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30 * Author: Thomas E. Dickey 1996-on
31 * @Id: resizeterm.3x,v 1.56 2024/03/16 15:35:01 tom Exp @
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43 <H1 class="no-header">resizeterm 3x 2024-03-16 ncurses 6.5 Library calls</H1>
45 <STRONG><A HREF="resizeterm.3x.html">resizeterm(3x)</A></STRONG> Library calls <STRONG><A HREF="resizeterm.3x.html">resizeterm(3x)</A></STRONG>
50 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
51 <STRONG>is_term_resized</STRONG>, <STRONG>resize_term</STRONG>, <STRONG>resizeterm</STRONG> - manage the terminal
52 dimensions understood by <EM>curses</EM>
55 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
56 <STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
58 <STRONG>bool</STRONG> <STRONG>is_term_resized(int</STRONG> <EM>lines</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>columns</EM><STRONG>);</STRONG>
59 <STRONG>int</STRONG> <STRONG>resize_term(int</STRONG> <EM>lines</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>columns</EM><STRONG>);</STRONG>
60 <STRONG>int</STRONG> <STRONG>resizeterm(int</STRONG> <EM>lines</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>columns</EM><STRONG>);</STRONG>
63 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
64 This is an extension to the <EM>curses</EM> library. It provides callers with a
65 hook into the <EM>ncurses</EM> data to resize windows, primarily for use by
66 programs running in an X Window terminal (e.g., xterm) when the
67 terminal's screen size is changed by the user:
69 <STRONG>o</STRONG> <EM>curses</EM> windows cannot extend outside the screen. If the terminal
70 is shrunk, <EM>curses</EM> windows must be shrunk to fit.
72 <STRONG>o</STRONG> If the terminal is stretched, rows and/or columns can be added to
73 existing windows. The added cells should match the current
74 attributes of the windows.
76 If the calling program has not set up a handler for <STRONG>SIGWINCH</STRONG> when it
77 initializes <EM>ncurses</EM> (e.g., using <STRONG><A HREF="curs_initscr.3x.html">initscr(3x)</A></STRONG> or <STRONG><A HREF="curs_initscr.3x.html">newterm(3x)</A></STRONG>), then
78 <EM>ncurses</EM> sets a handler for <STRONG>SIGWINCH</STRONG> which notifies the library when a
79 window-size event has occurred. The library checks for this
82 <STRONG>o</STRONG> when reading input data,
84 <STRONG>o</STRONG> when implicitly resuming program mode (e.g., between <STRONG><A HREF="curs_initscr.3x.html">endwin(3x)</A></STRONG> and
85 <STRONG><A HREF="curs_refresh.3x.html">wrefresh(3x)</A></STRONG>), and
87 <STRONG>o</STRONG> when explicitly resuming program mode in <STRONG><A HREF="curs_terminfo.3x.html">restartterm(3x)</A></STRONG>.
89 When the library has found that the terminal's window-size has changed,
90 it calls <STRONG>resizeterm</STRONG> to update its data structures.
92 An application which establishes its own <STRONG>SIGWINCH</STRONG> handler can call
93 <STRONG>resizeterm</STRONG>, but in that case, the library will not see <STRONG>SIGWINCH</STRONG>, and
94 proper layout will rely upon the application.
97 </PRE><H2><a name="h2-FUNCTIONS">FUNCTIONS</a></H2><PRE>
99 </PRE><H3><a name="h3-resizeterm">resizeterm</a></H3><PRE>
100 The function <STRONG>resizeterm</STRONG> resizes the standard and current windows (i.e.,
101 <STRONG>stdscr</STRONG> and <STRONG>curscr</STRONG>) to the specified dimensions, and adjusts other
102 bookkeeping data used by the <EM>ncurses</EM> library that record the window
103 dimensions such as the <STRONG>LINES</STRONG> and <STRONG>COLS</STRONG> variables.
106 </PRE><H3><a name="h3-resize_term">resize_term</a></H3><PRE>
107 Most of the work for <STRONG>resizeterm</STRONG> is done by the inner function
108 <STRONG>resize_term</STRONG>. The outer function <STRONG>resizeterm</STRONG> adds bookkeeping for the
109 <STRONG>SIGWINCH</STRONG> handler, as well as repainting the soft-key area (see
110 <STRONG><A HREF="curs_slk.3x.html">slk_touch(3x)</A></STRONG>).
112 The <STRONG>resize_term</STRONG> function attempts to resize all windows. This helps
113 with simple applications. However:
115 <STRONG>o</STRONG> It is not possible to automatically resize pads.
117 <STRONG>o</STRONG> Applications which have complicated layouts should check for
118 <STRONG>KEY_RESIZE</STRONG> returned from <STRONG>wgetch</STRONG>, and adjust their layout, e.g.,
119 using <STRONG>wresize</STRONG> and <STRONG>mvwin</STRONG>, or by recreating the windows.
