Signals Slots and Class Pointers

[Atomic_Sheep]

You are correct, this is a C++ question.

Objects are created in the order your code creates them, and the do what your code commands of them. Its irrelevant what file contains which class definition: classes don't do anything until you create an object or objects based on them.

In your code ui->horizontalSlider is a pointer to an object of the QSlider class. How have you created your GLWidget object, or is GLWidget the name of the class?

Yep I understand. The bit I don't get is that when I look under main.cpp, I can clearly see my main window object being created and called 'w'. After that, I don't see where my GLWidget gets created other than seeing the .ccp code and .h head files for it and know that it works when I run the application after compilation... so it's getting called somewhere, but no idea where... hence the confusion as to what get's called in what order.

How have you created your GLWidget object, or is GLWidget the name of the class?

It's the class itself.