Disabling web accounts plugin independently of extensions breaks Firefox quite badly

[Chris Coulson]

Disabling a plugin should be benign. However, in the case of the web accounts plugin, disabling this without also disabling the extensions breaks Firefox quite badly (see the "missing plugin" frame in the screenshot, which is impossible to dismiss).

There are several reasons why the plugin could be disabled. Perhaps there is a problem with the plugin cache, or the user just disabled it in the Plugins tab of Tools -> Addons without realizing what they were doing. In any case, a plugin being disabled shouldn't make the browser unusable

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: xul-ext-webaccounts 0.4.2-0ubuntu1
ProcVersionSignature: Ubuntu 3.5.0-10.10-generic 3.5.1
Uname: Linux 3.5.0-10-generic x86_64
ApportVersion: 2.5.1-0ubuntu2
Architecture: amd64
Date: Thu Aug 30 13:57:40 2012
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Beta amd64 (20110901)
SourcePackage: webaccounts-browser-extension
UpgradeStatus: Upgraded to quantal on 2011-11-16 (287 days ago)

[Alberto Mardegan (mardy)]

Hi Chris, thanks for reporting this -- I actually didn't know that the plugin itself could be disabled. The outcome for the user is somehow similar to that of bug #1039123 (which happens when firefox releases a new major version, and our extension declares that it's not compatible with it).

The plugin is instantiated here:

http://bazaar.launchpad.net/~online-accounts/online-accounts-browser-extension/trunk/view/head:/firefox-extension/content/browser.xul

Do you know of any tricks to make sure that the plugin will be always hidden (while still being loaded)? Or how do you suggest to fix this?

[Chris Coulson (chrisccoulson)]

It might stay hidden if you add the plugin inside another container, and set that container to display: none (in that case, the plugin should never get a frame).

But there might be another way, which would actually solve a couple of other things I've been thinking about. It might be possible to embed this in to the hidden window instead, and only embed it when it's first needed. The other issues this would solve are:

- Plugin startup is currently on the critical path at startup, and the startup budget is already tight (and spawning plugin-container is synchronous IIRC)
- You could share a single plugin instance across windows, rather than having one instance per window.

I'm not even sure that would work yet, but I might try it out later (unless there's another reason to have one instance per window?)

[Chris Coulson (chrisccoulson)]

In fact, that would solve bug 1039123 as well