Wednesday, May 30, 2007


Today's blog might sound a little muffled, that's because it's coming straight from the heart. Which is in direct opposition to all of the "What's Open Source community missing" blogs/articles, which are coming straight from a vastly less prominent body part. To not dwell to much on human anatomy, I'm going to move on to the main topic today which is peace, love and Qt 4.3. The first two are overrated and got their fair share of treatment in all kinds of literary works, therefore the only reasonable conclusion is that my perky-self focuses on Qt today.

A number of people surely have already pointed out in their blogs that Qt 4.3.0 has been released. The first thing you'll notice about this release is the version number. Rightfully so because 4.3.0 is the highest Qt version we've ever released. 4.2.0 was already taken and we felt very strongly about reusing a ".0". Although "13.13.0" was available we really came together as a team/body/unit/crew (pick one) to release 4.3.0.

Now, I'm not going to be doing marketing for 4.3.0 (mainly because others are being paid better to do that) or listing the "like totally awesome new features", what I wanted to do is present the perspective of people who actually spent days and nights working to make this piece of software the best they could. Whether from the loins of those geeks came something exceptional is a judgement call that I leave to you. This is your keyhole into our world.

The main focus of this release was for us the general increase in quality of Qt. In the darkness of our meeting rooms we were moving tons of paper, while from time to time lonely tears danced on our cheeks (due the fact that the light smoke coming from our pens and pencils was irritating our eyes). Immersed in this mysterious darkness, we sat and watched. The cracking of the projector, seemed to be the only noise that dared to challenge the insanable silence. We knew that we wanted to make people smile a little more with this new release. Very early in the release process we also agreed that shipping drugs with Qt was not an option. We turned for help to the happiness champions - Care Bears and Popples. We watched and analyzed. In the very end we decided that while we agree that Gi-Joe's are like totally cooler (the engineering department is unfortunately male dominated) we know what we have to do. We came to the conclusion that people seem to be a lot happier if things work the way they planned and there's no unpleasant surprises. That's what we focused on. Fixing bugs, making sure that things work the way they are expected to, all in all improving the quality of Qt. If you have ever spent extended periods of time just staring at the code and rerunning tests in order to fix bugs, you know it's a mundane process that takes a lot of concentration. This is what we've been doing for the last few months. Fixing bugs and running around screaming (a lot of screaming, not a whole lot of running) if someone broke one of the tests. Have you ever seen engineers play ping-pong after fixing bugs for weeks? Oh, it's quite a sight. A lot of raw energy (very raw, one could say that energy hardly touched by any kind of skill). Flying balls, paddles and often engineers were a common sight late in the evening (low flying engineers bring bad luck - especially if the flight schedule predicts a landing at "you").

No one is more critical of us than we are but we work together to improve all the things we don't like. While I was thinking about this today I couldn't stop thinking about Pythagoreans who despite achieving many great things, were often described as a group who cherished authority beyond anything else. That approach is completely different from any discussion we have here. Every argument is judged solely based on its soundness no matter who's making it. I think that what I'm trying to say in this, severely not hysterical, paragraph is that one thing you can be sure off is that every decision we have reached and every change we have made in Qt was not due to any kind of hidden agenda, religious beliefs or beauty of people pushing for it. It was done because 20+ engineers decided that the arguments for it are stronger than against it. I realize that due to the fact that we have those discussions at the office and in person, a lot of the transparency of them remains hidden behinds clouds for people outside Trolltech. We're working to improve the flow of the information from the heart of Qt's home to the outside and while we do that please remain assured that behind the clouds there's a world adhering to the strictest physical and logical rules and not an ocean of strings with muppets drowning underneath.

Having said that, we're very happy with Qt 4.3.0 so hopefully you'll enjoy it too.

If you want pure Qt release goodness with pictures of the chosen few who get to stare at Qt code until their eyes bleed make sure you read Girish's blog.

Sunday, May 27, 2007

Browser plugins

One of the perks of being a software engineer is that during the day you get to use such phrases as "oh, what the hell", "that's pure crack" and a large number of "expletive-deleted" without it seeming weird in any way. I can only feel sorry for doctors who rarely get the opportunity to scream "oh, what the hell" while looking at new patients. It's quite therapeutic.

I've spent a little time this week implementing support for plugins in WebKit Qt and the general situation of cross-browser plugins is the reason for the above, spot-on, observations. My blog is, of course, famous for hard-hitting political satire but not today. Today I'll talk technology. No politics, hardly any environmentalism, virtually no vegan propaganda - just straight to the point geek talk (well, "write" but "talk" sounds a lot better).

Given how important browsers are in our day-to-day computer usage it would seem that cross-browser plugins should be a well understood and in fact solved problem. Nope, that's definitely not the case here.

So while tapping your fingers on the messy desk, you roll your eyes and ask "so zack, what is wrong with browser plugins?".
The role of zack - young, careless and wild wacko is played by critically acclaimed me. The role of "you" is played by "you" and "you" really need to step up because you're not convincing anyone right now.

Currently cross-browser plugins use a very sexy (assuming of course that you're heavily into s&m) mix of Xt and another toolkit of their choice. The usage of Xt is just an utter disaster. In fact mixing event loops in any application is a cause of many subtle problems. George had the best idea when he implemented netscape plugins in an out of process application for Konqueror. It's really the only thing that makes sense.

In the Konqueror when a page has a plugin, an external application, the plugin viewer, is started. That process in turn loads and initializes the actual plugin and via DCOP informs the browser what is its window id. Once the hosting browser knows the window id of the plugin, it can XEmbed it. The neat side-effect of this approach is that if a plugin misbehaves one can kill it without any damages to the current browser session (besides the fact that the plugin doesn't render anymore).

