Hi! I have a pretty basic application. Basically it shuffles a list of ~150 strings. I’m concerned w...

# compose

[Nikita Prokopov]

Hi! I have a pretty basic application. Basically it shuffles a list of ~150 strings. I’m concerned with performance. Recompose alone takes ~50ms each time. Full rendering is ~100-120ms / per shuffle. I realize this is a worst case for Compose (fully reshuffling 150 elements). Anything ideas how to improve performance? Code https://gist.github.com/tonsky/bca64aeb0c0e79151c39dd0e5a508d22

[Luca Nicoletti]

Wait for a recycler component 😄

[Nikita Prokopov]

Scroll performance is not the issue. I guess what I am asking is if there’s a way to say to composer: this content is completely new, do not waste your time trying to match it up with what was there before?

[Luca Nicoletti]

Oh I see, like an invalidate on a view

[Luca Nicoletti]

You just want to force a re-rendering as you know the entire content changed

[Nikita Prokopov]

kinda

[Zsolt]

I wonder if Pivotal would help you? https://developer.android.com/reference/kotlin/androidx/compose/Pivotal

[matvei]

Hey. Can you try to wrap Line invocation in foreach with key(it) ?

[matvei]

It will, as mentioned above in docs, add a pivotal memorization param so runtime will know that they're the same composables, just reordered

[Nikita Prokopov]

@Zsolt yes it makes it slightly slower

[Nikita Prokopov]

@matvei I’m not sure what it wants from me

[Nikita Prokopov]

[Nikita Prokopov]

wrapping in Key (capital) makes it slightly slower, ~on par with @Pivotal

[matvei]

Yep, it's capital K in dev03, sorry.

wrapping in Key (capital) makes it slightly slower

Oh, it suppose to be the opposite. Can you file a bug please?

[Nikita Prokopov]

No, I can see why it is that way. It’s faster to create new components than trying to find old ones, because list is quite big (150 elements) and components are simple

[Nikita Prokopov]

it’s the absolute number that worries me. 120ms is a lot of time for such a simple component. Even on a first render

[Nikita Prokopov]

I guess that would be a way to turn off composer:

Key(Math.random()) {
  lines.value.forEach {
    Line(it)
  }
}

[matvei]

I'd assume 150 is the number we still want to be able provide good experience with. What's more important is that we shouldn't make it noticeably worth, as one of the primary Key functions is also correctness (proper invocation of onCommit/onDispose) .

As for first compositions / recompositions, we still have work to do in that areas, but there has been progress already and more to go.

[amar_1995]

I am making infinite scrolling view.
After making to the end of verticalScroller. I am calling api to load more data and store it in a local db.
I am observing the local db and as change happen i recieved a new list of data(with old data also).
Now the problem is that scroller is recomposing the whole view. I only want the data to load with new ids.
Is using Key or Pivotal helps ?