.\"***************************************************************************
-.\" Copyright (c) 1998 Free Software Foundation, Inc. *
+.\" Copyright 2018-2021,2022 Thomas E. Dickey *
+.\" Copyright 1998-2015,2017 Free Software Foundation, Inc. *
.\" *
.\" Permission is hereby granted, free of charge, to any person obtaining a *
.\" copy of this software and associated documentation files (the *
.\" authorization. *
.\"***************************************************************************
.\"
-.\" Author: Thomas E. Dickey <dickey@clark.net> 1996,1997
+.\" Author: Thomas E. Dickey 1996-on
.\"
-.\" $Id: resizeterm.3x,v 1.7 1998/03/14 23:42:52 tom Exp $
+.\" $Id: resizeterm.3x,v 1.32 2022/02/20 00:32:18 tom Exp $
.TH resizeterm 3X ""
-.SH NAME
-\fBresizeterm\fR - change the curses terminal size
+.de bP
+.ie n .IP \(bu 4
+.el .IP \(bu 2
..
+.SH NAME
+\fBis_term_resized\fP,
+\fBresize_term\fP,
+\fBresizeterm\fP \- change the curses terminal size
.SH SYNOPSIS
-\fB#include <curses.h>\fR
-
-\fBint resizeterm(int lines, int columns);\fR
-..
+\fB#include <curses.h>\fP
+.sp
+\fBbool is_term_resized(int \fIlines\fB, int \fIcolumns\fB);\fR
+.br
+\fBint resize_term(int \fIlines\fB, int \fIcolumns\fB);\fR
+.br
+\fBint resizeterm(int \fIlines\fB, int \fIcolumns\fB);\fR
.SH DESCRIPTION
+.PP
This is an extension to the curses library.
-It provides callers with a hook into the \fBncurses\fR data to resize windows,
-primarily for use by programs running in an X Window terminal (e.g., xterm).
-The function \fBresizeterm\fR resizes the standard and current windows
+It provides callers with a hook into the \fBncurses\fP data to resize windows,
+primarily for use by programs running in an X Window terminal (e.g., xterm)
+when the terminal's screen size is changed by the user:
+.bP
+Curses windows cannot extend outside the screen.
+If the terminal is shrunk, curses windows must be shrunk to fit.
+.bP
+If the terminal is stretched,
+rows and/or columns can be added to existing windows.
+The added cells should match the current attributes of the windows.
+.PP
+If the calling program has not set up a handler for \fBSIGWINCH\fP
+when it initializes \fBncurses\fP
+(e.g., using \fBinitscr\fP(3X) or \fBnewterm\fP(3X)),
+then \fBncurses\fP sets a handler for \fBSIGWINCH\fP which notifies
+the library when a window-size event has occurred.
+The library checks for this notification
+.bP
+when reading input data,
+.bP
+when implicitly resuming program mode
+(e.g., between \fBendwin\fP(3X) and \fBwrefresh\fP(3X)),
+and
+.bP
+when explicitly resuming program mode in \fBrestartterm\fP(3X).
+.PP
+When the library has found that the terminal's window-size has
+changed, it calls \fBresizeterm\fP to update its data structures.
+.PP
+An application which establishes its own \fBSIGWINCH\fP handler
+can call \fBresizeterm\fP, but in that case, the library will not
+see \fBSIGWINCH\fP, and proper layout will rely upon the application.
+.SH FUNCTIONS
+.SS resizeterm
+.PP
+The function \fBresizeterm\fP resizes the standard and current windows
+(i.e., \fBstdscr\fP and \fBcurscr\fP)
to the specified dimensions, and adjusts other bookkeeping data used by
-the \fBncurses\fR library that record the window dimensions.
-
-When resizing the windows, the function blank-fills the areas that are
-extended. The calling application should fill in these areas with
-appropriate data.
-
-The function attempts to resize all windows.
-However, due to the calling convention of pads,
-it is not possible to resize these
-without additional interaction with the application.
-..
+the \fBncurses\fP library that record the window dimensions
+such as the \fBLINES\fP and \fBCOLS\fP variables.
+.SS resize_term
+.PP
+Most of the work for \fBresizeterm\fP is
+done by the inner function \fBresize_term\fP.
+The outer function \fBresizeterm\fP adds bookkeeping
+for the \fBSIGWINCH\fP handler,
+as well as repainting the soft-key area (see \fBslk_touch\fP(3X)).
