GNU-devel ELPA - ement

Ement.el is published in GNU ELPA as ement, so it may be installed in Emacs with the command M-x package-install RET ement RET. This is the recommended way to install Ement.el, as it will install the current stable release.

The latest development build may be installed from ELPA-devel or from Git (see below).

Ement.el is available in GNU Guix as emacs-ement.

Ement.el is available in Debian as elpa-ement and in Ubuntu as elpa-ement.

Ement.el is available in NixOS as emacsPackages.ement.

Ement.el is also available in some other distributions. See Repology for details.

The master branch of the Git repository is intended to be usable at all times; only minor bugs are expected to be found in it before a new stable release is made.

To install, it is recommended to use quelpa-use-package, like this (using this helpful command for upgrading versions):

;; Install and load `quelpa-use-package'.
(package-install 'quelpa-use-package)
(require 'quelpa-use-package)

;; Install Ement.
(use-package ement
  :quelpa (ement :fetcher github :repo "alphapapa/ement.el"))

One might also use systems like Elpaca or Straight (which is also used by DOOM), but the author cannot offer support for them.

Ement.el is intended to be installed with Emacs's package system, which will ensure that the required autoloads are generated, etc. If you choose to install it manually, you're on your own.

These bindings are common to all of the following buffer types:

• Switch to a room buffer: M-g M-r
• Switch to the room list buffer: M-g M-l
• Switch to the mentions buffer: M-g M-m
• Switch to the notifications buffer: M-g M-n

• Desktop notifications are enabled by default for events that mention the local user. They can also be shown for all events in rooms with open buffers.
• Send messages in Org mode format by customizing the option ement-room-send-message-filter (which enables Org format by default), or by calling ement-room-compose-org in a compose buffer (which enables it for a single message). Then Org-formatted messages are automatically converted and sent as HTML-formatted messages (with the Org syntax as the plain-text fallback). You can send syntax such as:
  • Bold, italic, underline, strikethrough
  • Links
  • Tables
  • Source blocks (including results with :exports both)
  • Footnotes (okay, that might be pushing it, but you can!)
  • And, generally, anything that Org can export to HTML
  • Note that the default org-export-preserve-breaks value causes singular line breaks to be exported as spaces. To preserve the line breaks, indentation, and blank lines in a region, but otherwise use normal formatting, you can use the verse block type. Refer to (info "(org) Paragraphs") and (info "(org) Structure Templates") for details.
• Starting in the room list buffer, by pressing SPC repeatedly, you can cycle through and read all rooms with unread buffers. (If a room doesn't have a buffer, it will not be included.)
• Room buffers and the room-list buffer can be bookmarked in Emacs, i.e. using C-x r m. This is especially useful with Burly: you can arrange an Emacs frame with several room buffers displayed at once, use burly-bookmark-windows to bookmark the layout, and then you can restore that layout and all of the room buffers by opening the bookmark, rather than having to manually arrange them every time you start Emacs or change the window configuration.
• Images and other files can be uploaded to rooms using drag-and-drop.
• Mention members by typing a @ followed by their displayname or Matrix ID. (Members' names and rooms' aliases/IDs may be completed with completion-at-point commands.)
• Customize ement-room-use-variable-pitch to render messages using proportional fonts.
• You can customize settings in the ement group.
  • Note: setq should not be used for certain options, because it will not call the associated setter function. Users who have an aversion to the customization system may experience problems.

Ement.el doesn't support encrypted rooms natively, but it can be used transparently with the E2EE-aware reverse proxy daemon Pantalaimon. After configuring it according to its documentation, call ement-connect with the appropriate hostname and port, like:

(ement-connect :uri-prefix "http://localhost:8009")

Additions

• Customization groups for faces. (Thanks to Phil Sainty.)

Changes

• Disable underline for faces ement-room-list-direct and ement-room-list-name (in case a face they inherit from enables it, e.g. when themed).

Compatibility

• Use authenticated media requests (part of Matrix 1.11; see MSC3916 and matrix.org's sunsetting unauthenticated media).

Additions

• When option ement-room-images is disabled (preventing automatic download and display of images), individual images may be shown by clicking the button in their events.

Changes

• Option ement-room-coalesce-events may now be set to (and defaults to) a maximum number of events to coalesce together. (This avoids potential performance problems in rare cases. See #247. Thanks to Arto Jantunen for reporting and Sergio Durigan Junior for testing.)

