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https://github.com/mihonapp/mihon.git
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Fixed scrollbar sometimes not showing during scroll or not reaching the bottom with few items (#2304)
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anirudhn
GitHub
@@ -11,6 +11,8 @@ The format is a modified version of [Keep a Changelog](https://keepachangelog.co
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- `Other` - for technical stuff.
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## [Unreleased]
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### Fixes
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- Fixed scrollbar sometimes not showing during scroll or not reaching the bottom with few items ([@anirudhsnayak](https://github.com/anirudhsnayak)) ([#2304](https://github.com/mihonapp/mihon/pull/2304))
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## [v0.19.0] - 2025-08-04
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### Added
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@@ -44,6 +44,7 @@ import androidx.compose.ui.unit.LayoutDirection
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import androidx.compose.ui.unit.dp
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import androidx.compose.ui.util.fastFirstOrNull
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import androidx.compose.ui.util.fastForEach
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import androidx.compose.ui.util.fastLastOrNull
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import androidx.compose.ui.util.fastMaxBy
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import kotlinx.coroutines.channels.BufferOverflow
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import kotlinx.coroutines.flow.MutableSharedFlow
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@@ -79,8 +80,7 @@ fun VerticalFastScroller(
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val scrollerConstraints = constraints.copy(minWidth = 0, minHeight = 0)
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val scrollerPlaceable = subcompose("scroller") {
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val layoutInfo = listState.layoutInfo
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val showScroller = layoutInfo.visibleItemsInfo.size < layoutInfo.totalItemsCount
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if (!showScroller) return@subcompose
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if (layoutInfo.visibleItemsInfo.isEmpty() || layoutInfo.totalItemsCount == 0) return@subcompose
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val thumbTopPadding = with(LocalDensity.current) { topContentPadding.toPx() }
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var thumbOffsetY by remember(thumbTopPadding) { mutableFloatStateOf(thumbTopPadding) }
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@@ -94,6 +94,12 @@ fun VerticalFastScroller(
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)
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}
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// listState.isScrollInProgress occasionally flickers
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val scrollStateTracker = remember { MutableData(listState.isScrollInProgress) }
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val stableScrollInProgress = scrollStateTracker.value || listState.isScrollInProgress
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scrollStateTracker.value = listState.isScrollInProgress
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val anyScrollInProgress = stableScrollInProgress || isThumbDragged
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val thumbBottomPadding = with(LocalDensity.current) { bottomContentPadding.toPx() }
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val heightPx = contentHeight.toFloat() -
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thumbTopPadding -
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@@ -101,27 +107,65 @@ fun VerticalFastScroller(
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listState.layoutInfo.afterContentPadding
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val thumbHeightPx = with(LocalDensity.current) { ThumbLength.toPx() }
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val trackHeightPx = heightPx - thumbHeightPx
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val scrollHeightPx = contentHeight.toFloat() -
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listState.layoutInfo.beforeContentPadding -
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listState.layoutInfo.afterContentPadding -
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thumbBottomPadding
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val visibleItems = layoutInfo.visibleItemsInfo
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val topItem = visibleItems.fastFirstOrNull {
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it.bottom >= 0 &&
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(it.key as? String)?.startsWith(STICKY_HEADER_KEY_PREFIX)?.not() ?: true
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} ?: visibleItems.first()
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val bottomItem = visibleItems.fastLastOrNull {
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it.top <= scrollHeightPx &&
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(it.key as? String)?.startsWith(STICKY_HEADER_KEY_PREFIX)?.not() ?: true
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} ?: visibleItems.last()
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val topHiddenProportion = -1f * topItem.top / topItem.size.coerceAtLeast(1)
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val bottomHiddenProportion = (bottomItem.bottom - scrollHeightPx) / bottomItem.size.coerceAtLeast(1)
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val previousSections = topHiddenProportion + topItem.index
