ui/ui-core/src/commonMain/kotlin/androidx/ui/core/LayoutModifier.kt - platform/frameworks/support - Git at Google

 /*
  * 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,yout
  * 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.ui.core

 import androidx.ui.unit.Density
 import androidx.ui.unit.IntOffset
 import androidx.ui.unit.IntSize

 /**
  * A [Modifier.Element] that changes how its wrapped content is measured and laid out.
  * It has the same measurement and layout functionality as the [androidx.ui.core.Layout]
  * component, while wrapping exactly one layout due to it being a modifier. In contrast,
  * the [androidx.ui.core.Layout] component is used to define the layout behavior of
  * multiple children.
  *
  * @see androidx.ui.core.Layout
  */
 interface LayoutModifier : Modifier.Element {
     /**
      * The function used to measure the modifier. The [measurable] corresponds to the
      * wrapped content, and it can be measured with the desired constraints according
      * to the logic of the [LayoutModifier]. The modifier needs to choose its own
      * size, which can depend on the size chosen by the wrapped content (the obtained
      * [Placeable]), if the wrapped content was measured. The size needs to be returned
      * as part of a [MeasureScope.MeasureResult], alongside the placement logic of the
      * [Placeable], which defines how the wrapped content should be positioned inside
      * the [LayoutModifier]. A convenient way to create the [MeasureScope.MeasureResult]
      * is to use the [MeasureScope.layout] factory function.
      */
     fun MeasureScope.measure(
         measurable: Measurable,
         constraints: Constraints,
         layoutDirection: LayoutDirection
     ): MeasureScope.MeasureResult

     /**
      * The function used to calculate [IntrinsicMeasurable.minIntrinsicWidth].
      */
     fun IntrinsicMeasureScope.minIntrinsicWidth(
         measurable: IntrinsicMeasurable,
         height: Int,
         layoutDirection: LayoutDirection
     ): Int = MeasuringIntrinsics.minWidth(
         this@LayoutModifier,
         this,
         measurable,
         height,
         layoutDirection
     )

     /**
      * The lambda used to calculate [IntrinsicMeasurable.minIntrinsicHeight].
      */
     fun IntrinsicMeasureScope.minIntrinsicHeight(
         measurable: IntrinsicMeasurable,
         width: Int,
         layoutDirection: LayoutDirection
     ): Int = MeasuringIntrinsics.minHeight(
         this@LayoutModifier,
         this,
         measurable,
         width,
         layoutDirection
     )

     /**
      * The function used to calculate [IntrinsicMeasurable.maxIntrinsicWidth].
      */
     fun IntrinsicMeasureScope.maxIntrinsicWidth(
         measurable: IntrinsicMeasurable,
         height: Int,
         layoutDirection: LayoutDirection
     ): Int = MeasuringIntrinsics.maxWidth(
         this@LayoutModifier,
         this,
         measurable,
         height,
         layoutDirection
     )

     /**
      * The lambda used to calculate [IntrinsicMeasurable.maxIntrinsicHeight].
      */
     fun IntrinsicMeasureScope.maxIntrinsicHeight(
         measurable: IntrinsicMeasurable,
         width: Int,
         layoutDirection: LayoutDirection
     ): Int = MeasuringIntrinsics.maxHeight(
         this@LayoutModifier,
         this,
         measurable,
         width,
         layoutDirection
     )
 }

 // TODO(popam): deduplicate from the copy-pasted logic of Layout.kt without making it public
 private object MeasuringIntrinsics {
     internal fun minWidth(
         modifier: LayoutModifier,
         density: Density,
         intrinsicMeasurable: IntrinsicMeasurable,
         h: Int,
         layoutDirection: LayoutDirection
     ): Int {
         val measurable = DefaultIntrinsicMeasurable(
             intrinsicMeasurable,
             IntrinsicMinMax.Min,
             IntrinsicWidthHeight.Width
         )
         val constraints = Constraints(maxHeight = h)
         val layoutResult = with(modifier) {
             val receiver = IntrinsicsMeasureScope(density, layoutDirection)
             receiver.measure(measurable, constraints, layoutDirection)
         }
         return layoutResult.width
     }