Fixes

• Replies to edited messages are correctly sent to the original event (whereas previously they were sent to the edit, which caused reactions to not be shown). (#230, #277. Thanks to Phil Sainty for suggesting, and to dionisos for reporting.)
• Set filter-buffer-substring-function in room buffers to prevent undesired text properties from being included in copied text. (#278. Thanks to Phil Sainty.)
• Command ement-disconnect no longer shows an error message. (#208.)
• Retrieval of earlier events in a just-joined room. (#148. Thanks to Richard Brežák for reporting, and to Phil Sainty for testing.)
• Cache computed displaynames in rooms (avoiding unnecessary reiteration and recalculation). (#298. Thanks to Rutherther for reporting and testing, and to Phil Sainty.)
• Customization group for options ement-room-mode-hook and ement-room-self-insert-mode. (Thanks to Phil Sainty.)
• Inheritance for some faces. (#303. Thanks to Jonas Bernoulli.)

Fixes

• Handle unnamed rooms in ement-directory list. (See #248. Thanks to Hunter Jozwiak and Bharath Palavalli for reporting.)
• Don't use cl-type pcase form in Emacs versions before 28. (#279. Thanks to Adam Bark for reporting.)

Additions

Configurable emoji picker for sending reactions. (#199, #201. Thanks to Omar Antolín Camarena.)

• Option ement-room-reaction-picker sets the default picker. Within that, the user may press C-g to choose a different one with a key bound in ement-room-reaction-map.

A variety of enhancements for using compose buffers. (#140. Thanks to Phil Sainty.)

Chiefly, messages can now be composed in small windows below room windows, rather than in the minibuffer or a full-sized window. A variety of options and commands are available related to these features. See compose buffer enhancements.

Global minor mode ement-room-self-insert-mode enables "just typing" to start a message. (Thanks to Phil Sainty.)

See ement-room-self-insert-mode.

Options affecting how images are displayed in room buffers.

See image display.

Changes

• Improve prompt used when viewing a room that is not joined. (#241. Thanks to Phil Sainty.)
• Format "was kicked and rejoined" membership event pairs.
• Enclose reasons for membership events in quotes for clarity.
• Improve default room list grouping.
• When editing or replying to a message in a compose buffer, the related room event is highlighted persistently until the compose buffer is killed. (Thanks to Phil Sainty.)
• In compose buffers dabbrev will prioritise firstly the associated room, and secondly all other rooms, before looking to other buffers for completions. (Thanks to Phil Sainty.)
• Aborted messages are now added to ement-room-message-history rather than the kill-ring. (Thanks to Phil Sainty.)
• Prefix bindings in ement-room-mode-map now have named labels in which-key and similar. (Thanks to Phil Sainty.)
• Option: ement-room-use-variable-pitch (previously named ement-room-shr-use-fonts) enables variable-pitch fonts for all message types. (This option previously supported formatted messages, but now works for plain text messages as well.) Note: users who have customized the ement-room-message-text face to be variable-pitch should revert that change, as it causes problems for formatted messages, and is no longer necessary. (#174. Thanks to Phil Sainty.)

Fixes

• Edits to previous edit events are correctly sent to the server as edits to the original message event. (#230. Thanks to Phil Sainty.)
• Completion at point works more reliably in compose buffers. (Thanks to Phil Sainty.)
• Toggling images to fill the window body no longer triggers unintended scrolling. (Thanks to Phil Sainty.)
• Recognition of mentions after a newline. (#267. Thanks to Phil Sainty.)
• Newlines in ement-room-message-format-spec are considered when calculating the wrap-prefix. (Thanks to Phil Sainty.)
• Weight of face ement-room-list-direct (now correctly bold in room list heading).

Additions

• Audio events are rendered as a link to the audio file. (Thanks to Arto Jantunen.)
• Customization group ement-room-list.
• Option ement-room-list-space-prefix is applied to space names in the room list (e.g. set to empty string for cleaner appearance).
• Option ement-room-reaction-names-limit sets how many senders of a reaction are shown in the buffer (more than that many are shown in the tooltip).

Changes

• Bind TAB / BACKTAB to move between links in room and like buffers. (#113. Thanks to Eric S. Fraga for suggesting.)

