Linux perf is an immensely useful and powerful tool suite for profiling of C/C++ applications. I have used it extensively and successfully on various customer projects, both for desktop applications as well as automotive or industrial projects targeting low-end embedded Linux targets running on ARM hardware. The biggest problem with perf really is its usability, […]

Close to three months after the initial hotspot release, I'm happy to announce the release of version 1.1.0. Quick recap: Hotspot is a graphical frontend to the Linux perf profiler suite. It allows you to visually analyze perf.data files with the built-in Flame Graph and the Bottom-Up, Top-Down, or Caller-Callee data tables. It is a […]

QtQuick is a popular choice for creating HMIs for embedded devices. The hardware on these devices is often constrained and less performant than their desktop equivalents, this requires extra care from software developers in delivering a fluid user experience. KDAB is regularly involved in improving the performance of QtQuick HMIs on such devices for their […]

Property bindings are one of the most interesting features of the QML language. In QML, when we set a value on a property, the right hand side expression isn't evaluated just once to produce a value, like in a ordinary imperative language. In particular, if the expression involves other properties, then the property we're setting […]

After many months of work, I'm very pleased to finally announce KDAB's latest R&D project to the public: hotspot - a GUI for the Linux perf profiler. I have used Linux perf a lot over the past years. It is an extremely powerful and useful tool. But its complexity makes it very hard to use. […]

QZXing is a very useful library: It provides an easy to use Qt integration API around the barcode scanning library ZXing (zebras crossing). Because it is so easy to setup QZXing in a Qt application, we and most of our customers end up using it when they need to scan images for barcodes. There is, […]

In a previous blog post we introduced clazy, a clang plugin which makes the compiler understand Qt semantics, allowing you to get compile-time warnings about Qt best practices ranging from unneeded memory allocations to misuse of API, including fix-its for automatic refactoring. Today we'll do a round-up and present the checks related to connect statements, […]

All Qt developers have asked themselves at least once in their careers: "why isn't my slot invoked?" (I've asked myself that question many, many times). There are a number of reasons why a connection may fail to be properly set up, and ultimately cause our slot not to be invoked. This blog post is a […]

I'm extremely happy to finally announce the first stable release of heaptrack, the FOSS heap memory profiler for C/C++ Linux applications. You can download the source tarball from the KDE mirrors: https://download.kde.org/stable/heaptrack/1.0.0/src/ Heaptrack is a fast heap memory profiler that runs on Linux. It allows you to track all heap memory allocations at run-time. Afterwards, […]

Knowing what tools are at your disposal when looking to make a program faster or keep it operating smoothly is critical to your success as a programmer. We recently solved a performance problem using Linux Kernel Tracepoints so we thought we’d share the process with you so that you can see for yourself if this […]

In the last days, I was once again trying to convince fellow programmers that there's no such thing as a "benign" data race. This is a recurring theme, in particular fueled by the docs of MSVC and Intel x86, which basically seem to say "you don't need atomics here". I perused the excellent papers Benign […]

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 […]

GammaRay is a high-level runtime introspection tool for Qt applications. In this talk we will look at a number of real-world debugging and profiling problems and how the capabilities provided by GammaRay help you with those. When creating applications we strive to use higher-level frameworks to obtain results quickly and reduce development effort and long-term […]

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 […]

Physics Based Rendering (PBR) is the latest and greatest trend in real-time rendering yielding much more visually believable images than the traditional Phong or ad-hoc lighting models. The underlying concept is that the shaders should use physical principles in the encoded models - chief of which are conservation of energy and the Fresnel effect. PBR […]

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 […]

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 […]

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 […]

Holoplot UX - Example of modern user interface that could benefit from compressed textures. (KDAB designed UX, photo courtesy of Holoplot.) It’s every programmer’s worst nightmare. Your beautiful app is running at a snail’s pace, crippled by virtual memory swapping. Even worse, you’ve added one last bitmap resource, and suddenly unrelated chunks of the UX […]