Add support for getting the device's safe area insets.

redwood-layout-api/src/commonMain/kotlin/app/cash/redwood/layout/api/properties.kt

@@ -146,3 +146,17 @@ public fun Margin(
 public fun Margin(
   all: Int = 0,
 ): Margin = Margin(all, all, all, all)
+
+// Temporary constructor before migrating everything to doubles.
+@Stable
+public fun Margin(
+  left: Double = 0.0,
+  right: Double = 0.0,
+  top: Double = 0.0,
+  bottom: Double = 0.0,
+): Margin = Margin(
+  left = left.toInt(),
+  right = right.toInt(),
+  top = top.toInt(),
+  bottom = bottom.toInt(),
+)

redwood-treehouse-composeui-insets/build.gradle

@@ -0,0 +1,35 @@
+import app.cash.redwood.buildsupport.KmpTargets
+
+apply plugin: 'com.android.library'
+apply plugin: 'org.jetbrains.kotlin.multiplatform'
+apply plugin: 'app.cash.redwood.build.compose'
+apply plugin: 'com.vanniktech.maven.publish'
+apply plugin: 'org.jetbrains.dokka' // Must be applied here for publish plugin.
+
+kotlin {
+  android {
+    publishLibraryVariants('release')
+  }
+
+  KmpTargets.addAllTargets(project, true /* skipJs */)
+
+  sourceSets {
+    commonMain {
+      dependencies {
+        api projects.redwoodTreehouse
+        api projects.redwoodTreehouseHost
+        implementation libs.jetbrains.compose.foundation
+        implementation projects.redwoodWidgetCompose
+      }
+    }
+    androidMain {
+      dependencies {
+        implementation libs.androidx.core
+      }
+    }
+  }
+}
+
+android {
+  namespace 'app.cash.treehouse.composeui'
+}

redwood-treehouse-composeui-insets/gradle.properties

@@ -0,0 +1,2 @@
+POM_ARTIFACT_ID=redwood-treehouse-composeui-insets
+POM_NAME=Redwood Treehouse Compose UI Insets

redwood-treehouse-composeui-insets/src/androidMain/kotlin/app/cash/redwood/treehouse/composeui/insets.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2023 Square, Inc.
+ *
+ * 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.
+ */
+@file:JvmName("insetsAndroid")
+
+package app.cash.redwood.treehouse.composeui
+
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.WindowInsets
+import androidx.compose.foundation.layout.asPaddingValues
+import androidx.compose.foundation.layout.systemBars
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.platform.LocalLayoutDirection
+import androidx.compose.ui.unit.LayoutDirection
+import app.cash.redwood.layout.api.Margin
+
+@Composable
+public actual fun safeAreaInsets(): Margin {
+  val layoutDirection = LocalLayoutDirection.current
+  return WindowInsets.systemBars.asPaddingValues().toMargin(layoutDirection)
+}
+
+@Composable
+private fun PaddingValues.toMargin(layoutDirection: LayoutDirection) = Margin(
+  left = calculateLeftPadding(layoutDirection).value.toDouble(),
+  right = calculateRightPadding(layoutDirection).value.toDouble(),
+  top = calculateTopPadding().value.toDouble(),
+  bottom = calculateBottomPadding().value.toDouble(),
+)

redwood-treehouse-composeui-insets/src/commonMain/kotlin/app/cash/redwood/treehouse/composeui/insets.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2023 Square, Inc.
+ *
+ * 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 app.cash.redwood.treehouse.composeui
+
+import androidx.compose.runtime.Composable
+import app.cash.redwood.layout.api.Margin
+
+/** Return the device's insets in screen density-independent pixels. */
+@Composable
+public expect fun safeAreaInsets(): Margin
+
+internal operator fun Margin.div(density: Double) = Margin(
+  left = left / density,
+  right = right / density,
+  top = top / density,
+  bottom = bottom / density,
+)

redwood-treehouse-composeui-insets/src/iosMain/kotlin/app/cash/redwood/treehouse/composeui/insets.kt

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2023 Square, Inc.
+ *
+ * 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 app.cash.redwood.treehouse.composeui
+
+import app.cash.redwood.layout.api.Margin
+import kotlinx.cinterop.useContents
+import platform.UIKit.UIApplication
+import platform.UIKit.safeAreaInsets
+
+public actual fun safeAreaInsets(): Margin {
+  val keyWindow = UIApplication.sharedApplication.keyWindow ?: return Margin.Zero
+  return keyWindow.safeAreaInsets.useContents { Margin(left, right, top, bottom) }
+}

redwood-treehouse-composeui-insets/src/jvmMain/kotlin/app/cash/redwood/treehouse/composeui/insets.kt

