Thunderbird and Addons

Joshua Cranmer 🐧 pidgeot18 at
Mon Aug 24 19:38:29 UTC 2015

On 8/24/2015 1:35 PM, R Kent James wrote:
> We need to do some sort of announcement in the Thunderbird blog about 
> our plans concerning addons. I'd like to have feedback from folks to 
> see if there is any debate about what is the correct direction for us.
> We've at least agreed that we are continuing to support binary addons. 
> Concerning signing, we took steps months ago to not move forward on 
> requiring addons to be signed, so there are no current plans to 
> require signing. There is still some debate about that in bug 1168571. 
> We should probably come to a firm decision and announce it. Most 
> commenters were opposed to signing, though there were some holdouts.
> Then there is "The Future of Developing Firefox Add-ons - The Mozilla 
> Blog 
> <>" 
> that announces the complete disabling of current XUL addons at some 
> point in the future. Several Thunderbird community members commented 
> on that blog post, strongly opposed to that direction.
> Contrast that with Firefox/Go Faster 
> <> where there are plans to 
> expand the use of addons in Firefox, adding so-called "system add-ons" 
> and moving Hello to one. (This is similar to what we are doing with 
> Lightning, which should hopefully make our Lightning integration 
> easier in the future).
> At this point, I think that the prevailing viewpoint is probably the 
> following, and I would like to announce this if possible in a blog post:
> 1)    Thunderbird continues to support binary addons.
> 2)    Thunderbird will not require addon signing.
> 3)    Thunderbird has no current plans to disable the use of 
> traditional XUL/XPCOM addons in Thunderbird.
> This policy must be modified by the caveat "as long as core Mozilla 
> code can be used to support it".
> (I might also note that initial patches are being looked at for the 
> integration of the technology formerly know as Skinkglue into 
> Thunderbird core, to be called JsAccount, which makes it possible to 
> define new account types in Thunderbird using a traditional 
> XUL/XPCOM/JavaScript addon. This will almost certainly be in our next 
> major release).
> Could I have some comments or discussion on these proposed positions?

On the topic of binary addons and XUL/XPCOM:

To some degree, we are constrained by the infrastructure that the core 
XPCOM or toolkit code will provide for us. If they completely remove the 
functionality from the code, there is very little that we can do, since 
we likely don't have the bandwidth to maintain code ourselves. We are 
saved somewhat by the fact that, if B2G partner repacks demand this 
functionality, the core people can't do much but acquiesce, which I 
suspect gives us some breathing space, but it's not exactly a permanent 
solution. So we do need to make it clear that these technologies are 
effectively considered deprecated.

In particular, for binary addons, we have three main binary addons of 
any note (EWS, Lightning, and the libpurple chat). I think that once 
none of those are using binary addons, we should seriously consider 
flipping the switch, and if any other binary addons do exist, the 
developers should make us aware of their existence.

The question of XUL addons is harder to discuss, since I think that 
Mozilla itself has no idea what to do about them. I do think it's worth 
noting that where WebIDL exists for a feature, we should use that 
instead of XPIDL interfaces; a good example would be charset conversion.

Joshua Cranmer
Thunderbird and DXR developer
Source code archæologist

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