Oxymoronical

I’ve just rolled out a small update to the interface cross reference, nothing major, just fixing a few bugs and I’ve put up what looks like the final set of interfaces for 1.9.1b2.

I’ve now figured out the best way to gather the interface lists and so the cross reference now includes all interfaces used in all 3 major platforms of Firefox. It is relatively simple for me to add the interfaces for other applications now but this got me thinking about what kind of uses people are making of this and how the multi-OS, multi-app interfaces should be presented. A few ideas came to mind:

• App developers probably just want to see the interfaces in their app, either only those that appear for all operating systems or those for a specific OS in some cases.
• Add-on developers probably want to see some kind of shared set of interfaces (what you might call gecko/toolkit) that appear for all apps they are targeting, unfortunately this changes depending on the set of apps. Again they probably want for all OS or for a specific OS.
• Maybe I shouldn’t even bother doing anything and just include a note in the interface display about where the interface actually exists.

I’m sure other people have other ideas of how it might work, any suggestions?

I forgot to add to my last post some information about what I currently had in mind to improve about the API reference I’ve been working on. Any further suggestions people have are very welcome, but here is the current few ideas I have.

Currently it only indexes Firefox and Gecko interfaces, in fact it only indexes those used by an OSX build of Firefox. It would be nice to be able to index interfaces for all the main applications and for all the platforms. There are a couple of issues with this. Firstly I’d want the UI to work so people viewing it could select what set of interfaces they wanted to see. Secondly actually building the lists of interfaces for each application and OS is going to be pretty tricky I think. So far I’ve resorted to building Firefox then looking in dist/idl. This works but it is time consuming. Possibly I might be able to come up with some clever nonsense to make the build system only compile idls but we’ll see.

It would be nice to be able to include a list of the component contract ids available in the platform and what interfaces they implement. This is I think pretty difficult to do just by parsing the source files. Potentially a little extension could run in the app and do some looking through Components.classes to find this out. One issue here though is there is no way to tell whether components are services or not so instantiating them is potentially problematic. This is a problem that could be solved by brute force, or maybe doing a special instrumented build.

So those are my main two ideas, if anyone has any suggestions on how to make those tasks easier or for other things that should be there then shout them out.

Since my first announcement about my little api reference tool I’ve slowly been working on updates to make it more useful and easier to navigate around. I’ve now gone and pushed the latest version live. A few of the new features:

• The main and platform lists of interfaces are split by the module where the interface lives.
• Interface lists have a quick filter box, type in it to filter the list quickly.
• Any interfaces used as return types or parameters are now links to get you straight to the information about them.
• Full IDL support so it now lists all the special attributes and for the uninitiated they have tooltips that explain what they mean.
• You can now list all usage of an interface by other interfaces.
• Constants are ordered the same as in the source IDL since they tend to make more sense that way.
• Includes direct links to the source IDL file.

I’ve also updated the database with the latest APIs in 1.9.1b2pre and as soon as 1.9.1b2 is frozen I’ll update it again just to be sure it has the latest versions.

You can also search the API for interfaces. There isn’t any UI for this right now but it is perfectly set up for a smart bookmark. Just use http://www.oxymoronical.com/experiments/apidocs/search/interface/%s for the url and an appropriate keyword and you can do quick searches for substrings of the interface name.

For some time now I’ve been throwing around ideas for new features that we may want for the add-ons manager. After lots of thought and trying to take on board comments from anyone that would pipe up I decided it was high time to put together an actual plan for what features I have decided should be pursued and what order to start tackling them.

The roadmap itself should be pretty self explanatory, just remember that nothing is ever set in stone. I’ll try to keep it updated as things change, features seem less important or new items are added. But for now this is how I see the add-ons manager evolving over the course of about the next year or so, which may be the next two versions after Firefox 3.1.

Obviously the ordering of the goals may not be quite to everyone’s taste, but I’ve tried to strike a balance between getting new features done and getting groundwork laid to make things better in the future. I’m happy to take any comments people might have into consideration for altering the plan, but chances are I won’t be making any big changes unless you have some pretty damning evidence that a change is necessary

Faaborg has started a discussion on the newsgroups on the relative importance of polish and blocker bugs (I’d provide a link bug Google Groups seems to be refusing to acknowledge existence of the post). I have been for quite some time now very focused on the in-depth blocker issues, partly because that is where all the interesting work is for me, but also because I think it makes more sense for me or one of the other guys with good understandings of how the extension manager works to be making these changes rather than throwing others in at the deep end.

