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[Refactor/#7] Optimize recomposition using graphicsLayer #8

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Merged
DongChyeon merged 2 commits into from
Nov 9, 2025
Merged

[Refactor/#7] Optimize recomposition using graphicsLayer #8

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5fbe731
Refactor/#7: Extract curve effect logic into a Modifier extension usi…
DongChyeon Nov 9, 2025
39791bd
Refactor/#7: Optimize recomposition and frame performance using graph…
DongChyeon Nov 9, 2025
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58 changes: 40 additions & 18 deletions timepicker/src/main/java/com/dongchyeon/timepicker/ui/PickerItem.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -7,13 +7,14 @@ import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.LazyListItemInfo
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.derivedStateOf
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableIntStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberUpdatedState
import androidx.compose.runtime.setValue
import androidx.compose.runtime.snapshotFlow
import androidx.compose.ui.Alignment
Expand Down Expand Up @@ -104,6 +105,14 @@ internal fun <T> PickerItem(
val totalItemHeight = itemHeightDp + style.itemSpacing
val totalItemHeightPx = totalItemHeight.toPx()

val layoutInfo by rememberUpdatedState(listState.layoutInfo)

val itemInfoMap = remember(layoutInfo) {
layoutInfo.visibleItemsInfo.associateBy { it.index }
}

val viewportCenterOffset = layoutInfo.viewportStartOffset + (layoutInfo.viewportEndOffset - layoutInfo.viewportStartOffset) / 2

Box(modifier = modifier) {
LazyColumn(
state = listState,
Expand All @@ -115,20 +124,6 @@ internal fun <T> PickerItem(
.pointerInput(Unit) { detectVerticalDragGestures { change, _ -> change.consume() } }
) {
items(listScrollCount, key = { index -> index }) { index ->
val layoutInfo by remember { derivedStateOf { listState.layoutInfo } }

val viewportCenterOffset = layoutInfo.viewportStartOffset +
(layoutInfo.viewportEndOffset - layoutInfo.viewportStartOffset) / 2

val itemInfo = layoutInfo.visibleItemsInfo.find { it.index == index }
val itemCenterOffset = itemInfo?.offset?.let { it + (itemInfo.size / 2) } ?: 0

val distanceFromCenter = abs(viewportCenterOffset - itemCenterOffset).toFloat()
val maxDistance = totalItemHeightPx * visibleItemsMiddle

val alpha = curveEffect.calculateAlpha(distanceFromCenter, maxDistance)
val scaleY = curveEffect.calculateScaleY(distanceFromCenter, maxDistance)

val item = getItemForIndex(
index = index,
items = items,
Expand All @@ -140,11 +135,17 @@ internal fun <T> PickerItem(
text = item?.let { itemFormatter(it) } ?: "",
maxLines = 1,
style = style.textStyle,
color = style.textColor.copy(alpha = alpha),
color = style.textColor,
modifier = Modifier
.padding(vertical = style.itemSpacing / 2)
.graphicsLayer(scaleY = scaleY)
.onSizeChanged { size -> itemHeightPixels = size.height }
.curvedPickerEffect(
index = index,
viewportCenterOffset = viewportCenterOffset,
itemInfoMap = itemInfoMap,
totalItemHeightPx = totalItemHeightPx,
visibleItemsMiddle = visibleItemsMiddle,
curveEffect = curveEffect
).onSizeChanged { size -> itemHeightPixels = size.height }
.then(textModifier)
)
}
Expand Down Expand Up @@ -180,6 +181,27 @@ private fun getStartIndexForInfiniteScroll(
return listScrollMiddle - listScrollMiddle % itemSize - visibleItemsMiddle + startIndex
}

fun Modifier.curvedPickerEffect(
index: Int,
viewportCenterOffset: Int,
itemInfoMap: Map<Int, LazyListItemInfo>,
totalItemHeightPx: Float,
visibleItemsMiddle: Int,
curveEffect: CurveEffect
): Modifier = graphicsLayer {
val itemInfo = itemInfoMap[index]
val itemCenterOffset = itemInfo?.let { it.offset + (it.size / 2) } ?: 0

val distanceFromCenter = abs(viewportCenterOffset - itemCenterOffset).toFloat()
val maxDistance = totalItemHeightPx * visibleItemsMiddle

val alpha = curveEffect.calculateAlpha(distanceFromCenter, maxDistance)
val scaleY = curveEffect.calculateScaleY(distanceFromCenter, maxDistance)

this.alpha = alpha
this.scaleY = scaleY
}

@Composable
@Preview
private fun PickerItemPreview() {
Expand Down