A peek at Emacs 24

Prelude

Recently I’ve decided to have a look at the current development version of Emacs - namely Emacs 24. I was quite impressed with the work done by the development team so far so I decided to share some of the cool things I’ve found in Emacs 24.

It seems to me that this will be the most important Emacs release in quite some time.

Installation changes in Emacs 24

There are a couple of new build flags support in Emacs 24 - most notably there is GTK 3.0 support present. You can enable it by passing the –with-x-toolkit=gtk3 flag to configure. There is also built-in support for selinux (that can be disabled at build time) and the installed info and man pages are now compressed by default.

All in all - nothing major has changed with the installation process.

General changes

Completion improvements

There has been a lot of work done in the completion department. For instance shell-mode now uses pcomplete rules and the standard completion UI, which is pretty cool IMHO. Some other insteresting improvements (mostly copied directly from Emacs’ NEWS files):

• Many packages have been changed to use completion-at-point rather than their own completion code.
• Completion in a non-minibuffer now tries to detect the end of completion and pops down the *Completions* buffer accordingly.
• Completion can cycle, depending on completion-cycle-threshold.
• There is a new completion style called substring.
• Completion style can be set per-category with completion-category-overrides.
• Completion of buffers now uses substring completion by default.
• completing-read can be customized using the new variable completing-read-function.
• minibuffer-local-filename-must-match-map is not used any more. Instead, the bindings in minibuffer-local-filename-completion-map are combined with minibuffer-local-must-match-map.

Scrolling improvements

Scrolling has always been a sour subject in Emacs. Emacs 24 finally alleviates many of the long standing issues in the scrolling department:

• New scrolling commands scroll-up-command and scroll-down-command (bound to C-v/[next] and M-v/[prior]) do not signal errors at top/bottom of buffer at first key-press (instead move to top/bottom of buffer) when a new variable scroll-error-top-bottom is non-nil.

• New scrolling commands scroll-up-line and scroll-down-line scroll a line instead of full screen.

• New property scroll-command should be set on a command’s symbol to define it as a scroll command affected by scroll-preserve-screen-position.

• If you customize scroll-conservatively to a value greater than 100, Emacs will never recenter point in the window when it scrolls due to cursor motion commands or commands that move point (e.f., M-g M-g). Previously, you needed to use most-positive-fixnum as the value of scroll-conservatively to achieve the same effect.

• Aggressive scrolling now honors the scroll margins. If you customize scroll-up-aggressively or scroll-down-aggressively and move point off the window, Emacs now scrolls the window so as to avoid positioning point inside the scroll margin.

GTK improvements

Linux users are in for a treat:

• GTK scroll bars are finally placed on the right by default. You can still use set-scroll-bar-mode to change this.
• GTK tool bars can have just text, just images or images and text. Customize tool-bar-style to choose style. On a Gnome desktop, the default is taken from the desktop settings.
• GTK tool bars can be placed on the left/right or top/bottom of the frame. The frame-parameter tool-bar-position controls this. It takes the values top, left, right or bottom. The Options => Show/Hide menu has entries for this.
• The colors for selected text (the region face) are taken from the GTK theme when Emacs is built with GTK.
• Emacs uses GTK tooltips by default if built with GTK. You can turn that off by customizing x-gtk-use-system-tooltips.

Cocoa (OS X improvements)

OS X users seem to be a bit neglected, but still:

• the annoying bug with the cursor not having an inverse video face (meaning you couldn’t see the symbol under it) is finally fixed
• the menu bar can be hidden by customizing ns-auto-hide-menu-bar.

ELPA (a package manager for Emacs)

• An Emacs Lisp package manager (aka ELPA) is now included. This is a convenient way to download and install additional packages, from a package repository at elpa.gnu.org.

• The addition of external repositories is also supported ( I’m particularly fond of the Marmalade repo)

• M-x list-packages shows a list of packages, which can be selected for installation.

• New command describe-package, bound to C-h P.

• By default, all installed packages are loaded and activated automatically when Emacs starts up. To disable this, set package-enable-at-startup to nil. To change which packages are loaded, customize package-load-list.

I’m personally a little bit underwhelmed by ELPA at this point. It lacks something that I deem rather critical - the ability to upgrade already installed packages automatically. Hopefully, this deficiency will be amended in the near future.

There is also the restrictive licensing policy that GNU enforces that will certainly prevent a lot of packages from being distributed via the official ELPA repo.

Custom color themes

Most hackers are very fond of custom color themes. I’m no exception - after all I’m the maintainer of the Zenburn color theme for Emacs. The problems with custom color themes so far was that depended on the horrible external package color-theme, that wasn’t maintained particularly actively in the past few years.

Now Emacs 24 comes with a built-in theming infrastructure affectionately called deftheme and several quite nice themes that Emacs users can choose from (like tango). I’ve already ported Zenburn to the deftheme infrastructure, so if you like it be sure to give it a try. The magic command you’ll need to keep in mind is called load-theme.

