Compiling Qt with Clang

Published Friday October 29th, 2010 | 14 Comments on Compiling Qt with Clang
Posted in C++, Performance, Qt, Test

I’m happy to report that as of Qt revision 15f52e00 and Clang revision 116737 you’re now able to a complete build of Qt with Clang on both Linux and Mac, including support for precompiled headers. You’ll find the makespecs in Qt’s master branch: unsupported/macx-clang unsupported/linux-clang The mkspec are currently unsupported, but we’ve started running a few […]

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Unleashing the power of QPainterPath::addEllipse()

Published Wednesday October 13th, 2010 | 7 Comments on Unleashing the power of QPainterPath::addEllipse()
Posted in Performance, WebKit | Tags: , ,

Up until recently, WebKit used to draw SVG circles and ellipses by breaking them down into 100-segment paths. This was done to get consistent auto-test results across different platforms and rendering libraries. Unfortunately, it wasn’t very fast. With Qt 4.7’s WebKit, my machine reaches a meager 17 FPS on the SVG version of The Man […]

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Eskil Abrahamsen Blomfeldt

A second spring of text rasterization

Published Thursday September 9th, 2010 | 24 Comments on A second spring of text rasterization
Posted in C++, Graphics, Painting, Performance, Qt

Albert Camus said that “autumn is a second spring when every leaf is a flower”. Similarly, text rasterization on Mac OS X is a constant summer where every character is in permanent bloom. The background for this blog post is a text rendering task which has been sitting in my Jira for a while, and […]

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Improving the string performance with more SIMD (or not)

Published Wednesday August 25th, 2010 | 29 Comments on Improving the string performance with more SIMD (or not)
Posted in Performance, Qt

Inspired by some of the work that Benjamin, Samuel and others were doing with SIMD, and taking the opportunity of learn directly from Intel engineers who know this subject better than just about anybody, I decided to get my hands dirty and do some SIMD work too, after work hours. Since I don’t understand the […]

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Improving the rendering performance with more SIMD

Published Tuesday August 24th, 2010 | 24 Comments on Improving the rendering performance with more SIMD
Posted in Assembly, C++, Painting, Performance, WebKit

With the last two versions of Qt, we consistently improved performance. Qt 4.5 introduced pluggable graphics systems and numerous rendering optimizations. Qt 4.6 brought optimizations all over the place, and the performance on embedded improved continuously with each patch release. A problem with increasing the speed all the time is that we fall short on […]

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