Dynamic UI mode menu icon.

res/drawable/ic_baseline_night_mode_24.xml

@@ -0,0 +1,13 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="?android:colorControlNormal">
+  <path
+      android:fillColor="#FF000000"
+      android:strokeColor="#FF000000"
+      android:pathData="m11.6367,2.0156c-5.3859,0.1852 -9.6563,4.6051 -9.6563,9.9941 0,5.5228 4.4772,10 10,10 3.3578,-0.0007 6.4911,-1.6866 8.3418,-4.4883C12.136,17.7514 7.2211,8.8651 11.6367,2.0156Z"
+      android:strokeWidth="1.5"
+      android:strokeLineCap="round"/>
+</vector>

res/drawable/ic_baseline_palette_24.xml

@@ -1,10 +0,0 @@
-<vector xmlns:android="http://schemas.android.com/apk/res/android"
-    android:width="24dp"
-    android:height="24dp"
-    android:viewportWidth="24"
-    android:viewportHeight="24"
-    android:tint="?attr/colorControlNormal">
-  <path
-      android:fillColor="@android:color/white"
-      android:pathData="M12,3c-4.97,0 -9,4.03 -9,9s4.03,9 9,9c0.83,0 1.5,-0.67 1.5,-1.5 0,-0.39 -0.15,-0.74 -0.39,-1.01 -0.23,-0.26 -0.38,-0.61 -0.38,-0.99 0,-0.83 0.67,-1.5 1.5,-1.5L16,16c2.76,0 5,-2.24 5,-5 0,-4.42 -4.03,-8 -9,-8zM6.5,12c-0.83,0 -1.5,-0.67 -1.5,-1.5S5.67,9 6.5,9 8,9.67 8,10.5 7.33,12 6.5,12zM9.5,8C8.67,8 8,7.33 8,6.5S8.67,5 9.5,5s1.5,0.67 1.5,1.5S10.33,8 9.5,8zM14.5,8c-0.83,0 -1.5,-0.67 -1.5,-1.5S13.67,5 14.5,5s1.5,0.67 1.5,1.5S15.33,8 14.5,8zM17.5,12c-0.83,0 -1.5,-0.67 -1.5,-1.5S16.67,9 17.5,9s1.5,0.67 1.5,1.5 -0.67,1.5 -1.5,1.5z"/>
-</vector>

res/drawable/ic_outline_night_mode_24.xml

@@ -0,0 +1,12 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="?android:colorControlNormal">
+  <path
+      android:strokeColor="#FF000000"
+      android:strokeWidth="1.5"
+      android:pathData="m11.6367,2.0156c-5.3859,0.1852 -9.6563,4.6051 -9.6563,9.9941 0,5.5228 4.4772,10 10,10 3.3578,-0.0007 6.4911,-1.6866 8.3418,-4.4883C12.136,17.7514 7.2211,8.8651 11.6367,2.0156Z"
+      android:strokeLineCap="round"/>
+</vector>

res/drawable/ic_outline_night_mode_auto_24.xml

@@ -0,0 +1,15 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="?android:colorControlNormal">
+  <path
+      android:fillColor="#FF000000"
+      android:pathData="M17,2L13.8008,11L15.6992,11L16.4004,9L19.5996,9L20.3008,11L22.1992,11L19,2L17,2zM18,4L19.1504,7.6504L16.8496,7.6504L18,4z"/>
+  <path
+      android:strokeColor="#FF000000"
+      android:strokeWidth="1.5"
+      android:pathData="m11.6367,2.0156c-5.3859,0.1852 -9.6563,4.6051 -9.6563,9.9941 0,5.5228 4.4772,10 10,10 3.3578,-0.0007 6.4911,-1.6866 8.3418,-4.4883C12.136,17.7514 7.2211,8.8651 11.6367,2.0156Z"
+      android:strokeLineCap="round"/>
+</vector>

res/drawable/ic_ui_mode_24.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<level-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:maxLevel="0" android:drawable="@drawable/ic_outline_night_mode_24"/>
+    <item android:maxLevel="1" android:drawable="@drawable/ic_baseline_night_mode_24"/>
+    <item android:maxLevel="2" android:drawable="@drawable/ic_outline_night_mode_auto_24"/>
+</level-list>

res/menu/settings_general.xml

@@ -6,7 +6,7 @@
     <item
         android:id="@+id/action_change_theme"
         android:title=""
-        android:icon="@drawable/ic_baseline_palette_24"
+        android:icon="@drawable/ic_ui_mode_24"
         app:showAsAction="always" />
 
     <item

src/org/thoughtcrime/securesms/loki/activities/SettingsActivity.kt

@@ -32,6 +32,7 @@ import org.thoughtcrime.securesms.database.DatabaseFactory
 import org.thoughtcrime.securesms.loki.dialogs.ChangeUiModeDialog
 import org.thoughtcrime.securesms.loki.dialogs.ClearAllDataDialog
 import org.thoughtcrime.securesms.loki.dialogs.SeedDialog
+import org.thoughtcrime.securesms.loki.utilities.UiModeUtilities
 import org.thoughtcrime.securesms.loki.utilities.fadeIn
 import org.thoughtcrime.securesms.loki.utilities.fadeOut
 import org.thoughtcrime.securesms.loki.utilities.push
@@ -102,6 +103,12 @@ class SettingsActivity : PassphraseRequiredActionBarActivity() {
 
     override fun onCreateOptionsMenu(menu: Menu): Boolean {
         menuInflater.inflate(R.menu.settings_general, menu)
+
+        // Update UI mode menu icon.
+        // It uses three-level selector where each level corresponds to the related UiMode ordinal value.
+        val uiMode = UiModeUtilities.getUserSelectedUiMode(this)
+        menu.findItem(R.id.action_change_theme).icon!!.level = uiMode.ordinal
+
         return true
     }