Add custom modifier snippets (#169)

* Add custom modifier snippets

* Apply Spotless

compose/snippets/src/main/java/com/example/compose/snippets/modifiers/CustomModifierSnippets.kt

@@ -0,0 +1,351 @@
+/*
+ * Copyright 2023 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
+ *
+ *     https://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.example.compose.snippets.modifiers
+
+import android.annotation.SuppressLint
+import androidx.compose.animation.core.Animatable
+import androidx.compose.animation.core.DecayAnimationSpec
+import androidx.compose.animation.core.RepeatMode
+import androidx.compose.animation.core.animateFloatAsState
+import androidx.compose.animation.core.infiniteRepeatable
+import androidx.compose.animation.core.tween
+import androidx.compose.animation.splineBasedDecay
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.LocalContentColor
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.Shape
+import androidx.compose.ui.graphics.drawscope.ContentDrawScope
+import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.layout.Measurable
+import androidx.compose.ui.layout.MeasureResult
+import androidx.compose.ui.layout.MeasureScope
+import androidx.compose.ui.node.CompositionLocalConsumerModifierNode
+import androidx.compose.ui.node.DelegatableNode
+import androidx.compose.ui.node.DelegatingNode
+import androidx.compose.ui.node.DrawModifierNode
+import androidx.compose.ui.node.LayoutModifierNode
+import androidx.compose.ui.node.ModifierNodeElement
+import androidx.compose.ui.node.ObserverModifierNode
+import androidx.compose.ui.node.currentValueOf
+import androidx.compose.ui.node.invalidateDraw
+import androidx.compose.ui.node.invalidateMeasurement
+import androidx.compose.ui.node.observeReads
+import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.unit.Constraints
+import androidx.compose.ui.unit.Density
+import androidx.compose.ui.unit.IntSize
+import androidx.compose.ui.unit.constrain
+import androidx.compose.ui.unit.constrainHeight
+import androidx.compose.ui.unit.constrainWidth
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.offset
+import kotlinx.coroutines.launch
+
+@SuppressLint("ModifierFactoryUnreferencedReceiver") // graphics layer does the reference
+// [START android_compose_custom_modifiers_1]
+fun Modifier.clip(shape: Shape) = graphicsLayer(shape = shape, clip = true)
+// [END android_compose_custom_modifiers_1]
+
+// [START android_compose_custom_modifiers_2]
+fun Modifier.myBackground(color: Color) = this then Modifier
+    .padding(16.dp)
+    .clip(RoundedCornerShape(8.dp))
+    .background(color)
+// [END android_compose_custom_modifiers_2]
+
+// [START android_compose_custom_modifiers_3]
+@Composable
+fun Modifier.fade(enable: Boolean): Modifier {
+    val alpha by animateFloatAsState(if (enable) 0.5f else 1.0f)
+    return this then Modifier.graphicsLayer { this.alpha = alpha }
+}
+// [END android_compose_custom_modifiers_3]
+
+// [START android_compose_custom_modifiers_4]
+@Composable
+fun Modifier.fadedBackground(): Modifier {
+    val color = LocalContentColor.current
+    return this then Modifier.background(color.copy(alpha = 0.5f))
+}
+// [END android_compose_custom_modifiers_4]
+
+private object CustomModifierSnippets5 {
+    // [START android_compose_custom_modifiers_5]
+    @Composable
+    fun Modifier.myBackground(): Modifier {
+        val color = LocalContentColor.current
+        return this then Modifier.background(color.copy(alpha = 0.5f))
+    }
+
+    @Composable
+    fun MyScreen() {
+        CompositionLocalProvider(LocalContentColor provides Color.Green) {
+            // Background modifier created with green background
+            val backgroundModifier = Modifier.myBackground()
+
+            // LocalContentColor updated to red
+            CompositionLocalProvider(LocalContentColor provides Color.Red) {
+
+                // Box will have green background, not red as expected.
+                Box(modifier = backgroundModifier)
+            }
+        }
+    }
