Toluu

Well, I'm Back

Robert O'Callahan. Christian. Repatriate Kiwi. Mozilla hacker.

The Essence Of Web ApplicationsNovember 4

One theme for Web platform improvements over the last few years has been stripping away the limitations that have characterized Web applications compared to desktop applications. So we support drag-and-drop, we compile JS to machine code, we offer fancy graphics, we let Web apps run offline, we give them writable local storage. A natural question is: what, if any, are the essential differences between Web apps and "desktop" apps? Will they converge completely?

I don't think so. Here are features of Web apps that I think are essential:

• URL addressing You access a Web app by loading a URL. You can link to Web apps from other Web pages, you can save URLs in bookmarks or desktop shortcuts, and you can pass around URLs to your friends.
• Always sandboxed Users are not able to make good trust decisions, so apps must always be sandboxed. One of the themes of Web platform evolution is finding ways to design APIs and browser UI so that we can safely grant access to platform features to untrusted apps. For example, Web apps can't be granted general filesystem access, but we can satisfy most needs with per-domain persistent storage and and the trusty <input type="file"> control to grant an app access to particular files.
• Browser chrome Web apps are used in the context of a browser. Forward and back buttons are available (and usually work!), providing a universal navigation UI across applications. Bookmarks are available, status is availab

Grumble GrumbleNovember 3

I've been hacking up an implementation of interruptible reflow. Laying out large pages is sometimes a source of unacceptable delays. It would be a better user experience if, during a long layout, we could detect that there's pending user input, get out of the layout code, handle the user input, and then resume the layout. In principle this isn't that hard now that we use dirty bits to track what needs to be laid out. It's simply a matter of making sure the right dirty bits are set as we bail out of reflow, and then making sure we enter reflow again eventually to complete the unfinished work. We also have to make sure we accurately distinguish "interruptible" reflows from "uninterruptible" reflows. For example, if a reflow is triggered by script asking for the geometry of some element, that's uninterruptible since returning with some work undone would give incorrect results and break things.

I have a patch that basically works, at least for pages that are dominated by block layout. But I've run into a severe problem: I don't know how to detect pending user input in Mac OS X or GTK :-(. On Windows, for about 20 years there's been a function called GetInputState which does exactly what we need. OS X and GTK/X11 just don't have anything like it. I've tried Appkit's nextEventMatchingMask; it sometimes processes some events, which is unacceptable. X11 doesn't seem to provide a way to peek

American TidbitsOctober 26

It's been a crazy few days. I pulled into Boston late Wednesday night. On Thursday I hung out at MIT. I visited my friend's quantum computation lab; lasers and liquid helium make science so much more interesting. I gave a talk about Chronicle and Chronomancer to a pretty good-sized CSAIL audience. I had the honour of being hassled by Richard Stallman for suggesting that there was synergy between Chronicle and VMWare's record-and-replay features. (VMWare, as non-free software, is apparently never the solution to any problem.)

On Friday morning I took the train to Stamford and then visited the IBM Hawthorne lab to talk about the future of the open Web platform. My talk was too long so I sped up and skipped the demos (contrary to my own point that visual gratification is the driving force behind platform evolution). Still, it went well and I enjoyed catching up with a lot of my old colleagues.

On Saturday I was at another friend's wedding. It was too much fun hailing friends I hadn't seen for years and watching the multi-second transition from unrecognition, to recognition, to shock and exclamation. I left the party around 3pm and arrived at my hotel in Mountain View 13 hours later.

When I'm in the Bay Area I get my Sunday fix at Home Of Christ 5. I go because a few very good friends go there, but also because "Home Of Christ Five" is the coolest name for a church ever (I'm not sure why). It's a very Silicon Valley

The Tragedy Of Naive Software DevelopmentOctober 20

A friend of mine is doing a graduate project in geography and statistics. He's trying to do some kind of stochastic simulation of populations. His advisor suggested he get hold of another academic's simulator and adapt it for this project.

The problem is, the software is a disaster. It's a festering pile of copy-paste coding. There's lots of use of magic numbers instead of symbolic constants ("if (x == 27) y = 35;"). The names are all wrong, it's full of parallel arrays instead of records, there are no abstractions, there are no comments except for code that is commented out, half the code that isn't commented out is dead, and so on.

It gets worse. These people don't know how to use source control, which is why the comment code out so they can get it back if they need it. No-one told them about automated tests. They just make some changes, run the program (sometimes), and hope the output still looks OK.

This probably isn't anyone's fault. As far as I know, this was written by someone who had to get a job done quickly who had no training and little experience. But I think this is not uncommon. I know other people who did research in, say, aeronautics but spent most of their time grappling with gcc and gdb. That is a colossal waste of resources.

What's the solution? Obviously anyone who is likely to depend on programming to get their project done needs to take some good programming classes, just as I'd need to take classes before anyone let m

October TravelOctober 19

On Wednesday I'm taking off to the US for about 10 days. First I plan to visit Boston to see a few friends and give a talk at MIT about Chronicle on Thursday. Then I'm heading to New York on Friday where I'll give a talk at IBM Research about Web stuff (3pm, 1S-F40). On Saturday I'm at a friend's wedding. On Saturday night I fly back to California for a platform work week. Hopefully that week I'll also be able to attend the WHATWG social event in Mountain View.

It's going to be somewhat tiring and I probably won't be very responsive online until I get to California, but I should be quite responsive from then on --- especially if you manage to corner me in meatspace!