New API, RedwoodLayout.additionalInsets

Consumers can use this to impose additional insets for system
bars and floating action buttons.

CHANGELOG.md

@@ -9,6 +9,7 @@ Breaking:
 
 New:
 - `UIConfiguration.viewInsets` tracks the safe area of the specific `RedwoodView` being targeted. This is currently implemented for views on Android and UIViews on iOS.
+- `RedwoodLayout.additionalInsets` configures additional insets for application controls like tab bars and floating action buttons.
 - `ConsumeInsets {}` composable consumes insets. Most applications should call this in their root composable function.
 
 Changed:

redwood-treehouse-host/src/androidUnitTest/kotlin/app/cash/redwood/treehouse/TreehouseLayoutTest.kt

@@ -121,6 +121,42 @@ class TreehouseLayoutTest {
     }
   }
 
+  @Test fun viewInsetsSumsSystemBarsAndAdditionalInsets() = runTest {
+    val layout = TreehouseLayout(activity, throwingWidgetSystem, activity.onBackPressedDispatcher)
+    layout.uiConfiguration.test {
+      assertThat(awaitItem().viewInsets).isEqualTo(Margin.Zero)
+
+      layout.additionalInsets = Insets.of(5, 6, 7, 8)
+      assertThat(awaitItem().viewInsets).isEqualTo(
+        with(Density(activity.resources)) {
+          Margin(
+            start = 5.toDp(),
+            top = 6.toDp(),
+            end = 7.toDp(),
+            bottom = 8.toDp(),
+          )
+        },
+      )
+
+      ViewCompat.dispatchApplyWindowInsets(
+        layout,
+        WindowInsetsCompat.Builder()
+          .setInsets(WindowInsetsCompat.Type.systemBars(), Insets.of(10, 20, 30, 40))
+          .build(),
+      )
+      assertThat(awaitItem().viewInsets).isEqualTo(
+        with(Density(activity.resources)) {
+          Margin(
+            start = 15.toDp(),
+            top = 26.toDp(),
+            end = 37.toDp(),
+            bottom = 48.toDp(),
+          )
+        },
+      )
+    }
+  }
+
   @Test fun uiConfigurationEmitsLayoutDirectionChanges() = runTest {
     val layout = TreehouseLayout(activity, throwingWidgetSystem, activity.onBackPressedDispatcher)
     layout.uiConfiguration.test {

redwood-widget/api/android/redwood-widget.api

@@ -50,6 +50,7 @@ public final class app/cash/redwood/widget/MutableListChildren : app/cash/redwoo
 
 public class app/cash/redwood/widget/RedwoodLayout : android/view/ViewGroup, app/cash/redwood/widget/RedwoodView {
 	public fun <init> (Landroid/content/Context;Landroidx/activity/OnBackPressedDispatcher;)V
+	public final fun getAdditionalInsets ()Landroidx/core/graphics/Insets;
 	public final fun getChildren ()Lapp/cash/redwood/widget/Widget$Children;
 	public fun getOnBackPressedDispatcher ()Lapp/cash/redwood/ui/OnBackPressedDispatcher;
 	public fun getSavedStateRegistry ()Lapp/cash/redwood/widget/SavedStateRegistry;
@@ -59,6 +60,7 @@ public class app/cash/redwood/widget/RedwoodLayout : android/view/ViewGroup, app
 	protected fun onConfigurationChanged (Landroid/content/res/Configuration;)V
 	protected fun onLayout (ZIIII)V
 	protected fun onMeasure (II)V
+	public final fun setAdditionalInsets (Landroidx/core/graphics/Insets;)V
 }
 
 public abstract interface class app/cash/redwood/widget/RedwoodView {

redwood-widget/src/androidMain/kotlin/app/cash/redwood/widget/RedwoodLayout.kt

@@ -22,6 +22,7 @@ import android.view.View
 import android.view.ViewGroup
 import androidx.activity.OnBackPressedCallback as AndroidOnBackPressedCallback
 import androidx.activity.OnBackPressedDispatcher as AndroidOnBackPressedDispatcher
+import androidx.core.graphics.Insets
 import androidx.core.view.children as viewGroupChildren
 import androidx.savedstate.findViewTreeSavedStateRegistryOwner
 import app.cash.redwood.ui.Cancellable
@@ -46,15 +47,27 @@ public open class RedwoodLayout(
   final override val value: View
     get() = this
 
-  init {
-    // The view needs to have an ID to participate in instance state saving.
-    id = R.id.redwood_layout
-  }
+  private var windowInsets: Insets = Insets.NONE
+    set(value) {
+      if (field == value) return
+      field = value
+      mutableUiConfiguration.value = computeUiConfiguration()
+    }
+
+  /**
+   * Additional insets that are summed with this view's window insets to produce
+   * [UiConfiguration.viewInsets]. Use this when an application-layer control like a floating action
+   * button or toolbar requires content to be inset.
+   */
+  public var additionalInsets: Insets = Insets.NONE
+    set(value) {
+      if (field == value) return
+      field = value
+      mutableUiConfiguration.value = computeUiConfiguration()
+    }
 
   private val mutableUiConfiguration = MutableStateFlow(
-    computeUiConfiguration(
-      viewInsets = Margin.Zero,
-    ),
+    computeUiConfiguration(),
   )
 
   override val onBackPressedDispatcher: RedwoodOnBackPressedDispatcher =
@@ -85,10 +98,11 @@ public open class RedwoodLayout(
     get() = mutableUiConfiguration
 
   init {
+    // The view needs to have an ID to participate in instance state saving.
+    id = R.id.redwood_layout
+
     setOnWindowInsetsChangeListener { insets ->
-      mutableUiConfiguration.value = computeUiConfiguration(
-        viewInsets = insets.safeDrawing.toMargin(Density(resources)),
-      )
+      windowInsets = insets.safeDrawing
     }
   }
 
@@ -118,13 +132,19 @@ public open class RedwoodLayout(
 
   private fun computeUiConfiguration(
     config: Configuration = context.resources.configuration,
-    viewInsets: Margin = uiConfiguration.value.viewInsets,
   ): UiConfiguration {
     val viewportSize: Size
     val density: Double
+    val viewInsets: Margin
     with(Density(resources)) {
       density = rawDensity
       viewportSize = Size(width.toDp(), height.toDp())
+      viewInsets = Margin(
+        start = (windowInsets.left + additionalInsets.left).toDp(),
+        end = (windowInsets.right + additionalInsets.right).toDp(),
+        top = (windowInsets.top + additionalInsets.top).toDp(),
+        bottom = (windowInsets.bottom + additionalInsets.bottom).toDp(),
+      )
     }
     return UiConfiguration(
       darkMode = (config.uiMode and Configuration.UI_MODE_NIGHT_MASK) == Configuration.UI_MODE_NIGHT_YES,