     internal fun minHeight(
         modifier: LayoutModifier,
         density: Density,
         intrinsicMeasurable: IntrinsicMeasurable,
         w: Int,
         layoutDirection: LayoutDirection
     ): Int {
         val measurable = DefaultIntrinsicMeasurable(
             intrinsicMeasurable,
             IntrinsicMinMax.Min,
             IntrinsicWidthHeight.Height
         )
         val constraints = Constraints(maxWidth = w)
         val layoutResult = with(modifier) {
             val receiver = IntrinsicsMeasureScope(density, layoutDirection)
             receiver.measure(measurable, constraints, layoutDirection)
         }
         return layoutResult.height
     }

     internal fun maxWidth(
         modifier: LayoutModifier,
         density: Density,
         intrinsicMeasurable: IntrinsicMeasurable,
         h: Int,
         layoutDirection: LayoutDirection
     ): Int {
         val measurable = DefaultIntrinsicMeasurable(
             intrinsicMeasurable,
             IntrinsicMinMax.Max,
             IntrinsicWidthHeight.Width
         )
         val constraints = Constraints(maxHeight = h)
         val layoutResult = with(modifier) {
             val receiver = IntrinsicsMeasureScope(density, layoutDirection)
             receiver.measure(measurable, constraints, layoutDirection)
         }
         return layoutResult.width
     }

     internal fun maxHeight(
         modifier: LayoutModifier,
         density: Density,
         intrinsicMeasurable: IntrinsicMeasurable,
         w: Int,
         layoutDirection: LayoutDirection
     ): Int {
         val measurable = DefaultIntrinsicMeasurable(
             intrinsicMeasurable,
             IntrinsicMinMax.Max,
             IntrinsicWidthHeight.Height
         )
         val constraints = Constraints(maxWidth = w)
         val layoutResult = with(modifier) {
             val receiver = IntrinsicsMeasureScope(density, layoutDirection)
             receiver.measure(measurable, constraints, layoutDirection)
         }
         return layoutResult.height
     }

     private class DefaultIntrinsicMeasurable(
         val measurable: IntrinsicMeasurable,
         val minMax: IntrinsicMinMax,
         val widthHeight: IntrinsicWidthHeight
     ) : Measurable {
         override val parentData: Any?
             get() = measurable.parentData

         override fun measure(
             constraints: Constraints,
             layoutDirection: LayoutDirection
         ): Placeable {
             if (widthHeight == IntrinsicWidthHeight.Width) {
                 val width = if (minMax == IntrinsicMinMax.Max) {
                     measurable.maxIntrinsicWidth(constraints.maxHeight, layoutDirection)
                 } else {
                     measurable.minIntrinsicWidth(constraints.maxHeight, layoutDirection)
                 }
                 return DummyPlaceable(width, constraints.maxHeight)
             }
             val height = if (minMax == IntrinsicMinMax.Max) {
                 measurable.maxIntrinsicHeight(constraints.maxWidth, layoutDirection)
             } else {
                 measurable.minIntrinsicHeight(constraints.maxWidth, layoutDirection)
             }
             return DummyPlaceable(constraints.maxWidth, height)
         }

         override fun minIntrinsicWidth(height: Int, layoutDirection: LayoutDirection): Int {
             return measurable.minIntrinsicWidth(height, layoutDirection)
         }

         override fun maxIntrinsicWidth(height: Int, layoutDirection: LayoutDirection): Int {
             return measurable.maxIntrinsicWidth(height, layoutDirection)
         }

         override fun minIntrinsicHeight(width: Int, layoutDirection: LayoutDirection): Int {
             return measurable.minIntrinsicHeight(width, layoutDirection)
         }

         override fun maxIntrinsicHeight(width: Int, layoutDirection: LayoutDirection): Int {
             return measurable.maxIntrinsicHeight(width, layoutDirection)
         }
     }

     private class IntrinsicsMeasureScope(
         density: Density,
         override val layoutDirection: LayoutDirection
     ) : MeasureScope(), Density by density

     private class DummyPlaceable(width: Int, height: Int) : Placeable() {
         init {
             measuredSize = IntSize(width, height)
         }
         override fun get(line: AlignmentLine): Int = AlignmentLine.Unspecified
         override fun place(position: IntOffset) { }
     }

     private enum class IntrinsicMinMax { Min, Max }
     private enum class IntrinsicWidthHeight { Width, Height }
 }
	/*
	* 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,yout
	* 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.ui.core

	import androidx.ui.unit.Density
	import androidx.ui.unit.IntOffset
	import androidx.ui.unit.IntSize

