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resizeterm(3x)

resizeterm(3x)                   Library calls                  resizeterm(3x)

NAME
       is_term_resized,  resize_term,  resizeterm - manage the terminal dimen‐
       sions understood by curses

SYNOPSIS
       #include <ncursesw/curses.h>

       bool is_term_resized(int lines, int columns);
       int resize_term(int lines, int columns);
       int resizeterm(int lines, int columns);

DESCRIPTION
       This is an extension to the curses library.  It provides callers with a
       hook into the ncurses data to resize windows, primarily for use by pro‐
       grams running in an X Window terminal (e.g., xterm) when the terminal's
       screen size is changed by the user:

       •   curses windows cannot extend outside the screen.  If  the  terminal
           is shrunk, curses windows must be shrunk to fit.

       •   If  the  terminal is stretched, rows and/or columns can be added to
           existing windows.  The added cells should match the current attrib‐
           utes of the windows.

       If the application has not set up a handler for SIGWINCH when  it  ini‐
       tializes  ncurses (by calling initscr(3X) or newterm(3X)), then ncurses
       establishes a SIGWINCH handler that notifies the library when a window-
       resizing event has occurred.  The library checks for this notification

       •   when reading input data,

       •   when implicitly resuming program mode (e.g., between endwin(3X) and
           wrefresh(3X)), and

       •   when explicitly resuming program mode in restartterm(3X).

       When the library has found that the terminal's window-size has changed,
       it calls resizeterm to update its data structures.

       An application which establishes its  own  SIGWINCH  handler  can  call
       resizeterm,  but  in  that case, the library will not see SIGWINCH, and
       proper layout will rely upon the application.

   resizeterm
       The function resizeterm resizes the standard and current windows (i.e.,
       stdscr and curscr) to the specified dimensions, and adjusts other book‐
       keeping data used by the ncurses library that record the window  dimen‐
       sions such as the LINES and COLS variables.

   resize_term
       Most  of  the  work  for  resizeterm  is  done  by  the  inner function
       resize_term.  The outer function resizeterm adds  bookkeeping  for  the
       SIGWINCH  handler,  as  well  as  repainting  the  soft-key  area  (see
       slk_touch(3X)).

       The resize_term function attempts to resize all  windows.   This  helps
       with simple applications.  However:

       •   It is not possible to automatically resize pads.

       •   Applications  which  have  complicated  layouts  should  check  for
           KEY_RESIZE returned from wgetch, and adjust their layout, e.g., us‐
           ing wresize and mvwin, or by recreating the windows.

       When resizing  windows,  resize_term  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, resize_term will keep the window extending to the corresponding
       limit, regardless of whether the screen has shrunk or grown.

   is_term_resized
       A support function is_term_resized is provided so that applications can
       check if the resize_term function would modify the  window  structures.
       It returns TRUE if the windows would be modified, and FALSE otherwise.

RETURN VALUE
       Except  as  noted,  these functions return the integer ERR upon failure
       and OK 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  mem‐
       ory for the windows.


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:

       box; cbp-1 | cbp-1 l | l .  ATTRIBUTE TYPE ATTRIBUTE VALUE = Availabil‐
       ity   library/ncurses = Stability Uncommitted

NOTES
       While  these functions are intended to be used to support a signal han‐
       dler (i.e., for SIGWINCH), care should be taken to avoid invoking  them
       in  a  context where malloc or realloc may have been interrupted, since
       it uses those functions.

       If ncurses is configured to supply its own SIGWINCH handler,

       •   on receipt of a SIGWINCH, the handler sets a flag

       •   which is tested in wgetch(3X), doupdate(3X) and restartterm(3X),

       •   in turn, calling the resizeterm function,

       •   which ungetch's a KEY_RESIZE which will be read on the next call to
           wgetch.

           The KEY_RESIZE alerts an  application  that  the  screen  size  has
           changed,  and  that it should repaint special features such as pads
           that cannot be done automatically.

           Calling resizeterm or resize_term directly from a signal handler is
           unsafe.  This indirect method is used to provide a safe way to  re‐
           size the ncurses data structures.

       If  the  environment variables LINES or COLUMNS are set, this overrides
       the library's use of the window size obtained from the  operating  sys‐
       tem.   Thus,  even if a SIGWINCH is received, no screen size change may
       be recorded.

       Source code for open source software components in Oracle  Solaris  can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-
       code-downloads.html.

       This software was built from source available at:
       https://github.com/oracle/solaris-userland

       The original community source was downloaded from:
       https://invisible-mirror.net/archives/ncurses/cur‐
       rent/ncurses-6.5-20250614.tgz

       Further information about this software can be found on the open source
       community website at https://invisible-island.net/ncurses/.

PORTABILITY
       It is possible to resize the screen with SVr4 curses, by

       •   exiting curses with endwin(3X) and

       •   resuming using refresh(3X).

       Doing that clears the screen and is visually distracting.

       ncurses  introduced  this extension in mid-1995.  NetBSD curses adopted
       it in 2001 and PDCurses in 2003.

AUTHORS
       Thomas Dickey (from an equivalent function  written  in  1988  for  BSD
       curses)

SEE ALSO
       curs_getch(3X), curs_variables(3X), wresize(3X)


ncurses 6.5                       2025-04-05                    resizeterm(3x)
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