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val remainingSections = bottomHiddenProportion + (layoutInfo.totalItemsCount - (bottomItem.index + 1))
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val scrollableSections = previousSections + remainingSections
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val layoutChangeTracker = remember { MutableData(scrollableSections) }
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val layoutChanged = !anyScrollInProgress && abs(layoutChangeTracker.value - scrollableSections) > 0.1
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layoutChangeTracker.value = scrollableSections
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val estimateConfidence = remember { MutableData(remainingSections) }
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if (layoutChanged) estimateConfidence.value = remainingSections
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val maxRemainingSections = remember(estimateConfidence.value) { scrollableSections }
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estimateConfidence.value = max(estimateConfidence.value, remainingSections)
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if (maxRemainingSections < 0.5) return@subcompose
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// When thumb dragged
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LaunchedEffect(thumbOffsetY) {
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if (layoutInfo.totalItemsCount == 0 || !isThumbDragged) return@LaunchedEffect
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val scrollRatio = (thumbOffsetY - thumbTopPadding) / trackHeightPx
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val scrollItem = layoutInfo.totalItemsCount * scrollRatio
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val scrollItemRounded = scrollItem.roundToInt()
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val scrollItemSize = layoutInfo.visibleItemsInfo.find { it.index == scrollItemRounded }?.size ?: 0
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val scrollItemOffset = scrollItemSize * (scrollItem - scrollItemRounded)
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listState.scrollToItem(index = scrollItemRounded, scrollOffset = scrollItemOffset.roundToInt())
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val thumbProportion = (thumbOffsetY - thumbTopPadding) / trackHeightPx
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if (thumbProportion <= 0.001f) {
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estimateConfidence.value = -1f
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listState.scrollToItem(index = 0, scrollOffset = 0)
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scrolled.tryEmit(Unit)
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return@LaunchedEffect
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}
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val scrollRemainingSections = (1f - thumbProportion) * maxRemainingSections
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val currentSection = layoutInfo.totalItemsCount - scrollRemainingSections
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val scrollSectionIndex = currentSection.toInt().coerceAtMost(layoutInfo.totalItemsCount)
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val expectedScrollItem = visibleItems.find { it.index == scrollSectionIndex } ?: visibleItems.first()
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val scrollRelativeOffset = expectedScrollItem.size * (currentSection - scrollSectionIndex)
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val scrollSectionOffset = (scrollRelativeOffset - scrollHeightPx).roundToInt()
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val scrollItemIndex = scrollSectionIndex.coerceIn(0, layoutInfo.totalItemsCount - 1)
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val scrollItemOffset = scrollSectionOffset + (scrollSectionIndex - scrollItemIndex) * bottomItem.size
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listState.scrollToItem(index = scrollItemIndex, scrollOffset = scrollItemOffset)
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scrolled.tryEmit(Unit)
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}
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// When list scrolled
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LaunchedEffect(listState.firstVisibleItemScrollOffset) {
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if (listState.layoutInfo.totalItemsCount == 0 || isThumbDragged) return@LaunchedEffect
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val scrollOffset = computeScrollOffset(state = listState)
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val scrollRange = computeScrollRange(state = listState)
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val proportion = scrollOffset.toFloat() / (scrollRange.toFloat() - heightPx)
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if (layoutInfo.totalItemsCount != 0 && !isThumbDragged) {
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val proportion = 1f - remainingSections / maxRemainingSections
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thumbOffsetY = trackHeightPx * proportion + thumbTopPadding
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scrolled.tryEmit(Unit)
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if (stableScrollInProgress) scrolled.tryEmit(Unit)
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}
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// Thumb alpha
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@@ -220,6 +264,11 @@ private fun rememberColumnWidthSums(
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}
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}
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/*
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VerticalGridFastScroller was written with a regularity assumption, so it is slightly inaccurate for layouts with
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varying row sizes.