121 When resizing windows, <STRONG>resize_term</STRONG> recursively adjusts subwindows,
122 keeping them within the updated parent window's limits. If a top-level
123 window happens to extend to the screen's limits, then on resizing the
124 window, <STRONG>resize_term</STRONG> will keep the window extending to the corresponding
125 limit, regardless of whether the screen has shrunk or grown.
128 </PRE><H3><a name="h3-is_term_resized">is_term_resized</a></H3><PRE>
129 A support function <STRONG>is_term_resized</STRONG> is provided so that applications can
130 check if the <STRONG>resize_term</STRONG> function would modify the window structures.
131 It returns <STRONG>TRUE</STRONG> if the windows would be modified, and <STRONG>FALSE</STRONG> otherwise.
134 </PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
135 Except as noted, these functions return the integer <STRONG>ERR</STRONG> upon failure
136 and <STRONG>OK</STRONG> on success. They will fail if either of the dimensions are less
137 than or equal to zero, or if an error occurs while (re)allocating
138 memory for the windows.
141 </PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
142 While these functions are intended to be used to support a signal
143 handler (i.e., for <STRONG>SIGWINCH</STRONG>), care should be taken to avoid invoking
144 them in a context where <STRONG>malloc</STRONG> or <STRONG>realloc</STRONG> may have been interrupted,
145 since it uses those functions.
147 If <EM>ncurses</EM> is configured to supply its own <STRONG>SIGWINCH</STRONG> handler,
149 <STRONG>o</STRONG> on receipt of a <STRONG>SIGWINCH</STRONG>, the handler sets a flag
151 <STRONG>o</STRONG> which is tested in <STRONG><A HREF="curs_getch.3x.html">wgetch(3x)</A></STRONG>, <STRONG><A HREF="curs_refresh.3x.html">doupdate(3x)</A></STRONG> and <STRONG><A HREF="curs_terminfo.3x.html">restartterm(3x)</A></STRONG>,
153 <STRONG>o</STRONG> in turn, calling the <STRONG>resizeterm</STRONG> function,
155 <STRONG>o</STRONG> which <STRONG>ungetch</STRONG>'s a <STRONG>KEY_RESIZE</STRONG> which will be read on the next call to
156 <STRONG>wgetch</STRONG>.
158 The <STRONG>KEY_RESIZE</STRONG> alerts an application that the screen size has
159 changed, and that it should repaint special features such as pads
160 that cannot be done automatically.
162 Calling <STRONG>resizeterm</STRONG> or <STRONG>resize_term</STRONG> directly from a signal handler is
163 unsafe. This indirect method is used to provide a safe way to
164 resize the <EM>ncurses</EM> data structures.
166 If the environment variables <EM>LINES</EM> or <EM>COLUMNS</EM> are set, this overrides
167 the library's use of the window size obtained from the operating
168 system. Thus, even if a <STRONG>SIGWINCH</STRONG> is received, no screen size change
172 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
173 It is possible to resize the screen with SVr4 <EM>curses</EM>, by
175 <STRONG>o</STRONG> exiting <EM>curses</EM> with <STRONG><A HREF="curs_initscr.3x.html">endwin(3x)</A></STRONG> and
177 <STRONG>o</STRONG> resuming using <STRONG><A HREF="curs_refresh.3x.html">refresh(3x)</A></STRONG>.
179 Doing that clears the screen and is visually distracting.
181 This extension of <EM>ncurses</EM> was introduced in mid-1995. It was adopted
182 in NetBSD <EM>curses</EM> (2001) and PDCurses (2003).
185 </PRE><H2><a name="h2-AUTHORS">AUTHORS</a></H2><PRE>
186 Thomas Dickey (from an equivalent function written in 1988 for BSD
190 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
191 <STRONG><A HREF="curs_getch.3x.html">curs_getch(3x)</A></STRONG>, <STRONG><A HREF="curs_variables.3x.html">curs_variables(3x)</A></STRONG>, <STRONG><A HREF="wresize.3x.html">wresize(3x)</A></STRONG>
195 ncurses 6.5 2024-03-16 <STRONG><A HREF="resizeterm.3x.html">resizeterm(3x)</A></STRONG>
199 <li><a href="#h2-NAME">NAME</a></li>
200 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
201 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a></li>
202 <li><a href="#h2-FUNCTIONS">FUNCTIONS</a>
204 <li><a href="#h3-resizeterm">resizeterm</a></li>
205 <li><a href="#h3-resize_term">resize_term</a></li>
206 <li><a href="#h3-is_term_resized">is_term_resized</a></li>
209 <li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
210 <li><a href="#h2-NOTES">NOTES</a></li>
211 <li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
212 <li><a href="#h2-AUTHORS">AUTHORS</a></li>
213 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>