Editing improvements

Emacs is after all mostly an editor and there is a lot of work done in the editing area in 24:

Search changes

• C-y in Isearch is now bound to isearch-yank-kill, instead of isearch-yank-line.

• M-y in Isearch is now bound to isearch-yank-pop, instead of isearch-yank-kill.

• M-s C-e in Isearch is now bound to isearch-yank-line.

General

• There is a new command count-words-region, which does what you expect.

• completion-at-point now handles tags and semantic completion.

• The default value of backup-by-copying-when-mismatch is now t.

• The command just-one-space (C-SPC), if given a negative argument, also deletes newlines around point.

Deletion changes

• New option delete-active-region. If non-nil, C-d, [delete], and DEL delete the region if it is active and no prefix argument is given. If set to kill, these commands kill instead.

• New command delete-forward-char, bound to C-d and [delete]. This is meant for interactive use, and obeys delete-active-region. The command delete-char does not obey delete-active-region.

• delete-backward-char is now a Lisp function. Apart from obeying delete-active-region, its behavior is unchanged. However, the byte compiler now warns if it is called from Lisp; you should use delete-char with a negative argument instead.

• The option mouse-region-delete-keys has been deleted.

Selection changes

The default handling of clipboard and primary selections was changed to conform with modern X applications. In short, most commands for killing and yanking text now use the clipboard, while mouse commands use the primary selection.

In the following, we provide a list of these changes, followed by a list of steps to get the old behavior back if you prefer that.

• select-active-regions now defaults to t. Merely selecting text (e.g. with drag-mouse-1) no longer puts it in the kill ring. The selected text is put in the primary selection, if the system possesses a separate primary selection facility (e.g. X).

• select-active-regions also accepts a new value, only. This means to only set the primary selection for temporarily active regions (usually made by mouse-dragging or shift-selection); “ordinary” active regions, such as those made with C-SPC followed by point motion, do not alter the primary selection.

• mouse-drag-copy-region now defaults to nil.

• mouse-2 is now bound to mouse-yank-primary. This pastes from the primary selection, ignoring the kill-ring. Previously, mouse-2 was bound to mouse-yank-at-click.

• x-select-enable-clipboard now defaults to t on all platforms.

• x-select-enable-primary now defaults to nil. Thus, commands that kill text or copy it to the kill-ring (such as M-w, C-w, and C-k) also use the clipboard—not the primary selection.

• The “Copy”, “Cut”, and “Paste” items in the “Edit” menu are now exactly equivalent to, respectively M-w, C-w, and C-y.

• Note that on MS-Windows, x-select-enable-clipboard was already non-nil by default, as Windows does not support the primary selection between applications.

• Support for X cut buffers has been removed.

• Support for X clipboard managers has been added.

• To inhibit use of the clipboard manager, set x-select-enable-clipboard-manager to nil.

New modes

• Occur Edit mode applies edits made in *Occur* buffers to the original buffers. It is bound to C-x C-q in Occur mode. This basically removes the need for an external package such as iedit.el.

• New global minor modes electric-pair-mode, electric-indent-mode, and electric-layout-mode. One of my favourite new additions. electric-pair-mode renders obsolete the popular autopair-mode and electric-indent-mode and electric-layout-mode provide a much more IDE feel to the editing experience in Emacs. This triumvirate of modes has been a long time coming

• secrets.el is an implementation of the Secret Service API, an interface to password managers like GNOME Keyring or KDE Wallet. The Secret Service API requires D-Bus for communication. The command secrets-show-secrets offers a buffer with a visualization of the secrets.

• notifications.el provides an implementation of the Desktop Notifications API. It requires D-Bus for communication.

• soap-client.el supports access to SOAP web services from Emacs. soap-inspect.el is an interactive inspector for SOAP WSDL structures.

Epilogue

Emacs 24 brings quite a lot to the table. I’ve barely scratch the surface as far as the new features are concerned. There is so much more - improvements to lots of the existing modes (most notably much better support for distributed VC systems such as Git, Mercurial and Bazaar), internal cleanups and improvements, etc.

I truly feel that Emacs 24 will be the most important Emacs release in a long long time and I commend the new dev team leads for their passion and resolve to modernize Emacs.

Expect future blog posts dedicated to specific new features and improvements.

P.S. Btw The Emacs Prelude already makes use of some the new features from Emacs 24. In due time it will make use of much more of them. It’s one of the very few advanced Emacs setups targeting exclusively Emacs 24.

Update

A lot of people have been asking me about the level of stability and usability of Emacs 24 at this point since I didn’t mention them at my article. I’ve been using Emacs 24 for all of my work for about a month now and I’ve experienced absolutely no crashes/freezes/any sort of instabilities. On the usability side I’ve encountered a few bugs that might be related to some work in progress (for instance face inheritance doesn’t work with deftheme), but nothing major.

If you’re considering trying out Emacs 24 more seriously - my advice is to go for it. With no clear release date in sight you might be in for a long wait before the final release is here and you’ll be missing on some really great features in the meantime. I’ll write a separate article soon detailing how to get started with Emacs 24 on the most popular platforms (Linux, OS X and Windows).