Automatically break help output at the actual terminal width.

Works only with programs using the cli_parser_c class. This is only
mkvpropedit so far, but the others will follow.

Oh, and this only works if ioctl & TIOCGWINSZ are available.

ac/tiocgwinsz.m4

@@ -0,0 +1,14 @@
+AC_CACHE_CHECK([for ioctl & TIOCGWINSZ], [ac_cv_tiocgwinsz],[
+  ac_cv_tiocgwinsz="no"
+  AC_LANG_PUSH(C++)
+  AC_TRY_COMPILE([
+      #include <sys/ioctl.h>
+    ],[
+      struct winsize ws;
+      ioctl(0, TIOCGWINSZ, &ws);
+    ],[ac_cv_tiocgwinsz="yes"])
+  AC_LANG_POP
+])
+if test x"$ac_cv_posix_fadvise" = "xyes" ; then
+  AC_DEFINE([HAVE_TIOCGWINSZ], 1, [define if ioctl & TIOCGWINSZ are available])
+fi

configure.in

@@ -43,6 +43,7 @@ m4_include(ac/ax_boost_foreach.m4)
 m4_include(ac/boost.m4)
 m4_include(ac/etags.m4)
 m4_include(ac/ax_docbook.m4)
+m4_include(ac/tiocgwinsz.m4)
 
 AC_OUTPUT(
   Makefile

src/common/strings/formatting.cpp

@@ -16,6 +16,7 @@
 #include "common/common.h"
 #include "common/strings/formatting.h"
 #include "common/strings/utf8.h"
+#include "common/terminal.h"
 #include "common/translation.h"
 
 std::string
@@ -152,6 +153,9 @@ format_paragraph(const std::wstring &text_to_wrap,
   int current_column  = get_width_in_em(text);
   bool break_anywhere = translation_c::get_active_translation().m_line_breaks_anywhere;
 
+  if (WRAP_AT_TERMINAL_WIDTH == wrap_column)
+    wrap_column = get_terminal_columns() - 1;
+
   if ((0 != indent_column) && (current_column >= indent_column)) {
     text           += L"\n";
     current_column  = 0;

src/common/strings/formatting.h

@@ -34,21 +34,21 @@
                             (int32_t)( (t)                         % 1000000000)
 #define ARG_TIMECODEN(t) ARG_TIMECODENINT((int64_t)(t))
 
-#define WRAP_COLUMN 79
+#define WRAP_AT_TERMINAL_WIDTH -1
 
 std::string MTX_DLL_API format_timecode(int64_t timecode, unsigned int precision = 9);
 std::string MTX_DLL_API format_paragraph(const std::string &text_to_wrap,
                                          int indent_column                    = 0,
                                          const std::string &indent_first_line = empty_string,
                                          std::string indent_following_lines   = empty_string,
-                                         int wrap_column                      = WRAP_COLUMN,
+                                         int wrap_column                      = WRAP_AT_TERMINAL_WIDTH,
                                          const char *break_chars              = " ,.)/:");
 
 std::wstring MTX_DLL_API format_paragraph(const std::wstring &text_to_wrap,
                                           int indent_column                     = 0,
                                           const std::wstring &indent_first_line = L" ",
                                           std::wstring indent_following_lines   = L" ",
-                                          int wrap_column                       = WRAP_COLUMN,
+                                          int wrap_column                       = WRAP_AT_TERMINAL_WIDTH,
                                           const std::wstring &break_chars       = L" ,.)/:");
 
 void MTX_DLL_API fix_format(const char *fmt, std::string &new_fmt);

src/common/terminal.cpp

@@ -0,0 +1,37 @@
+/*
+   mkvmerge -- utility for splicing together matroska files
+   from component media subtypes
+
+   Distributed under the GPL
+   see the file COPYING for details
+   or visit http://www.gnu.org/copyleft/gpl.html
+
+   terminal access functions
+
+   Written by Moritz Bunkus <moritz@bunkus.org>.
+*/
+
+#include "common/os.h"
+
+#if defined(HAVE_TIOCGWINSZ)
+# include <sys/ioctl.h>
+#endif  // HAVE_TIOCGWINSZ
+
+#include "common/terminal.h"
+
+#define DEFAULT_TERMINAL_COLUMNS 80
+
+int
+get_terminal_columns() {
+#if defined(HAVE_TIOCGWINSZ)
+  struct winsize ws;
+
+  if (ioctl(0, TIOCGWINSZ, &ws) != 0)
+    return DEFAULT_TERMINAL_COLUMNS;
+  return ws.ws_col;
+
+#else  // HAVE_TIOCGWINSZ
+  return DEFAULT_TERMINAL_COLUMNS;
+#endif  // HAVE_TIOCGWINSZ
+}
+

src/common/terminal.h

@@ -0,0 +1,21 @@
+/*
+   mkvmerge -- utility for splicing together matroska files
+   from component media subtypes
+
+   Distributed under the GPL
+   see the file COPYING for details
+   or visit http://www.gnu.org/copyleft/gpl.html
+
+   terminal access functions
+
+   Written by Moritz Bunkus <moritz@bunkus.org>.
+*/
+
+#ifndef __MTX_COMMON_TERMINAL_H
+#define __MTX_COMMON_TERMINAL_H
+
+#include "common/os.h"
+
+int MTX_DLL_API get_terminal_columns();
+
+#endif  // __MTX_COMMON_TERMINAL_H