/*
* Copyright 2019 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.layout
import androidx.compose.runtime.Composable
import androidx.compose.ui.Alignment
import androidx.compose.ui.unit.Constraints
import androidx.compose.ui.Layout
import androidx.compose.ui.Placeable
import androidx.compose.ui.unit.Dp
import androidx.compose.ui.unit.IntSize
import androidx.compose.ui.unit.dp
import androidx.compose.ui.util.fastForEachIndexed
import kotlin.math.max
/**
* A composable that places its children in a horizontal flow. Unlike [Row], if the
* horizontal space is too small to put all the children in one row, multiple rows may be used.
*
* Note that just like [Row], flex values cannot be used with [FlowRow].
*
* Example usage:
*
* @sample androidx.compose.foundation.layout.samples.SimpleFlowRow
*
* @param mainAxisSize The size of the layout in the main axis direction.
* @param mainAxisAlignment The alignment of each row's children in the main axis direction.
* @param mainAxisSpacing The main axis spacing between the children of each row.
* @param crossAxisAlignment The alignment of each row's children in the cross axis direction.
* @param crossAxisSpacing The cross axis spacing between the rows of the layout.
* @param lastLineMainAxisAlignment Overrides the main axis alignment of the last row.
*/
@ExperimentalLayout
@Composable
fun FlowRow(
mainAxisSize: SizeMode = SizeMode.Wrap,
mainAxisAlignment: FlowMainAxisAlignment = FlowMainAxisAlignment.Start,
mainAxisSpacing: Dp = 0.dp,
crossAxisAlignment: FlowCrossAxisAlignment = FlowCrossAxisAlignment.Start,
crossAxisSpacing: Dp = 0.dp,
lastLineMainAxisAlignment: FlowMainAxisAlignment = mainAxisAlignment,
children: @Composable () -> Unit
) {
Flow(
orientation = LayoutOrientation.Horizontal,
mainAxisSize = mainAxisSize,
mainAxisAlignment = mainAxisAlignment,
mainAxisSpacing = mainAxisSpacing,
crossAxisAlignment = crossAxisAlignment,
crossAxisSpacing = crossAxisSpacing,
lastLineMainAxisAlignment = lastLineMainAxisAlignment,
children = children
)
}
/**
* A composable that places its children in a vertical flow. Unlike [Column], if the
* vertical space is too small to put all the children in one column, multiple columns may be used.
*
* Note that just like [Column], flex values cannot be used with [FlowColumn].
*
* Example usage:
*
* @sample androidx.compose.foundation.layout.samples.SimpleFlowColumn
*
* @param mainAxisSize The size of the layout in the main axis direction.
* @param mainAxisAlignment The alignment of each column's children in the main axis direction.
* @param mainAxisSpacing The main axis spacing between the children of each column.
* @param crossAxisAlignment The alignment of each column's children in the cross axis direction.
* @param crossAxisSpacing The cross axis spacing between the columns of the layout.
* @param lastLineMainAxisAlignment Overrides the main axis alignment of the last column.
*/
@ExperimentalLayout
@Composable
fun FlowColumn(
mainAxisSize: SizeMode = SizeMode.Wrap,
mainAxisAlignment: FlowMainAxisAlignment = FlowMainAxisAlignment.Start,
mainAxisSpacing: Dp = 0.dp,
crossAxisAlignment: FlowCrossAxisAlignment = FlowCrossAxisAlignment.Start,
crossAxisSpacing: Dp = 0.dp,
lastLineMainAxisAlignment: FlowMainAxisAlignment = mainAxisAlignment,
children: @Composable () -> Unit
) {
Flow(
orientation = LayoutOrientation.Vertical,
mainAxisSize = mainAxisSize,
mainAxisAlignment = mainAxisAlignment,
mainAxisSpacing = mainAxisSpacing,
crossAxisAlignment = crossAxisAlignment,
crossAxisSpacing = crossAxisSpacing,
lastLineMainAxisAlignment = lastLineMainAxisAlignment,
children = children
)
}
/**
* Used to specify the alignment of a layout's children, in cross axis direction.
*/
enum class FlowCrossAxisAlignment {
/**
* Place children such that their center is in the middle of the cross axis.
*/
Center,
/**
* Place children such that their start edge is aligned to the start edge of the cross axis.
*/
Start,
/**
* Place children such that their end edge is aligned to the end edge of the cross axis.
*/
End,
}
typealias FlowMainAxisAlignment = MainAxisAlignment
/**
* Layout model that arranges its children in a horizontal or vertical flow.
