GNU Emacs NEWS -- history of user-visible changes.

Copyright (C) 2017 Free Software Foundation, Inc.
See the end of the file for license conditions.

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This file is about changes in Emacs version 27.

See file HISTORY for a list of GNU Emacs versions and release dates.
See files NEWS.26, NEWS.25, ..., NEWS.18, and NEWS.1-17 for changes
in older Emacs versions.

You can narrow news to a specific version by calling 'view-emacs-news'
with a prefix argument or by typing C-u C-h C-n.

Temporary note:
+++ indicates that all necessary documentation updates are complete.
    (This means all relevant manuals in doc/ AND lisp doc-strings.)
--- means no change in the manuals is needed.
When you add a new item, use the appropriate mark if you are sure it applies,

\f
* Installation Changes in Emacs 27.1

\f
* Startup Changes in Emacs 27.1

\f
* Changes in Emacs 27.1

---
** The new option 'tooltip-resize-echo-area' avoids truncating tooltip text
on GUI frames when tooltips are displayed in the echo area.  Instead,
it resizes the echo area as needed to accommodate the full tool-tip
text.

+++
** New function 'logcount' calculates an integer's Hamming weight.

+++
** New function 'libxml-available-p'.
This function returns non-nil if libxml support is both compiled in
and available at run time.  Lisp programs should use this function to
detect built-in libxml support, instead of testing for that
indirectly, e.g., by checking that functions like
'libxml-parse-html-region' return nil.

\f
* Editing Changes in Emacs 27.1

---
** New variable 'x-wait-for-event-timeout'.
This controls how long Emacs will wait for updates to the graphical
state to take effect (making a frame visible, for example).

+++
** The new user option 'electric-quote-replace-double' controls
whether '"' is also replaced in 'electric-quote-mode'.  If non-nil,
'"' is replaced by a double typographic quote.

\f
* Changes in Specialized Modes and Packages in Emacs 27.1

** Dired

+++
*** The new user option 'dired-create-destination-dirs' controls whether
'dired-do-copy' and 'dired-rename-file' should create non-existent
directories in the destination.

** Ibuffer

---
*** New filter ibuffer-filter-by-process; bound to '/E'.

** Edebug

+++
*** The runtime behavior of Edebug's instrumentation can be changed
using the new variables 'edebug-behavior-alist',
'edebug-after-instrumentation-function' and
'edebug-new-definition-function'. Edebug's behavior can be changed
globally or for individual definitions.

** Enhanced xterm support

*** New variable 'xterm-set-window-title' controls whether Emacs sets
the XTerm window title.  This feature is experimental and is disabled
by default.

** Gamegrid

** ERT

+++
*** New variable 'ert-quiet' allows to make ERT output in batch mode
less verbose by removing non-essential information.

---
*** Gamegrid now determines its default glyph size based on display
dimensions, instead of always using 16 pixels. As a result, Tetris,
Snake and Pong are more playable on HiDPI displays.

** Filecache

---
*** Completing filenames in the minibuffer via 'C-TAB' now uses the
styles as configured by the variable 'completion-styles'.

\f
* New Modes and Packages in Emacs 27.1

\f
* Incompatible Lisp Changes in Emacs 27.1

** The FILENAME argument to 'file-name-base' is now mandatory and no
longer defaults to 'buffer-file-name'.

---
** The function 'eldoc-message' now accepts a single argument.
Programs that called it with multiple arguments before should pass
them through 'format' first.  Even that is discouraged: for ElDoc
support, you should set 'eldoc-documentation-function' instead of
calling 'eldoc-message' directly.

\f
* Lisp Changes in Emacs 27.1

---
** The new macros 'lazy-let' and 'lazy-let*' are analogue to `let' and
`let*' but create bindings that are evaluated lazily.

---
** The 'file-system-info' function is now available on all platforms.
instead of just Microsoft platforms.  This fixes a 'get-free-disk-space'
bug on OS X 10.8 and later (Bug#28639).

---
** The function 'get-free-disk-space' returns now a non-nil value for
remote systems, which support this check.

+++
** The function 'make-string' accepts an additional optional argument.
If the optional third argument is non-nil, 'make-string' will produce
a multibyte string even if its second argument is an ASCII character.

\f
* Changes in Emacs 27.1 on Non-Free Operating Systems

\f
----------------------------------------------------------------------
This file is part of GNU Emacs.

GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

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