GNU Emacs 26

https://www.gnu.org/savannah-checkouts/gnu/emacs/emacs.html#Releases

What's new in Emacs 26

Emacs now provides a limited form of concurrency with Lisp threads.

Emacs now provides a limited form of concurrency with Lisp threads. Concurrency in Emacs Lisp is "mostly cooperative", meaning that Emacs will only switch execution between threads at well-defined times: when Emacs waits for input, during blocking operations related to threads (such as mutex locking), or when the current thread explicitly yields. Global variables are shared among all threads, but a 'let' binding is thread-local. Each thread also has its own current buffer and its own match data.

See the chapter "(elisp) Threads" in the ELisp manual for full documentation of these facilities.

Flymake has been completely redesigned

Flymake now annotates arbitrary buffer regions, not just lines. It supports arbitrary diagnostic types, not just errors and warnings (see variable 'flymake-diagnostic-types-alist').

It also supports multiple simultaneous backends, meaning that you can check your buffer from different perspectives (see variable 'flymake-diagnostic-functions'). Backends for Emacs Lisp mode are provided.

The old Flymake behavior is preserved in the so-called "legacy backend", which has been updated to benefit from the new UI features.

(note: see Flycheck)

child-frames provide an alternate way to prompt the user or display information

see packages like

• https://github.com/casouri/eldoc-box
• https://github.com/alexmurray/flycheck-posframe
• https://github.com/clemera/frog-menu

see more:

• https://www.gnu.org/software/emacs/manual/html_node/elisp/Child-Frames.html#Child-Frames
• https://with-emacs.com/posts/frog-menu/catch-flyspell-errors-using-frog-menus/

The networking code has been reworked so that it's more asynchronous

The networking code has been reworked so that it's more asynchronous than it was (when specifying :nowait t in 'make-network-process'). How asynchronous it is varies based on the capabilities of the system, but on a typical GNU/Linux system the DNS resolution, the connection, and (for TLS streams) the TLS negotiation are all done without blocking the main Emacs thread. To get asynchronous TLS, the TLS boot parameters have to be passed in (see the manual for details).

Certain process oriented functions (like 'process-datagram-address') will block until socket setup has been performed. The recommended way to deal with asynchronous sockets is to avoid interacting with them until they have changed status to "run". This is most easily done from a process sentinel.

Emacs can scroll horizontally using mouse, touchpad, and trackbar

You can enable this by customizing 'mouse-wheel-tilt-scroll'. If you want to reverse the direction of the scroll, customize 'mouse-wheel-flip-direction'.

Emacs now supports optional display of line numbers in the buffer.

This is similar to what 'linum-mode' provides, but much faster and doesn't usurp the display margin for the line numbers. Customize the buffer-local variable 'display-line-numbers' to activate this optional display. Alternatively, you can use the 'display-line-numbers-mode' minor mode or the global 'global-display-line-numbers-mode'. When using these modes, customize 'display-line-numbers-type' with the same value as you would use with 'display-line-numbers'.

The 'occur' command can now operate on the region

(but don't miss the awesome helm-occur, swoop and helm-swoop packages)

Emacs no longer prompts about editing a changed file when the file's content is unchanged

Instead of only checking the modification time, Emacs now also checks the file's actual content before prompting the user.

File local and directory local variables are now initialized each time the major mode is set

not just when the file is first visited. These local variables will thus not vanish on setting a major mode.

Connection-local variables can be used to specify local variables

with a value depending on the connected remote server

'switch-to-buffer-preserve-window-point' now defaults to t

Applications that call 'switch-to-buffer' and want to show the buffer at the position of its point should use 'pop-to-buffer-same-window' in lieu of 'switch-to-buffer'.

Emacsclient has a new option '-T' / '--tramp'

This helps with using a local Emacs session as the server for a remote emacsclient. With appropriate setup, one can now set the EDITOR environment variable on a remote machine to emacsclient, and use the local Emacs to edit remote files via Tramp. See the node "(emacs) emacsclient Options" in the user manual for the details.

Changes in packages and specialized modes

Org-mode

• Emacs 26.1 comes with Org v9.1.6.

Dired

• You can answer 'all' in 'dired-do-delete' to delete recursively all remaining directories without more prompts

• Dired supports wildcards in the directory part of the file names.

(no more need of find-name-dired for simple globbing)

• Users can now customize mouse clicks in Dired in a more flexible way.

The new command 'dired-mouse-find-file' can be bound to a mouse click and used to visit files/directories in Dired in the selected window. The new command 'dired-mouse-find-file-other-frame' similarly visits files/directories in another frame. You can write your own commands that invoke 'dired-mouse-find-file' with non-default optional arguments, to tailor the effects of mouse clicks on file names in Dired buffers.

• In wdired, when editing files to contain slash characters,

the resulting directories are automatically created

• 'W' is now bound to 'browse-url-of-dired-file', and is useful for

viewing HTML files and the like

Compilation mode

In compilation mode, Messages from CMake are now recognized.

Emacs Web Browser (EWW)

• New 'M-RET' command for opening a link at point in a new eww buffer.

• A new 's' command for switching to another eww buffer via the minibuffer.

• A new command 'C' ('eww-toggle-colors') can be used to toggle

whether to use the HTML-specified colors or not. The user can also customize the 'shr-use-colors' variable.

Images

A new library for creating and manipulating SVG images has been added. See the "(elisp) SVG Images" section in the ELisp reference manual for details.

Image-dired

Thumbnail generation is now asynchronous.

Tramp

Access to Google Drive

New connection method "gdrive", which allows access to Google Drive onsite repositories.

Prog mode

Prog mode has some support for multi-mode indentation. This allows better indentation support in modes that support multiple programming languages in the same buffer, like literate programming environments or ANTLR programs with embedded Python code.

Enchant is now supported as a spell-checker

Enchant is a meta-spell-checker that uses providers such as Hunspell to do the actual checking. With it, users can use spell-checkers not directly supported by Emacs, such as Voikko, Hspell and AppleSpell, more easily share personal word-lists with other programs, and configure different spelling-checkers for different languages. (Version 2.1.0 or later of Enchant is required.)

See more

For a full review of what's new in Emacs 26: https://www.masteringemacs.org/article/whats-new-in-emacs-26-1

See the NEWS file here: https://www.gnu.org/savannah-checkouts/gnu/emacs/news/NEWS.26.1