	/**
	* A [Modifier.Element] that changes how its wrapped content is measured and laid out.
	* It has the same measurement and layout functionality as the [androidx.ui.core.Layout]
	* component, while wrapping exactly one layout due to it being a modifier. In contrast,
	* the [androidx.ui.core.Layout] component is used to define the layout behavior of
	* multiple children.
	*
	* @see androidx.ui.core.Layout
	*/
	interface LayoutModifier : Modifier.Element {
	/**
	* The function used to measure the modifier. The [measurable] corresponds to the
	* wrapped content, and it can be measured with the desired constraints according
	* to the logic of the [LayoutModifier]. The modifier needs to choose its own
	* size, which can depend on the size chosen by the wrapped content (the obtained
	* [Placeable]), if the wrapped content was measured. The size needs to be returned
	* as part of a [MeasureScope.MeasureResult], alongside the placement logic of the
	* [Placeable], which defines how the wrapped content should be positioned inside
	* the [LayoutModifier]. A convenient way to create the [MeasureScope.MeasureResult]
	* is to use the [MeasureScope.layout] factory function.
	*/
	fun MeasureScope.measure(
	measurable: Measurable,
	constraints: Constraints,
	layoutDirection: LayoutDirection
	): MeasureScope.MeasureResult

	/**
	* The function used to calculate [IntrinsicMeasurable.minIntrinsicWidth].
	*/
	fun IntrinsicMeasureScope.minIntrinsicWidth(
	measurable: IntrinsicMeasurable,
	height: Int,
	layoutDirection: LayoutDirection
	): Int = MeasuringIntrinsics.minWidth(
	this@LayoutModifier,
	this,
	measurable,
	height,
	layoutDirection
	)

	/**
	* The lambda used to calculate [IntrinsicMeasurable.minIntrinsicHeight].
	*/
	fun IntrinsicMeasureScope.minIntrinsicHeight(
	measurable: IntrinsicMeasurable,
	width: Int,
	layoutDirection: LayoutDirection
	): Int = MeasuringIntrinsics.minHeight(
	this@LayoutModifier,
	this,
	measurable,
	width,
	layoutDirection
	)

	/**
	* The function used to calculate [IntrinsicMeasurable.maxIntrinsicWidth].
	*/
	fun IntrinsicMeasureScope.maxIntrinsicWidth(
	measurable: IntrinsicMeasurable,
	height: Int,
	layoutDirection: LayoutDirection
	): Int = MeasuringIntrinsics.maxWidth(
	this@LayoutModifier,
	this,
	measurable,
	height,
	layoutDirection
	)

	/**
	* The lambda used to calculate [IntrinsicMeasurable.maxIntrinsicHeight].
	*/
	fun IntrinsicMeasureScope.maxIntrinsicHeight(
	measurable: IntrinsicMeasurable,
	width: Int,
	layoutDirection: LayoutDirection
	): Int = MeasuringIntrinsics.maxHeight(
	this@LayoutModifier,
	this,
	measurable,
	width,
	layoutDirection
	)
	}

	// TODO(popam): deduplicate from the copy-pasted logic of Layout.kt without making it public
	private object MeasuringIntrinsics {
	internal fun minWidth(
	modifier: LayoutModifier,
	density: Density,
	intrinsicMeasurable: IntrinsicMeasurable,
	h: Int,
	layoutDirection: LayoutDirection
	): Int {
	val measurable = DefaultIntrinsicMeasurable(
	intrinsicMeasurable,
	IntrinsicMinMax.Min,
	IntrinsicWidthHeight.Width
	)
	val constraints = Constraints(maxHeight = h)
	val layoutResult = with(modifier) {
	val receiver = IntrinsicsMeasureScope(density, layoutDirection)
	receiver.measure(measurable, constraints, layoutDirection)
	}
	return layoutResult.width
	}

