resizeterm(3x) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | FUNCTIONS | RETURN VALUE | NOTES | PORTABILITY | SEE ALSO | AUTHOR | COLOPHON

resizeterm(3X)                                            resizeterm(3X)

NAME         top

       is_term_resized, resize_term, resizeterm - change the curses
       terminal size

SYNOPSIS         top

       #include <curses.h>

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

DESCRIPTION         top

       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 programs 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 attributes of the windows.

       If the calling program has not set up a handler for SIGWINCH when
       it initializes ncurses (e.g., using initscr(3X) or newterm(3X)),
       then ncurses sets a handler for SIGWINCH which notifies the
       library when a window-size 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.

FUNCTIONS         top

   resizeterm
       The function resizeterm resizes the standard and current windows
       (i.e., stdscr and curscr) to the specified dimensions, and
       adjusts other bookkeeping data used by the ncurses library that
       record the window dimensions 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., using 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         top

       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 memory for the windows.

NOTES         top

       While these functions are intended to be used to support a signal
       handler (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 resize 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 system.  Thus, even if a SIGWINCH is received, no
       screen size change may be recorded.

PORTABILITY         top

       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.

       This extension of ncurses was introduced in mid-1995.  It was
       adopted in NetBSD curses (2001) and PDCurses (2003).

SEE ALSO         top

       curs_getch(3X), curs_variables(3X), wresize(3X).

AUTHOR         top

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

COLOPHON         top

       This page is part of the ncurses (new curses) project.
       Information about the project can be found at 
       ⟨https://www.gnu.org/software/ncurses/ncurses.html⟩.  If you have
       a bug report for this manual page, send it to
       bug-ncurses-request@gnu.org.  This page was obtained from the
       project's upstream Git mirror of the CVS repository
       ⟨https://github.com/mirror/ncurses.git⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-03-12.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
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                                                          resizeterm(3X)