Initial support for updating settings during emulation + observing settings changes

app/src/main/cpp/emu_jni.cpp

@@ -60,6 +60,8 @@ template<> void skyline::Settings::Update<skyline::KtSettings>(KtSettings newSet
     systemLanguage = newSettings.GetInt<skyline::language::SystemLanguage>("systemLanguage");
     forceTripleBuffering = newSettings.GetBool("forceTripleBuffering");
     disableFrameThrottling = newSettings.GetBool("disableFrameThrottling");
+
+    OnSettingsChanged();
 }
 
 extern "C" JNIEXPORT void Java_emu_skyline_SkylineApplication_initializeLog(
@@ -239,3 +241,11 @@ extern "C" JNIEXPORT void JNICALL Java_emu_skyline_EmulationActivity_setTouchSta
     input->touch.SetState(points);
     env->ReleaseIntArrayElements(pointsJni, reinterpret_cast<jint *>(points.data()), JNI_ABORT);
 }
+
+extern "C" JNIEXPORT void JNICALL Java_emu_skyline_utils_SettingsValues_updateNative(JNIEnv *env, jobject settingsInstance) {
+    auto settings{SettingsWeak.lock()};
+    if (!settings)
+        return; // We don't mind if we miss settings updates while settings haven't been initialized
+    skyline::KtSettings ktSettings{env, settingsInstance};
+    settings->Update(ktSettings);
+}

app/src/main/cpp/skyline/common/settings.cpp

@@ -4,6 +4,16 @@
 #include "settings.h"
 
 namespace skyline {
+    void Settings::Subscribe(Callback callback) {
+        callbacks.push_back(std::move(callback));
+    }
+
+    void Settings::OnSettingsChanged() {
+        std::for_each(callbacks.begin(), callbacks.end(), [&](const Callback& listener) {
+            listener(*this);
+        });
+    }
+
     /**
      * @note This is a placeholder implementation, it must be overridden via template specialisation for platform-specific behavior
      */

app/src/main/cpp/skyline/common/settings.h

@@ -27,9 +27,23 @@ namespace skyline {
 
         /**
          * @brief Updates settings with the given values
+         * @note The implementations of this method must call OnSettingsChanged
          * @param newSettings A platform-specific object containing the new settings' values
          */
         template<class T>
         void Update(T newSettings);
+
+        using Callback = std::function<void(const Settings &)>;
+
+        /**
+         * @brief Subscribe to settings changes
+         * @param callback The function to be called when settings change
+         */
+        void Subscribe(Callback callback);
+
+      private:
+        std::vector<Callback> callbacks; //!< Callbacks to be called when settings change
+
+        void OnSettingsChanged();
     };
 }

app/src/main/java/emu/skyline/utils/SettingsValues.kt

@@ -13,4 +13,9 @@ class SettingsValues(pref: Settings) : Serializable {
     var systemLanguage : Int = pref.systemLanguage
     var forceTripleBuffering : Boolean = pref.forceTripleBuffering
     var disableFrameThrottling : Boolean = pref.disableFrameThrottling
+
+    /**
+     * Updates settings in libskyline during emulation
+     */
+    external fun updateNative()
 }