Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Improving the reusability and maintainability in ScrollbarExt.kt file and Fix the scroll bar thumb jumping a little bit due to lack of smothness on interpolatedIndex #1550

Closed
wants to merge 3 commits into from
Closed

Improving the reusability and maintainability in ScrollbarExt.kt file and Fix the scroll bar thumb jumping a little bit due to lack of smothness on interpolatedIndex #1550

Changes from 1 commit
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
13d4e26
Improving the reusability and maintainability in ScrollbarExt.kt file
rodrigodiasferreira Jul 14, 2024
e8d5d12
Remove the inline qualifier from the genericScrollbarState and make i…
rodrigodiasferreira Jul 14, 2024
31b77d5
Fix the scroll bar thumb jumping a little bit due to lack of smothnes…
rodrigodiasferreira Jul 15, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
208 changes: 83 additions & 125 deletions ...om/google/samples/apps/nowinandroid/core/designsystem/component/scrollbar/ScrollbarExt.kt
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
package com.google.samples.apps.nowinandroid.core.designsystem.component.scrollbar

import androidx.compose.foundation.gestures.Orientation
import androidx.compose.foundation.gestures.ScrollableState
import androidx.compose.foundation.lazy.LazyListItemInfo
import androidx.compose.foundation.lazy.LazyListState
import androidx.compose.foundation.lazy.grid.LazyGridItemInfo
Expand All @@ -32,42 +33,57 @@ import kotlinx.coroutines.flow.filterNotNull
import kotlin.math.min

/**
* Calculates a [ScrollbarState] driven by the changes in a [LazyListState].
* Calculates a [ScrollbarState] driven by the changes in a [LazyState].
*
* @param itemsAvailable the total amount of items available to scroll in the lazy list.
* @param itemIndex a lookup function for index of an item in the list relative to [itemsAvailable].
* @param itemsAvailable the total amount of items available to scroll in the [LazyState].
* @param itemSize a lookup function for the size of an item in the layout.
* @param offset a lookup function for the offset of an item relative to the start of the view port.
* @param nextItemOnMainAxis a lookup function for the next item on the main axis in the direction
* of the scroll.
* @param itemSize next [LazyStateItem] on the main axis of [LazyState], null if none.
* @param index a lookup function for index of an item in the layout relative to
* @param viewportStartOffset a lookup function for the start offset of the view port
* @param viewportEndOffset a lookup function for the end offset of the view port
* @param reverseLayout a lookup function for the reverseLayout of [LazyState].
*/
@Composable
fun LazyListState.scrollbarState(
internal inline fun <LazyState : ScrollableState, LazyStateItem> LazyState.genericScrollbarState(
rodrigodiasferreira marked this conversation as resolved.
Show resolved Hide resolved
itemsAvailable: Int,
itemIndex: (LazyListItemInfo) -> Int = LazyListItemInfo::index,
crossinline visibleItems: () -> List<LazyStateItem>,
crossinline itemSize: LazyState.(LazyStateItem) -> Int,
crossinline offset: LazyState.(LazyStateItem) -> Int,
crossinline nextItemOnMainAxis: LazyState.(LazyStateItem) -> LazyStateItem?,
crossinline index: (LazyStateItem) -> Int,
crossinline viewportStartOffset: () -> Int,
crossinline viewportEndOffset: () -> Int,
crossinline reverseLayout: () -> Boolean = { false },
): ScrollbarState {
val state = remember { ScrollbarState() }
LaunchedEffect(this, itemsAvailable) {
snapshotFlow {
if (itemsAvailable == 0) return@snapshotFlow null

val visibleItemsInfo = layoutInfo.visibleItemsInfo
val visibleItemsInfo = visibleItems()
if (visibleItemsInfo.isEmpty()) return@snapshotFlow null

val firstIndex = min(
a = interpolateFirstItemIndex(
visibleItems = visibleItemsInfo,
itemSize = { it.size },
offset = { it.offset },
nextItemOnMainAxis = { first -> visibleItemsInfo.find { it != first } },
itemIndex = itemIndex,
itemSize = itemSize,
offset = offset,
nextItemOnMainAxis = nextItemOnMainAxis,
itemIndex = index,
),
b = itemsAvailable.toFloat(),
)
if (firstIndex.isNaN()) return@snapshotFlow null

