MisterNeutron,

Perhaps it can be done. The primary developer of calendar writes "the AMO version doesn't use a chrome.jar but has the files extracted". So, the version distributed with Thunderbird uses a single chrome.jar which probably achieves what you want.

In order to get the distributed version, I think you will need to - remove the calendar add-on (and delete the calendar add-on directory in your profile directory [1]) - in pref editor set mail.calendar-integration.opt-out false and calendar.integration.notify true - delete the thunderbird program folder - install thunderbird from https://www.mozilla.org/en-US/thunderbird/ and let it install calendar

Does that work?

[1] https://support.mozilla.org/en-US/kb/profiles

That's not getting me there, I'm afraid. In prefs, mail.calendar-integration.opt-out was already set to false. There is no entry for calendar.integration.notify at all. I added it manually, but that made no difference.

I reinstalled Thunderbird 38, but there's no sign of the calendar unless I add it as an extension. In short, the bundled version doesn't seem to be accessible at all. There's nothing on any menu that refers to it.

I got suspicious - I had a nasty feeling that I might have to create a new profile in order to trigger it, which I'm unwilling to tackle at the moment. I have multiple email addresses on different servers, multiple address books, calendar entries, a task list, and so on, so importing all of that to a new profile is going to be a bit of a mess. The process for doing that appears to be a model of bad software design.

Sure enough, if I create a new profile, it pops up with the calendar active. Sigh....

Possible hack - delete the calendar addon directory in <profile>\extensions - delete extensions.json in <profile> - copy calendar addon directory from that new profile in to the old <profile>\extensions

That appears to have done the trick! I had to re-enable Lightning, but the profile no longer contains the endless language files - instead, chrome.jar is sitting in there.

Many thanks. :)

You're welcome.

So, the next hurdle is, when the update for 38.6.0 comes, does calendar addon update correctly :) Please let us know when that happens. Thanks

I'll check back in after the next automatic Thunderbird update. Hope springs eternal.

Alas, Lightning just updated itself from 4.0.5.1 to 4.0.5.2, and all of the language files reappeared. The chrome.jar file has vanished. Thunderbird itself is still at 38.5.1.

Edit: And it's worse than I thought. Even in a newly-created profile, which starts off with chrome.jar for Lightning and no language files, the 4.0.5.2 update deletes chrome.jar, and populates the chrome subdirectory with hundreds of language files.

I can confirm that. Not happy.

The primary developer of calendar writes "the AMO version doesn't use a chrome.jar but has the files extracted".

I'm wondering what's the reason for this.

An entertaining update. Thunderbird 38.6.0 just installed, and it uses chrome.jar. It happily wiped out all those separate language files.

But I'm betting that if there's a LIghtning update down the road, they'll all come back!

It looks like this problem may be solved. I'm now up to Thunderbird 38.7.2 and Lightning 4.0.7.2, with no sign of a return of the dreaded lanuage files. It's continuing to use chrome.jar.