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 win-
dows, primarily for use by programs running in an X Window
terminal (e.g., xterm).
The function resizeterm resizes the standard and current
windows 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 vari-
ables.
Most of the work is done by the inner function
resize_term. The outer function resizeterm adds bookkeep-
ing for the SIGWINCH handler. When resizing the windows,
resize_term blank-fills the areas that are extended. The
calling application should fill in these areas with appro-
priate data. The resize_term function attempts to resize
all windows. However, due to the calling convention of
pads, it is not possible to resize these without addi-
tional interaction with the application.
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 win-
dows 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 real-
loc may have been interrupted, since it uses those func-
tions.
If ncurses is configured to supply its own SIGWINCH han-
dler,
o on receipt of a SIGWINCH, the handler sets a flag
o which is tested in wgetch(3x) and doupdate,
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 automati-
cally.
Calling resizeterm or resize_term directly from a sig-
nal 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 SIG-
WINCH is received, no screen size change may be recorded.
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).
curs_getch(3x), curs_variables(3x), wresize(3x).
Thomas Dickey (from an equivalent function written in 1988
for BSD curses).
resizeterm(3x)