doc/lispref/anti.texi

   1 @c -*-texinfo-*-
   2 @c This is part of the GNU Emacs Lisp Reference Manual.
   3 @c Copyright (C) 1999, 2002-2012 Free Software Foundation, Inc.
   4 @c See the file elisp.texi for copying conditions.
   5
   6 @c This node must have no pointers.
   7
   8 @node Antinews, GNU Free Documentation License, Packaging, Top
   9 @appendix Emacs 23 Antinews
  10 @c Update the elisp.texi Antinews menu entry with the above version number.
  11
  12 For those users who live backwards in time, here is information about
  13 downgrading to Emacs version 23.4.  We hope you will enjoy the greater
  14 simplicity that results from the absence of many Emacs @value{EMACSVER}
  15 features.
  16
  17 @section Old Lisp Features in Emacs 23
  18
  19 @itemize @bullet
  20 @item
  21 Support for lexical scoping has been removed; all variables are
  22 dynamically scoped.  The @code{lexical-binding} variable has been
  23 removed, and so has the @var{lexical} argument to @code{eval}.  The
  24 @code{defvar} and @code{defconst} forms no longer mark variables as
  25 dynamic, since all variables are dynamic.
  26
  27 Having only dynamic binding follows the spirit of Emacs extensibility,
  28 for it allows any Emacs code to access any defined variable with a
  29 minimum of fuss.  But @xref{Dynamic Binding Tips}, for tips to avoid
  30 making your programs hard to understand.
  31
  32 @item
  33 Calling a minor mode function from Lisp with a nil or omitted argument
  34 does not enable the minor mode unconditionally; instead, it toggles
  35 the minor mode---which is the straightforward thing to do, since that
  36 is the behavior when invoked interactively.  One downside is that it
  37 is more troublesome to enable minor modes from hooks; you have to do
  38 something like
  39
  40 @example
  41 (add-hook 'foo-hook (lambda () (bar-mode 1)))
  42 @end example
  43
  44 @noindent
  45 or define @code{turn-on-bar-mode} and call that from the hook.
  46
  47 @item
  48 The @code{prog-mode} dummy major mode has been removed.  Instead of
  49 using it as a crutch to meet programming mode conventions, you should
  50 explicitly ensure that your mode follows those conventions.
  51 @xref{Major Mode Conventions}.
  52
  53 @item
  54 Emacs no longer supports bidirectional display and editing.  Since
  55 there is no need to worry about the insertion of right-to-left text
  56 messing up how lines and paragraphs are displayed, the function
  57 @code{bidi-string-mark-left-to-right} has been removed; so have many
  58 other functions and variables related to bidirectional display.
  59 Unicode directionality characters like @code{U+200E} ("left-to-right
  60 mark") have no special effect on display.
  61
  62 @item
  63 Emacs windows now have most of their internal state hidden from Lisp.
  64 Internal windows are no longer visible to Lisp; functions such as
  65 @code{window-parent}, window parameters related to window arrangement,
  66 and window-local buffer lists have all been removed.  Functions for
  67 resizing windows can delete windows if they become too small.
  68
  69 The ``action function'' feature for controlling buffer display has
  70 been removed, including @code{display-buffer-overriding-action} and
  71 related variables, as well as the @var{action} argument to
  72 @code{display-buffer} and other functions.  The way to
  73 programmatically control how Emacs chooses a window to display a
  74 buffer is to bind the right combination of
  75 @code{special-display-regexps}, @code{pop-up-frames}, and other
  76 variables.
  77
  78 @item
  79 The standard completion interface has been simplified, eliminating the
  80 @code{completion-extra-properties} variable, the @code{metadata}
  81 action flag for completion functions, and the concept of
  82 ``completion categories''.  Lisp programmers may now find the choice
  83 of methods for tuning completion less bewildering, but if a package
  84 finds the streamlined interface insufficient for its needs, it must
  85 implement its own specialized completion feature.
  86
  87 @item
  88 @code{copy-directory} now behaves the same whether or not the
  89 destination is an existing directory: if the destination exists, the
  90 @emph{contents} of the first directory are copied into it (with
  91 subdirectories handled recursively), rather than copying the first
  92 directory into a subdirectory.
  93
  94 @item
  95 The @var{trash} arguments for @code{delete-file} and
  96 @code{delete-directory} have been removed.  The variable
  97 @code{delete-by-moving-to-trash} must now be used with care; whenever
  98 it is non-@code{nil}, all calls to @code{delete-file} or
  99 @code{delete-directory} use the trash.
 100
 101 @item
 102 Because Emacs no longer supports SELinux file contexts, the
 103 @var{preserve-selinux-context} argument to @code{copy-file} has been
 104 removed.  The return value of @code{backup-buffer} no longer has an
 105 entry for the SELinux file context.
 106
 107 @item
 108 For mouse click input events in the text area, the Y pixel coordinate
 109 in the @var{position} list (@pxref{Click Events}) now counts from the
 110 top of the header line, if there is one, rather than the top of the
 111 text area.
 112
 113 @item
 114 Bindings in menu keymaps (@pxref{Format of Keymaps}) now sometimes get
 115 an additional @var{cache} entry in their definitions, like this:
 116
 117 @example
 118 (@var{type} @var{item-name} @var{cache} . @var{binding})
 119 @end example
 120
 121 @noindent
 122 The @var{cache} entry is used internally by Emacs to record equivalent
 123 keyboard key sequences for invoking the same command; Lisp programs
 124 should never use it.
 125 @c Not really NEWS-worthy then...
 126
 127 @item
 128 The @code{gnutls} library has been removed, and the function
 129 @code{open-network-stream} correspondingly simplified.
 130 Lisp programs that want an encrypted network connection must now call
 131 external utilities such as @command{starttls} or @command{gnutls-cli}.
 132
 133 @item
 134 Tool bars can no longer display separators, which frees up several
 135 pixels of space on each graphical frame.
 136
 137 @item
 138 As part of the ongoing quest for simplicity, many other functions and
 139 variables have been eliminated.
 140 @end itemize