1resizeterm(3X) resizeterm(3X)
2
6 is_term_resized, resize_term, resizeterm - change the curses terminal
7 size
8
10 #include <curses.h>
11 bool is_term_resized(int lines, int columns);
13 int resize_term(int lines, int columns);
14 int resizeterm(int lines, int columns);
15
17 This is an extension to the curses library. It provides callers with a
18 hook into the ncurses data to resize windows, primarily for use by pro‐
19 grams running in an X Window terminal (e.g., xterm) when the terminal's
20 screen size is changed by the user:
21 • Curses windows cannot extend outside the screen. If the terminal
23 is shrunk, curses windows must be shrunk to fit.
24 • If the terminal is stretched, rows and/or columns can be added to
26 existing windows. The added cells should match the current at‐
27 tributes of the windows.
28 If the calling program has not set up a handler for SIGWINCH when it
30 initializes ncurses (e.g., using initscr(3X) or newterm(3X)), then
31 ncurses sets a handler for SIGWINCH which notifies the library when a
32 window-size event has occurred. The library checks for this notifica‐
33 tion
34 • when reading input data,
36 • when implicitly resuming program mode (e.g., between endwin(3X) and
38 wrefresh(3X)), and
39 • when explicitly resuming program mode in restartterm(3X).
41 When the library has found that the terminal's window-size has changed,
43 it calls resizeterm to update its data structures.
44 An application which establishes its own SIGWINCH handler can call re‐
46 sizeterm, but in that case, the library will not see SIGWINCH, and
47 proper layout will rely upon the application.
48
50 resizeterm
51 The function resizeterm resizes the standard and current windows (i.e.,
52 stdscr and curscr) to the specified dimensions, and adjusts other book‐
53 keeping data used by the ncurses library that record the window dimen‐
54 sions such as the LINES and COLS variables.
55 resize_term
57 Most of the work for resizeterm is done by the inner function re‐
58 size_term. The outer function resizeterm adds bookkeeping for the SIG‐
59 WINCH handler, as well as repainting the soft-key area (see
60 slk_touch(3X)).
61 The resize_term function attempts to resize all windows. This helps
63 with simple applications. However:
64 • It is not possible to automatically resize pads.
66 • Applications which have complicated layouts should check for
68 KEY_RESIZE returned from wgetch, and adjust their layout, e.g., us‐
69 ing wresize and mvwin, or by recreating the windows.
70 When resizing windows, resize_term recursively adjusts subwindows,
72 keeping them within the updated parent window's limits. If a top-level
73 window happens to extend to the screen's limits, then on resizing the
74 window, resize_term will keep the window extending to the corresponding
75 limit, regardless of whether the screen has shrunk or grown.
76 is_term_resized
78 A support function is_term_resized is provided so that applications can
79 check if the resize_term function would modify the window structures.
80 It returns TRUE if the windows would be modified, and FALSE otherwise.
81
83 Except as noted, these functions return the integer ERR upon failure
84 and OK on success. They will fail if either of the dimensions are less
85 than or equal to zero, or if an error occurs while (re)allocating mem‐
86 ory for the windows.
87
89 While these functions are intended to be used to support a signal han‐
90 dler (i.e., for SIGWINCH), care should be taken to avoid invoking them
91 in a context where malloc or realloc may have been interrupted, since
92 it uses those functions.
93 If ncurses is configured to supply its own SIGWINCH handler,
95 • on receipt of a SIGWINCH, the handler sets a flag
97 • which is tested in wgetch(3X), doupdate(3X) and restartterm(3X),
99 • in turn, calling the resizeterm function,
101 • which ungetch's a KEY_RESIZE which will be read on the next call to
103 wgetch.
104 The KEY_RESIZE alerts an application that the screen size has
106 changed, and that it should repaint special features such as pads
107 that cannot be done automatically.
108 Calling resizeterm or resize_term directly from a signal handler is
110 unsafe. This indirect method is used to provide a safe way to re‐
111 size the ncurses data structures.
112 If the environment variables LINES or COLUMNS are set, this overrides
114 the library's use of the window size obtained from the operating sys‐
115 tem. Thus, even if a SIGWINCH is received, no screen size change may
116 be recorded.
117
119 It is possible to resize the screen with SVr4 curses, by
120 • exiting curses with endwin(3X) and
122 • resuming using refresh(3X).
124 Doing that clears the screen and is visually distracting.
126 This extension of ncurses was introduced in mid-1995. It was adopted
128 in NetBSD curses (2001) and PDCurses (2003).
129
131 curs_getch(3X), curs_variables(3X), wresize(3X).
132
134 Thomas Dickey (from an equivalent function written in 1988 for BSD
135 curses).
136 resizeterm(3X)