Fixes

• Insertion of sender headers (when using "Elemental" message format). (Refactoring contributed by Steven Allen.)
• Some room event data was being unintentionally serialized to disk when caching the room list visibility state. (#256)
• Notifications buffer restores properly when bookmarked.
• Command ement-room-send-reaction checks for an event at point. (Thanks to Phil Sainty.)

Additions

• Group joined direct rooms in directory buffers.
• Command end-of-buffer is bound to N in room buffers.

Changes

• Command ement-room-image-show use frame parameters to maximize the frame, making it easier for users to override. (#223. Thanks to Nicholas Vollmer.)

Fixes

• Name for direct rooms in directory buffers.
• Editing a message from the compose buffer would be sent as a reply to the edited message. (Fixes #189. Thanks to Phil Sainty for reporting.)
• Editing an already-edited message. (#226. Thanks to Phil Sainty for reporting.)
• Replying to an already-edited message. (#227. Thanks to Phil Sainty for reporting.)
• Rendering redactions of edited messages. (#228. Thanks to Phil Sainty for reporting.)
• Redacting an edited message. (#228. Thanks to Phil Sainty for reporting.)
• Command ement-room-flush-colors maintains point position.

Additions

• Command ement-notifications shows recent notifications, similar to the pane in the Element client. (This new command fetches recent notifications from the server and allows scrolling up to retrieve older ones. Newly received notifications, as configured in the ement-notify options, are displayed in the same buffer. This functionality will be consolidated in the future.)
• Face ement-room-quote, applied to quoted parts of replies.

Changes

• Commands ement-room-goto-next and ement-room-goto-prev work more usefully at the end of a room buffer. (Now pressing n on the last event moves point to the end of the buffer so it will scroll automatically for new messages, and then pressing p skips over any read marker to the last event.)
• Room buffer bindings:
  • ement-room-goto-next and ement-room-goto-prev are bound to n and p, respectively.
  • ement-room-goto-fully-read-marker is bound to M-g M-p (the mnemonic being "go to previously read").
• The quoted part of a reply now omits the face applied to the rest of the message, helping to distinguish them.
• Commands that read a string from the minibuffer in ement-room buffers and ement-connect user ID prompts use separate history list variables.
• Use Emacs's Jansson-based JSON-parsing functions when available. (This results in a 3-5x speed improvement for parsing JSON responses, which can be significant for large initial sync responses. Thanks to Ryan Rix for discovering this!)

Fixes

• File event formatter assumed that file size metadata would be present (a malformed, e.g. spam, event might not have it).
• Send correct file size when sending files/images.
• Underscores are no longer interpreted as denoting subscripts when sending messages in Org format. (Thanks to Phil Sainty.)
• Add workaround for savehist-mode's serializing of the command-history variable's arguments. (For ement- commands, that may include large data structures, like ement-session structs, which should never be serialized or reused, and savehist's doing so could cause noticeable delays for users who enabled it). (See #216. Thanks to Phil Sainty and other users who helped to discover this problem.)

Additions

• Commands ement-room-image-show and ement-room-image-scale (bound to RET and M-RET when point is at an image) view and scale images. (Thanks to Steven Allen for these and other image-related improvements.)
• Command ement-room-image-show-mouse is used to show an image with the mouse.

Changes

• Enable image-mode when showing images in a new buffer. (Thanks to Steven Allen.)
• Command ement-room-image-show is not used for mouse events.
• Show useful message in SSO login page.

Fixes

• Allow editing of already-edited events.
• Push rules' actions may be listed in any order. (Fixes compatibility with v1.7 of the spec. Thanks to Steven Allen.)
• Call external browser for SSO login page. (JavaScript is usually required, which EWW doesn't support, and loading the page twice seems to change state on the server that causes the SSO login to fail, so it's best to load the page in the external browser directly).
• Clean up SSO server process after two minutes in case SSO login fails.
• Don't stop syncing if an error is signaled while sending a notification.
• Command ement-room-list-next-unread could enter an infinite loop. (Thanks to Visuwesh and @mrtnmrtn:matrix.org.)
• Events in notifications buffer could appear out-of-order. (#191. Thanks to Phil Sainty.)

Internal

• The ement-read-receipt-idle-timer could be duplicated when using multiple sessions. (#196. Thanks to Phil Sainty.)

