looong time ago, we've discussed with a colleague who was building some UI for a game as side project, about what "hierarchies" (essentialy, aspects of structur

looong time ago, we've discussed with a colleague who was building some UI for a game as side project, about what "hierarchies" (essentialy, aspects of structure) are there in an UI. So we ended with about 4: * encapsulation - what includes what / belongs to what * visual - what overlays/obscures what * event-passing - if X gets clicked, or otherwise interacted with, who else would get the event passed to/notified * ??? can't remember this one.. but i remember it took many conversations to find out we need it. Probably was dependency-linkage (in aspects other than above 3, e.g. some model-logic dependencies) This aspect-distinguishing may or may not be usable for you. For example, a usual "scrollbar" is composed of multiple smaller elements, which are tied together in all above aspects. But it does not have to be like that, e.g. the position-mover ("thumb") and the lower/higher buttons need not be on same visual place, e.g. a circle volume knob and separate quieter + louder knobs elsewhere (and that may be very far). One may argue it's not a scrollbar anymore.. expect it does the same thing, just visually differently. It would be interesting if one can really separate these aspects in the code, somehow. That said, how would your toolkit handle this: a small "innocent" interaction that causes lots of small changes all over the tree. Think taxforms: a form, mixture of subforms and fields, many levels deep, and i need to highlight the user-changed fields (or subforms containing changed fields), all the way up. What i ended up recently, in React (i.e. in DOM-recipe-tree), is, anytime the user presses some keystroke in some text field down in the depths, the whole thing needs be repainted. A few hundred fields probably. Which.. isn't that fast anymore, when depth goes beyond 3-4. (From user perspective there are 2-3 times less levels than programatical). Probably i've missed some "i have not changed, don't repaint me" step somewhere.