Comment 31 for bug 711305

(In reply to Brian Vanderburg from comment #8)
> I'm running Debian Jessie and I seem to have the problem as well.
>
> First, I have two main Firefox profiles, "default" and "empty". Empty has
> few extensions while default is my fully loaded profile. In order to be
> able to easily run them, I create custom .desktop files that execute
> "firefox -P <default|empty> -new-instance %U" If I don't use the
> "-new-instance" (or "-no-remote"), and I decided I want to run the empty
> profile but the default is already running or vice versa, I get the "already
> running error".
>
> It seems, when I create a shell script to execute "xterm" and set it as the
> mail application in Firefox, I get a bunch of MOZ_ environment variables. I
> played around with un-setting the variables before running Thunderbird. It
> just so happens that, at least for me, if I unset a variable
> "MOZ_NEW_INSTANCE" then it seems to work. To verify I start Thunderbird and
> then open a terminal without any MOZ_VARIABLES and execute "thunderbird
> mailto:<email address hidden>". Everything works. If I then execute
> "MOZ_NEW_INSTANCE=1 thunderbird mailto:<email address hidden>" I get the "already
> running" error.
>
> So it seems that what is happening, at least for me, is when I run Firefox
> with -new-instance, it sets an environment variable that is in turn passed
> to child processes. When I click on an email link it launches Thunderbird,
> but that environment variable is set and Thunderbird tries to start a new
> instance. The same seems to happen if I use -no-remote instead, it just
> sets a variable MOZ_NO_REMOTE=1
>
> I create the following script and set it as the mail handler for the time
> being.
>
> #!/bin/sh
> env -u MOZ_NEW_INSTANCE -u MOZ_NO_REMOTE thunderbird "$@"
>
> Currently there is no way around "-no-remote" or "-new-instance" with
> Firefox it seems. If I launch one profile, and wish to launch another
> profile, then it will complain unless I use one or the other. Ideally,
> there should be a way to launch multiple profiles, but to have "remote"
> features with both, either designating one as the default to receive remote
> commands or a chooser to list available instances to receive remote
> commands. For now, the shell script to remove the environment variables
> seems to help.

This is great, this would be the flatpak version

```
#!/bin/bash
env -u MOZ_NEW_INSTANCE -u MOZ_NO_REMOTE flatpak run --branch=stable --command=thunderbird org.mozilla.Thunderbird
```

but how to set as a handler?

This is a test: [testlink-to-email](mailto:<email address hidden>)