[SystemUiController] Add Window.isNavigationBarContrastEnforced APIs

systemuicontroller/api/systemuicontroller.api

@@ -1,24 +1,27 @@
 public final class com/google/accompanist/systemuicontroller/AndroidSystemUiController : com/google/accompanist/systemuicontroller/SystemUiController {
 	public static final field $stable I
 	public fun <init> (Landroid/view/View;)V
-	public fun setNavigationBarColor-ek8zF_U (JZLkotlin/jvm/functions/Function1;)V
+	public fun isNavigationBarContrastEnforced ()Z
+	public fun setNavigationBarColor-Iv8Zu3U (JZZLkotlin/jvm/functions/Function1;)V
 	public fun setStatusBarColor-ek8zF_U (JZLkotlin/jvm/functions/Function1;)V
-	public fun setSystemBarsColor-ek8zF_U (JZLkotlin/jvm/functions/Function1;)V
+	public fun setSystemBarsColor-Iv8Zu3U (JZZLkotlin/jvm/functions/Function1;)V
 }
 
 public abstract interface class com/google/accompanist/systemuicontroller/SystemUiController {
-	public abstract fun setNavigationBarColor-ek8zF_U (JZLkotlin/jvm/functions/Function1;)V
+	public abstract fun isNavigationBarContrastEnforced ()Z
+	public abstract fun setNavigationBarColor-Iv8Zu3U (JZZLkotlin/jvm/functions/Function1;)V
 	public abstract fun setStatusBarColor-ek8zF_U (JZLkotlin/jvm/functions/Function1;)V
-	public abstract fun setSystemBarsColor-ek8zF_U (JZLkotlin/jvm/functions/Function1;)V
+	public abstract fun setSystemBarsColor-Iv8Zu3U (JZZLkotlin/jvm/functions/Function1;)V
 }
 
 public final class com/google/accompanist/systemuicontroller/SystemUiController$DefaultImpls {
-	public static fun setNavigationBarColor-ek8zF_U (Lcom/google/accompanist/systemuicontroller/SystemUiController;JZLkotlin/jvm/functions/Function1;)V
-	public static synthetic fun setNavigationBarColor-ek8zF_U$default (Lcom/google/accompanist/systemuicontroller/SystemUiController;JZLkotlin/jvm/functions/Function1;ILjava/lang/Object;)V
+	public static fun isNavigationBarContrastEnforced (Lcom/google/accompanist/systemuicontroller/SystemUiController;)Z
+	public static fun setNavigationBarColor-Iv8Zu3U (Lcom/google/accompanist/systemuicontroller/SystemUiController;JZZLkotlin/jvm/functions/Function1;)V
+	public static synthetic fun setNavigationBarColor-Iv8Zu3U$default (Lcom/google/accompanist/systemuicontroller/SystemUiController;JZZLkotlin/jvm/functions/Function1;ILjava/lang/Object;)V
 	public static fun setStatusBarColor-ek8zF_U (Lcom/google/accompanist/systemuicontroller/SystemUiController;JZLkotlin/jvm/functions/Function1;)V
 	public static synthetic fun setStatusBarColor-ek8zF_U$default (Lcom/google/accompanist/systemuicontroller/SystemUiController;JZLkotlin/jvm/functions/Function1;ILjava/lang/Object;)V
-	public static fun setSystemBarsColor-ek8zF_U (Lcom/google/accompanist/systemuicontroller/SystemUiController;JZLkotlin/jvm/functions/Function1;)V
-	public static synthetic fun setSystemBarsColor-ek8zF_U$default (Lcom/google/accompanist/systemuicontroller/SystemUiController;JZLkotlin/jvm/functions/Function1;ILjava/lang/Object;)V
+	public static fun setSystemBarsColor-Iv8Zu3U (Lcom/google/accompanist/systemuicontroller/SystemUiController;JZZLkotlin/jvm/functions/Function1;)V
+	public static synthetic fun setSystemBarsColor-Iv8Zu3U$default (Lcom/google/accompanist/systemuicontroller/SystemUiController;JZZLkotlin/jvm/functions/Function1;ILjava/lang/Object;)V
 }
 
 public final class com/google/accompanist/systemuicontroller/SystemUiControllerKt {

systemuicontroller/src/androidTest/java/com/google/accompanist/systemuicontroller/SystemUiControllerTest.kt