Security Fixes

• When uploading a GPG-encrypted file (i.e. one whose filename ends in .gpg), if the recipient's private key or the symmetric encryption key were cached by Emacs (or a configured agent, like gpg-agent), Emacs would automatically decrypt the file while reading its contents and then upload the decrypted contents. (This happened because the function insert-file-contents was used, which does many things automatically, some of which are not even mentioned in its docstring; refer to its entry in the Elisp Info manual for details. The fix is to use insert-file-contents-literally instead.) Thanks to @welkinsl:matrix.org for reporting.

Additions

• Support for Single Sign-On (SSO) authentication. (#24. Thanks to Jeffrey Stoffers for development, and to Phil Sainty, Jakub Kadlčík, and Juanjo Presa for testing.)
• Bind m in room buffers to ement-room-mark-read (which moves read markers to point).

Changes

• Activating a space in the room list uses ement-view-space (which shows a directory of rooms in the space) instead of ement-view-room (which shows events in the space, which is generally not useful).
• Command ement-view-room, when used for a space, shows a footer explaining that the buffer is showing a space rather than a normal room, with a button to call ement-view-space for it (which lists rooms in the space).
• Command ement-describe-room shows whether a room is a space or a normal room.
• Command ement-view-space shows the space's name and alias.
• Command ement-room-scroll-up-mark-read moves the fully read marker to the top of the window (when the marker's position is within the range of known events), rather than only moving it when at the end of the buffer. (This eases the process of gradually reading a long backlog of messages.)
• Improve readme export settings.

Fixes

• Extra indentation of some membership events. (Thanks to Steven Allen.)
• Customization group for faces.
• Don't reinitialize ement-room-list-mode when room list buffer is refreshed. (#146. Thanks to Ted Reed for reporting.)
• Don't fetch old events when scrolling to the bottom of a room buffer (only when scrolling to the top). (Thanks to Steven Allen.)
• Minor improvements to auto-detection of homeserver URIs. (See #24. Thanks to Phil Sainty.)
• Uploading of certain filetypes (e.g. Emacs would decompress some archives before uploading). Thanks to @welkinsl:matrix.org for reporting.
• Messages edited multiple times sometimes weren't correctly replaced.

Fixes

• Another attempt at restoring position in room list when refreshing.
• Command ement-room-list-next-unread.

Fixes

• Restore position in room list when refreshing.
• Completion in minibuffer.

Fixes

• Error in ement-room-list command upon initial sync.

Additions

• Option ement-room-timestamp-header-align controls how timestamp headers are aligned in room buffers.
• Option ement-room-view-hook runs functions when ement-room-view is called. (By default, it refreshes the room list buffer.)
• In the room list, middle-clicking a room which has a buffer closes its buffer.
• Basic support for video events. (Thanks to Arto Jantunen.)

Changes

• Using new option ement-room-timestamp-header-align, timestamp headers default to right-aligned. (With default settings, this keeps them near message timestamps and makes for a cleaner appearance.)

Fixes

• Recognition of certain MXID or displayname forms in outgoing messages when linkifying (aka "pilling") them.
• Unreadable room avatar images no longer cause errors. (Fixes #147. Thanks to @jgarte for reporting.)
• Don't error in ement-room-list when no rooms are joined. (Fixes #123. Thanks to @Kabouik and Omar Antolín Camarena for reporting.)
• Enable member/room completion in compose buffers. (Fixes #115. Thanks to Thanks to Justus Piater and Caleb Chase for reporting.)

Fixes

• Avoid use of pcase's (map :KEYWORD) form. (This can cause a broken installation on older versions of Emacs that have an older version of the map library loaded, such as Emacs 27.2 included in Debian 11. Since there's no way to force Emacs to actually load the version of map required by this package before installing it (which would naturally happen upon restarting Emacs), we can only avoid using such forms while these versions of Emacs are widely used.)

Fixes

• Deduplicate grouped membership events.

Added missing changelog entry (of course).

Additions

• Command ement-create-space creates a new space.
• Command ement-room-toggle-space toggles a room's membership in a space (a way to group rooms in Matrix).
• Visibility of sections in the room list is saved across sessions.
• Command ement-room-list-kill-buffer kills a room's buffer from the room list.
• Set device_id and initial_device_display_name upon login (e.g. Ement.el: username@hostname). (#134. Thanks to Arto Jantunen for reporting.)

Changes

• Room-related commands may be called interactively with a universal prefix to prompt for the room/session (allowing to send events or change settings in rooms other than the current one).
• Command ement-room-list reuses an existing window showing the room list when possible. (#131. Thanks to Jeff Bowman for suggesting.)
• Command ement-tag-room toggles tags (rather than adding by default and removing when called with a prefix).
• Default room grouping now groups "spaced" rooms separately.

