XML also has a LONG history of being used for UI in stuff like QT, which is great.
The one problem I see is that as developers, we shouldn't give a rat's ass about the otuput format's readability when compared to the API ergonomics. If the API for describing the UI is good enough (Can I do stuff like "App.Transition(App.findOne(Sidebar), 500, {width:"1%"}, {width:"30%"}, Ease.EASE_IN_OUT)" or is it a 300loc tutorial?) then the storage format at the end of the day is not THAT important, at least for me, a guy who does a lot of GUI work every day.
it isnt that important for me either, and imo shouldn’t be...BUT
when you are in a formal setting, people like to code review, and in that case, in the absence of some special diff tool, people will complain they can’t review your ui changes in github and suddenly your format matters alot more than before
The one problem I see is that as developers, we shouldn't give a rat's ass about the otuput format's readability when compared to the API ergonomics. If the API for describing the UI is good enough (Can I do stuff like "App.Transition(App.findOne(Sidebar), 500, {width:"1%"}, {width:"30%"}, Ease.EASE_IN_OUT)" or is it a 300loc tutorial?) then the storage format at the end of the day is not THAT important, at least for me, a guy who does a lot of GUI work every day.