Merge "Introduce SizeMatcher" into main
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/modifiers/SizeMatcher.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/modifiers/SizeMatcher.kt
new file mode 100644
index 0000000..a4bd2be
--- /dev/null
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/modifiers/SizeMatcher.kt
@@ -0,0 +1,202 @@
+/*
+ * Copyright (C) 2024 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 com.android.compose.animation.scene.modifiers
+
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.layout.Measurable
+import androidx.compose.ui.layout.MeasureResult
+import androidx.compose.ui.layout.MeasureScope
+import androidx.compose.ui.node.LayoutModifierNode
+import androidx.compose.ui.node.ModifierNodeElement
+import androidx.compose.ui.node.invalidateMeasurement
+import androidx.compose.ui.unit.Constraints
+import androidx.compose.ui.unit.IntSize
+import androidx.compose.ui.unit.constrain
+
+/**
+ * An object to make one or more destination node be the same size as a source node.
+ *
+ * Important: Most of the time, you should not use this class and instead use `Box` together with
+ * `Modifier.matchParentSize()`. Use this only if you need to use both `Modifier.element()` and
+ * `Modifier.matchParentSize()` (see b/347910697 for details).
+ *
+ * Example:
+ * ```
+ * Box {
+ * val sizeMatcher = remember { SizeMatcher() }
+ *
+ * // The content.
+ * Content(Modifier.sizeMatcherSource(sizeMatcher))
+ *
+ * // The background. Note that this has to be composed after Content() so that it
+ * // is measured after it. We set its zIndex to -1 so that it is still placed
+ * // (drawn) before/below it. We don't use BoxScope.matchParentSize() because it
+ * // does not play well with Modifier.element().
+ * Box(
+ * Modifier.zIndex(-1f)
+ * .element(Background)
+ * // Set the preferred size of this element.
+ * // Important: This must be *after* the Modifier.element() so that
+ * // Modifier.element() can override the size.
+ * .sizeMatcherDestination(sizeMatcher)
+ * .background(
+ * MaterialTheme.colorScheme.primaryContainer,
+ * RoundedCornerShape(32.dp),
+ * )
+ * )
+ * }
+ * ```
+ *
+ * @see sizeMatcherSource
+ * @see sizeMatcherDestination
+ */
+class SizeMatcher {
+ internal var source: LayoutModifierNode? = null
+ set(value) {
+ if (value != null && field != null && value != field) {
+ error("Exactly one Modifier.sizeMatcherSource() should be specified")
+ }
+ }
+
+ internal var destinations = mutableSetOf<LayoutModifierNode>()
+ internal var sourceSize: IntSize = InvalidSize
+ get() {
+ if (field == InvalidSize) {
+ error(
+ "SizeMatcher size was retrieved before it was set. You should make sure that " +
+ "all matcher destination are measured *after* the matcher source."
+ )
+ }
+ return field
+ }
+ set(value) {
+ if (value != field) {
+ field = value
+ destinations.forEach { it.invalidateMeasurement() }
+ }
+ }
+
+ companion object {
+ private val InvalidSize = IntSize(Int.MIN_VALUE, Int.MIN_VALUE)
+ }
+}
+
+/**
+ * Mark this node as the source of a [SizeMatcher].
+ *
+ * Important: There must be only a single source node associated to a [SizeMatcher] and it must be
+ * measured before any destination.
+ */
+fun Modifier.sizeMatcherSource(matcher: SizeMatcher): Modifier {
+ return this.then(SizeMatcherSourceNodeElement(matcher))
+}
+
+/**
+ * Mark this node as the destination of a [SizeMatcher] so that its *preferred* size is the same
+ * size as the source size.
+ *
+ * Important: Destination nodes must be measured *after* the source node, otherwise it might cause
+ * crashes or 1-frame flickers. For most simple layouts (like Box, Row or Column), this usually
+ * means that the destinations nodes must be composed *after* the source node. If doing so is
+ * causing layering issues, you can use `Modifier.zIndex` to explicitly set the placement order of
+ * your composables.
