Oxymoronical

Tab Sidebar is probably my favourite extension that I’ve created. It is certainly the most polished, thanks mostly to other people pushing me to make it so. For those that haven’t used it it creates a thumbnail preview of all of your tabs in the sidebar. The thumbnails automatically update whenever the page changes, even things like popup menus generally show up. This automatic updating comes at a cost though.

In order to detect changes to the page content the extension mostly uses DOM mutation events. These are in theory sent out whenever a change to the page’s structure happens, which covers adding/removing content, style changes, text entry and all manner of things. What I wasn’t aware of when I first used this technique was that Gecko performs certain optimisations when there are no DOM mutation listeners registered for a document (the normal case). Simply the presence of a mutation listener impacts the speed of any DOM manipulation by the page. How much? Well nothing like a graph to illustrate things.

Performance impact of mutation listeners

These are numbers gathered from the Dromaeo test suite, averaging 5 runs with and without Tab Sidebar installed. A little perf loss is inevitable as the extension must perform some checks on the mutation and occasionally repaint the thumbnail, but nowhere near the sort of regression that actually occurs. I’ve combined some of the test results for simplicity but it is pretty clear that while the regular JS tests are essentially unaffected, the DOM tests can have wildly different results. Don’t ask me why DOM Queries get faster with the extension installed, but DOM modifications are a nice round 4 times slower.

That isn’t to say that using mutation listeners is a complete sin to be avoided at all costs. In some cases they are the only safe option. I discovered this problem some time ago and never before found a better way to detect the changes for Tab Sidebar. Last I checked Firebug uses them in similar ways. The point I think is that there are many features in the platform that can have unexpected side effects.

Of course I guess I wouldn’t be making this post if I hadn’t finally come up with a solution. While I’m no longer actively working on my extensions, I’m afraid I couldn’t resist the opportunity of the new MozAfterPaint event that landed on trunk recently. Quite simply whenever an area of the page is repainted on the screen this event is dispatched with details of what the area painted was. This is absolutely perfect for Tab Sidebar, which isn’t surprising since the use case it was written for is essentially what Tab Sidebar is doing anyway. After a few hours of ripping out most of the event handling code I now have a working prototype that redraws solely based on this event, only painting the areas that might have changed.

Performance impact of the MozAfterPaint listener

Boy does it work well. As you can see from the graph essentially all of the performance loss is gone. For some reason the faster DOM queries are still there (who am I to complain if my extension makes Firefox run faster!). And what’s more the previews are now updated not just for DOM changes, on OSX at least it even sees repaints of plugins. It is quite bizarre to be watching a movie on youtube and see the little thumbnail at the side showing the movie as well.

I guess now I have whetted your appetite it would be unfair not to make the test version available. Use at your own risk of course, the sheer amount of code change means there are likely some problems lurking, but you can install Tab Sidebar 2.5a1 and see how it goes. If you set the preference extensions.tabsidebar.selecteddelay to -1 then it won’t even delay before repainting and just repaint the thumbnail as soon as the main page is painted, this actually seems to work out best for me, particularly on sites with fast animations.

I guess it isn’t going to come as much of a surprise to people when I say I’ve been having a hard time finding the time to maintain the extensions I develop. I’ll go over some of the reasons why shortly, but I guess the highlight (or lowlight depending on your point of view) of this post is that I’m no longer going to really put in any effort to keep them updated.

Nightly Tester Tools will probably continue to get the odd update here and there where I find something interesting to add, and Update Channel Selector is due to get an update to make it actually work on most platforms, but otherwise I would not expect to see any further updates for any of my other extensions.

I came to this conclusion last week when doing some updates and I realised that I really wasn’t enjoying it. The things I generally enjoy doing in my spare time are things that are new and interesting. All of my main extensions were born out of finding something cool to do with the platform. Fast ways to perform regular expressions on large html documents, painting thumbnails of webpages (back when it was actually new and exciting), taking enough control of the toolbar customisation service to be able to dynamically add many instances of the same widgets. All of this stuff was interesting enough to make me knock up a quick extension to play with it. When they seemed useful I would go through and try to iron out some of the rough edges to make it something I’d consider release-worthy. Only Tab Sidebar had real effort put into it to try to make it into a real user friendly product.