@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2023 Square, Inc.
+ *
+ * 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.
+ */
+@file:JvmName("insetsJvm")
+
+package app.cash.redwood.treehouse.composeui
+
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.platform.LocalDensity
+import app.cash.redwood.layout.api.Margin
+import java.awt.GraphicsEnvironment
+import java.awt.Insets
+import java.awt.Toolkit
+
+@Composable
+public actual fun safeAreaInsets(): Margin {
+  val configuration = GraphicsEnvironment.getLocalGraphicsEnvironment()
+    .defaultScreenDevice.defaultConfiguration
+  val rawSpacing = Toolkit.getDefaultToolkit().getScreenInsets(configuration).toMargin()
+  return rawSpacing / LocalDensity.current.density.toDouble()
+}
+
+private fun Insets.toMargin() = Margin(
+  left = left.toDouble(),
+  right = right.toDouble(),
+  top = top.toDouble(),
+  bottom = bottom.toDouble(),
+)

redwood-treehouse-composeui-insets/src/macosMain/kotlin/app/cash/redwood/treehouse/composeui/insets.kt

@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2023 Square, Inc.
+ *
+ * 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 app.cash.redwood.treehouse.composeui
+
+import app.cash.redwood.layout.api.Margin
+import kotlinx.cinterop.useContents
+import platform.AppKit.NSScreen
+
+public actual fun safeAreaInsets(): Margin {
+  val mainScreen = NSScreen.mainScreen ?: return Margin.Zero
+  return mainScreen.safeAreaInsets.useContents { Margin(left, right, top, bottom) }
+}

redwood-treehouse-composeui/build.gradle

@@ -1,3 +1,5 @@
+import app.cash.redwood.buildsupport.KmpTargets
+
 apply plugin: 'com.android.library'
 apply plugin: 'org.jetbrains.kotlin.multiplatform'
 apply plugin: 'app.cash.redwood.build.compose'
@@ -9,14 +11,7 @@ kotlin {
     publishLibraryVariants('release')
   }
 
-  iosArm64()
-  iosX64()
-  iosSimulatorArm64()
-
-  jvm()
-
-  macosArm64()
-  macosX64()
+  KmpTargets.addAllTargets(project, true /* skipJs */)
 
   sourceSets {
     commonMain {
@@ -25,6 +20,7 @@ kotlin {
         api projects.redwoodTreehouseHost
         implementation libs.jetbrains.compose.foundation
         implementation projects.redwoodWidgetCompose
+        implementation projects.redwoodTreehouseComposeuiInsets
       }
     }
   }

redwood-treehouse-composeui/src/commonMain/kotlin/app/cash/redwood/treehouse/composeui/TreehouseContent.kt

@@ -42,6 +42,7 @@ public fun <A : AppService> TreehouseContent(
 ) {
   val hostConfiguration = HostConfiguration(
     darkMode = isSystemInDarkTheme(),
+    safeAreaInsets = safeAreaInsets(),
   )
 
   val treehouseView = remember(widgetSystem) {

redwood-treehouse-configuration/build.gradle

@@ -11,6 +11,7 @@ kotlin {
   sourceSets {
     commonMain {
       dependencies {
+        api projects.redwoodLayoutApi
         api libs.kotlinx.serialization.core
       }
     }

redwood-treehouse-configuration/src/commonMain/kotlin/app/cash/redwood/treehouse/HostConfiguration.kt

@@ -15,11 +15,13 @@
  */
 package app.cash.redwood.treehouse
 
+import app.cash.redwood.layout.api.Margin
 import kotlinx.serialization.Serializable
 
 @Serializable
 public data class HostConfiguration(
   val darkMode: Boolean = false,
+  val safeAreaInsets: Margin = Margin.Zero,
 ) {
   public companion object
 }

redwood-treehouse-host/build.gradle

@@ -27,6 +27,7 @@ kotlin {
     androidMain {
       dependencies {
         api libs.okHttp
+        implementation libs.androidx.core
       }
     }
 

redwood-treehouse-host/src/androidInstrumentedTest/kotlin/app/cash/redwood/treehouse/TreehouseWidgetViewTest.kt

