22.10.2021 
These are some really cool or obfuscated code snippets for your amusement. We didn’t want to rate them, so the order doesn’t mean anything at all 🙂 Just to make sure that there’s no misunderstanding: This code really is/was in the Qt or KDE repositories. From Kivio, main.cpp From Qt 2.2.1 (src/canvas/qcanvas.cpp) Writing code that […]
Author Archives: David Faure
Auto-Accepting in QSortFilterProxyModel Since Qt 6.0, QSortFilterProxyModel Can Auto-accept Child Rows of Rows Matching the Filter.
In Qt 5.10, we added support for recursive filtering in QSortFilterProxyModel, which means keeping all parents of items matching the filter. One of the comments in the blog post about that feature was “Sometimes, you do not only want to show parents for a match (so the match is visible), you may (also) want to […]
The cmake-project Script Generating a CMake Project For a Single Executable in C++
If you ever need to create a project around a single C++ file (or just a few C++ files) in CMake, as you might for quick test cases, you might find it tedious to write a CMakeLists.txt file by hand every time. To make this easier, I’ve written a script called cmake-project that you can […]
Hotspot: How const Can Improve Performance
Some time ago, I noticed that a unit test was quite slow, using 100% CPU for a number of seconds at one point in the test. I used perf and KDAB’s Hotspot to record and examine where the CPU cycles were spent in that unit test, and I quickly noticed that a lot of time […]
New in Qt 5.10: recursive filtering for QSortFilterProxyModel
When using Qt’s model/view framework, filtering has always been very easy with QSortFilterProxyModel. To filter a list using text typed by the user in a line-edit, you have certainly been applying the standard recipe: instantiate the proxy; insert it between view and source model; connect the lineedit’s textChanged signal to the proxy’s setFilterFixedString slot; done! […]
KDE development how it was done in the last century QtCon presentation
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 […]
Additional Qt libraries outside Qt Project
David Faure speaks about additional Qt libraries outside Qt Projects.
Copying files over the network in a Qt application
Last week I visited a new customer who is making medical and industrial devices which have one thing in common: image and video capturing, and letting the user save these files onto a USB key. These devices run embedded Linux and the application is done in Qt (and gstreamer for the video capture). The new […]
How to use helgrind to debug multithreaded Qt applications Finding thread race conditions in Qt4 and Qt 5
You’ve heard of valgrind before, its default tool (memcheck) is such a life saver, being able to detect memory-related bugs in your code (leaks, double deletions, use of deleted memory, use of uninitialized memory, etc.). Well, it turns out that valgrind also comes with a tool to detect race conditions between threads, in multithreaded applications. […]