I’ve also had quite a large change in my life since I last really actively worked on my extensions. Back then I was a small business owner, most of my day to day work was IT support and web development. Getting home and sitting down for a few hours hacking away on extensions worked as quite a diversion, completely taking my mind off the stresses at work. Now I work for Mozilla. Working on extensions is basically no different from what I do during the day. It is no longer a diversion, it is just like work. How many of you like to get home from work, kick back and then go back over more work to relax?

These things, as well as other issues, have left me really uninterested in doing anything except the exciting new stuff. Turning that into a usable tool, fixing bugs, making things work in new releases, all of that is just dull and no longer worth the spare time it loses me.

And that is pretty much that. I’m not totally out of the extensions game, while I might still create a few experimental add-ons in the future, they probably won’t be fully useful, just little things for fun. I’m not really going to be interested in hearing about bugs in my existing stuff or that it hasn’t yet been updated to the latest version of Firefox. I’m not going to do anything about it. Of course all of my add-ons are open source, under the MPL/GPL/LGPL tri-license, and I’d happily talk to anyone thinking of taking over official development of them for the future.

To those of you who have kept using my extensions and let me know how much you liked them I’d like to say thank you, and I’m sorry that there will be nothing more even though I know you were hoping. It’s taken me a while to reach this decision and I’m sure some will feel a little left in the lurch by it, but I can’t keep fooling myself that I’ll find the time to put in the effort you all deserve.

Obviously for those keeping up with this rather minimal blog I’m somewhat behind where I hoped to be since my last post. Still no new release of Nightly Tester Tools so I thought it worth giving a quick roundup of the few extension’s I’m still working actively on and what’s happening with them:

Nightly Tester Tools is getting the main development work right now. My previous few weekends have been spent working on coding zip support so that it can update an extension’s compatibility info on the fly in the xpi file. This will allow the Mozilla extension manager to do it’s job, which is handling the safe install of the extension itself. Right now I’ve slowed down because I’m about to start talking to Mozilla about getting the zip writing component into the Mozilla platform which will undoubtedly require some API changes. That and I don’t have a Linux or Windows platform to do a build of the component on. If anyone wants to volunteer to assist (you need to already have experience of building a mozilla app) then please get in touch.

Tab Sidebar is an extension that many are waiting for the updates that I currently have in development. A lot of it is there and working, unfortunately there are also some broken bits so it’s really a case of finding the time to get those fixed.

/Find Bar/ is now totally broken on trunk builds of Firefox, but should still be ok on 2.0.0.x builds, though I have had a few error reports and suggestions on how to proceed. The next steps are to make this handle block content in pages as paragraphs and then to try to find and fix what’s causing a rare crash. I also need to work out how toadd to the new find bar widget on trunk without duplicating too much of it, but so far that’s proving to be tough.

Toolbar Thinger is not receiving a lot of attention. I have had some good reports that people are finding it very useful, also a couple of reports of problems unfortunately not in enough detail for me to be able to track the issues down. At some point I want to find a nice icon for it, do a full track through for any issues I’ve missed and then do a first proper release.

Update Channel Selector was always a very simple extension and so unsurprisingly it’s not needed a lot of work. Unfortunately it seems that Vista has changed that. In order to change the channel, the extension has to overwrite a file in the application’s installation directory. Vista doesn’t let you do that as easily as previous versions of Windows did. Unfortunately I do not have a Vista machine to play with so resolving that could take time.

Finally I have taken the step of marking JavaScript Options and Cookie Extras as officially discontinued. It’s unfortunate but I do all this work in my spare time and as you can see from above, I simply do not have enough of it to be able to keep up with the extensions that I want to spend time on, let alone those that I have lost interest in. I will continue to make the extension’s available on my site and I have decided that if enough people let me know that the extension works flawlessly in newer versions of the application then I will update the compatibility information (I am about to do this for Cookie Extras). However I will be releasing no new versions of these extensions.

Since both those extensions are open source (as are all my extensions) if anyone particularly wants to take over development of them then I am happy to discuss that possibility.