Originally, I was going to call this section Writing faster Qt code, but as I was developing the outline, I realized that what I was really talking about is writing efficient Qt code. Let me explain.
When I was young, unmarried, and living with my parents, I had money to play with so that I could build faster cars. One time, I decided to make the motor of my car more powerful without having to increase its displacement. When I was finished, the car had 50% more horsepower, and when I used the horsepower, it went through fuel 50% faster.
However, I also got something else out of this. I took the car on a long (several hour) expressway trip. What I found was that the fuel economy of the car (when driven like a sane person) went up by 50%. Why? Because in order to get more power out of the engine, I have to increase the efficiency of the engine. I used...