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resizeterm(3)                                                    resizeterm(3)




NAME

       is_term_resized, resize_term, resizeterm - change the curses terminal
       size


SYNOPSIS

       #include <curses.h>

       bool is_term_resized(int lines, int columns);
       int resize_term(int lines, int columns);
       resizeterm(3) 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
       programs running in an X Window terminal (e.g., xterm) when the
       terminal's screen size is changed by the user:

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

       o   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

       o   when reading input data,

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

       o   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

   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:

       o   It is not possible to automatically resize pads.

       o   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

       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

       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,

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

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

       o   in turn, calling the resizeterm function,

       o   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

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

       o   exiting curses with endwin(3X) and

       o   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

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


AUTHOR

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



                                                                  resizeterm(3)

ncurses 6.4 - Generated Fri Jan 6 09:23:14 CST 2023
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