Add support for embedding game process in the Android Editor

- Add support for using an Android Service to host the Godot engine
- Provide an abstract `GodotService` implementation which can be extended to build an Android Service that host an instance of the Godot engine
- Implement editor-specific `EmbeddedGameService` (extending from `GodotService`) to support embedding the game process in the Android editor
- Implement `EmbeddedGameFragment` to provide the view and logic to wrap `EmbeddedGameService`

doc/classes/DisplayServer.xml

@@ -1943,7 +1943,7 @@
 			Display server supports [constant WINDOW_FLAG_EXCLUDE_FROM_CAPTURE] window flag.
 		</constant>
 		<constant name="FEATURE_WINDOW_EMBEDDING" value="29" enum="Feature">
-			Display server supports embedding a window from another process. [b]Windows, Linux (X11)[/b]
+			Display server supports embedding a window from another process. [b]Android, Windows, Linux (X11)[/b]
 		</constant>
 		<constant name="FEATURE_NATIVE_DIALOG_FILE_MIME" value="30" enum="Feature">
 			Native file selection dialog supports MIME types as filters.

platform/android/java/editor/src/main/AndroidManifest.xml

@@ -71,6 +71,14 @@
                 android:defaultWidth="@dimen/editor_default_window_width"
                 android:defaultHeight="@dimen/editor_default_window_height" />
         </activity>
+
+        <service
+            android:name=".embed.EmbeddedGameService"
+            android:label="@string/godot_embedded_game_service_name"
+            android:process=":EmbeddedGame"
+            android:description="@string/godot_embedded_game_service_description"
+            android:exported="false"
+            android:icon="@mipmap/ic_play_window"/>
     </application>
 
 </manifest>

platform/android/java/editor/src/main/java/org/godotengine/editor/BaseGodotEditor.kt

@@ -45,6 +45,7 @@ import android.widget.Toast
 import androidx.annotation.CallSuper
 import androidx.core.splashscreen.SplashScreen.Companion.installSplashScreen
 import androidx.window.layout.WindowMetricsCalculator
+import org.godotengine.editor.embed.EmbeddedGameFragment
 import org.godotengine.editor.utils.signApk
 import org.godotengine.editor.utils.verifyApk
 import org.godotengine.godot.GodotActivity
@@ -119,6 +120,8 @@ abstract class BaseGodotEditor : GodotActivity() {
 	private val commandLineParams = ArrayList<String>()
 	private val editorLoadingIndicator: View? by lazy { findViewById(R.id.editor_loading_indicator) }
 
+	private var embeddedGameFragment: EmbeddedGameFragment? = null
+
 	override fun getGodotAppLayout() = R.layout.godot_editor_layout
 
 	internal open fun getEditorWindowInfo() = EDITOR_MAIN_INFO
@@ -169,6 +172,21 @@ abstract class BaseGodotEditor : GodotActivity() {
 		}
 
 		super.onCreate(savedInstanceState)
+
+		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
+			val embeddedFragment =
+				supportFragmentManager.findFragmentById(R.id.godot_embedded_game_container)
+			if (embeddedFragment is EmbeddedGameFragment) {
+				Log.v(TAG, "Reusing existing embedded game fragment instance.")
+				embeddedGameFragment = embeddedFragment
+			} else {
+				Log.v(TAG, "Creating new embedded game fragment instance.")
+				embeddedGameFragment = EmbeddedGameFragment()
+				supportFragmentManager.beginTransaction()
+					.replace(R.id.godot_embedded_game_container, embeddedGameFragment!!, EmbeddedGameFragment.TAG)
+					.commitNowAllowingStateLoss()
+			}
+		}
 	}
 
 	override fun onGodotSetupCompleted() {
@@ -283,10 +301,15 @@ abstract class BaseGodotEditor : GodotActivity() {
 		return newInstance
 	}
 
-	override fun onNewGodotInstanceRequested(args: Array<String>): Int {
+	final override fun onNewGodotInstanceRequested(args: Array<String>): Int {
 		val editorWindowInfo = retrieveEditorWindowInfo(args)
+		val shouldRunGameEmbedded = Build.VERSION.SDK_INT >= Build.VERSION_CODES.R && true // TODO: Add logic behind it
+		if (editorWindowInfo == RUN_GAME_INFO && shouldRunGameEmbedded) {
+			embeddedGameFragment?.startEmbeddedGame(args)
+			return EmbeddedGameFragment.WINDOW_ID
+		}
 
-		// Launch a new activity
+		// We're not running embedded so launch a new activity
 		val sourceView = godotFragment?.view
 		val activityOptions = if (sourceView == null) {
 			null
@@ -317,6 +340,11 @@ abstract class BaseGodotEditor : GodotActivity() {
 	}
 
 	final override fun onGodotForceQuit(godotInstanceId: Int): Boolean {
+		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R && godotInstanceId == EmbeddedGameFragment.WINDOW_ID) {
+			embeddedGameFragment?.stopEmbeddedGame()
+			return true
+		}
+
 		val editorWindowInfo = getEditorWindowInfoForInstanceId(godotInstanceId) ?: return super.onGodotForceQuit(godotInstanceId)
 
 		if (editorWindowInfo.windowClassName == javaClass.name) {