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Simplify duplicated code with generics. LazyGridStateController
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@nanihadesuka
nanihadesuka committed Apr 20, 2024
1 parent 67cfd7d commit 859613d
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Showing 3 changed files with 306 additions and 230 deletions.
259 changes: 30 additions & 229 deletions lib/src/main/java/my/nanihadesuka/compose/LazyGridVerticalScrollbar.kt
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Original file line number Diff line number Diff line change
@@ -1,36 +1,22 @@
package my.nanihadesuka.compose

import androidx.compose.foundation.gestures.Orientation
import androidx.compose.foundation.gestures.draggable
import androidx.compose.foundation.gestures.rememberDraggableState
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.BoxWithConstraints
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.lazy.grid.LazyGridItemInfo
import androidx.compose.foundation.lazy.grid.LazyGridState
import androidx.compose.foundation.shape.CircleShape
import androidx.compose.runtime.Composable
import androidx.compose.runtime.derivedStateOf
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableFloatStateOf
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberCoroutineScope
import androidx.compose.runtime.setValue
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.Shape
import androidx.compose.ui.unit.Dp
import androidx.compose.ui.unit.dp
import kotlinx.coroutines.launch
import my.nanihadesuka.compose.foundation.ScrollbarLayoutSettings
import my.nanihadesuka.compose.foundation.VerticalScrollbarLayout
import kotlin.math.floor
import my.nanihadesuka.compose.controller.rememberLazyGridStateController
import my.nanihadesuka.compose.generic.ElementScrollbar

/**
* @param thickness Thickness of the scrollbar thumb
* @param padding Padding of the scrollbar
* @param thumbMinHeight Thumb minimum height proportional to total scrollbar's height (eg: 0.1 -> 10% of total)
* @param thumbMinLength Thumb minimum length proportional to total scrollbar's length (eg: 0.1 -> 10% of total)
*/
@Composable
fun LazyGridVerticalScrollbar(
Expand All @@ -40,7 +26,7 @@ fun LazyGridVerticalScrollbar(
alwaysShowScrollBar: Boolean = false,
thickness: Dp = 6.dp,
padding: Dp = 8.dp,
thumbMinHeight: Float = 0.1f,
thumbMinLength: Float = 0.1f,
thumbColor: Color = Color(0xFF2A59B6),
thumbSelectedColor: Color = Color(0xFF5281CA),
thumbShape: Shape = CircleShape,
Expand All @@ -61,7 +47,7 @@ fun LazyGridVerticalScrollbar(
alwaysShowScrollBar = alwaysShowScrollBar,
thickness = thickness,
padding = padding,
thumbMinHeight = thumbMinHeight,
thumbMinLength = thumbMinLength,
thumbColor = thumbColor,
thumbSelectedColor = thumbSelectedColor,
selectionActionable = selectionActionable,
Expand All @@ -74,10 +60,9 @@ fun LazyGridVerticalScrollbar(
}

/**
* internal function
* @param thickness Thickness of the scrollbar thumb
* @param padding Padding of the scrollbar
* @param thumbMinHeight Thumb minimum height proportional to total scrollbar's height (eg: 0.1 -> 10% of total)
* @param thumbMinLength Thumb minimum height proportional to total scrollbar's height (eg: 0.1 -> 10% of total)
*/
@Composable
internal fun InternalLazyGridVerticalScrollbar(
Expand All @@ -87,7 +72,7 @@ internal fun InternalLazyGridVerticalScrollbar(
alwaysShowScrollBar: Boolean = false,
thickness: Dp = 6.dp,
padding: Dp = 8.dp,
thumbMinHeight: Float = 0.1f,
thumbMinLength: Float = 0.1f,
thumbColor: Color = Color(0xFF2A59B6),
thumbSelectedColor: Color = Color(0xFF5281CA),
thumbShape: Shape = CircleShape,
Expand All @@ -96,211 +81,27 @@ internal fun InternalLazyGridVerticalScrollbar(
hideDelayMillis: Int = 400,
indicatorContent: (@Composable (index: Int, isThumbSelected: Boolean) -> Unit)? = null,
) {
val firstVisibleItemIndex = remember { derivedStateOf { state.firstVisibleItemIndex } }

