Small steps

I was on vacations last week but I'm being all jealous of my luggage. It got a free trip around the world. During my last 8 flights my luggage has been lost 5 times. Is that a record? Confetti anyone? It's a celebration. If you're going to meet me during any of the upcoming conferences I'll be the outgoing and highly sarcastic naked guy with a sign on my chest saying "for my face look this way" and an arrow pointing up.

I neglected to mention that, as Simon said, QtWebKit is working on Windows. Simon did an amazing job of porting all the quirks of the build system but "amazing" is the default state for all of his code so it's not a surprise at all. While he was doing that I've sat down and ported XML tokenizer to QXmlStream from LibXML. If you never wrote a web rendering tokenizer (and unless you're crazy, the chances of that are pretty high, and if you did you're crazy and won't remember doing it anyway) you know that "fragile" is a term that nicely describes it. After it was ported Lars and I sat down to fix the regressions and they didn't even know what hit them (ha! ninja reference).

In other news I've merged in FreeType2 rasterization algorithm patches in Qt. Our raster engine, uses the beauty that is FreeType's rasterizer, with a few patches on top. Because they break BC in FreeType's public interfaces we can't merge them back at the moment. In any case the patches improve rendering speed in general antialiased paths of the raster engine (meaning on Windows, Qtopia Core and in general whenever rendering to a QImage) by about 10% which is gangsta awesome ("gangsta awesome" is a very high level of awesomeness, at least judging from MTV).

I've also optimized the path clipping code. Andreas uses the path clipping code in GraphicsView for collision detection, so when I say "path clipping code" you should read "path clipping and GraphicsView collision detection". A lot of the time in that algorithm has been spent on vertex allocation for tested paths. I've used a few tricks to speed it up by about 15%. The code for that algorithm is the number two reason why baby seals die (the first is still undisputed). It's not even the algorithm itself but the inherent complexity of the problem. I'm a big fan of computational geometry in computer graphics because it makes grown man cry, except me and I like feeling like the lean, mean, killing machine that I am. My favorite part of the path clipping problem is that there are two ways of solving the precision problems and neither of them really works. The trick is that paths operate in double coordinate system, efficient snap-rounding implementations that I've seen operate in fixed-point coordinate system which falls apart in this case because of absolutely random distribution of vertices across the full double spectrum. Tessellation and clipping itself can be done in a screen coordinate system, which makes it possible to consistently represent your coordinates with fixed-point representation. That doesn't work for paths because, e.g. boolean operations on paths need to be done in native path coordinates not screen coordinates. So the algorithm forces an absolutely crazy mix of dynamic fixed-point size, reduced-predicates, magic and good-will to work. Aren't you happy that I'm doing it for you? You better be.

Yours(1) Latino(2) Lover(3)

1) Not really "yours", more "community". I love "you" but "you" need to realize that I need to be seeing other people.
2) Not really "Latino". Unless of course my Spanish or Brazilian friends would like to name me an "honorary Latino" or "Latino by association". I'd be definitely down with that. The only food I can make that is eatable and doesn't force the fire department to evacuate the building before are nachos. I'm a definition of grace in the kitchen. "Whatever you have in the kitchen I will make it burn" is my motto. Plus I'm sporting quite an attitude to boot. "Make Zack a Latino" campaign. We can make it work!
3) Not really "lover". More "no feelings haver". Though technically I've worked on software for so long that hate is, next to sarcasm, my primary export.

Scripter

Before boarding a flight I'm eagerly awaiting the security presentation that is about to ensue. I figure that these people spent their valuable time learning how to point to the ground, back, forward and to the side and someone needs to appreciate that effort. During my last flight I even went ahead and tried to inspect my life jacket. "Tried" because as it turned out my seat was missing it. As the security announcement advised, I "calmly" informed the fellow sitting next to me that "in the unlikely event of a water landing" he's screwed because as a stronger man I'm taking his life jacket. This also prompted me to think about tools that make our life easier (just to clarify, when I say "our" I mean "my"). I've spent a little time yesterday creating a tool that will make my (when I say "my" I mean "our") life a lot easier. So today I wanted to tell him (when I say "him" I mean "you") about us (when I say "us" I mean "it").

I've spent a lot of time writing simple C++ applications to test out some kind of rendering algorithm. Internally we had a tool that automated a lot of it. The tool uses a very simplistic, reg-exp based language to specify commands. I wanted something more powerful. This is how scripter came to be. Scripter is a very simple application that uses QtScript's bindings to Arthur to do its rendering. It allows for rapid prototyping of algorithms and most importantly for me, quick testing of Qt's rendering framework. At first it was a whole IDE with its own code editor, very quickly though I decided to remove the editor and just make it a content widget that monitors the file it was opened with for changes. The reason for that is that I wanted to keep working in my own editor and just have a dynamic, visual preview of everything I was doing. So with Scripter one can be writing rendering code while the visuals effects of the editing are immediately visible. Here are two screenshots of examples included with it:



But the whole beauty of this application is ability to create animations, while seeing the changes done in real-time. I recorded two demos:

• The first one shows me just playing around with an example. In this case it's a freedesktop.org clock.
• The second shows me writing a simple animation from scratch. This one has an added benefit of seeing me hack in real-time, no copy&pasting, a little bit of chaos (next time I should probably figure out what kind of animation I want to do before start recording, but oh, well, live and learn). Fun. This one is 12mb though.