Fixes

• Message format filter works properly when writing replies.
• Improve insertion of sender name headers when using the "Elemental" message format.
• Prompts in commands ement-leave-room and ement-forget-room.

Additions

• Command ement-room-override-name sets a local override for a room's display name. (Especially helpful for 1:1 rooms and bridged rooms. See MSC3015.)

Changes

• Improve display of room tombstones (displayed at top and bottom of buffer, and new room ID is linked to join).
• Use descriptive prompts in ement-leave-room and ement-forget-room commands.

Fixes

• Command ement-view-space when called from a room buffer. (Thanks to Richard Brežák for reporting.)
• Don't call display-buffer when reverting room list buffer. (Fixes #121. Thanks to mekeor for reporting.)
• Retry sync for network timeouts. (Accidentally broken in v0.6.)

Internal

• Function ement-put-account-data accepts :room argument to put on a room's account data.

Additions

• Command ement-view-space to view a space's rooms in a directory buffer.

Changes

• Improve ement-describe-room command (formatting, bindings).

Fixes

• Retry sync for HTTP 502 "Bad Gateway" errors.
• Formatting of unban events.
• Update password authentication according to newer Matrix spec. (Fixes compatibility with Conduit servers. #66. Thanks to Travis Peacock, Arto Jantunen, and Stephen D.)
• Image scaling issues. (Thanks to Visuwesh.)

Fixes

• Apply ement-initial-sync-timeout properly (important for when the homeserver is slow to respond).

Fixes

• Autoload ement-directory commands.
• Faces in ement-directory listings.

Additions

• Present "joined-and-left" and "rejoined-and-left" membership event pairs as such.
• Process and show rooms' canonical alias events.

Changes

• The taxy.el-based room list, with programmable, smart grouping, is now the default ement-room-list. (The old, tabulated-list-mode-based room list is available as ement-tabulated-room-list.)
• When selecting a room to view with completion, don't offer spaces.
• When selecting a room with completion, empty aliases and topics are omitted instead of being displayed as nil.

Fixes

• Use of send-message filter when replying.
• Replies may be written in compose buffers.

Fixes

• Don't show "curl process interrupted" message when updating a read marker's position again.

Additions

• Option ement-room-unread-only-counts-notifications, now enabled by default, causes rooms' unread status to be determined only by their notification counts (which are set by the server and depend on rooms' notification settings).
• Command ement-room-set-notification-state sets a room's notification state (imitating Element's user-friendly presets).
• Room buffers' Transient menus show the room's notification state (imitating Element's user-friendly presets).
• Command ement-set-display-name sets the user's global displayname.
• Command ement-room-set-display-name sets the user's displayname in a room (which is also now displayed in the room's Transient menu).
• Column Notifications in the ement-taxy-room-list buffer shows rooms' notification state.
• Option ement-interrupted-sync-hook allows customization of how sync interruptions are handled. (Now, by default, a warning is displayed instead of merely a message.)

Changes

• When a room's read receipt is updated, the room's buffer is also marked as unmodified. (In concert with the new option, this makes rooms' unread status more intuitive.)

Fixes

• Binding of command ement-forget-room in room buffers.
• Highlighting of @room mentions.

Fixes

• Room unread status (when the last event in a room is sent by the local user, the room is considered read).

Additions

• Command ement-directory shows a server's room directory.
• Command ement-directory-search searches a server's room directory.
• Command ement-directory-next fetches the next batch of rooms in a directory.
• Command ement-leave-room accepts a FORCE-P argument (interactively, with prefix) to leave a room without prompting.
• Command ement-forget-room accepts a FORCE-P argument (interactively, with prefix) to also leave the room, and to forget it without prompting.
• Option ement-notify-mark-frame-urgent-predicates marks the frame as urgent when (by default) a message mentions the local user or "@room" and the message's room has an open buffer.

Changes

• Minor improvements to date/time headers.

Fixes

• Command ement-describe-room for rooms without topics.
• Improve insertion of old messages around existing timestamp headers.
• Reduce D-Bus notification system check timeout to 2 seconds (from the default of 25).
• Compatibility with Emacs 27.

Fixes

• Info manual export filename.