	internal fun minHeight(
	modifier: LayoutModifier,
	density: Density,
	intrinsicMeasurable: IntrinsicMeasurable,
	w: Int,
	layoutDirection: LayoutDirection
	): Int {
	val measurable = DefaultIntrinsicMeasurable(
	intrinsicMeasurable,
	IntrinsicMinMax.Min,
	IntrinsicWidthHeight.Height
	)
	val constraints = Constraints(maxWidth = w)
	val layoutResult = with(modifier) {
	val receiver = IntrinsicsMeasureScope(density, layoutDirection)
	receiver.measure(measurable, constraints, layoutDirection)
	}
	return layoutResult.height
	}

	internal fun maxWidth(
	modifier: LayoutModifier,
	density: Density,
	intrinsicMeasurable: IntrinsicMeasurable,
	h: Int,
	layoutDirection: LayoutDirection
	): Int {
	val measurable = DefaultIntrinsicMeasurable(
	intrinsicMeasurable,
	IntrinsicMinMax.Max,
	IntrinsicWidthHeight.Width
	)
	val constraints = Constraints(maxHeight = h)
	val layoutResult = with(modifier) {
	val receiver = IntrinsicsMeasureScope(density, layoutDirection)
	receiver.measure(measurable, constraints, layoutDirection)
	}
	return layoutResult.width
	}

	internal fun maxHeight(
	modifier: LayoutModifier,
	density: Density,
	intrinsicMeasurable: IntrinsicMeasurable,
	w: Int,
	layoutDirection: LayoutDirection
	): Int {
	val measurable = DefaultIntrinsicMeasurable(
	intrinsicMeasurable,
	IntrinsicMinMax.Max,
	IntrinsicWidthHeight.Height
	)
	val constraints = Constraints(maxWidth = w)
	val layoutResult = with(modifier) {
	val receiver = IntrinsicsMeasureScope(density, layoutDirection)
	receiver.measure(measurable, constraints, layoutDirection)
	}
	return layoutResult.height
	}

	private class DefaultIntrinsicMeasurable(
	val measurable: IntrinsicMeasurable,
	val minMax: IntrinsicMinMax,
	val widthHeight: IntrinsicWidthHeight
	) : Measurable {
	override val parentData: Any?
	get() = measurable.parentData

	override fun measure(
	constraints: Constraints,
	layoutDirection: LayoutDirection
	): Placeable {
	if (widthHeight == IntrinsicWidthHeight.Width) {
	val width = if (minMax == IntrinsicMinMax.Max) {
	measurable.maxIntrinsicWidth(constraints.maxHeight, layoutDirection)
	} else {
	measurable.minIntrinsicWidth(constraints.maxHeight, layoutDirection)
	}
	return DummyPlaceable(width, constraints.maxHeight)
	}
	val height = if (minMax == IntrinsicMinMax.Max) {
	measurable.maxIntrinsicHeight(constraints.maxWidth, layoutDirection)
	} else {
	measurable.minIntrinsicHeight(constraints.maxWidth, layoutDirection)
	}
	return DummyPlaceable(constraints.maxWidth, height)
	}

	override fun minIntrinsicWidth(height: Int, layoutDirection: LayoutDirection): Int {
	return measurable.minIntrinsicWidth(height, layoutDirection)
	}

	override fun maxIntrinsicWidth(height: Int, layoutDirection: LayoutDirection): Int {
	return measurable.maxIntrinsicWidth(height, layoutDirection)
	}

	override fun minIntrinsicHeight(width: Int, layoutDirection: LayoutDirection): Int {
	return measurable.minIntrinsicHeight(width, layoutDirection)
	}

	override fun maxIntrinsicHeight(width: Int, layoutDirection: LayoutDirection): Int {
	return measurable.maxIntrinsicHeight(width, layoutDirection)
	}
	}

	private class IntrinsicsMeasureScope(
	density: Density,
	override val layoutDirection: LayoutDirection
	) : MeasureScope(), Density by density

	private class DummyPlaceable(width: Int, height: Int) : Placeable() {
	init {
	measuredSize = IntSize(width, height)
	}
	override fun get(line: AlignmentLine): Int = AlignmentLine.Unspecified
	override fun place(position: IntOffset) { }
	}

	private enum class IntrinsicMinMax { Min, Max }
	private enum class IntrinsicWidthHeight { Width, Height }
	}