Dynamic viewport example

[axelson]

Description

Adds a dynamic view port example and allows creating the view port dynamically with the least amount of code changes. A different API may be desired, I didn't think too hard about this particular implementation. I thought about adding the example to the guides but since the guides are currently empty, putting it directly in the view port docs seemed to make the most sense.

Previously the Scenic.Driver.validate/1 function was considered private (because it used @doc false)

Types of changes

• [ ] Bug fix (a non-breaking change which fixes an issue)
• [ ] New feature (a non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] Improvement/refactoring (non-breaking change that doesn't add any feature but make things better)

Checklist

• [x] Check other PRs and make sure that the changes are not done yet.
• [x] The PR title is no longer than 64 characters.

[boydm]

The :namefield in the Viewport options is causing people trouble as they don't understand that it is purely optional. In fact it is only there as a debugging hint when you look at processes in Observer.

So what everybody does is copy the example options from scenic_new (which gives a name), and then get confused when the dynamic Viewport fails - because they gave two Viewports the same name. This is effectively trying to give two GenServer processes the same name, which would also fail.

So: Please remove the :name option from the example.

The name option also needs to be removed from the scenic_new examples. @bwheatie was talking about putting a PR in for that, if he doesn't get to it, then I'll do it.

[crertel]

@boydm weird idea: could we change the param name to something like process_debug_name or whatever to make it painfully obvious it's just used in that capacity?

[BWheatie]

I like where you are thinking @crertel but I think if we remove it entirely and keep it as optional in the docs with some notes on gotchas when using that field would help.

[axelson]

I've removed the name from the newly created view port in 8c4997aef8f95d9cf92f917428bad665dd175dec

Although it still depends on finding the original view port via Scenic.ViewPort.info and passing in the view port name. I'm not sure how to do that in a more generic way without depending on the view port having a name.