+.PP
+The \fBresize_term\fP function attempts to resize all windows.
+This helps with simple applications.
+However:
+.bP
+It is not possible to automatically resize pads.
+.bP
+Applications which have complicated layouts should check for
+\fBKEY_RESIZE\fP returned from \fBwgetch\fP,
+and adjust their layout, e.g., using \fBwresize\fP and \fBmvwin\fP,
+or by recreating the windows.
+.PP
+When resizing windows, \fBresize_term\fP recursively adjusts subwindows,
+keeping them within the updated parent window's limits.
+If a top-level window happens to extend to the screen's limits,
+then on resizing the window, \fBresize_term\fP will keep the window
+extending to the corresponding limit, regardless of whether the
+screen has shrunk or grown.
+.SS is_term_resized
+.PP
+A support function \fBis_term_resized\fP is provided so that applications
+can check if the \fBresize_term\fP function would modify the window structures.
+It returns \fBTRUE\fP if the windows would be modified,
+and \fBFALSE\fP otherwise.
.SH RETURN VALUE
-The function returns the integer \fBERR\fR upon failure and \fBOK\fR on success.
-It will fail if either of the dimensions less than or equal to zero,
-or if an error occurs while (re)allocating memory for the windows.
-..
+Except as noted, these functions return
+the integer \fBERR\fP upon failure and \fBOK\fP on success.
+They will fail if either of the dimensions are less than or equal to zero,
+or if an error occurs while (re)allocating memory for the windows.
.SH NOTES
-While this function is intended to be used to support a signal handler
-(i.e., for SIGWINCH), care should be taken to avoid invoking it in a
-context where \fBmalloc\fR or \fBrealloc\fR may have been interrupted,
+While these functions are intended to be used to support a signal handler
+(i.e., for \fBSIGWINCH\fP), care should be taken to avoid invoking them in a
+context where \fBmalloc\fP or \fBrealloc\fP may have been interrupted,
since it uses those functions.
-..
.PP
-If ncurses is configured to supply its own SIGWINCH handler,
-the \fBresizeterm\fR function ungetch's a \fBKEY_RESIZE\fR which
-will be read on the next call to \fBgetch\fR.
-This is used to alert an application that the screen size has changed,
+If ncurses is configured to supply its own \fBSIGWINCH\fP handler,
+.bP
+on receipt of a \fBSIGWINCH\fP, the handler sets a flag
+.bP
+which is tested in
+\fBwgetch\fP(3X),
+\fBdoupdate\fP(3X) and
+\fBrestartterm\fP(3X),
+.bP
+in turn, calling the \fBresizeterm\fP function,
+.bP
+which \fBungetch\fP's a \fBKEY_RESIZE\fP which
+will be read on the next call to \fBwgetch\fP.
+.IP
+The \fBKEY_RESIZE\fP alerts an application that the screen size has changed,
and that it should repaint special features such as pads that cannot
be done automatically.
-..
+.IP
+Calling \fBresizeterm\fP or \fBresize_term\fP
+directly from a signal handler is unsafe.
+This indirect method is used to provide a safe way to resize the ncurses
+data structures.
+.PP
+If the environment variables \fBLINES\fP or \fBCOLUMNS\fP are set,
+this overrides the library's use of the window size obtained from
+the operating system.
+Thus, even if a \fBSIGWINCH\fP is received,
+no screen size change may be recorded.
+.SH PORTABILITY
+.PP
+It is possible to resize the screen with SVr4 curses,
+by
+.bP
+exiting curses with \fBendwin\fP(3X) and
+.bP
+resuming using \fBrefresh\fP(3X).
+.PP
+Doing that clears the screen and is visually distracting.
+.PP
+This extension of ncurses was introduced in mid-1995.
+It was adopted in NetBSD curses (2001) and PDCurses (2003).
.SH SEE ALSO
-\fBwresize\fR(3X).
-..
+\fBcurs_getch\fP(3X),
+\fBcurs_variables\fP(3X),
+\fBwresize\fP(3X).
.SH AUTHOR
Thomas Dickey (from an equivalent function written in 1988 for BSD curses).
-.\"#
-.\"# The following sets edit modes for GNU EMACS
-.\"# Local Variables:
-.\"# mode:nroff
-.\"# fill-column:79
-.\"# End:
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