val coroutineScope = rememberCoroutineScope()

var isSelected by remember { mutableStateOf(false) }

var dragOffset by remember { mutableFloatStateOf(0f) }

val reverseLayout by remember { derivedStateOf { state.layoutInfo.reverseLayout } }

val realFirstVisibleItem by remember {
derivedStateOf {
state.layoutInfo.visibleItemsInfo.firstOrNull {
it.index == state.firstVisibleItemIndex
}
}
}

// Workaround to know indirectly how many columns are being used (LazyGridState doesn't store it)
val nColumns by remember {
derivedStateOf {
var count = 0
for (item in state.layoutInfo.visibleItemsInfo) {
if (item.column == -1)
break
if (count == item.column) {
count += 1
} else {
break
}
}
count.coerceAtLeast(1)
}
}

val isStickyHeaderInAction by remember {
derivedStateOf {
val realIndex = realFirstVisibleItem?.index ?: return@derivedStateOf false
val firstVisibleIndex = state.layoutInfo.visibleItemsInfo.firstOrNull()?.index
?: return@derivedStateOf false
realIndex != firstVisibleIndex
}
}

fun LazyGridItemInfo.fractionHiddenTop(firstItemOffset: Int) =
if (size.height == 0) 0f else firstItemOffset / size.height.toFloat()

fun LazyGridItemInfo.fractionVisibleBottom(viewportEndOffset: Int) =
if (size.height == 0) 0f else (viewportEndOffset - offset.y).toFloat() / size.height.toFloat()

val normalizedThumbSizeReal by remember {
derivedStateOf {
state.layoutInfo.let {
if (it.totalItemsCount == 0)
return@let 0f

val firstItem = realFirstVisibleItem ?: return@let 0f
val firstPartial =
firstItem.fractionHiddenTop(state.firstVisibleItemScrollOffset)
val lastPartial =
1f - it.visibleItemsInfo.last().fractionVisibleBottom(it.viewportEndOffset)

val realSize =
(it.visibleItemsInfo.size / nColumns) - if (isStickyHeaderInAction) 1 else 0
val realVisibleSize = realSize.toFloat() - firstPartial - lastPartial
realVisibleSize / (it.totalItemsCount / nColumns).toFloat()
}
}
}

val normalizedThumbSize by remember {
derivedStateOf {
normalizedThumbSizeReal.coerceAtLeast(thumbMinHeight)
}
}

fun offsetCorrection(top: Float): Float {
val topRealMax = (1f - normalizedThumbSizeReal).coerceIn(0f, 1f)
if (normalizedThumbSizeReal >= thumbMinHeight) {
return when {
reverseLayout -> topRealMax - top
else -> top
}
}

val topMax = 1f - thumbMinHeight
return when {
reverseLayout -> (topRealMax - top) * topMax / topRealMax
else -> top * topMax / topRealMax
}
}

fun offsetCorrectionInverse(top: Float): Float {
if (normalizedThumbSizeReal >= thumbMinHeight)
return top
val topRealMax = 1f - normalizedThumbSizeReal
val topMax = 1f - thumbMinHeight
return top * topRealMax / topMax
}

val normalizedOffsetPosition by remember {
derivedStateOf {
state.layoutInfo.let {
if (it.totalItemsCount == 0 || it.visibleItemsInfo.isEmpty())
return@let 0f

val firstItem = realFirstVisibleItem ?: return@let 0f
val top = firstItem.run {
(index / nColumns).toFloat() + fractionHiddenTop(state.firstVisibleItemScrollOffset)
} / (it.totalItemsCount / nColumns).toFloat()
offsetCorrection(top)
}
}
}

