Given a strictly positive integer i, this code will calculate i+1 "equally spaced" values between 1 and 0: If you're looking for a trap, this does actually work for any i > 0. One can verify it experimentally; run the code with i from 1 to INT_MAX. For simplicity, just consider the case j = […]

A very common implementation pattern for QObject subclasses is to declare its child QObjects as data members of type "pointer to child." Raise your hand No, keep your hand on your computer input device :-) Nod if you have ever seen code like this (and maybe even written code like this yourself): A fairly common […]

Are you already convinced and just want to download the library? We're glad you liked it: https://github.com/KDAB/KDAlgorithms I'm sure many people have told you time and time again, "Don't use raw for loops; use algorithms." Still, each time you tried, you found your code harder to read. In case you're wondering, the above simply prints […]

If you're following our Youtube channel you might have heard me talking about QVarLengthArray. If you're not... you should follow us! But let me give you a quick recap. QVarLengthArray is a Qt container that acts like a vector; its elements are stored contiguously in memory and it has a dynamic size. At any time […]

This blog will give you a brief overview of profiling C and C++ applications. Additionally, it will lay before you all of the tools available, with the purpose of aiding you in choosing the right tools at the right times. The Steps for Profiling Before we look at the actual tools, let's go over the […]

We just released CXX-Qt version 0.4! CXX-Qt is a set of Rust crates for creating bidirectional Rust ⇄ C++ bindings with Qt. It can be used to integrate Rust into C++ applications using CMake or build Rust applications with Cargo. CXX-Qt provides tools for implementing QObject subclasses in Rust that can be used from C++, […]

Every now and then, when I submit some code for a code review, people tell me that I forgot qAsConst. Now I have one more enemy, namely: Clazy! It has also started saying this, and I guess it's about time for me to figure out what is going on. When do I need qAsConst and […]

In this blog on debugging and profiling, I would like to give you an overview of the debugging tools that exist for C and C++ applications. Automated Testing The first thing you need to do is make sure your code is properly tested. This, in itself, is not debugging, but it enables you to make […]

There are a few small, and sometimes already quite old, features in Qt that, when combined, can be a very nice way to deal with assets in your QML application -- especially if some of them live on the file system, some in a resource, and some may need localization or translation. Let's dive in! […]

Some time ago, I wrote a post about integrating Qt's associative containers with the fancy new C++ features, range-based for loops with structured bindings. That post inspired KDAB's own Giuseppe D'Angelo to add the asKeyValueRange member function to both QHash and QMap. Now it's possible to iterate over them with a simple range-based for loop, […]

You have two choices when it comes to giving a custom style to your Qt widgets. Qt Style Sheets are very convenient for getting started -- just a few CSS-like rules, and they work. It is our experience, however, that Qt Style Sheets create too much trouble and a QStyle subclass (*) gives a better […]

The nlohmann/json library is everything a developer can expect from a modern library -- easy to integrate and JSON objects are treated as first class citizens with a very intuitive API. However, it has one problem that is widely mentioned across the internet, which I'll tell you about below. Various solutions to the problem have […]

C++23 is feature complete and on track to be released next year. While many people are complaining that it's, after all, a "minor" release (as the pandemic made the Committee work very difficult), C++23 still has a few very significant changes. In this blog post, I want to talk about what I think is my […]

At KDAB, we have been investigating how to integrate Rust with Qt in a safe and idiomatic way. The solution we are currently working on is called CXX-Qt. It's available in the GitHub and on crates.io. This blog post discusses the journey of CXX-Qt -- where it started, where it can be used right now, […]

A couple of weeks ago, we guided you through setting up a chat application and server in our first blog of this series. This is the second and final blog of this Qt Allstack series. Firebase Messaging Now that we have a functional chat application, it’s time to add real world features, like push notifications. […]

Writing mobile apps can be a lot of fun, especially with Qt and QML. But if your background is all about C++ and Qt, writing the entire required stack for a mobile app can be challenging. Adding push notifications, storing information, and having to write that with another language and framework might make you give […]

Here at KDAB, we recently published a library called KDBindings, which aims to reimplement both Qt signals and slots and data binding in pure C++17. To get an introduction to the KDBindings implementation of signals and slots, I recommend that you take a look at the KDBindings Getting Started Guide. It will give you an […]

All Qt developers should know about signals, slots, and properties. Those of you who have used QML will know that property bindings are super useful and cool. Bindings allow us to write more reactive and declarative style code. However, they are only available within QML, which means there are no compile time errors when you […]

In a well-designed QML application, the UI is built using re-usable components, while the data and logic live in C++ based components we call controllers here. The QML part of the application uses these components (that themselves may be written in QML or C++) to build up the user interface and connect these components with […]

Another day, another small addition to KDToolBox, KDAB's collection of miscellaneous useful C++ classes and stuff. In this post, we're going to talk about KDFunctionalSortFilterProxyModel, which is a convenience subclass of QSortFilterProxyModel. What's a proxy model to begin with, and what's QSortFilterProxyModel? Well, that explanation requires a bigger space than what I have in this […]