I don't usually do GUI-related work, but each time I do I typically want to do something complex like plotting charts or drawing diagrams. Each time, I look for a tutorial, but I never find something helpful. The results I get are similar to this QPainter tutorial: https://doc.qt.io/qt-5/qtwidgets-painting-basicdrawing-examp... . They show you that painting is possible, but figuring out how to get interactivity is left as an exercise to the reader.

Compare that to working with d3 or react, where the mouse and keyboard events are easy to create. For example, the first time I used d3, I created a bar chart, and it took just a few minutes of googling to add tooltips on hover and other behaviors when clicking on the bars. I honestly do not know a straightforward way to draw a bar chart with hover affects in QT or Gtk.

So how do I assume other people use them? Well, for the above problem you could write your own mouse picker to map from mouse location to the expected bar location. Having to write your own mouse picker certainly works, but it changes the task from something you can crank out in a few hours to needing to allocate a day or two to set up the infrastructure you need to write a good custom widget. This is also why I assumed people use Electron nowadays: you can get unusual UIs without the rigamarole of making a custom widget. So yes, I know it's possible to make GUIs that don't just compose standard widgets, but I assumed it's arduous.

I'm glad you asked. I didn't realize how controversial my original comment was (it was in negative points for a while). But what am I missing here? Have I just been unable to find a good tutorial? If you were trying to do the "Circle Drawer" example, what tutorial or examples would you follow to get it done quickly?

Depending on your needs, you can also have a good look at QGraphicsView. Maybe you'll have an easier time when you compose your UI using QGraphicsItems.