Some additional information and examples:

Implementing Radio Button-Like Behavior in iOS Applications

https://gkbrown.wordpress.com/2015/08/10/using-lmtableview-t...

Creating Custom Table View Cells in Markup

https://gkbrown.wordpress.com/2015/08/19/creating-custom-tab...

Using UIStackView with MarkupKit

https://gkbrown.wordpress.com/2015/09/29/using-uistackview-w...

MarkupKit Examples

https://gkbrown.wordpress.com/2015/08/14/markupkit-examples/

A Practical Example Using MarkupKit and WebRPC

https://gkbrown.wordpress.com/2015/09/08/a-practical-example...

So this looks a lot like XAML[1] for WPF (Windows Presentation Foundation)[2] to me. and I'm actually quite surprised that this was not the case for iOS development from the beginning! (declaimer: I never touched native iOS development before as a 100% Microsoft technologies professional)

[1] https://en.wikipedia.org/wiki/Extensible_Application_Markup_... [2] https://en.wikipedia.org/wiki/Windows_Presentation_Foundatio...

XAML was definitely one of the inspirations for MarkupKit. It was also inspired in part by MXML (Apache Flex), FXML (JavaFX), and to some extent HTML. It's also conceptually similar to the markup language used to build Android applications, though I don't have much experience with that.

How are the controls sized and placed? Is there a layout engine in there?

It uses autolayout. The details of constraint management are abstracted by layout views such as LMRowView and LMColumnView. You can also use the new UIStackView class Apple added in iOS 9. See this article for more information:

https://gkbrown.wordpress.com/2015/09/29/using-uistackview-w...