Hey, some more info:
hxScout was built a while ago on OpenFL 3 or something (aka legacy). Coming from AS3 / Flash, I wrote the UI with many Flash-like features such as
BitmapData.draw. See all those things at work here:
Fun fact, with very few modifications, it also works great with NME!
Today, OpenFL is evolving with more focus on games and Shaders and performance, which is great. But I still use legacy OpenFL and NME, because of the perfect rendering of the features I used in hxScout’s UI.
So, it all depends on what framework you know best, what kinds of UI components you use, what targets you need (e.g. NME doesn’t target web). And if you don’t want to build it all the UI pieces from scratch (which personally, I like to), check out haxeui, which supports basically every framework and target.