+    // [END android_compose_custom_modifiers_5]
+}
+
+// [START android_compose_custom_modifiers_6]
+val extractedModifier = Modifier.background(Color.Red) // Hoisted to save allocations
+
+@Composable
+fun Modifier.composableModifier(): Modifier {
+    val color = LocalContentColor.current.copy(alpha = 0.5f)
+    return this then Modifier.background(color)
+}
+
+@Composable
+fun MyComposable() {
+    val composedModifier = Modifier.composableModifier() // Cannot be extracted any higher
+}
+// [END android_compose_custom_modifiers_6]
+
+// [START android_compose_custom_modifiers_7]
+// Modifier.Node
+private class CircleNode(var color: Color) : DrawModifierNode, Modifier.Node() {
+    override fun ContentDrawScope.draw() {
+        drawCircle(color)
+    }
+}
+// [END android_compose_custom_modifiers_7]
+
+// [START android_compose_custom_modifiers_8]
+// ModifierNodeElement
+private data class CircleElement(val color: Color) : ModifierNodeElement<CircleNode>() {
+    override fun create() = CircleNode(color)
+
+    override fun update(node: CircleNode) {
+        node.color = color
+    }
+}
+// [END android_compose_custom_modifiers_8]
+
+// [START android_compose_custom_modifiers_9]
+// Modifier factory
+fun Modifier.circle(color: Color) = this then CircleElement(color)
+// [END android_compose_custom_modifiers_9]
+
+private object CustomModifierSnippets10 {
+    // [START android_compose_custom_modifiers_10]
+    // Modifier factory
+    fun Modifier.circle(color: Color) = this then CircleElement(color)
+
+    // ModifierNodeElement
+    private data class CircleElement(val color: Color) : ModifierNodeElement<CircleNode>() {
+        override fun create() = CircleNode(color)
+
+        override fun update(node: CircleNode) {
+            node.color = color
+        }
+    }
+
+    // Modifier.Node
+    private class CircleNode(var color: Color) : DrawModifierNode, Modifier.Node() {
+        override fun ContentDrawScope.draw() {
+            drawCircle(color)
+        }
+    }
+    // [END android_compose_custom_modifiers_10]
+}
+
+// [START android_compose_custom_modifiers_11]
+fun Modifier.fixedPadding() = this then FixedPaddingElement
+
+data object FixedPaddingElement : ModifierNodeElement<FixedPaddingNode>() {
+    override fun create() = FixedPaddingNode()
+    override fun update(node: FixedPaddingNode) {}
+}
+
+class FixedPaddingNode : LayoutModifierNode, Modifier.Node() {
+    private val PADDING = 16.dp
+
+    override fun MeasureScope.measure(
+        measurable: Measurable,
+        constraints: Constraints
+    ): MeasureResult {
+        val paddingPx = PADDING.roundToPx()
+        val horizontal = paddingPx * 2
+        val vertical = paddingPx * 2
+
+        val placeable = measurable.measure(constraints.offset(-horizontal, -vertical))
+
+        val width = constraints.constrainWidth(placeable.width + horizontal)
+        val height = constraints.constrainHeight(placeable.height + vertical)
+        return layout(width, height) {
+            placeable.place(paddingPx, paddingPx)
+        }
+    }
+}
+// [END android_compose_custom_modifiers_11]
+
+// [START android_compose_custom_modifiers_12]
+class BackgroundColorConsumerNode :
+    Modifier.Node(),
+    DrawModifierNode,
+    CompositionLocalConsumerModifierNode {
+    override fun ContentDrawScope.draw() {
+        val currentColor = currentValueOf(LocalContentColor)
+        drawRect(color = currentColor)
+        drawContent()
+    }
+}
+// [END android_compose_custom_modifiers_12]
+
+private object UnityDensity : Density {
+    override val density: Float
+        get() = 1f
+    override val fontScale: Float
+        get() = 1f
+}
+data class DefaultFlingBehavior(var flingDecay: DecayAnimationSpec<Density>)
+// [START android_compose_custom_modifiers_13]
+class ScrollableNode :
+    Modifier.Node(),
+    ObserverModifierNode,
+    CompositionLocalConsumerModifierNode {
+
+    // Place holder fling behavior, we'll initialize it when the density is available.
