Android: Expose config changed callbacks

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/features/settings/model/ConfigChangedCallback.kt

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package org.dolphinemu.dolphinemu.features.settings.model
+
+import androidx.annotation.Keep
+
+/**
+ * Calls the passed-in Runnable when Dolphin's config changes.
+ *
+ * Please note: The Runnable may be called from any thread.
+ */
+class ConfigChangedCallback(runnable: Runnable) {
+    @Keep
+    private var pointer: Long = initialize(runnable)
+
+    /**
+     * Stops the callback from being called in the future.
+     */
+    fun unregister() {
+        if (pointer != 0L) {
+            deinitialize(pointer)
+            pointer = 0L
+        }
+    }
+
+    companion object {
+        @JvmStatic
+        private external fun initialize(runnable: Runnable): Long
+
+        @JvmStatic
+        private external fun deinitialize(pointer: Long)
+    }
+}