| /* |
| * 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.staggeredgrid |
| |
| import androidx.compose.foundation.ExperimentalFoundationApi |
| import androidx.compose.foundation.OverscrollEffect |
| import androidx.compose.foundation.checkScrollableContainerConstraints |
| import androidx.compose.foundation.gestures.Orientation |
| import androidx.compose.foundation.layout.Arrangement |
| import androidx.compose.foundation.layout.PaddingValues |
| import androidx.compose.foundation.layout.calculateEndPadding |
| import androidx.compose.foundation.layout.calculateStartPadding |
| import androidx.compose.foundation.lazy.layout.LazyLayoutItemProvider |
| import androidx.compose.foundation.lazy.layout.LazyLayoutMeasureScope |
| import androidx.compose.runtime.Composable |
| import androidx.compose.runtime.remember |
| import androidx.compose.ui.unit.Constraints |
| import androidx.compose.ui.unit.Density |
| import androidx.compose.ui.unit.Dp |
| import androidx.compose.ui.unit.IntOffset |
| import androidx.compose.ui.unit.LayoutDirection |
| import androidx.compose.ui.unit.constrainHeight |
| import androidx.compose.ui.unit.constrainWidth |
| |
| @Composable |
| @ExperimentalFoundationApi |
| internal fun rememberStaggeredGridMeasurePolicy( |
| state: LazyStaggeredGridState, |
| itemProvider: LazyLayoutItemProvider, |
| contentPadding: PaddingValues, |
| reverseLayout: Boolean, |
| orientation: Orientation, |
| verticalArrangement: Arrangement.Vertical, |
| horizontalArrangement: Arrangement.Horizontal, |
| slotSizesSums: Density.(Constraints) -> IntArray, |
| overscrollEffect: OverscrollEffect |
| ): LazyLayoutMeasureScope.(Constraints) -> LazyStaggeredGridMeasureResult = remember( |
| state, |
| itemProvider, |
| contentPadding, |
| reverseLayout, |
| orientation, |
| verticalArrangement, |
| horizontalArrangement, |
| slotSizesSums, |
| overscrollEffect, |
| ) { |
| { constraints -> |
| checkScrollableContainerConstraints( |
| constraints, |
| orientation |
| ) |
| val resolvedSlotSums = slotSizesSums(this, constraints) |
| val isVertical = orientation == Orientation.Vertical |
| |
| // setup information for prefetch |
| state.laneWidthsPrefixSum = resolvedSlotSums |
| state.isVertical = isVertical |
| |
| val beforeContentPadding = contentPadding.beforePadding( |
| orientation, reverseLayout, layoutDirection |
| ).roundToPx() |
| val afterContentPadding = contentPadding.afterPadding( |
| orientation, reverseLayout, layoutDirection |
| ).roundToPx() |
| val startContentPadding = contentPadding.startPadding( |
| orientation, layoutDirection |
| ).roundToPx() |
| |
| val maxMainAxisSize = if (isVertical) constraints.maxHeight else constraints.maxWidth |
| val mainAxisAvailableSize = maxMainAxisSize - beforeContentPadding - afterContentPadding |
| val contentOffset = if (isVertical) { |
| IntOffset(startContentPadding, beforeContentPadding) |
| } else { |
| IntOffset(beforeContentPadding, startContentPadding) |
| } |
| |
| val mainAxisSpacing = if (isVertical) { |
| verticalArrangement.spacing |
| } else { |
| horizontalArrangement.spacing |
| }.roundToPx() |
| |
| val crossAxisSpacing = if (isVertical) { |
| horizontalArrangement.spacing |
| } else { |
| verticalArrangement.spacing |
| }.roundToPx() |
| |
| val horizontalPadding = contentPadding.run { |
| calculateStartPadding(layoutDirection) + calculateEndPadding(layoutDirection) |
| }.roundToPx() |
| val verticalPadding = contentPadding.run { |
| calculateTopPadding() + calculateBottomPadding() |
| }.roundToPx() |
| |
| measureStaggeredGrid( |
| state = state, |
| itemProvider = itemProvider, |
| resolvedSlotSums = resolvedSlotSums, |
| constraints = constraints.copy( |
| minWidth = constraints.constrainWidth(horizontalPadding), |
| minHeight = constraints.constrainHeight(verticalPadding) |
| ), |
| mainAxisSpacing = mainAxisSpacing, |
| crossAxisSpacing = crossAxisSpacing, |
| contentOffset = contentOffset, |
| mainAxisAvailableSize = mainAxisAvailableSize, |
| isVertical = isVertical, |
| beforeContentPadding = beforeContentPadding, |
| afterContentPadding = afterContentPadding, |
| ).also { |
| state.applyMeasureResult(it) |
| overscrollEffect.isEnabled = it.canScrollForward || it.canScrollBackward |
| } |
| } |
| } |
| |
| private fun PaddingValues.startPadding( |
| orientation: Orientation, |
| layoutDirection: LayoutDirection |
| ): Dp = |
| when (orientation) { |
| Orientation.Vertical -> calculateStartPadding(layoutDirection) |
| Orientation.Horizontal -> calculateTopPadding() |
| } |
| |
| private fun PaddingValues.beforePadding( |
| orientation: Orientation, |
| reverseLayout: Boolean, |
| layoutDirection: LayoutDirection |
| ): Dp = |
| when (orientation) { |
| Orientation.Vertical -> |
| if (reverseLayout) calculateBottomPadding() else calculateTopPadding() |
| Orientation.Horizontal -> |
| if (reverseLayout) { |
| calculateEndPadding(layoutDirection) |
| } else { |
| calculateStartPadding(layoutDirection) |
| } |
| } |
| |
| private fun PaddingValues.afterPadding( |
| orientation: Orientation, |
| reverseLayout: Boolean, |
| layoutDirection: LayoutDirection |
| ): Dp = |
| when (orientation) { |
| Orientation.Vertical -> |
| if (reverseLayout) calculateTopPadding() else calculateBottomPadding() |
| Orientation.Horizontal -> |
| if (reverseLayout) { |
| calculateStartPadding(layoutDirection) |
| } else { |
| calculateEndPadding(layoutDirection) |
| } |
| } |