Programmer’s Log Programmers Writing Stuff – Garry Bodsworth

WebKit keeps me spinning round

So after all the issues I was having with WebKitGTK having undebuggable crashes somewhere in the nvidia binary blob I decided to have a go at QtWebKit integration. It was fairly quick and easy to do (I cheated and used PySide for brevity). That was good - no crashes, some nice looking fonts, Flash working and generally all was good, so I started to think how to do a proper integration.

This is where it all goes wrong. I find with most things an initial test implementation is quick and gives you a feel for the problem, when you actually have to do the real thing you discover all kinds of creepy crawlies hiding under rocks. QtWebKit has now split out from Qt, but there is no packaging for this new branch that I could find under Ubuntu, not too much of an issue since I am used to packaging stuff up. I found HTML5 playback with the gstreamer Phonon backend simply did not work in any half decent fasion and they were concentrating on QtMultimedia which unfortunately is part of the development release.

The deal breaker was the speed of CSS animations, which I am lucky I actually got around to checking since I was juggling so many variables. It was unfeasibly slow. So I decided to use the new QtWebKit 2.0 as it contains compositing acceleration support for just this problem. Indeed, using raster or opengl graphics backends did speed up the animation to very smooth. What I then discovered was I could have smooth animations and no working Flash or rough animations and a kind of working Flash.

This was all most depressing, so I have gone back to WebkitGTK. It is only this crash issue I have to get to the bottom of but it only shows itself in one of my tests which is very specific, and I am thinking it is related to the way xlib is working in the nvidia driver. I do prefer GTK to Qt, so that is also good for me! I would have given EFL Webkit a go, but unfortunately they seem to have removed features in getting the functionality into the Webkit trunk.

The Many Faces Of WebKit

I've been back into the belly of the beast investigating different implementations of WebKit again. So I thought I'd share some of the things I picked up about them.

Obviously the Apple implementation is the cream of the crop for speed an features. In fact the Mac OSX version isn't top of the tree, it's the iPhone/iPad version that has been furthest ahead. It got the accelerated compositing of web elements first and could do all kinds of funky 3D transforms using OpenGL. The OS X version got those features only in the middle of last year.

Other ports vary in stability, features and usefulness.

WebkitGTK
This is the port of WebKit to the GTK+ widget set. It has been through a lot of changes like where the network backend moved to a new library which meant that proxies could not work for a fair while. The rendering itself uses Cairo (good stuff), but it is just a shame you can't easily switch backend (like swapping from xlib to opengl). It uses Pango for font rendering which I know is very good, but it has a serious limitation, it can't load temporary fonts directly from a file, this means that the new font-face features in HTML will be a long way off.

QtWebKit
The rendering quality does look seriously good, but as usual with Qt I am finding very bad performance metrics. I've tried changing rendering backends where "native" seems to perform best and "opengl" fails then segfaults (which is even more surprising when you consider I am using the nvidia binary drivers on Linux which are pretty full featured).

HTML5support seems a bit flaky at best with one of my sample set completely freezing the process. On the plus side there is integration work already done for compositing, and fonts look seriously good. I got Flash working and it seems OK, but not quite as fast as WebkitGTK.

The biggest advantage though is PySide which are comprehensive generated Python bindings for Qt. It allowed me to a do a very quick integration with the gobject mainloop in Python as well.

They have also broken away from the protracted Qt release process which allow them to release WebKit features much faster. This makes life a lot easier and they are allowing targetting of more than one version (although not officially supported).

EFL Webkit
I have a soft spot for EFL and Enlightenment, it gets a lot of the basics very right (small reusable components and fast and low footprint). EFL Webkit shares a majority of infrastructure with GTK including the Cairo rendering and network backend. The project has also recently picked up sponsorship from Samsung.

There is a really cool demo of the web browser being drawn on a 3D surface using the EFL libraries. You can see it here. It's got gstreamer integration for HTML5 video and plugin support for Flash (oh well).

Now that just covers those main ones available on Linux. There is still the Palm WebOS version, Blackberry, OWB, and tons more. OWB looks the simplest for enabling porting to new platforms and I have built the SDL version in the past. Then there is the Windows version of WebKit and the standalone Mac build...