External Editor for MailExtension

External Editor for MailExtension (exteditor-mailext) is add-on for a Thunderbird 78.x (or later) that allows you to compose e-mail using an external editor.
This add-on is based on Textern (Firefox add-on) and MailExtension verion of External Editor.

The add-on is divided into two parts:

• The MailExtension add-on, which handles UI (key-mapping, add-on button and refresh text area in compose window) on Thunderbird and connect to the native application to communicate e-mail data.
  Currently, you need to create the xpi package by yourself and install it in Thunderbird.
• The native application, which handles writing e-mail data from MailExtension add-on to a file at first time, text editor launching with the file, monitoring the file and sending data of the file to MailExtension add-on.
  You also need to install the native application to your system

The native application currently only supports Linux with Python 3.5 or later.
Patches to add support for other platforms are welcome!

Installation

To clone the repository:

git clone https://github.com/presuku/exteditor-mailext
cd exteditor-mailext

To make the xpi file, run:

make xpi

To install the native app, run:

sudo make native-install

To uninstall it, run:

sudo make native-uninstall

On distros which do not use /usr/lib64 (such as Debian/Ubuntu), you'll want to override LIBDIR:

sudo make native-install LIBDIR=/usr/lib

If you do not have root privileges or wish to only install the native app for the current user, run:

make native-install USER=1

Usage

Once both the MailExtension and the native application are installed, you can press Ctrl+E (default) or click add-on button on a compose window to open an external editor.
The textarea in the compose window will flash yellow after the file is saved by external editor.

Headers Edition

If you choose to edit the headers on add-on's preferences, the headers can be edited in the external editor, given as a comma separated list in a paragraph before the message content.

Supported headers are: Subject, To, Cc, Bcc, Reply-To, Newsgroup, Followup-To.

Subject:  Here is the subject
To:       adressTo1, adressTo2
Cc:       adressCc1
Bcc:
Reply-To:
-=-=-=-=-=-=-=-=-=# Don't remove this line #=-=-=-=-=-=-=-=-=-
... the mail content begins here ...

But you can then modify it, use multiple lines, and add as many headers type as you want.

Example:

To: adresseTo1, adresseTo
adresseTo3
adresseTo4, adresseTo5
Cc: adresseCc1
adresseCc2, adresseCc3
To:adresseTo6
To:adresseTo7
...
-=-=-=-=-=-=-=-=-=# Don't remove this line #=-=-=-=-=-=-=-=-=-

(many part of this section from original external editor)

Setting

You can change editor, key mapping, document extension and editing e-mail header as well as the configured editor in the add-on preferences.

Path and arguments of external editor

The default external editor is set to gedit (from Textern but I don't use it).
Set the path to the external editor and additional parameters to be JSON-like as shown below.

["gedit", "+%l:%c"]

It means,

["myeditor", "--custom-arg"]

will launch myeditor --custom-arg /path/to/file.txt.
You may use %s as a variable for the file path if don't want it to be the last argument.

Key mapping (Shortcut key)

The default key mapping is set to Ctrl-E (from original external editor).
Also you can use other shortcut values.

Note that for now, I recommend to set key-mapping on add-on's preferences instead of "Manage Extension Shortcuts".
Because Ctrl+E on compose window isn't used by default but you can't set it on "Manage Extension Shortcuts".

Document extension

The default document extension opend by extenal editor is set to eml (from original external editor).

Edit headers

You can choose to edit the header and what header you want to edit.

Setting examples

Terminal editors

If you would like to use a terminal editor such as vim or emacs, you will need to modify the configuration such that Textern starts a terminal emulator which runs the text editor.

For example, for vim this could look like

["xterm", "-e", "vim", "+call cursor(%l,%c)"]

Here, xterm is the terminal emulator, -e instructs it to start a program, which is nvim (the editor we're actually interested in) with the given parameters.
This works similarly with konsole or gnome-terminal instead of xterm.

For example, starting vim with gnome-terminal:

["gnome-terminal", "--wait", "--", "vim", "+call cursor(%l,%c)"]

Note that by default the gnome-terminal process won't wait for the spawned process to finish before exiting so you'll need to make sure you add the --wait flag.

Another example for xfce4-terminal

["xfce4-terminal", "--disable-server", "-x", "vim", "+call cursor(%l,%c)"]

Note that behaviour of --disable-sever is similar to the --wait flag of gnome-terminal, but it is documented in the help text as "Do not register with D-BUS session message bus".

GUI editors

Non-terminal-based editors can also suffer from the same waiting problem described above. For example, gedit does not fork and thus can be used directly:

["gedit"]

On the other hand, gvim by default will fork and detach.
One must thus make sure to pass the -f switch for it to stay in the foreground:

["gvim", "-f"]

Flatpak

Flatpak-packaged editors should work fine, as long as the application has access to the XDG_RUNTIME_DIR directory.
For example, to use the GNOME gedit flatpak, use:

["flatpak", "run", "--filesystem=xdg-run/exteditor.py", "org.gnome.gedit"]

Caret position

If your editor supports it, you can also use %l and %c to pass the line and column number of the caret position. (The capitalized versions %L and %C also exist which are smaller by one for text editors that count from zero).

For example, passing this information to gvim (or vim):

• Mostly when using single-byte characters

  ["gvim", "-f", "+call cursor(%l,%c)"]

• Support multi-byte characters

  • patch 8.2.2324 or later

    ["gvim", "-f", "+call setcursorcharpos(%l, %c)"]

  • vim 8.0 (avaliable lambda function) to before patch 8.2.2324

    ["gvim", "-f", "+call cursor(%l, {c -> c != -1 ? c : len(getline(%l))}(byteidx(getline(%l),%c)))"]

  • before vim 8.0

    ["gvim", "-f", "+let b:c = byteidx(getline(%l),%c) | call cursor(%l, b:c != -1 ? b:c : len(getline(%l)))"]

    Note that b:c is buffer-local variable in this example so b:c leaks to buffer-local scope.

Example for emacs:

["emacs", "%s", "--eval", "(progn (goto-line %l) (move-to-column (1- %c)))"]

FAQ

• Why is something different from the original External Editor ?
  I have used a part of it, so I don't know all original feature (especially editing in html mode).
  If you know someting about original External editor, issue report and pull requests are welcome.

Troubleshooting

Some things to try if it doesn't work properly:

• Ensure you are running the latest version of Thunderbird
• Try configuring exteditor to launch using a different shortcut
• Try configuring exteditor to use the following as the external editor: ["sh", "-c", "echo foobar > $0"] (that should just echo foobar into the textarea box)
• Check the browser console for errors (Ctrl+Shift+I)
• Check the extension's console for errors (Go to about:debugging, find exteditor-mailext in the list of extensions, and click Inspect)
• Try re-installing but for your local user (make native-install USER=1 instead of sudo make native-install)
• Check if exteditor is running in the background (ps aux | grep exteditor)

Special Thanks

Textern

https://github.com/jlebon/textern

Textern is Firefox add-on but similar feture of this add-on and source code of this add-on is based on Textern.

Extenal Editor

https://github.com/exteditor/exteditor

This is the project that inspired this add-on.
Unfortunately, it is not compatible with MailExtensions and thus cannot be installed on Thunderbird 78 or later.