/*
* Copyright 2022 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.compose.foundation.lazy.grid
import androidx.compose.animation.core.FiniteAnimationSpec
import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.ui.layout.Placeable
import androidx.compose.ui.unit.IntOffset
import androidx.compose.ui.unit.IntSize
import androidx.compose.ui.unit.LayoutDirection
import androidx.compose.ui.util.fastForEach
/**
* Represents one measured item of the lazy grid. It can in fact consist of multiple placeables
* if the user emit multiple layout nodes in the item callback.
*/
@OptIn(ExperimentalFoundationApi::class)
internal class LazyGridMeasuredItem(
val index: ItemIndex,
val key: Any,
private val isVertical: Boolean,
/**
* Cross axis size is the same for all [placeables]. Take it as parameter for the case when
* [placeables] is empty.
*/
val crossAxisSize: Int,
val mainAxisSpacing: Int,
private val reverseLayout: Boolean,
private val layoutDirection: LayoutDirection,
private val beforeContentPadding: Int,
private val afterContentPadding: Int,
val placeables: List<Placeable>,
private val placementAnimator: LazyGridItemPlacementAnimator,
/**
* The offset which shouldn't affect any calculations but needs to be applied for the final
* value passed into the place() call.
*/
private val visualOffset: IntOffset
) {
/**
* Main axis size of the item - the max main axis size of the placeables.
*/
val mainAxisSize: Int
/**
* The max main axis size of the placeables plus mainAxisSpacing.
*/
val mainAxisSizeWithSpacings: Int
init {
var maxMainAxis = 0
placeables.fastForEach {
maxMainAxis = maxOf(maxMainAxis, if (isVertical) it.height else it.width)
}
mainAxisSize = maxMainAxis
mainAxisSizeWithSpacings = (maxMainAxis + mainAxisSpacing).coerceAtLeast(0)
}
/**
* Calculates positions for the inner placeables at [mainAxisOffset], [crossAxisOffset].
* [layoutWidth] and [layoutHeight] should be provided to not place placeables which are ended
* up outside of the viewport (for example one item consist of 2 placeables, and the first one
* is not going to be visible, so we don't place it as an optimization, but place the second
* one). If [reverseOrder] is true the inner placeables would be placed in the inverted order.
*/
fun position(
mainAxisOffset: Int,
crossAxisOffset: Int,
layoutWidth: Int,
layoutHeight: Int,
row: Int,
column: Int
): LazyGridPositionedItem {
val mainAxisLayoutSize = if (isVertical) layoutHeight else layoutWidth
val crossAxisLayoutSize = if (isVertical) layoutWidth else layoutHeight
@Suppress("NAME_SHADOWING")
val crossAxisOffset = if (isVertical && layoutDirection == LayoutDirection.Rtl) {
crossAxisLayoutSize - crossAxisOffset - crossAxisSize
} else {
crossAxisOffset
}
return LazyGridPositionedItem(
offset = if (isVertical) {
IntOffset(crossAxisOffset, mainAxisOffset)
} else {
IntOffset(mainAxisOffset, crossAxisOffset)
},
index = index.value,
key = key,
row = row,
column = column,
size = if (isVertical) {
IntSize(crossAxisSize, mainAxisSize)
} else {
IntSize(mainAxisSize, crossAxisSize)
},
minMainAxisOffset = -beforeContentPadding,
maxMainAxisOffset = mainAxisLayoutSize + afterContentPadding,
isVertical = isVertical,
placeables = placeables,
placementAnimator = placementAnimator,
visualOffset = visualOffset,
mainAxisLayoutSize = mainAxisLayoutSize,
reverseLayout = reverseLayout
)
}
}
internal class LazyGridPositionedItem(
override val offset: IntOffset,
override val index: Int,
override val key: Any,
override val row: Int,
override val column: Int,
override val size: IntSize,
private val minMainAxisOffset: Int,
private val maxMainAxisOffset: Int,
private val isVertical: Boolean,
private val placeables: List<Placeable>,
private val placementAnimator: LazyGridItemPlacementAnimator,
private val visualOffset: IntOffset,
private val mainAxisLayoutSize: Int,
private val reverseLayout: Boolean
) : LazyGridItemInfo {
val placeablesCount: Int get() = placeables.size
fun getMainAxisSize(index: Int) = placeables[index].mainAxisSize
fun getMainAxisSize() = if (isVertical) size.height else size.width
fun getCrossAxisSize() = if (isVertical) size.width else size.height
fun getCrossAxisOffset() = if (isVertical) offset.x else offset.y
@Suppress("UNCHECKED_CAST")
fun getAnimationSpec(index: Int) =
placeables[index].parentData as? FiniteAnimationSpec<IntOffset>?
val hasAnimations = run {
repeat(placeablesCount) { index ->
if (getAnimationSpec(index) != null) {
return@run true
}
}
false
}
fun place(
scope: Placeable.PlacementScope,
) = with(scope) {
repeat(placeablesCount) { index ->
val placeable = placeables[index]
val minOffset = minMainAxisOffset - placeable.mainAxisSize
val maxOffset = maxMainAxisOffset
val offset = if (getAnimationSpec(index) != null) {
placementAnimator.getAnimatedOffset(
key, index, minOffset, maxOffset, offset
)
} else {
offset
}
val reverseLayoutAwareOffset = if (reverseLayout) {
offset.copy { mainAxisOffset ->
mainAxisLayoutSize - mainAxisOffset - placeable.mainAxisSize
}
} else {
offset
}
if (isVertical) {
placeable.placeWithLayer(reverseLayoutAwareOffset + visualOffset)
} else {
placeable.placeRelativeWithLayer(reverseLayoutAwareOffset + visualOffset)
}
}
}
private val Placeable.mainAxisSize get() = if (isVertical) height else width
private inline fun IntOffset.copy(mainAxisMap: (Int) -> Int): IntOffset =
IntOffset(if (isVertical) x else mainAxisMap(x), if (isVertical) mainAxisMap(y) else y)
}