Scripter requires Qt 4.4. If you don't have Qt 4.4's snapshot it won't work. Get it from the SVN at labs.trolltech.com with :

 svn co svn://labs.trolltech.com/svn/graphics/scripter

Revelations

Like many other geeky people I've spent the last week in Scotland. The insane abundance of overgrown egos caused wrinkles at the very fabric of weather conditions in Glasgow and it rained the whole week. It happened to be my second birthday in a row that I've spent on a KDE hackfest. If things continue like this Aaron will have to adopt me, because I refuse to marry him and we're spending way too many "family holidays" together to be "just friends".
I've been always highly supportive of the "Earth is the center of the universe" theory. I considered this to be a side-effect of the fact that I'm the very center of the creation. By association this small piece of rock has got to be in the smack-middle of the universe.
That is until I find a way of developing a dust-powered interstellar spacecraft (dust being the only material possession that I have at my disposal in numbers even remotely close enough to those necessary for intergalactic travel) and I leave this place in pursuit of happiness/aliens. Unlike all other people I don't really want to meet aliens or exchange knowledge/ideas with them, I just want to punch a foreign life form in whatever is their equivalent of a face. Stay with me here, because there's an elaborate reason for that: I'm spending a lot of my time talking to people and for the purposes of a story "I've seen aliens, met them and we chatted a bit about the meaning of life, technology, universe and then I got anal probed" makes a boring story. One that is so prevalent in Alabama. Now if I've met someone who has seen an alien, met an alien and punched it in the face - that person has got my full attention. A way better story.
But for now I'm stuck here, so I used this week to look over some of the graphics code that was written for KDE4. It looks pretty good. Clearly a lot of it has been influenced by heavy drugs and some people have got to be shooting it straight down their aortas for them to have that severe effects. I'm trying to figure out whether to write a FAQ or some scripts to clean some of the mess up. I've also done a little fun hacking. I added sample 3D plasmoids looking like this:


They work very nicely and taking that code allows you to write 3D plasmoids. The examples animate (pretty nicely I might add, but everything I do is at least "pretty nice" so that's a redundant statement). The code is in KDE SVN playground/base/plasma/applets/samplegl* module.

Since for some cards we still don't have terribly good 3D drivers I created a sample plasmoid that shows how to rotate it and have something shown on the back. The code is in the playground/base/plasma/applets/rotator. A movie with the rotating widget is here. And statically it looks like this:



With much love
Yours Truly: militant interstellar dominator (by day), graphics voodoo practitioner (by night)

Reflections

In the spirit of my never ending "pimp your Qt application" series comes another example. This time, "how to make iTunes-like album selector". It's funny how much attention this widget got. I looked at it yesterday on one of the Macs at the office and just implemented it. I probably should make it a view for a list model but for now it's just a simple widget. It runs at perfectly smooth 60 frames per second while utilizing ~7% cpu on my 3GHz Pentium4 with NVIDIA GeForce 6600, so by no means a monster of a machine. Oh, and of course this is all done with pure Qt. Reflections are actually a vector effect, so they would work equally well for any vector based graphics (by using the same code as this example, you can reflect your svg's or even whole widgets with no problem). Mandatory screenshot:
And as with every animated example a movie (again, framerate of the screencapture does not come close to the real world performance) is available here . Finally the code is available here.

Gradient bounds

The most unfriendly thing about rendering gradients with Qt has been the fact that you had to specify gradients in coordinates of the shape they were to be rendered on. It wasn't ideal especially for all applications which included any kind of animations or were rendering large number of items because it meant that the gradient had to be individually created for each and every one of items/frames. I've fixed that two days ago by adding a coordinate-mode property to QGradient, which now accepts ObjectBoundingMode. Object bounding mode, just like in SVG, means that the gradient coordinates are percentages of bounding box of the shape that the gradient is about to fill. So all the coordinates are between 0 and 1 and Qt automatically adjusts the bounds for gradient when it's being rendered. This makes it possible to easily use QGradient's with QPalette. An example where I'm drawing a bunch of rectangles and animate them along while the gradient is set only once with (0,0, 1, 1) coordinate box (meaning starting at the topleft and ending at the bottom right corner of each rectangle).
And since it's an animation (including a widget show/hide effect) here's a movie showing it in action.

Browsers, performance and interventions

This week I beat WebKit Qt's rendering into shape. I rewrote the theming and canvas code.
It works so nicely that I'm actually pretty happy with it. The rewrite helped me fix issues with statically positioned elements (which just didn't work on a scrollview/canvas combination I did before). Due to which my blog finally looks and behaves correctly as seen on the screenshot above. That plus scrolling is about 10x faster and you never see gray areas on scrolling as you did before.
This week George Staikos has been here in Oslo to work with us on the networking code. George and I have been friends for five or six years and he has this nasty habit that forces me to start an intervention and try to get him off it. What I'm referring to is the fact that George has been Canadian for, well his entire life, and it is my professional opinion (but I'm not a doctor) that he needs to move on. I'm not sure in which culture it is customary to bring Snapple ice-tea to your friends when you come to see them but we need to change him to that because he definitely didn't bring me any this time and that's just rude.
Going back to work, I'm sure Lars will blog about the networking magic they did so I'll keep my mouth shut. Once the code they were working on will be ready (which should happen within next week or two) and we'll start using in WebKit, we'll make the transition and start using WebKit Qt based browser on a daily basis. So we're close which is pretty exciting.

We have also started optimization run for Qt 4.3. My grand plan is to make sure Qt 4.3 is 2x faster in general rendering code than Qt 4.2 was. I have a list of algorithms to shave and rewrite over the next few weeks which will be rather challenging.
By the way of performance some people noticed that Qt OpenGL in recent snapshots with Antialiasing turned on is actually slower than it was in Qt 4.2. It's because of an experiment that we're trying on. We're now using GLSL to antialias primitives. Of course it's a lot slower than the old code but produces very high quality results. I don't really like it though because the performance hit is just too big.