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For those users who live backwards in time, here is information about downgrading to Emacs version 23.4. We hope you will enjoy the greater simplicity that results from the absence of many Emacs 24.4 features.
lexical-binding variable has been
removed, and so has the lexical argument to eval. The
defvar and defconst forms no longer mark variables as
dynamic, since all variables are dynamic.
Having only dynamic binding follows the spirit of Emacs extensibility, for it allows any Emacs code to access any defined variable with a minimum of fuss. But See Dynamic Binding Tips, for tips to avoid making your programs hard to understand.
nil or omitted argument
does not enable the minor mode unconditionally; instead, it toggles
the minor mode—which is the straightforward thing to do, since that
is the behavior when invoked interactively. One downside is that it
is more troublesome to enable minor modes from hooks; you have to do
something like
(add-hook 'foo-hook (lambda () (bar-mode 1)))
or define turn-on-bar-mode and call that from the hook.
prog-mode dummy major mode has been removed. Instead of
using it as a crutch to meet programming mode conventions, you should
explicitly ensure that your mode follows those conventions.
See Major Mode Conventions.
bidi-string-mark-left-to-right has been removed; so have many
other functions and variables related to bidirectional display.
Unicode directionality characters like U+200E ("left-to-right
mark") have no special effect on display.
window-parent, window parameters related to window arrangement,
and window-local buffer lists have all been removed. Functions for
resizing windows can delete windows if they become too small.
The “action function” feature for controlling buffer display has
been removed, including display-buffer-overriding-action and
related variables, as well as the action argument to
display-buffer and other functions. The way to
programmatically control how Emacs chooses a window to display a
buffer is to bind the right combination of pop-up-frames and
other variables.
completion-extra-properties variable, the metadata
action flag for completion functions, and the concept of
“completion categories”. Lisp programmers may now find the choice
of methods for tuning completion less bewildering, but if a package
finds the streamlined interface insufficient for its needs, it must
implement its own specialized completion feature.
copy-directory now behaves the same whether or not the
destination is an existing directory: if the destination exists, the
contents of the first directory are copied into it (with
subdirectories handled recursively), rather than copying the first
directory into a subdirectory.
delete-file and
delete-directory have been removed. The variable
delete-by-moving-to-trash must now be used with care; whenever
it is non-nil, all calls to delete-file or
delete-directory use the trash.
copy-file has been
removed. The return value of backup-buffer no longer has an
entry for the SELinux file context.
(type item-name cache . binding)
The cache entry is used internally by Emacs to record equivalent keyboard key sequences for invoking the same command; Lisp programs should never use it.
gnutls library has been removed, and the function
open-network-stream correspondingly simplified.
Lisp programs that want an encrypted network connection must now call
external utilities such as starttls or gnutls-cli.