val itemsVisible = visibleItemsInfo.floatSumOf { itemInfo ->
itemVisibilityPercentage(
itemSize = itemInfo.size,
itemStartOffset = itemInfo.offset,
viewportStartOffset = layoutInfo.viewportStartOffset,
viewportEndOffset = layoutInfo.viewportEndOffset,
itemSize = itemSize(itemInfo),
itemStartOffset = offset(itemInfo),
viewportStartOffset = viewportStartOffset(),
viewportEndOffset = viewportEndOffset(),
)
}

Expand All @@ -82,7 +98,7 @@ fun LazyListState.scrollbarState(
scrollbarStateValue(
thumbSizePercent = thumbSizePercent,
thumbMovedPercent = when {
layoutInfo.reverseLayout -> 1f - thumbTravelPercent
reverseLayout() -> 1f - thumbTravelPercent
else -> thumbTravelPercent
},
)
Expand All @@ -94,6 +110,28 @@ fun LazyListState.scrollbarState(
return state
}

/**
* Calculates a [ScrollbarState] driven by the changes in a [LazyListState].
*
* @param itemsAvailable the total amount of items available to scroll in the lazy list.
* @param itemIndex a lookup function for index of an item in the list relative to [itemsAvailable].
*/
@Composable
fun LazyListState.scrollbarState(
itemsAvailable: Int,
itemIndex: (LazyListItemInfo) -> Int = LazyListItemInfo::index,
) = genericScrollbarState(
itemsAvailable = itemsAvailable,
visibleItems = { layoutInfo.visibleItemsInfo },
itemSize = { it.size },
offset = { it.offset },
nextItemOnMainAxis = { first -> layoutInfo.visibleItemsInfo.find { it != first } },
index = itemIndex,
viewportStartOffset = { layoutInfo.viewportStartOffset },
viewportEndOffset = { layoutInfo.viewportEndOffset },
reverseLayout = { layoutInfo.reverseLayout },
)

/**
* Calculates a [ScrollbarState] driven by the changes in a [LazyGridState]
*
Expand All @@ -104,68 +142,27 @@ fun LazyListState.scrollbarState(
fun LazyGridState.scrollbarState(
itemsAvailable: Int,
itemIndex: (LazyGridItemInfo) -> Int = LazyGridItemInfo::index,
): ScrollbarState {
val state = remember { ScrollbarState() }
LaunchedEffect(this, itemsAvailable) {
snapshotFlow {
if (itemsAvailable == 0) return@snapshotFlow null

val visibleItemsInfo = layoutInfo.visibleItemsInfo
if (visibleItemsInfo.isEmpty()) return@snapshotFlow null

val firstIndex = min(
a = interpolateFirstItemIndex(
visibleItems = visibleItemsInfo,
itemSize = { layoutInfo.orientation.valueOf(it.size) },
offset = { layoutInfo.orientation.valueOf(it.offset) },
nextItemOnMainAxis = { first ->
when (layoutInfo.orientation) {
Orientation.Vertical -> visibleItemsInfo.find {
it != first && it.row != first.row
}

Orientation.Horizontal -> visibleItemsInfo.find {
it != first && it.column != first.column
}
}
},
itemIndex = itemIndex,
),
b = itemsAvailable.toFloat(),
)
if (firstIndex.isNaN()) return@snapshotFlow null

val itemsVisible = visibleItemsInfo.floatSumOf { itemInfo ->
itemVisibilityPercentage(
itemSize = layoutInfo.orientation.valueOf(itemInfo.size),
itemStartOffset = layoutInfo.orientation.valueOf(itemInfo.offset),
viewportStartOffset = layoutInfo.viewportStartOffset,
viewportEndOffset = layoutInfo.viewportEndOffset,
)
) = genericScrollbarState(
itemsAvailable = itemsAvailable,
visibleItems = { layoutInfo.visibleItemsInfo },
itemSize = { layoutInfo.orientation.valueOf(it.size) },
offset = { layoutInfo.orientation.valueOf(it.offset) },
nextItemOnMainAxis = { first ->
when (layoutInfo.orientation) {
Orientation.Vertical -> layoutInfo.visibleItemsInfo.find {
it != first && it.row != first.row
}