@@ -183,6 +183,40 @@ class SystemUiControllerTest {
         val windowInsetsController = ViewCompat.getWindowInsetsController(view)!!
         assertThat(windowInsetsController.isAppearanceLightNavigationBars).isTrue()
     }
+
+    @Test
+    @UiThreadTest
+    @SdkSuppress(minSdkVersion = 29)
+    fun navigationBar_contrastEnforced() {
+        val view = composeTestRule.contentView
+        val window = composeTestRule.activity.window
+
+        // Now create an AndroidSystemUiController()
+        val controller = AndroidSystemUiController(view)
+
+        // Assert that the contrast is not enforced initially
+        assertThat(controller.isNavigationBarContrastEnforced()).isFalse()
+
+        // and set the navigation bar with dark icons and enforce contrast
+        controller.setNavigationBarColor(
+            Color.Transparent,
+            darkIcons = true,
+            navigationBarContrastEnforced = true
+        ) {
+            // Here we can provide custom logic to 'darken' the color to maintain contrast.
+            // We return red just to assert below.
+            Color.Red
+        }
+
+        // Assert that the colors were darkened color is not used
+        assertThat(Color(window.navigationBarColor)).isEqualTo(Color.Transparent)
+
+        // Assert that the system applied the contrast enforced property
+        assertThat(window.isNavigationBarContrastEnforced).isTrue()
+
+        // Assert that the controller reflects that the contrast is enforced
+        assertThat(controller.isNavigationBarContrastEnforced()).isTrue()
+    }
 }
 
 val AndroidComposeTestRule<*, *>.contentView

systemuicontroller/src/main/java/com/google/accompanist/systemuicontroller/SystemUiController.kt

@@ -19,6 +19,7 @@ package com.google.accompanist.systemuicontroller
 import android.app.Activity
 import android.content.Context
 import android.content.ContextWrapper
+import android.os.Build
 import android.view.View
 import android.view.Window
 import androidx.compose.runtime.Composable
@@ -63,12 +64,16 @@ interface SystemUiController {
      * and [Color.Transparent] will be used on API 29+ where gesture navigation is preferred or the
      * system UI automatically applies background protection in other navigation modes.
      * @param darkIcons Whether dark navigation bar icons would be preferable.
+     * @param navigationBarContrastEnforced Whether the system should ensure that the navigation
+     * bar has enough contrast when a fully transparent background is requested. Only supported on
+     * API 29+.
      * @param transformColorForLightContent A lambda which will be invoked to transform [color] if
      * dark icons were requested but are not available. Defaults to applying a black scrim.
      */
     fun setNavigationBarColor(
         color: Color,
         darkIcons: Boolean = color.luminance() > 0.5f,
+        navigationBarContrastEnforced: Boolean = true,
         transformColorForLightContent: (Color) -> Color = BlackScrimmed
     ) = Unit
 
@@ -81,11 +86,25 @@ interface SystemUiController {
     fun setSystemBarsColor(
         color: Color,
         darkIcons: Boolean = color.luminance() > 0.5f,
+        isNavigationBarContrastEnforced: Boolean = true,
         transformColorForLightContent: (Color) -> Color = BlackScrimmed
     ) {
         setStatusBarColor(color, darkIcons, transformColorForLightContent)
-        setNavigationBarColor(color, darkIcons, transformColorForLightContent)
+        setNavigationBarColor(
+            color,
+            darkIcons,
+            isNavigationBarContrastEnforced,
+            transformColorForLightContent
+        )
     }
+
+    /**
+     * Returns whether the system is ensuring that the navigation bar has enough contrast when a
+     * fully transparent background is requested.
+     *
+     * @return true, if API is 29+ and the system is ensuring contrast, false otherwise.
+     */
+    fun isNavigationBarContrastEnforced(): Boolean = false
 }
 
 /**
@@ -129,6 +148,7 @@ class AndroidSystemUiController(view: View) : SystemUiController {
     override fun setNavigationBarColor(
         color: Color,
         darkIcons: Boolean,
+        navigationBarContrastEnforced: Boolean,
         transformColorForLightContent: (Color) -> Color
     ) {
         windowInsetsController?.isAppearanceLightNavigationBars = darkIcons
@@ -142,6 +162,14 @@ class AndroidSystemUiController(view: View) : SystemUiController {
             }
             else -> color
         }.toArgb()
+
+        if (Build.VERSION.SDK_INT >= 29) {
+            window?.isNavigationBarContrastEnforced = navigationBarContrastEnforced
+        }
+    }
+
+    override fun isNavigationBarContrastEnforced(): Boolean {
+        return Build.VERSION.SDK_INT >= 29 && window?.isNavigationBarContrastEnforced == true
     }
 
     private fun Context.findWindow(): Window? {