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*/
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// TODO: Ideally rewrite VerticalGridFastScroller to use similar logic as VerticalFastScroller
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@Composable
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fun VerticalGridFastScroller(
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state: LazyGridState,
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@@ -248,7 +297,9 @@ fun VerticalGridFastScroller(
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val scrollerConstraints = constraints.copy(minWidth = 0, minHeight = 0)
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val scrollerPlaceable = subcompose("scroller") {
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val layoutInfo = state.layoutInfo
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val showScroller = layoutInfo.visibleItemsInfo.size < layoutInfo.totalItemsCount
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val showScroller = remember(columns, layoutInfo.totalItemsCount) {
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layoutInfo.visibleItemsInfo.size < layoutInfo.totalItemsCount
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}
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if (!showScroller) return@subcompose
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val thumbTopPadding = with(LocalDensity.current) { topContentPadding.toPx() }
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var thumbOffsetY by remember(thumbTopPadding) { mutableFloatStateOf(thumbTopPadding) }
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@@ -270,41 +321,38 @@ fun VerticalGridFastScroller(
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val thumbHeightPx = with(LocalDensity.current) { ThumbLength.toPx() }
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val trackHeightPx = heightPx - thumbHeightPx
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val columnCount = remember { slotSizesSums(constraints).size }
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val columnCount = remember(columns) { slotSizesSums(constraints).size.coerceAtLeast(1) }
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val scrollRange = remember(columns) { computeGridScrollRange(state = state, columnCount = columnCount) }
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// When thumb dragged
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LaunchedEffect(thumbOffsetY) {
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if (layoutInfo.totalItemsCount == 0 || !isThumbDragged) return@LaunchedEffect
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val visibleItems = state.layoutInfo.visibleItemsInfo
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val startChild = visibleItems.first()
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val endChild = visibleItems.last()
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val laidOutArea = (endChild.offset.y + endChild.size.height) - startChild.offset.y
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val laidOutRows = 1 + abs(endChild.index - startChild.index) / columnCount
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val avgSizePerRow = laidOutArea.toFloat() / laidOutRows
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val scrollRatio = (thumbOffsetY - thumbTopPadding) / trackHeightPx
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val scrollItem = layoutInfo.totalItemsCount * scrollRatio
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// I can't think of anything else rn but this'll do
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val scrollItemWhole = scrollItem.toInt()
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val columnNum = ((scrollItemWhole + 1) % columnCount).takeIf { it != 0 } ?: columnCount
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val scrollItemFraction = if (scrollItemWhole == 0) scrollItem else scrollItem % scrollItemWhole
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val offsetPerItem = 1f / columnCount
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val offsetRatio = (offsetPerItem * scrollItemFraction) + (offsetPerItem * (columnNum - 1))
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val scrollAmt = scrollRatio * (scrollRange.toFloat() - heightPx).coerceAtLeast(1f)
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val rowNumber = (scrollAmt / avgSizePerRow).toInt()
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val rowOffset = scrollAmt - rowNumber * avgSizePerRow
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// TODO: Sometimes item height is not available when scrolling up
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val scrollItemSize = (1..columnCount).maxOf { num ->
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val actualIndex = if (num != columnNum) {
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scrollItemWhole + num - columnCount
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} else {
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scrollItemWhole
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}
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layoutInfo.visibleItemsInfo.find { it.index == actualIndex }?.size?.height ?: 0
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}
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val scrollItemOffset = scrollItemSize * offsetRatio
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state.scrollToItem(index = scrollItemWhole, scrollOffset = scrollItemOffset.roundToInt())
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state.scrollToItem(index = columnCount * rowNumber, scrollOffset = rowOffset.roundToInt())
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scrolled.tryEmit(Unit)
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}
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// When list scrolled
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LaunchedEffect(state.firstVisibleItemScrollOffset) {
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if (state.layoutInfo.totalItemsCount == 0 || isThumbDragged) return@LaunchedEffect
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val scrollOffset = computeScrollOffset(state = state)
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val scrollRange = computeScrollRange(state = state)
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val proportion = scrollOffset.toFloat() / (scrollRange.toFloat() - heightPx)
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val scrollOffset = computeGridScrollOffset(state = state, columnCount = columnCount)
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/*
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LazyGridItemInfo doesn't always give the accurate height of the object, so we clamp the proportion
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at 1 to ensure that there are no issues due to this -- ideally we would correctly compute the value
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*/
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val extraScrollRange = (scrollRange.toFloat() - heightPx).coerceAtLeast(1f)
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val proportion = (scrollOffset.toFloat() / extraScrollRange).coerceAtMost(1f)
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thumbOffsetY = trackHeightPx * proportion + thumbTopPadding