fun setDragOffset(value: Float) {
val maxValue = (1f - normalizedThumbSize).coerceAtLeast(0f)
dragOffset = value.coerceIn(0f, maxValue)
}

fun setScrollOffset(newOffset: Float) {
setDragOffset(newOffset)
val totalItemsCount = state.layoutInfo.totalItemsCount.toFloat() / nColumns.toFloat()
val exactIndex = offsetCorrectionInverse(totalItemsCount * dragOffset)
val index: Int = floor(exactIndex).toInt() * nColumns
val remainder: Float = exactIndex - floor(exactIndex)

coroutineScope.launch {
state.scrollToItem(index = index, scrollOffset = 0)
val offset = realFirstVisibleItem
?.size
?.let { it.height.toFloat() * remainder }
?.toInt() ?: 0
state.scrollToItem(index = index, scrollOffset = offset)
}
}

val isInAction = state.isScrollInProgress || isSelected || alwaysShowScrollBar

BoxWithConstraints(
modifier = modifier.fillMaxWidth()
) {
val maxHeightFloat = constraints.maxHeight.toFloat()

VerticalScrollbarLayout(
thumbSizeNormalized = normalizedThumbSize,
thumbOffsetNormalized = normalizedOffsetPosition,
thumbIsInAction = isInAction,
settings = ScrollbarLayoutSettings(
durationAnimationMillis = 500,
hideDelayMillis = hideDelayMillis,
scrollbarPadding = padding,
thumbShape = thumbShape,
thumbThickness = thickness,
thumbColor = if (isSelected) thumbSelectedColor else thumbColor,
side = side,
selectionActionable = selectionActionable
),
indicator = indicatorContent?.let {
{ it(firstVisibleItemIndex.value, isSelected) }
},
draggableModifier = Modifier.draggable(
state = rememberDraggableState { delta ->
val displace = if (reverseLayout) -delta else delta // side effect ?
if (isSelected) {
setScrollOffset(dragOffset + displace / maxHeightFloat)
}
},
orientation = Orientation.Vertical,
enabled = selectionMode != ScrollbarSelectionMode.Disabled,
startDragImmediately = true,
onDragStarted = onDragStarted@{ offset ->
if (maxHeightFloat <= 0f) return@onDragStarted
val newOffset = when {
reverseLayout -> (maxHeightFloat - offset.y) / maxHeightFloat
else -> offset.y / maxHeightFloat
}
val currentOffset = when {
reverseLayout -> 1f - normalizedOffsetPosition - normalizedThumbSize
else -> normalizedOffsetPosition
}

when (selectionMode) {
ScrollbarSelectionMode.Full -> {
if (newOffset in currentOffset..(currentOffset + normalizedThumbSize))
setDragOffset(currentOffset)
else
setScrollOffset(newOffset)
isSelected = true
}

ScrollbarSelectionMode.Thumb -> {
if (newOffset in currentOffset..(currentOffset + normalizedThumbSize)) {
setDragOffset(currentOffset)
isSelected = true
}
}

ScrollbarSelectionMode.Disabled -> Unit
}
},
onDragStopped = {
isSelected = false
}
)
)
}
val controller = rememberLazyGridStateController(
state = state,
thumbMinLength = thumbMinLength,
alwaysShowScrollBar = alwaysShowScrollBar,
selectionMode = selectionMode,
orientation = Orientation.Vertical
)

ElementScrollbar(
orientation = Orientation.Vertical,
stateController = controller,
modifier = modifier,
side = side,
thickness = thickness,
padding = padding,
thumbColor = thumbColor,
thumbSelectedColor = thumbSelectedColor,
thumbShape = thumbShape,
selectionMode = selectionMode,
selectionActionable = selectionActionable,
hideDelayMillis = hideDelayMillis,
indicatorContent = indicatorContent
)
}
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