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NAME | SYNOPSIS | DESCRIPTION | FUNCTIONS | RETURN VALUE | NOTES | PORTABILITY | SEE ALSO | AUTHOR | COLOPHON |
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resizeterm(3X) resizeterm(3X)
is_term_resized, resize_term, resizeterm - change the curses
terminal size
#include <curses.h>
bool is_term_resized(int lines, int columns);
int resize_term(int lines, int columns);
int resizeterm(int lines, int columns);
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.
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.
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.
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.
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).
curs_getch(3X), curs_variables(3X), wresize(3X).
Thomas Dickey (from an equivalent function written in 1988 for
BSD curses).
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
[email protected]. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨https://github.com/mirror/ncurses.git⟩ on 2024-06-14. (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
[email protected]
resizeterm(3X)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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