For today's blog I would like to share with you the little adventure I had when fixing a very strange bug in Qt. Pop quiz Don't think about this too much, just guess: what does this QML snippet print? There are no JavaScript semantic tricks involved; and using either == or === does not change […]

Are you a Qt developer and do you use Linux as your development platform of choice? Then this talk is for you: I will introduce you to perf, the Linux tool suite for performance analysis. The talk will not only cover a broad part of what perf has to offer, it will also dive into […]

A retrospective on the KDE community from 20 years ago and how things were done back then, with an emphasis on community spirit and fun facts. Over time, the KDE community has seen many people join and leave, as with any open source community, which means that very few people in the current community still […]

The past year was very important for the KDE PIM community. We released the first Qt5-based version, restructured our code base and set ourselves more ambitious goals. Let's look a bit deeper into some of the important changes that have happened in KDE PIM in the past year, and peak a little into the future. […]

Many KDAB engineers are part of the Qt Security Team. The purpose of this team is to get notified of security-related issues, and then decide the best course of action for the Qt project. Most of the time, this implies identifying the problem, creating and submitting a patch through the usual Qt contribution process, waiting […]

Design, Technical Excellence and Superb User Experience Why does a tipper truck need an app? Meiller is the leading manufacturer of tippers in Europe. KDAB software developers and UI/UX designers worked with Meiller to create a mobile app that interacts with embedded hardware on the truck, allowing drivers to diagnose and fix problems - even […]

Quick: When you design C++ APIs, when and how should you use pair and tuple? The answer is as simple as it is surprising: Never. Ever. When we design APIs, we naturally strive for qualities such as readability, ease-of-use, and discoverability. Some C++ types are enablers in this regard: std::optional, std::variant, std::string_view/gsl::string_span, and, of course, […]

Hello! This is a small wrap-up fromQtCon, the biggest Qt event in Europe in 2016, that happened at the beginning of September. At QtCon the Qt community joined forces with the KDE, FSFE and VideoLAN communities, to create an exciting event in the spirit of open collaboration and participation amongst projects. During QtCon many KDAB […]

Q_FOREACH (or the alternative form, foreach) will be deprecated soon, probably in Qt 5.9. Starting with Qt 5.7, you can use the QT_NO_FOREACH define to make sure that your code does not depend on Q_FOREACH. You may have wondered what all the fuss is about. Why is there a continuous stream of commits going to […]

Are you a victim of premature pessimisation? Here’s a short definition from Herb Sutter: Premature pessimization is when you write code that is slower than it needs to be, usually by asking for unnecessary extra work, when equivalently complex code would be faster and should just naturally flow out of your fingers. Despite how amazing […]

From time to time I scroll through Qt-related forums and mailing lists, and whenever possible I try to help fellow developers out. The other day a StackOverflow thread caught my attention: a developer was asking "What is the purpose of operator RestrictedBool in QScopedPointer?" Indeed, looking at QScopedPointer's implementation, one notices the strange RestrictedBool usage. […]

Is your code burning a lot of cycles hunting for strings? Maybe you need to find the proper charset nestled in a chunk of HTML, or look for the dimensions in an XPM image file, or locate the email attachment boundaries in a block of MIME. If you string search a lot and performance is […]

A novel solution to an old problem The QRegion class specifies a clip region for a painter. You can also query a QPaintEvent for the region() to limit the paint operations necessary in partial repaints. A region can be anything from a simple rectangle to a bitmap mask, but virtually all code that inspects a […]

Qt 5.6 has just been released! Packed with incredible new features, 5.6 is also the first long term support release of Qt: it will be supported for the next 3 years, giving developers a solid foundation for their current and upcoming projects. Once more, KDAB is confirmed to be the largest independent contributor to Qt, […]

What is GammaRay? For starters, it's a powerful electromagnetic wave, as well as a way to treat cancer. It’s also an under-appreciated German speed metal band. And it’s what gives Dr. Bruce Banner his big green alter ego. But Qt aficionados will know the GammaRay that we're talking about is an uber-powerful Qt debugger and […]

The Qt World Summit was a rocking blast! More than 800 delegates, two days packed with sessions (and an additional training day presented by KDAB). Many old faces, lots of new ones, and a packed programme of sessions with terrific technical content. Yours truly also happened to give a talk, "Integrating OpenGL with Qt Quick […]

It's usually said "only improve performance where a profiler tells you to". I don't completely agree. Take a big C++ library like Qt: can you profile all classes and all code paths ? It would take a couple of years to accomplish and analyse the results. It's expensive: It usually only happens if the speed-up […]

In the last episode of this blog series we learned about the overall concepts of input methods in Qt, with a look behind the scenes to see how a key press event from the native windowing system travels through the Qt input stack until it appears on screen inside a QLineEdit. In that context, the […]

What is an Input Method and what do we need it for? To answer that question, let's see what Wikipedia says: "An input method (or input method editor, commonly abbreviated IME) is an operating system component or program that allows any data, such as keyboard strokes or mouse movements, to be received as input. In […]

Qt is a native library at the heart. As a native (C++) library, it already outperforms most higher-level language libraries when it comes to startup performance. But if you're using native languages, you usually do so because you need to get the most out of the available hardware and being just fast may not be […]