VerticalScroller no longer has `onScrolledPositionChanged` , was it removed on purpose?

# compose

[Bruno_]

VerticalScroller no longer has onScrolledPositionChanged , was it removed on purpose?

[Adam Powell]

The ScrollerPosition object that it accepts as a parameter is an @Model object, so its value property is observable for the current scroll position

[Adam Powell]

so yes, it was removed on purpose, but I'm not sure we're finalized on this particular approach as a replacement just yet. At a minimum we need the better convenience helpers to observe @Model changes outside of compose; it's really raw in the current artifacts

[matvei]

Partial reason why it was removed: animation inside (smoothScrollTo, fling after scroll) couldn't guarantee consistency if you do something more fancy like

onScrolledPositionChanged = { newValue ->  scrollPosition.value = calcMyCustomParallaxDelta(newValue) }

Above will work for dragging, but won't for fling/smoothScrolling. So we decide to remove inconsistency, while leaving ability to observe (just read scrollPosition.value, as Adam suggested) and explore more 🙂

[Bruno_]

if it's a @Model, won't it have a massive impact on the performance?
also, I could figure stuff out myself but I can't donwload sources, is it even possible?

[matvei]

It probably will impact performance now, yes.

But in this case, it's on us to fix performance, and to provide APIs that won't give false promises

[matvei]

Not sure about the second question 🙂