How does Qt draw a border around a rectangle?

Question

I want to know how Qt does a border when using QPainter's drawRect. The reason for this is I am trying to draw three rectangles next to each other, but I'm having trouble getting them to touch perfectly at all pen sizes.

Answer 1

QPainter's documentation for drawRect says:

A stroked rectangle has a size of [the input rectangle] plus the pen width.

So it goes like this: