Nice. I did my ui using viewpoirts for containers. And you can nest containers inside containers. Each container also uses a backing camera for scrolling etc.
It was a bit tricky to get flawless but basically I needed to translate the draw and the input for each container.
Getting the draw and update order was interesting too
Cool, I am nesting controls in controls here, in the window, the title bar is a control, as is the button. Each has its own scissor rectangle so they can’t over flow,
They can be camera specific too, and it should be possible to render them as billboards and use them in world space oo, but not tested that yet.
I thought I would do a bit of a round up post on where I am with my MonoGame Engine. Doing this post made me realize, there is quite a bit in here 
Next post is up, now starting to look at creating an editor for my game engine, exciting eh!
Check it out here.
Thoguht I would show you the sort of thing I am aiming for with my engine and it’s editor, this is an old vid of a game I started writing with my old engine and editor, one of my fav old arcade games Gyrus.
OK, so I have had a gread few weeks on my Patreon engine, and the editor is actually starting to come together
Editing a new scene, each of the different basic lights are shown in here, point, direcitonal and cone. I have a procedural skybox in here, as you would find in Unity3D and is the exact same code that can be found in GPU Gems Chapter 16
Object seelction is in, either from the panel on the left or clicking in the scen render window. I can drag and drop items in the left panel to make them child objects of the object I drag them to.
I have scale, translate and rotate widget tools in here now, both of which can be set to AA (axis aligned) or OA (object aligned).
Progress is feeling good at the moment 
If you would like to check out my Patreon page, it can be found here.
Still here, still posting, this covers the scene viewer, object picker and some widgets in my @MonoGame engine and editor.
