LazyItemScopeImpl.kt

/*
 * Copyright 2021 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

import androidx.compose.animation.core.FiniteAnimationSpec
import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.layout.width
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.setValue
import androidx.compose.ui.Modifier
import androidx.compose.ui.layout.ParentDataModifier
import androidx.compose.ui.platform.InspectorInfo
import androidx.compose.ui.platform.InspectorValueInfo
import androidx.compose.ui.platform.debugInspectorInfo
import androidx.compose.ui.unit.Density
import androidx.compose.ui.unit.Dp
import androidx.compose.ui.unit.IntOffset

internal class LazyItemScopeImpl : LazyItemScope {

    var maxWidth: Dp by mutableStateOf(Dp.Unspecified)
    var maxHeight: Dp by mutableStateOf(Dp.Unspecified)

    override fun Modifier.fillParentMaxSize(fraction: Float) = size(
        maxWidth * fraction,
        maxHeight * fraction
    )

    override fun Modifier.fillParentMaxWidth(fraction: Float) =
        width(maxWidth * fraction)

    override fun Modifier.fillParentMaxHeight(fraction: Float) =
        height(maxHeight * fraction)

    @ExperimentalFoundationApi
    override fun Modifier.animateItemPlacement(animationSpec: FiniteAnimationSpec<IntOffset>) =
        this.then(AnimateItemPlacementModifier(animationSpec, debugInspectorInfo {
            name = "animateItemPlacement"
            value = animationSpec
        }))
}

private class AnimateItemPlacementModifier(
    val animationSpec: FiniteAnimationSpec<IntOffset>,
    inspectorInfo: InspectorInfo.() -> Unit,
) : ParentDataModifier, InspectorValueInfo(inspectorInfo) {
    override fun Density.modifyParentData(parentData: Any?): Any = animationSpec

    override fun equals(other: Any?): Boolean {
        if (this === other) return true
        if (other !is AnimateItemPlacementModifier) return false
        return animationSpec != other.animationSpec
    }

    override fun hashCode(): Int {
        return animationSpec.hashCode()
    }
}