val thumbTravelPercent = min(
a = firstIndex / itemsAvailable,
b = 1f,
)
val thumbSizePercent = min(
a = itemsVisible / itemsAvailable,
b = 1f,
)
scrollbarStateValue(
thumbSizePercent = thumbSizePercent,
thumbMovedPercent = when {
layoutInfo.reverseLayout -> 1f - thumbTravelPercent
else -> thumbTravelPercent
},
)
Orientation.Horizontal -> layoutInfo.visibleItemsInfo.find {
it != first && it.column != first.column
}
}
.filterNotNull()
.distinctUntilChanged()
.collect { state.onScroll(it) }
}
return state
}
},
index = itemIndex,
viewportStartOffset = { layoutInfo.viewportStartOffset },
viewportEndOffset = { layoutInfo.viewportEndOffset },
reverseLayout = { layoutInfo.reverseLayout },
)

/**
* Remembers a [ScrollbarState] driven by the changes in a [LazyStaggeredGridState]
Expand All @@ -178,57 +175,18 @@ fun LazyGridState.scrollbarState(
fun LazyStaggeredGridState.scrollbarState(
itemsAvailable: Int,
itemIndex: (LazyStaggeredGridItemInfo) -> Int = LazyStaggeredGridItemInfo::index,
): ScrollbarState {
val state = remember { ScrollbarState() }
LaunchedEffect(this, itemsAvailable) {
snapshotFlow {
if (itemsAvailable == 0) return@snapshotFlow null

val visibleItemsInfo = layoutInfo.visibleItemsInfo
if (visibleItemsInfo.isEmpty()) return@snapshotFlow null

val firstIndex = min(
a = interpolateFirstItemIndex(
visibleItems = visibleItemsInfo,
itemSize = { layoutInfo.orientation.valueOf(it.size) },
offset = { layoutInfo.orientation.valueOf(it.offset) },
nextItemOnMainAxis = { first ->
visibleItemsInfo.find { it != first && it.lane == first.lane }
},
itemIndex = itemIndex,
),
b = itemsAvailable.toFloat(),
)
if (firstIndex.isNaN()) return@snapshotFlow null

val itemsVisible = visibleItemsInfo.floatSumOf { itemInfo ->
itemVisibilityPercentage(
itemSize = layoutInfo.orientation.valueOf(itemInfo.size),
itemStartOffset = layoutInfo.orientation.valueOf(itemInfo.offset),
viewportStartOffset = layoutInfo.viewportStartOffset,
viewportEndOffset = layoutInfo.viewportEndOffset,
)
}

val thumbTravelPercent = min(
a = firstIndex / itemsAvailable,
b = 1f,
)
val thumbSizePercent = min(
a = itemsVisible / itemsAvailable,
b = 1f,
)
scrollbarStateValue(
thumbSizePercent = thumbSizePercent,
thumbMovedPercent = thumbTravelPercent,
)
}
.filterNotNull()
.distinctUntilChanged()
.collect { state.onScroll(it) }
}
return state
}
) = genericScrollbarState(
itemsAvailable = itemsAvailable,
visibleItems = { layoutInfo.visibleItemsInfo },
itemSize = { layoutInfo.orientation.valueOf(it.size) },
offset = { layoutInfo.orientation.valueOf(it.offset) },
nextItemOnMainAxis = { first ->
layoutInfo.visibleItemsInfo.find { it != first && it.lane == first.lane }
},
index = itemIndex,
viewportStartOffset = { layoutInfo.viewportStartOffset },
viewportEndOffset = { layoutInfo.viewportEndOffset },
)

private inline fun <T> List<T>.floatSumOf(selector: (T) -> Float): Float =
fold(initial = 0f) { accumulator, listItem -> accumulator + selector(listItem) }