This has of course left little time for me to fix the trivial issues that Faaborg talks about. The things that users probably notice more and make the product look complete or half-done. This is why I’m really pleased that when I posted a list of simple bugs that anyone should be able to tackle there was a fairly good response. Of the 12 bugs on the original list, 9 have been fixed. I wanted to extend my thanks to those guys that took the time to work on those, some of them probably ended up being a little harder work than anticipated.

Of course the polish list is almost never ending. I’ve been adding more to the list of good first bugs, if anyone is interested in helping out then don’t be afraid to just email me or find me on IRC as Mossop and ask how much work something really involves.

I started a small discussion on the newsgroups the other day wondering about the numbers of API changes that had landed on trunk since 1.9.0. It was a short discussion, maybe partly because all I had to go on were the vague metrics that mercurial could give me. It also evolved a little into a discussion of how add-on developers we’re meant to find out about API changes. It’s true that as developers we are getting better at trying to announce our changes as much as possible, but inevitably we miss some, and if you don’t track the announcements what then?

Yesterday on IRC ted jokingly made the comment that I could use the idl parser than bsmedberg wrote in python a short time ago to find out more about the API changes. I’ve been hard pressed on other work lately so it wasn’t long before the prospect of knocking together a little side project had me too interested to do anything else. In a short space of time I had something that could parse all the in-tree idl files into a sqlite database that I could then query. It wasn’t long after that that I got a small web app written to display the content of the database, but I spent some more time today getting it a bit more useful before I showed it to the rest of the world.

So here it is, the API viewer. You can look at any interface in any of the platform versions that I’ve bothered to scan. And here is the more interesting bit, you can compare two platforms to see what interfaces changed. Not happy there? Well you can also compare an interface in different platform versions in a sort of diff like display.

I should note that it is only indexing the core and Firefox interfaces for now, and it’s close to indexing all of the idl files from the sources, many of which don’t make it into the final build (which makes life interesting as it turns out some of them are invalid xpidl!). So you can’t trust that interfaces you find are necessarily useful etc.

The web app is really a prototype right now. Navigation is probably a bit clunky and it’ll need more work to be really useful but I wondered what other people thought of it. So what do you think? Is it useful? What other interesting information might we be able to grab automatically like this?

Update: I’ve added details of the current trunk, 1.9.1b2pre as of today so you can see what changes are coming since the last beta. Not sure how often I’ll keep that up to date though.

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.

It’s been a hectic couple of weeks for me and I wanted to touch on a few of the highs and lows before I forget them all.

It started with flights to get me to Toronto (for those of you that don’t know I live and work out of the UK). I was speaking at the Toronto Developer Day as well as attending a Firefox team work week (two things that conflicted more than I would have liked unfortunately). I normally manage to find direct flights but this time I had to connect through Amsterdam which wasn’t too bad, even if they seem even more mad for security than Heathrow. Incidentally terminal 4 at Heathrow is miles nicer than 3 where I normally come from, even if the 6 police officers armed with automatic weapons was a little disconcerting.

The Developer Day seemed to be a success and I hope all the attendees got something out of it. I’d encourage those that didn’t to let us know where we went wrong of course, not point in us running these things if they don’t give you anything. I think the people at my session found it useful, though I suspect I really need to work on my presentation style for such things. I feel kinda bad though that I’m not more confident about speaking and so could have taken some of the massive workload that Mark Finkle took on off his shoulders.

The rest of the week was spent with the rest of the Firefox team either figuring out concrete plans for the immediate future or working on those plans, interspersed with pizza, barbecue and poutine (Who’d have thought that Canadians would mash together some of the quick takeaway foods I used to get here and serve it in a restaurant!).

Next stop was Mountain View, via Detroit this time. I have to say that Detroit is a really nice airport to change at, even if it does mean that you’re probably flying Northwest if you do so.

I had a weekend to kill so on the Saturday a friend took me to a Renaissance Faire. I thought it might be a bit too geeky even for my tastes at first but it turned out to be a lot of fun, not sure you’d ever get me dressing up to attend like many do though. Fairly fun to watch Americans celebrating a history they never had.

