How do I code UI widgets

[SinbadEV]

I don't consider myself dumb, but I've looked at the code for a couple widgets and they make my brain hurt, is there any "simple", like "make stuff show up on the screen" documentation or do I need to learn ALL of Lua and then learn ALL of the Spring command hooks to do anything?

What I want to do is, CvC has this "Upgrade" building that builds upgrades which are a special kind of unit, so I was thinking, a little widget that shows up when you build the upgrade building and duplicates it's command list, tells you if the building is idle, tells you which upgrades have been built, and which is currently being built and it's health as a %age and which upgrades are available as clickable buttons that will give the command to the upgrade building... or something like that...