The new plugin standard tries to use XEmbed all way. Unfortunately it assumes in-process communication between the browser and the plugin which again is a bad idea. It's a bad idea because it removes this neat concept of an "event loop" from the equation and assumes that whatever event-loop the plugin uses is the same as the one hosting browser is running. Which in turn doesn't do wonders for the whole "cross-browser" aspect of plugins (as long as the definition of "browsers" includes at least two entries and at least one of them is not Firefox).

So lets say you'd like go nuts (like young people tend to do) and display a slider in your plugin which, of course, good, god-fearing people never do. But lets push forward with this highly dubious example and say that maybe you wouldn't want to go all out and display, maybe not right away a slider but some kind of an animating widget. Well, you're pretty screwed because you need the event-loop native to the toolkit in which the widget is implemented to receive the timing events.. Just ask SwfDec guys. They wrote this awesome piece of software, then wrote a browser plugin using, what claims to be, a cross-browser standard just to find out that in that particular standard "cross-browser" meant that it works in Firefox and Firefox. So SwfDec guys found out that Konqueror is not part of that set (unfortunately they also found out a few other things).

So how could we fix it, without having a large groups of grownups sharing some quiet time in a corner, while the sound of weeping fills the room. Hosting plugins in an external process has clear advantages. To the list that I mentioned above we can add another point - by running a plugin in an external process plugins could easily specify what kind of an event loop they need. If your plugin needs Glib's event loop, GTK+ container would be started, if your plugin uses Qt, Qt container would be started (which might or might not use Glib's event loop in Qt 4) if your plugin needs Xt then you should be punched in the face and it all would just work. Containers would announce their window id's through DBUS so that hosting applications could XEmbed them and the world would be a better place (because clearly "browser plugin woes" are occupying one of the top spots on the list of "what's wrong with the world", right between "dust" and "rich people").

At the moment I'm trying to see how feasible it is to lay npruntime implementation, which serves as a bridge between the plugin and the hosting browser on top of DBUS. If that works then we can move to running all plugins as external processes. Which means:
  • plugins taking a lot of CPU can be stopped/killed without affecting the browser
  • when a plugin crashes the browser keeps running without any problems
  • external event loops don't pollute the browser
  • a lot of code for plugin viewers could be shared (besides networking interface) between browsers on systems running X11. Which means that for a change plugin working in one browser would run in all of the others using those containers.
This is basically what we're doing in WebKit Qt. I just really want a simply working plugin infrastructure for browsers. I'm not a man who holds grudges, but last year I didn't get what I wanted, even though I've been exceptionally good, so this better work (last year I wanted to win the lottery. Sure, some might point out that I made it exceedingly difficult by not playing (did you see the odds?) but lets not get bogged down by minor details).

Oh, and a mandatory screenshot of the Diamond plugin in QtWebKit.

Thursday, May 24, 2007

Mesa and LLVM

I've been toying for a while with the idea of rewriting programmable pipeline in Mesa. The most obvious reason is the fact that fragment shaders are absolutely crucial when it comes to modern graphics. We use them extensively in Qt and I'm using it all over the place in my special effects library. As those small (mostly GLSL based) programs become more and more complicated a need for an extensive compiler framework with especially good optimization support becomes apparent. We already have such a framework in LLVM.

I managed to convince the person I consider an absolutely genius when it comes to compiler technology, Roberto Raggi to donate some of his time and together with me rewrite the programmable pipeline in Mesa. The day after I told Roberto that we need to lay Mesa on top of LLVM I got an email from him with GLSL parser he wrote (and holly crap, it's so good...). After picking up what was left of my chin from the floor I removed the current GLSL implementation from Mesa, integrated the code Roberto sent me, did some ninja magic (which is part of my job description) and pushed the newly created git repository to

So between layers of pure and utter black magic (of course not "voodoo", voodoo and graphics just don't mix) what does this mean, you ask (at least for the purpose of this post). As I pointed out in the email to the Mesa list last week:
  • it means that Mesa gets an insanely comprehensive shading framework
  • it means that we get insane optimization passes for free (strong emphasis on "insane". They're so cool I drool about being able to execute shading languages with this framework and I drool very rarely nowadays... And largely in a fairly controllable fashion.)
  • it means we get well documented and understood IR,
  • it means we get maintenance of parts of the code for free, (the parts especially difficult for graphics people)
  • it means that there's less code in Mesa,
  • it means that we can basically for free add execution of C/C++, soon Python, Java and likely other languages, code on GPU's because frontend's for those are already available/"in work" for LLVM. (and even though I'm not a big fan of Python the idea of executing it on GPU is giving me goose-bumps the way only some of Japanese horror movies can)
I think it has all the potential to be by far the best shading framework in any of the OpenGL implementations out there. Now having said that there's a lot of tricky parts that we haven't even begin solving. Most of them are due to the fact that a lot of modern graphics hardware is, well, to put it literary "freaking wacky" (it's a technical term). We'll need to add pretty extensive lowering pass and most likely some kind of transformation pass that does something sensible with branch instructions for hardware that doesn't have support for them. We'll cross that bridge once we get to it. Plus we'll need to port drivers... But for now we'll bask in the sheer greatness of this project.

Ah, the git repository is at;a=shortlog;h=llvm , Roberto and I have tons of unpushed changes though . Of course this is an ongoing research project that both Roberto and I work on in our very limited spare time (in fact Roberto seems to now have almost what you'd call a "life". Apparently those take time. Personally I still enjoy sleepless nights and diet by starvation patched by highly suspicious activities in between. Which by the way does wonders to my figure and if this is not going to work I'll try my luck as a male super-model) so we can only hope that it will all end up as smoothly as we think it should. And in KDE 4 most graphics code will be able to utilize eye-popping effects with virtually no CPU price.