdupwin\fP creates an exact duplicate of the window \fIwin\fP.
.SS wsyncup
Calling \fBwsyncup\fP touches all locations in ancestors of \fIwin\fP that are
changed in \fIwin\fP.
If \fBsyncok\fP is called with second argument
\fBTRUE\fP then \fBwsyncup\fP is called automatically whenever there is a
change in the window.
.SS wsyncdown
The \fBwsyncdown\fP routine touches each location in \fIwin\fP that has been
touched in any of its ancestor windows.
This routine is called by
\fBwrefresh\fP, so it should almost never be necessary to call it manually.
.SS wcursyncup
The routine \fBwcursyncup\fP updates the current cursor position of all the
ancestors of the window to reflect the current cursor position of the
window.
.SH RETURN VALUE
Routines that return an integer return the integer \fBERR\fP upon failure and
\fBOK\fP (SVr4 only specifies "an integer value other than \fBERR\fP") upon
successful completion.
.PP
Routines that return pointers return \fBNULL\fP on error.
.PP
X/Open defines no error conditions.
In this implementation
.TP 5
\fBdelwin\fP
returns an error if the window pointer is null, or
if the window is the parent of another window.
.TP 5
\fBderwin\fP
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.
.TP 5
\fBdupwin\fP
returns an error if the window pointer is null.
.IP
This implementation also maintains a list of windows,
and checks that the pointer passed to \fBdelwin\fP is one that
it created, returning an error if it was not..
.TP 5
\fBmvderwin\fP
returns an error
if the window pointer is null, or
if some part of the window would be placed off-screen.
.TP 5
\fBmvwin\fP
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.
.TP 5
\fBnewwin\fP
will fail if either of its beginning ordinates is negative, or
if either the number of lines or columns is negative.
.TP 5
\fBsyncok\fP
returns an error
if the window pointer is null.
.TP 5
\fBsubwin\fP
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.
.PP
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 \fBinitscr\fP or \fBnewterm\fP.
.SH NOTES
If many small changes are made to the window, the \fBwsyncup\fP option could
degrade performance.
.PP
Note that \fBsyncok\fP may be a macro.
.SH BUGS
The subwindow functions (\fBsubwin\fP, \fBderwin\fP, \fBmvderwin\fP,
\fBwsyncup\fP, \fBwsyncdown\fP, \fBwcursyncup\fP, \fBsyncok\fP) are flaky,
incompletely implemented, and not well tested.
.PP
The System V curses documentation is very unclear about what \fBwsyncup\fP
and \fBwsyncdown\fP actually do.
It seems to imply that they are only
supposed to touch exactly those lines that are affected by ancestor changes.
The language here, and the behavior of the \fBcurses\fP implementation,
is patterned on the XPG4 curses standard.
The weaker XPG4 spec may result in slower updates.
.SH PORTABILITY
The XSI Curses standard, Issue 4 describes these functions.
.PP
X/Open Curses states regarding \fBdelwin\fP:
.bP
It must delete subwindows before deleting their parent.
.bP
If \fBdelwin\fP 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 \fBERR\fP 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.
.bP
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.
.bP
NetBSD copied this feature of ncurses in 2003.
.br
PDCurses follows the scheme used in Solaris X/Open curses.
.SH SEE ALSO
\fBcurses\fP(3),
\fBcurs_initscr\fP(3),
\fBcurs_refresh\fP(3),
\fBcurs_touch\fP(3),
\fBcurs_variables\fP(3)