Windows are not blocking update of components under it

[JD557]

Imagine a situation like this

Even though the window calls UiContext.registerItem(id, windowArea, passive = true), this only stops the input if the window is defined first, as in:

onTop(window(...))
button(...)

However, it's much more natural to do the opposite:

button(...)
window(...)

While I think it should be possible to address the button click, the hot button is unfixable with the current model (as, by the time the window code runs, the button already decided that it's hot).

One alternative that can be explored is to delay everything by one frame, namely:

• The UiContext keeps both the hot/active/selected state and a scratch state
• registerItem updates the scratch state and returns the ItemStatus based on the current state
• Before the next frame, the UiContext updates the state with the content of the scratch

It's possible that I'm missing some obvious issue with this approach, but I think with this the components would never see invalid intermediate values of InputStatus.