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Fix the scroll bar thumb jumping when at the end of the LazyStaggeredList with more than one lane and improve smothness of the scroll #1553

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Fix the scroll bar thumb jumping when at the end of the LazyStaggeredList with more than one lane and improve smothness of the scroll #1553

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2aea083
Bug fix: scroll bar thumb jumping when at the end of the LazyStaggere…
rodrigodiasferreira Jul 15, 2024
32514c1
Fix the scroll bar thumb jumping a little bit due to lack of smothnes…
rodrigodiasferreira Aug 11, 2024
3c7e485
Returning the function name: interpolateIndex to the original name: i…
rodrigodiasferreira Aug 12, 2024
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38 changes: 38 additions & 0 deletions ...samples/apps/nowinandroid/core/designsystem/component/scrollbar/LazyScrollbarUtilities.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -74,6 +74,19 @@ internal fun itemVisibilityPercentage(
viewportEndOffset: Int,
): Float {
if (itemSize == 0) return 0f
// TODO: Workaround due to issue b/353143657, monitor if compose team will agree it's an issue
// and fix it, if so, below safeguard probably can be removed
if (
isItemOutOfViewport(
itemSize = itemSize,
itemStartOffset = itemStartOffset,
viewportStartOffset = viewportStartOffset,
viewportEndOffset = viewportEndOffset,
)
) {
return 0f
}

val itemEnd = itemStartOffset + itemSize
val startOffset = when {
itemStartOffset > viewportStartOffset -> 0
Expand All @@ -86,3 +99,28 @@ internal fun itemVisibilityPercentage(
val size = itemSize.toFloat()
return (size - startOffset - endOffset) / size
}

private fun isItemOutOfViewport(
itemSize: Int,
itemStartOffset: Int,
viewportStartOffset: Int,
viewportEndOffset: Int,
) = isItemBeforeViewport(
itemSize = itemSize,
itemStartOffset = itemStartOffset,
viewportStartOffset = viewportStartOffset,
) || isItemAfterViewport(
itemStartOffset = itemStartOffset,
viewportEndOffset = viewportEndOffset,
)

private fun isItemBeforeViewport(
itemSize: Int,
itemStartOffset: Int,
viewportStartOffset: Int,
) = (viewportStartOffset - itemStartOffset) > itemSize

private fun isItemAfterViewport(
itemStartOffset: Int,
viewportEndOffset: Int,
) = itemStartOffset > viewportEndOffset
7 changes: 5 additions & 2 deletions ...om/google/samples/apps/nowinandroid/core/designsystem/component/scrollbar/ScrollbarExt.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -115,7 +115,10 @@ fun LazyGridState.scrollbarState(

val firstIndex = min(
a = interpolateFirstItemIndex(
visibleItems = visibleItemsInfo,
visibleItems = when (layoutInfo.orientation) {
Orientation.Vertical -> layoutInfo.visibleItemsInfo.filter { it.row == 0 }
Orientation.Horizontal -> layoutInfo.visibleItemsInfo.filter { it.column == 0 }
},
itemSize = { layoutInfo.orientation.valueOf(it.size) },
offset = { layoutInfo.orientation.valueOf(it.offset) },
nextItemOnMainAxis = { first ->
Expand Down Expand Up @@ -189,7 +192,7 @@ fun LazyStaggeredGridState.scrollbarState(

val firstIndex = min(
a = interpolateFirstItemIndex(
visibleItems = visibleItemsInfo,
visibleItems = layoutInfo.visibleItemsInfo.filter { it.lane == 0 },
itemSize = { layoutInfo.orientation.valueOf(it.size) },
offset = { layoutInfo.orientation.valueOf(it.offset) },
nextItemOnMainAxis = { first ->
Expand Down