Just saw that a new <https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:com...

# compose

[Stylianos Gakis]

Just saw that a new onRectChanged modifier was created. What are the use cases for such a modifier?
And provided you do not use the debounce/throttle params, when would one use this over onPlaced or onGloballyPositioned (depending on what info you need)?

[romainguy]

It is part of a new set of APIs to track visibility/occlusion of nodes. To measure impressions for instance

[shikasd]

I think it is intended to be a more performant replacement for onGloballyPositioned as well

[romainguy]

If you need to track things like scrolling and such, yes absolutely

[Stylianos Gakis]

Which use cases would onGloballyPositioned still be useful for then?
Is it just a strictly better version of it, or did it have to compromise on some information it provides to you to get that better performance?

[shikasd]

I think it is a strictly better version, but maybe I am missing some cases

[Alex Vanyo]

Is there a phase ordering guarantee for onRectChanged?

[Alex Vanyo]

Ah “This will be called after layout pass.” (reading the docs closer)

[sindrenm]

g st

[Zach Klippenstein (he/him) [MOD]]

omg does this mean focusable() can finally stop observing onGloballyPositioned?

[romainguy]

The author says “yes please” to the question of “should folks use onRectChanged instead of onGloballyPositioned”. We’ll try though to implement onGloballyPositioned on top of onRectChanged

[Zach Klippenstein (he/him) [MOD]]

this is exciting!

[Stylianos Gakis]

Well, I am really glad I asked! Thanks for all the info everyone

[Bryan Herbst]

Really excited for this one, I was about to dive into the weeds of benchmarking a modifer we use for impression analytics that uses onGloballyPositioned and here you just offer me a solution to all my concerns with our current implementation ❤️

[romainguy]

There's gonna be APIs on top of this specifically to let you know about visibility. That's what you'll want to use