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Try improved version using snapshotFlow, which seems more performant, as well as an extended threshold (-40 items)

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This commit is contained in:
Jorge Martín 2025-03-17 16:30:43 +01:00
parent d15b227c33
commit 8f129eb285
1 changed files with 42 additions and 11 deletions
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53
features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/TimelineView.kt
View file

@ -36,6 +36,7 @@ import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberCoroutineScope
import androidx.compose.runtime.rememberUpdatedState
import androidx.compose.runtime.setValue
import androidx.compose.runtime.snapshotFlow
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.rotate
@ -72,6 +73,10 @@ import io.element.android.libraries.matrix.api.core.EventId
import io.element.android.libraries.matrix.api.core.UserId
import io.element.android.libraries.matrix.api.timeline.Timeline
import io.element.android.libraries.ui.strings.CommonStrings
import kotlinx.coroutines.ExperimentalCoroutinesApi
import kotlinx.coroutines.flow.collectLatest
import kotlinx.coroutines.flow.combine
import kotlinx.coroutines.flow.distinctUntilChanged
import kotlinx.coroutines.launch
import timber.log.Timber
@ -177,17 +182,8 @@ fun TimelineView(
onClearFocusRequestState = ::clearFocusRequestState
)
val isCloseToStartOfLoadedTimeline by remember {
derivedStateOf {
lazyListState.firstVisibleItemIndex + lazyListState.layoutInfo.visibleItemsInfo.size >= lazyListState.layoutInfo.totalItemsCount - 10
}
}
LaunchedEffect(isCloseToStartOfLoadedTimeline) {
// Only back paginate when we're close to the start of the loaded timeline items and the user is actively scrolling
if (lazyListState.isScrollInProgress && isCloseToStartOfLoadedTimeline) {
Timber.d("Prefetching pagination with ${lazyListState.layoutInfo.totalItemsCount} items")
state.eventSink(TimelineEvents.LoadMore(Timeline.PaginationDirection.BACKWARDS))
}
TimelinePrefetchingHelper(lazyListState = lazyListState) {
state.eventSink(TimelineEvents.LoadMore(Timeline.PaginationDirection.BACKWARDS))
}
TimelineScrollHelper(
@ -218,6 +214,41 @@ private fun MessageShieldDialog(state: TimelineState) {
)
}
@OptIn(ExperimentalCoroutinesApi::class)
@Composable
private fun TimelinePrefetchingHelper(
lazyListState: LazyListState,
prefetch: () -> Unit,
) {
// We're using snapshot flows for these because using `LaunchedEffect` with `derivedState` doesn't seem to be responsive enough
val firstVisibleItemIndexFlow = snapshotFlow {
lazyListState.firstVisibleItemIndex
}
val layoutInfoFlow = snapshotFlow {
lazyListState.layoutInfo
}
val isScrollingFlow = snapshotFlow {
lazyListState.isScrollInProgress
}
LaunchedEffect(Unit) {
val isCloseToStartOfLoadedTimelineFlow = combine(layoutInfoFlow, firstVisibleItemIndexFlow) { layoutInfo, firstVisibleItemIndex ->
firstVisibleItemIndex + layoutInfo.visibleItemsInfo.size >= layoutInfo.totalItemsCount - 40
}
combine(isCloseToStartOfLoadedTimelineFlow, isScrollingFlow) { needsPrefetch, isScrolling ->
needsPrefetch && isScrolling
}
.distinctUntilChanged()
.collectLatest { needsPrefetch ->
if (needsPrefetch) {
Timber.d("Prefetching pagination with ${lazyListState.layoutInfo.totalItemsCount} items")
prefetch()
}
}
}
}
@Composable
private fun BoxScope.TimelineScrollHelper(
hasAnyEvent: Boolean,