Merge pull request #7453 from hayaksi1/fix/4639-system-theme

Apply the system theme when switching back to it from a forced light or dark theme

libraries/compound/src/main/kotlin/io/element/android/compound/theme/Theme.kt

@@ -8,8 +8,11 @@
 
 package io.element.android.compound.theme
 
-import androidx.compose.foundation.isSystemInDarkTheme
+import android.content.res.Configuration
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.platform.LocalConfiguration
+import androidx.compose.ui.platform.LocalContext
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.map
 
@@ -27,12 +30,28 @@ private fun Theme.coerceBlackTheme(allowBlackTheme: Boolean): Theme {
 @Composable
 fun Theme.isDark(): Boolean {
     return when (this) {
-        Theme.System -> isSystemInDarkTheme()
+        Theme.System -> isSystemThemeDark()
         Theme.Dark, Theme.Black -> true
         Theme.Light -> false
     }
 }
 
+/**
+ * Whether the system-wide theme is dark.
+ *
+ * This deliberately does not use [androidx.compose.foundation.isSystemInDarkTheme], which reads the activity configuration: `AppCompatDelegate` rewrites
+ * that configuration whenever a non-system theme is selected, so it keeps reporting the previously forced value. The application configuration is left
+ * untouched by AppCompat and is what AppCompat itself reads to expand `MODE_NIGHT_FOLLOW_SYSTEM`.
+ */
+@Composable
+private fun isSystemThemeDark(): Boolean {
+    val applicationContext = LocalContext.current.applicationContext
+    val activityConfiguration = LocalConfiguration.current
+    return remember(activityConfiguration) {
+        applicationContext.resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_MASK == Configuration.UI_MODE_NIGHT_YES
+    }
+}
+
 fun Flow<String?>.mapToTheme(allowBlackTheme: Boolean): Flow<Theme> = map {
     when (it) {
         null -> Theme.System

libraries/compound/src/test/kotlin/io/element/android/compound/theme/ThemeTest.kt

@@ -11,19 +11,22 @@ package io.element.android.compound.theme
 import android.content.res.Configuration
 import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.ui.platform.LocalConfiguration
+import androidx.compose.ui.platform.LocalContext
 import app.cash.molecule.RecompositionMode
 import app.cash.molecule.moleculeFlow
 import app.cash.turbine.test
 import com.google.common.truth.Truth.assertThat
+import io.element.android.tests.testutils.robolectric.RobolectricTest
 import kotlinx.coroutines.flow.flowOf
 import kotlinx.coroutines.test.runTest
 import org.junit.Test
+import org.robolectric.RuntimeEnvironment
 
-class ThemeTest {
+class ThemeTest : RobolectricTest() {
     @Test
     fun `isDark for System dark returns true`() {
         `isDark for System`(
-            uiMode = Configuration.UI_MODE_NIGHT_YES,
+            systemUiMode = Configuration.UI_MODE_NIGHT_YES,
             expected = true,
         )
     }
@@ -31,21 +34,38 @@ class ThemeTest {
     @Test
     fun `isDark for System light return false`() {
         `isDark for System`(
-            uiMode = Configuration.UI_MODE_NIGHT_NO,
+            systemUiMode = Configuration.UI_MODE_NIGHT_NO,
             expected = false,
         )
     }
 
-    fun `isDark for System`(
-        uiMode: Int,
+    @Test
+    fun `isDark for System ignores the night mode AppCompat forced on the activity`() {
+        `isDark for System`(
+            systemUiMode = Configuration.UI_MODE_NIGHT_YES,
+            activityUiMode = Configuration.UI_MODE_NIGHT_NO,
+            expected = true,
+        )
+        `isDark for System`(
+            systemUiMode = Configuration.UI_MODE_NIGHT_NO,
+            activityUiMode = Configuration.UI_MODE_NIGHT_YES,
+            expected = false,
+        )
+    }
+
+    private fun `isDark for System`(
+        systemUiMode: Int,
+        activityUiMode: Int = systemUiMode,
         expected: Boolean,
     ) = runTest {
+        val application = RuntimeEnvironment.getApplication()
+        application.resources.configuration.uiMode = systemUiMode
         moleculeFlow(RecompositionMode.Immediate) {
             var result: Boolean? = null
             CompositionLocalProvider(
-                // Let set the system to dark
+                LocalContext provides application,
                 LocalConfiguration provides Configuration().apply {
-                    this.uiMode = uiMode
+                    this.uiMode = activityUiMode
                 },
             ) {
                 result = Theme.System.isDark()