Changes

• Read receipts are re-enabled. (They're now implemented with a global idle timer rather than window-scroll-functions, which sometimes caused a strange race condition that could cause Emacs to become unresponsive or crash.)
• When determining whether a room is considered unread, non-message events like membership changes, reactions, etc. are ignored. This fixes a bug that caused certain rooms that had no message events (like some bridged rooms) to appear as unread when they shouldn't have. But it's unclear whether this is always preferable (e.g. one might want a member leaving a room to cause it to be marked unread), so this is classified as a change rather than simply a fix, and more improvements may be made to this in the future. (Fixes #97. Thanks to Julien Roy for reporting and testing.)
• The ement-taxy-room-list view no longer automatically refreshes the list if the region is active in the buffer. (This allows the user to operate on multiple rooms without the contents of the buffer changing before completing the process.)

Fixes

• Links to only rooms (as opposed to links to events in rooms) may be activated to join them.
• Read receipts mark the last completely visible event (rather than one that's only partially displayed).
• Prevent error when a room avatar image fails to load.

Fixed

• Info manual directory headers.

Fixed

• Temporarily disable sending of read receipts due to an unusual bug that could cause Emacs to become unresponsive. (The feature will be re-enabled in a future release.)

Fixed

• Function ement-room-sync correctly updates room-list buffers. (Thanks to Visuwesh.)
• Only send D-Bus notifications when supported. (Fixes #83. Thanks to Tassilo Horn.)

Fixed

• Function ement-room-scroll-up-mark-read selects the correct room window.
• Option ement-room-list-avatars defaults to what function display-images-p returns.

After almost two years of development, the first tagged release. Submitted to GNU ELPA.

Ement.el is published in GNU ELPA and is considered part of GNU Emacs. Therefore, cumulative contributions of more than 15 lines of code require that the author assign copyright of such contributions to the FSF. Authors who are interested in doing so may contact assign@gnu.org to request the appropriate form.

An Org-formatted version of the Matrix spec is available in the meta/spec branch.

This section is preserved for posterity. As it says, Ement.el has long since surpassed matrix-client, which should no longer be used.

Why write a new Emacs Matrix client when there is already matrix-client.el, by the same author, no less? A few reasons:

• matrix-client uses an older version of the Matrix spec, r0.3.0, with a few elements of r0.4.0 grafted in. Bringing it up to date with the current version of the spec, r0.6.1, would be more work than to begin with the current version. Ement.el targets r0.6.1 from the beginning.
• matrix-client does not use Matrix's lazy-loading feature (which was added to the specification later), so initial sync requests can take a long time for the server to process and can be large (sometimes tens of megabytes of JSON for the client to process!). Ement.el uses lazy-loading, which significantly improves performance.
• matrix-client automatically makes buffers for every room a user has joined, even if the user doesn't currently want to watch a room. Ement.el opens room buffers on-demand, improving performance by not having to insert events into buffers for rooms the user isn't watching.
• matrix-client was developed without the intention of publishing it to, e.g. MELPA or ELPA. It has several dependencies, and its code does not always install or compile cleanly due to macro-expansion issues (apparently depending on the user's Emacs config). Ement.el is designed to have minimal dependencies outside of Emacs (currently only one, plz, which could be imported into the project), and every file is linted and compiles cleanly using makem.sh.
• matrix-client uses EIEIO, probably unnecessarily, since few, if any, of the benefits of EIEIO are realized in it. Ement.el uses structs instead.
• matrix-client uses bespoke code for inserting messages into buffers, which works pretty well, but has a few minor bugs which are difficult to track down. Ement.el uses Emacs's built-in (and perhaps little-known) ewoc library, which makes it much simpler and more reliable to insert and update messages in buffers, and enables the development of advanced UI features more easily.
• matrix-client was, to a certain extent, designed to imitate other messaging apps. The result is, at least when used with the matrix-client-frame command, fairly pleasing to use, but isn't especially "Emacsy." Ement.el is intended to better fit into Emacs's paradigms.
• matrix-client's long name makes for long symbol names, which makes for tedious, verbose code. ement is easy to type and makes for concise, readable code.
• The author has learned much since writing matrix-client and hopes to write simpler, more readable, more maintainable code in Ement.el. It's hoped that this will enable others to contribute more easily.

Note that, while matrix-client remains usable, and probably will for some time to come, Ement.el has now surpassed it in every way. The only reason to choose matrix-client instead is if one is using an older version of Emacs that isn't supported by Ement.el.