Sunday I headed to the Winchester mystery house. I probably wasn’t in a good mood for it to be honest, jet lag had hit me and then the tour guide was a stereotypical over the top American tour guide trying to make every little oddity out to be spooky. Still it was an interesting place to walk around and the gardens were quite spectacular.

Tuesday I headed into San Francisco proper and went to meet up with the guys at Songbird. One of the things I really want to do is avoid writing the add-ons manager for just Firefox so it was good to chat with them about what they would like to see and how important they find the future plans that we’ve already toyed with.

That evening I had a great meal with some new friends at a German restaurant (yes I had to go to California in order to eat at a German place for the first time). I also got to experience the fun of driving out of the city back to MV at eight in the morning. I think I’ll be avoiding that in the future.

Thursday it was fun to attend one of the monthly labs meetups. Pretty cool to see plans for what is coming both in experimental stuff and in Firefox itself. I think it’d be really useful to stream these events so more people can get an insight in what is coming and why. Too often we can land things in the nightlies seemingly without any discussion when in actual fact a lot of thought does go into pretty much everything.

Finally Friday morning was painful. I maybe took people too seriously when they advised me on how long it would take to get to the airport and to check in, and then I added some for safety leaving me getting up at 5am and then ending up waiting at the gate for an hour and a half.

Seriously, why are so many people carrying on multple bags rather than checking them. I suppose I understand the risk of lost luggage but it is getting really annoying when I have to stick my single carry-on bag under my feet, decreasing the already sparse space there, because the overhead lockers are filled with trolley cases.

Northwest has to be one of the worst airlines I have flown. Poor food, very little movie selection, no tv episodes available at all. Thank god I have taken to putting movies onto my iPod so I always have something decent to watch.

Now I’m sat in a hotel room trying to stay awake for a bit longer. After I get back to Heathrow, after some 20 odd hours travelling (and I can never sleep on planes) it seems to be a good idea for me to sleep before taking the final 3 hour drive back home. But I also need to start the shift back to UK time. I shall probably be waking myself at around 3am for a leisurely drive back to Wales and then slowly shifting myself a couple of hours a day for the rest of this week.

In case you hadn’t heard Mozilla are running a developer day in a week or so’s time in Toronto. The first day is aimed at giving a good overview of the Mozilla platform and what technologies it offers. The second day will be a more hands on workshop where you can try your hand at extensions, applications and testing with friendly experienced people around to lend a hand when you hit problems. It isn’t far off now so get yourself signed up if you’re coming.

I’m in the midst of trying to put together what I’ll be talking about so if you have anything you particularly want to hear then make a suggestion.

I was very excited to learn at the Firefox Summit that Rob Strong was handing over ownership of the Extension Manager module to me. He did great work making the extension manager what it is today but has lately had to be more focused on Installer and windows integration issues.

Last week I spent a large part of my time trying to get myself up to speed on all the old filed bugs, clearing out things that clearly aren’t going to happen and trying to consolidate others. In particular I made the effort to go over every single unconfirmed bug and either resolve as appropriate or request any additional information from the reporter. It is rather sad that many of these were issues that noone commented in after the initial report or even worse the reporter responded with additional information but people (including me) dropped the ball and nothing further happened.

This big triage has been quite useful. Firstly the number of unconfirmed bugs for the add-ons manager has dropped from the mid 70s to under 30 (I would give you exact figures and pretty graphs but bugzilla’s charting is broken). I expect it to drop even further next week when I resolve the issues where the reporter is no longer responding to bugmail. Secondly it has allowed me to spot a pattern amongst 6 or so filed bugs which strongly suggests a new issue that can break add-on installations. While I have yet to be able to reproduce it in a test environment I certainly have more information to go on than previously.

Finally I have been marking all the trivial little issues that I think we could fix, but are unlikely to be priorities. These are the kinds of things that if you were interested in helping out and getting started in developing for Mozilla you could start out on. Many will end up being a few lines of patch, just need to figure out where to put it and test it.

So if you are interested in tackling any of these please give it a go. You can find me on IRC (for reasons best left alone I appear as Mossop) or by email if you need any guidance on getting started. I’m going to try to keep this list updated as I find new bugs that fit there, I still have yet to go through all of the 263 confirmed bugs, maybe a job for next week.