+    val defaultFlingBehavior = DefaultFlingBehavior(splineBasedDecay(UnityDensity))
+
+    override fun onAttach() {
+        updateDefaultFlingBehavior()
+        observeReads { currentValueOf(LocalDensity) } // monitor change in Density
+    }
+
+    override fun onObservedReadsChanged() {
+        // if density changes, update the default fling behavior.
+        updateDefaultFlingBehavior()
+    }
+
+    private fun updateDefaultFlingBehavior() {
+        val density = currentValueOf(LocalDensity)
+        defaultFlingBehavior.flingDecay = splineBasedDecay(density)
+    }
+}
+// [END android_compose_custom_modifiers_13]
+
+object CustomModifierSnippets14 {
+    // [START android_compose_custom_modifiers_14]
+    class CircleNode(var color: Color) : Modifier.Node(), DrawModifierNode {
+        private val alpha = Animatable(1f)
+
+        override fun ContentDrawScope.draw() {
+            drawCircle(color = color, alpha = alpha.value)
+            drawContent()
+        }
+
+        override fun onAttach() {
+            coroutineScope.launch {
+                alpha.animateTo(
+                    0f,
+                    infiniteRepeatable(tween(1000), RepeatMode.Reverse)
+                ) {
+                }
+            }
+        }
+    }
+    // [END android_compose_custom_modifiers_14]
+}
+
+class InteractionData
+class FocusableNode(val interactionData: InteractionData) : DelegatableNode {
+    override val node: Modifier.Node
+        get() = TODO("Not yet implemented")
+}
+class IndicationNode(val interactionData: InteractionData) : DelegatableNode {
+    override val node: Modifier.Node
+        get() = TODO("Not yet implemented")
+}
+// [START android_compose_custom_modifiers_15]
+class ClickableNode : DelegatingNode() {
+    val interactionData = InteractionData()
+    val focusableNode = delegate(
+        FocusableNode(interactionData)
+    )
+    val indicationNode = delegate(
+        IndicationNode(interactionData)
+    )
+}
+// [END android_compose_custom_modifiers_15]
+
+class ClickablePointerInputNode(var onClick: () -> Unit) : Modifier.Node(), DelegatableNode {
+    fun update(onClick: () -> Unit) {
+        this.onClick = onClick
+    }
+}
+// [START android_compose_custom_modifiers_16]
+class SampleInvalidatingNode(
+    var color: Color,
+    var size: IntSize,
+    var onClick: () -> Unit
+) : DelegatingNode(), LayoutModifierNode, DrawModifierNode {
+    override val shouldAutoInvalidate: Boolean
+        get() = false
+
+    private val clickableNode = delegate(
+        ClickablePointerInputNode(onClick)
+    )
+
+    fun update(color: Color, size: IntSize, onClick: () -> Unit) {
+        if (this.color != color) {
+            this.color = color
+            // Only invalidate draw when color changes
+            invalidateDraw()
+        }
+
+        if (this.size != size) {
+            this.size = size
+            // Only invalidate layout when size changes
+            invalidateMeasurement()
+        }
+
+        // If only onClick changes, we don't need to invalidate anything
+        clickableNode.update(onClick)
+    }
+
+    override fun ContentDrawScope.draw() {
+        drawRect(color)
+    }
+
+    override fun MeasureScope.measure(
+        measurable: Measurable,
+        constraints: Constraints
+    ): MeasureResult {
+        val size = constraints.constrain(size)
+        val placeable = measurable.measure(constraints)
+        return layout(size.width, size.height) {
+            placeable.place(0, 0)
+        }
+    }
+}
+// [END android_compose_custom_modifiers_16]

gradle/libs.versions.toml

@@ -21,14 +21,14 @@ androidxHiltNavigationCompose = "1.0.0"
 coil = "2.4.0"
 # @keep
 compileSdk = "34"
-compose-compiler = "1.4.7"
+compose-compiler = "1.5.4"
 coroutines = "1.7.3"
 google-maps = "18.2.0"
 gradle-versions = "0.49.0"
 hilt = "2.48.1"
 junit = "4.13.2"
 # @pin Update in conjuction with Compose Compiler
-kotlin = "1.8.21"
+kotlin = "1.9.20"
 ksp = "1.8.0-1.0.9"
 maps-compose = "3.1.1"
 material = "1.11.0-beta01"