+ */
+fun Modifier.sizeMatcherDestination(matcher: SizeMatcher): Modifier {
+ return this.then(SizeMatcherDestinationElement(matcher))
+}
+
+private data class SizeMatcherSourceNodeElement(
+ private val matcher: SizeMatcher,
+) : ModifierNodeElement<SizeMatcherSourceNode>() {
+ override fun create(): SizeMatcherSourceNode = SizeMatcherSourceNode(matcher)
+
+ override fun update(node: SizeMatcherSourceNode) {
+ node.update(matcher)
+ }
+}
+
+private class SizeMatcherSourceNode(
+ private var matcher: SizeMatcher,
+) : Modifier.Node(), LayoutModifierNode {
+ override fun onAttach() {
+ matcher.source = this
+ }
+
+ override fun onDetach() {
+ matcher.source = null
+ }
+
+ fun update(matcher: SizeMatcher) {
+ val previous = this.matcher
+ this.matcher = matcher
+
+ previous.source = null
+ matcher.source = this
+ }
+
+ override fun MeasureScope.measure(
+ measurable: Measurable,
+ constraints: Constraints
+ ): MeasureResult {
+ return measurable.measure(constraints).run {
+ matcher.sourceSize = IntSize(width, height)
+ layout(width, height) { place(0, 0) }
+ }
+ }
+}
+
+private data class SizeMatcherDestinationElement(
+ private val matcher: SizeMatcher,
+) : ModifierNodeElement<SizeMatcherDestinationNode>() {
+ override fun create(): SizeMatcherDestinationNode = SizeMatcherDestinationNode(matcher)
+
+ override fun update(node: SizeMatcherDestinationNode) {
+ node.update(matcher)
+ }
+}
+
+private class SizeMatcherDestinationNode(
+ private var matcher: SizeMatcher,
+) : Modifier.Node(), LayoutModifierNode {
+ override fun onAttach() {
+ this.matcher.destinations.add(this)
+ }
+
+ override fun onDetach() {
+ this.matcher.destinations.remove(this)
+ }
+
+ fun update(matcher: SizeMatcher) {
+ val previous = this.matcher
+ this.matcher = matcher
+
+ previous.destinations.remove(this)
+ matcher.destinations.add(this)
+ }
+
+ override fun MeasureScope.measure(
+ measurable: Measurable,
+ constraints: Constraints
+ ): MeasureResult {
+ val preferredSize = matcher.sourceSize
+ val preferredConstraints = Constraints.fixed(preferredSize.width, preferredSize.height)
+
+ // Make sure we still respect the incoming constraints.
+ val placeable = measurable.measure(constraints.constrain(preferredConstraints))
+ return layout(placeable.width, placeable.height) { placeable.place(0, 0) }
+ }
+}
diff --git a/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/modifiers/SizeMatcherTest.kt b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/modifiers/SizeMatcherTest.kt
new file mode 100644
index 0000000..fa24966
--- /dev/null
+++ b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/modifiers/SizeMatcherTest.kt
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2024 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 com.android.compose.animation.scene.modifiers
+
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.size
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.testTag
+import androidx.compose.ui.test.junit4.createComposeRule
+import androidx.compose.ui.test.onNodeWithTag
+import androidx.compose.ui.unit.DpSize
+import androidx.compose.ui.unit.dp
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.android.compose.test.assertSizeIsEqualTo
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+class SizeMatcherTest {
+ @get:Rule val rule = createComposeRule()
+
+ @Test
+ fun sizeMatcher() {
+ val contentSize = DpSize(200.dp, 100.dp)
+ val sizeMatcher = SizeMatcher()
+ val backgroundTag = "background"
+
+ rule.setContent {
+ Box {
+ Box(Modifier.sizeMatcherSource(sizeMatcher).size(contentSize))
+ Box(Modifier.testTag(backgroundTag).sizeMatcherDestination(sizeMatcher))
+ }
+ }
+
+ rule.onNodeWithTag(backgroundTag).assertSizeIsEqualTo(contentSize.width, contentSize.height)
+ }
+}
