检测终端调整 ncurses 大小，无需使用 --enable-sigwinch 进行编译

Question

On Arch--enable-sigwinch不会编译成 ncurses。根据此论坛帖子，它可用于检测终端大小调整。让他们打开该选项似乎没有一些阻力，是否有另一种通用方法来检测终端大小调整C？

Answer 1

引用自INSTALL：

    --enable-sigwinch
        Compile support for ncurses' SIGWINCH handler.  If your application has
        its own SIGWINCH handler, ncurses will not use its own.  The ncurses
        handler causes wgetch() to return KEY_RESIZE when the screen-size
        changes.  This option is the default, unless you have disabled the
        extended functions.

如果它不存在，则它已被禁用。原则上，您可以按照test/view.cCAN_RESIZE文件中最近删除（早已过时）的部分所示进行操作。ncurses 库比这做得更好；该示例于 1995 年 7 月添加。注释引用了 SunOS 4：

/*
 * This uses functions that are "unsafe", but it seems to work on SunOS. 
 * Usually: the "unsafe" refers to the functions that POSIX lists which may be
 * called from a signal handler.  Those do not include buffered I/O, which is
 * used for instance in wrefresh().  To be really portable, you should use the
 * KEY_RESIZE return (which relies on ncurses' sigwinch handler).
 *
 * The 'wrefresh(curscr)' is needed to force the refresh to start from the top
 * of the screen -- some xterms mangle the bitmap while resizing.
 */

现代的等效方法只是在信号处理程序中设置一个标志，如库中所做的那样：

#if USE_SIGWINCH
static void
handle_SIGWINCH(int sig GCC_UNUSED)
{
    _nc_globals.have_sigwinch = 1;
# if USE_PTHREADS_EINTR
    if (_nc_globals.read_thread) {
    if (!pthread_equal(pthread_self(), _nc_globals.read_thread))
        pthread_kill(_nc_globals.read_thread, SIGWINCH);
    _nc_globals.read_thread = 0;
    }
# endif
}
#endif /* USE_SIGWINCH */

顺便说一下，包脚本没有显示该功能已被禁用：

  ./configure --prefix=/usr --mandir=/usr/share/man \
    --with-pkg-config-libdir=/usr/lib/pkgconfig \
    --with-static --with-normal --without-debug --without-ada \
    --enable-widec --enable-pc-files --with-cxx-binding --with-cxx-static \
    --with-shared --with-cxx-shared

回顾一下库，SIGWINCH如果信号是默认（未设置）值，它会初始化其处理程序：

#if USE_SIGWINCH
        CatchIfDefault(SIGWINCH, handle_SIGWINCH);
#endif

如果已经有一个SIGWINCH处理程序，ncurses 将不会执行任何操作。