I have vivid memories of WxWidgets. I used it ~20 years ago to develop a program to browse a collection of artistic works (mainly sculptures and paintings) that was distributed on a CD (no internet at the time, this is the way knowledge was spread!). It was a bit clunky to use but extremely solid, and the end result was nice: it stored information in XML and displayed it in a window, letting the user to do simple searches and export images as JPG. I was able to seamlessly put in the same CD executables for Windows and for Linux, which was quite a big deal at the time.
A few years later (~2009), I used Qt to develop a big codebase that needed to be used on Windows, Linux, and Mac. It was admittedly nicer than WxWidgets, but my impression was that it was harder to understand what Qt did under the hood… It was as if Qt was trying to be more clever than the C++ compiler, while with WxWidgets it had always be more or less evident what the library was doing.
A few years later (~2009), I used Qt to develop a big codebase that needed to be used on Windows, Linux, and Mac. It was admittedly nicer than WxWidgets, but my impression was that it was harder to understand what Qt did under the hood… It was as if Qt was trying to be more clever than the C++ compiler, while with WxWidgets it had always be more or less evident what the library was doing.