*/
@Composable
@OptIn(InternalLayoutApi::class)
private fun Flow(
orientation: LayoutOrientation,
mainAxisSize: SizeMode,
mainAxisAlignment: FlowMainAxisAlignment,
mainAxisSpacing: Dp,
crossAxisAlignment: FlowCrossAxisAlignment,
crossAxisSpacing: Dp,
lastLineMainAxisAlignment: FlowMainAxisAlignment,
children: @Composable () -> Unit
) {
fun Placeable.mainAxisSize() =
if (orientation == LayoutOrientation.Horizontal) width else height
fun Placeable.crossAxisSize() =
if (orientation == LayoutOrientation.Horizontal) height else width
Layout(children) { measurables, outerConstraints ->
val sequences = mutableListOf<List<Placeable>>()
val crossAxisSizes = mutableListOf<Int>()
val crossAxisPositions = mutableListOf<Int>()
var mainAxisSpace = 0
var crossAxisSpace = 0
val currentSequence = mutableListOf<Placeable>()
var currentMainAxisSize = 0
var currentCrossAxisSize = 0
val constraints = OrientationIndependentConstraints(outerConstraints, orientation)
val childConstraints = if (orientation == LayoutOrientation.Horizontal) {
Constraints(maxWidth = constraints.mainAxisMax)
} else {
Constraints(maxHeight = constraints.mainAxisMax)
}
// Return whether the placeable can be added to the current sequence.
fun canAddToCurrentSequence(placeable: Placeable) =
currentSequence.isEmpty() || currentMainAxisSize + mainAxisSpacing.toIntPx() +
placeable.mainAxisSize() <= constraints.mainAxisMax
// Store current sequence information and start a new sequence.
fun startNewSequence() {
if (sequences.isNotEmpty()) {
crossAxisSpace += crossAxisSpacing.toIntPx()
}
sequences += currentSequence.toList()
crossAxisSizes += currentCrossAxisSize
crossAxisPositions += crossAxisSpace
crossAxisSpace += currentCrossAxisSize
mainAxisSpace = max(mainAxisSpace, currentMainAxisSize)
currentSequence.clear()
currentMainAxisSize = 0
currentCrossAxisSize = 0
}
for (measurable in measurables) {
// Ask the child for its preferred size.
val placeable = measurable.measure(childConstraints)
// Start a new sequence if there is not enough space.
if (!canAddToCurrentSequence(placeable)) startNewSequence()
// Add the child to the current sequence.
if (currentSequence.isNotEmpty()) {
currentMainAxisSize += mainAxisSpacing.toIntPx()
}
currentSequence.add(placeable)
currentMainAxisSize += placeable.mainAxisSize()
currentCrossAxisSize = max(currentCrossAxisSize, placeable.crossAxisSize())
}
if (currentSequence.isNotEmpty()) startNewSequence()
val mainAxisLayoutSize = if (constraints.mainAxisMax != Constraints.Infinity &&
mainAxisSize == SizeMode.Expand
) {
constraints.mainAxisMax
} else {
max(mainAxisSpace, constraints.mainAxisMin)
}
val crossAxisLayoutSize = max(crossAxisSpace, constraints.crossAxisMin)
val layoutWidth = if (orientation == LayoutOrientation.Horizontal) {
mainAxisLayoutSize
} else {
crossAxisLayoutSize
}
val layoutHeight = if (orientation == LayoutOrientation.Horizontal) {
crossAxisLayoutSize
} else {
mainAxisLayoutSize
}
layout(layoutWidth, layoutHeight) {
sequences.fastForEachIndexed { i, placeables ->
val childrenMainAxisSizes = placeables.mapIndexed { j, placeable ->
placeable.mainAxisSize() +
if (j < placeables.lastIndex) mainAxisSpacing.toIntPx() else 0
}
val arrangement = if (i < sequences.lastIndex) {
mainAxisAlignment.arrangement
} else {
lastLineMainAxisAlignment.arrangement
}
// TODO(soboleva): rtl support
// Handle vertical direction
val mainAxisPositions = MutableList(childrenMainAxisSizes.size) { 0 }
arrangement.arrange(
mainAxisLayoutSize,
childrenMainAxisSizes,
this@Layout,
mainAxisPositions
)
placeables.fastForEachIndexed { j, placeable ->
val crossAxis = when (crossAxisAlignment) {
FlowCrossAxisAlignment.Start -> 0
FlowCrossAxisAlignment.End ->
crossAxisSizes[i] - placeable.crossAxisSize()
FlowCrossAxisAlignment.Center ->
Alignment.Center.align(
IntSize(
width = 0,
height = crossAxisSizes[i] - placeable.crossAxisSize()
)
).y
}
if (orientation == LayoutOrientation.Horizontal) {
placeable.place(
x = mainAxisPositions[j],
y = crossAxisPositions[i] + crossAxis
)
} else {
placeable.place(
x = crossAxisPositions[i] + crossAxis,
y = mainAxisPositions[j]
)
}
}
}
}
}
}