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scrolled.tryEmit(Unit)
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}
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@@ -374,57 +422,36 @@ fun VerticalGridFastScroller(
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}
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}
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private fun computeScrollOffset(state: LazyGridState): Int {
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if (state.layoutInfo.totalItemsCount == 0) return 0
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val visibleItems = state.layoutInfo.visibleItemsInfo
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val startChild = visibleItems.first()
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val endChild = visibleItems.last()
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val minPosition = min(startChild.index, endChild.index)
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val maxPosition = max(startChild.index, endChild.index)
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val itemsBefore = minPosition.coerceAtLeast(0)
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val startDecoratedTop = startChild.offset.y
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val laidOutArea = abs((endChild.offset.y + endChild.size.height) - startDecoratedTop)
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val itemRange = abs(minPosition - maxPosition) + 1
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val avgSizePerRow = laidOutArea.toFloat() / itemRange
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return (itemsBefore * avgSizePerRow + (0 - startDecoratedTop)).roundToInt()
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}
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// TODO: not sure why abs corrections are in the following functions; these can probably be removed
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private fun computeScrollRange(state: LazyGridState): Int {
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private fun computeGridScrollOffset(state: LazyGridState, columnCount: Int): Int {
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if (state.layoutInfo.totalItemsCount == 0) return 0
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val visibleItems = state.layoutInfo.visibleItemsInfo
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val startChild = visibleItems.first()
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val endChild = visibleItems.last()
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val laidOutArea = (endChild.offset.y + endChild.size.height) - startChild.offset.y
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val laidOutRange = abs(startChild.index - endChild.index) + 1
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return (laidOutArea.toFloat() / laidOutRange * state.layoutInfo.totalItemsCount).roundToInt()
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val laidOutRows = 1 + abs(endChild.index - startChild.index) / columnCount
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val avgSizePerRow = laidOutArea.toFloat() / laidOutRows
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val rowsBefore = min(startChild.index, endChild.index).coerceAtLeast(0) / columnCount
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return (rowsBefore * avgSizePerRow - startChild.offset.y).roundToInt()
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}
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private fun computeScrollOffset(state: LazyListState): Int {
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private fun computeGridScrollRange(state: LazyGridState, columnCount: Int): Int {
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if (state.layoutInfo.totalItemsCount == 0) return 0
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val visibleItems = state.layoutInfo.visibleItemsInfo
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val startChild = visibleItems
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.fastFirstOrNull { (it.key as? String)?.startsWith(STICKY_HEADER_KEY_PREFIX)?.not() ?: true }!!
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val startChild = visibleItems.first()
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val endChild = visibleItems.last()
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val minPosition = min(startChild.index, endChild.index)
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val maxPosition = max(startChild.index, endChild.index)
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val itemsBefore = minPosition.coerceAtLeast(0)
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val startDecoratedTop = startChild.top
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val laidOutArea = abs(endChild.bottom - startDecoratedTop)
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val itemRange = abs(minPosition - maxPosition) + 1
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val avgSizePerRow = laidOutArea.toFloat() / itemRange
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return (itemsBefore * avgSizePerRow + (0 - startDecoratedTop)).roundToInt()
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val laidOutArea = (endChild.offset.y + endChild.size.height) - startChild.offset.y
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val laidOutRows = 1 + abs(endChild.index - startChild.index) / columnCount
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val avgSizePerRow = laidOutArea.toFloat() / laidOutRows
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val totalRows = 1 + (state.layoutInfo.totalItemsCount - 1) / columnCount
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val endSpacing = avgSizePerRow - endChild.size.height
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return (endSpacing + (laidOutArea.toFloat() / laidOutRows) * totalRows).roundToInt()
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}
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private fun computeScrollRange(state: LazyListState): Int {
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if (state.layoutInfo.totalItemsCount == 0) return 0
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val visibleItems = state.layoutInfo.visibleItemsInfo
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val startChild = visibleItems
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.fastFirstOrNull { (it.key as? String)?.startsWith(STICKY_HEADER_KEY_PREFIX)?.not() ?: true }!!
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val endChild = visibleItems.last()
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val laidOutArea = endChild.bottom - startChild.top
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val laidOutRange = abs(startChild.index - endChild.index) + 1
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return (laidOutArea.toFloat() / laidOutRange * state.layoutInfo.totalItemsCount).roundToInt()
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}
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private class MutableData<T>(var value: T)
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object Scroller {
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const val STICKY_HEADER_KEY_PREFIX = "sticky:"
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