@@ -21,7 +21,11 @@ import android.content.res.Configuration.UI_MODE_NIGHT_MASK
 import android.content.res.Configuration.UI_MODE_NIGHT_YES
 import android.view.View
 import android.view.ViewGroup
+import androidx.core.graphics.Insets
+import androidx.core.view.ViewCompat
+import androidx.core.view.WindowInsetsCompat
 import app.cash.redwood.LayoutModifier
+import app.cash.redwood.layout.api.Margin
 import app.cash.redwood.treehouse.TreehouseView.WidgetSystem
 import app.cash.redwood.widget.ViewGroupChildren
 import app.cash.redwood.widget.Widget
@@ -113,6 +117,26 @@ class TreehouseWidgetViewTest {
     }
   }
 
+  @Test fun hostConfigurationEmitsSafeAreaInsetsChanges() = runTest {
+    val layout = TreehouseWidgetView(context, throwingWidgetSystem)
+    layout.hostConfiguration.test {
+      assertEquals(HostConfiguration(safeAreaInsets = Margin.Zero), awaitItem())
+      val insets = Insets.of(10, 20, 30, 40)
+      val windowInsets = WindowInsetsCompat.Builder()
+        .setInsets(WindowInsetsCompat.Type.systemBars(), insets)
+        .build()
+      ViewCompat.dispatchApplyWindowInsets(layout, windowInsets)
+      val density = context.resources.displayMetrics.density.toDouble()
+      val expectedInsets = Margin(
+        left = density * insets.left,
+        right = density * insets.right,
+        top = density * insets.top,
+        bottom = density * insets.bottom,
+      )
+      assertEquals(HostConfiguration(safeAreaInsets = expectedInsets), awaitItem())
+    }
+  }
+
   private fun viewWidget(view: View) = object : Widget<View> {
     override val value: View get() = view
     override var layoutModifiers: LayoutModifier = LayoutModifier

redwood-treehouse-host/src/androidMain/kotlin/app/cash/redwood/treehouse/TreehouseWidgetView.kt

@@ -23,6 +23,7 @@ import android.content.res.Configuration.UI_MODE_NIGHT_YES
 import android.view.View
 import android.view.ViewGroup.LayoutParams.MATCH_PARENT
 import android.widget.FrameLayout
+import androidx.core.graphics.Insets
 import app.cash.redwood.treehouse.TreehouseView.ReadyForContentChangeListener
 import app.cash.redwood.treehouse.TreehouseView.WidgetSystem
 import app.cash.redwood.widget.ViewGroupChildren
@@ -51,12 +52,17 @@ public class TreehouseWidgetView(
   private val _children = ViewGroupChildren(this)
   override val children: Widget.Children<View> get() = _children
 
-  private val mutableHostConfiguration =
-    MutableStateFlow(computeHostConfiguration(context.resources.configuration))
+  private val mutableHostConfiguration = MutableStateFlow(computeHostConfiguration())
 
   override val hostConfiguration: StateFlow<HostConfiguration>
     get() = mutableHostConfiguration
 
+  init {
+    setOnWindowInsetsChangeListener { insets ->
+      mutableHostConfiguration.value = computeHostConfiguration(insets = insets.systemBars)
+    }
+  }
+
   override fun reset() {
     _children.remove(0, _children.widgets.size)
 
@@ -78,17 +84,19 @@ public class TreehouseWidgetView(
 
   override fun onConfigurationChanged(newConfig: Configuration) {
     super.onConfigurationChanged(newConfig)
-    mutableHostConfiguration.value = computeHostConfiguration(newConfig)
+    mutableHostConfiguration.value = computeHostConfiguration(config = newConfig)
   }
 
   override fun generateDefaultLayoutParams(): LayoutParams =
     LayoutParams(MATCH_PARENT, MATCH_PARENT)
-}
 
-private fun computeHostConfiguration(
-  config: Configuration,
-): HostConfiguration {
-  return HostConfiguration(
-    darkMode = (config.uiMode and UI_MODE_NIGHT_MASK) == UI_MODE_NIGHT_YES,
-  )
+  private fun computeHostConfiguration(
+    config: Configuration = context.resources.configuration,
+    insets: Insets = rootWindowInsetsCompat.systemBars,
+  ): HostConfiguration {
+    return HostConfiguration(
+      darkMode = (config.uiMode and UI_MODE_NIGHT_MASK) == UI_MODE_NIGHT_YES,
+      safeAreaInsets = insets.toMargin(resources.displayMetrics.density.toDouble()),
+    )
+  }
 }