I understood that at a certain level Lazarus as the IDE isolates us from those details. The whole point of the Delphi style interface is that you plop components down onto the form and link to the various events. Makes for easy graphical applications development. Whether under the covers it's Windows, GTK or Qt should, to the applications programmer be irrelevant.
What I do not know yet, but appears I'm going to have to learn is how a component is shown on the form during development. Seems as if the code that makes up the 'paint' function or 'change' or 'refresh' is also called by the IDE to display the components on the form during development.
Unlike Delphi the IDE needs to be rebuilt every time a component is added. So what I really need to do is take a step back and create a canvas rectangle, set the brush and pen colours and create canvas polygons. All without the IDE forms design side since then it's part of the IDE.
And because the BBB and Pi are painfully slow I'll have to do it on a Linux desktop (the LinuxCNC one) since unfortunately the Windows PC Lazarus works the in the expected way.
It may be a few days before I get to this. Work-work unfortunately has to come first.