Use dummy driver when JS AudioContext is unavailable.

platform/javascript/audio_driver_javascript.cpp

@@ -36,6 +36,15 @@
 
 AudioDriverJavaScript *AudioDriverJavaScript::singleton = nullptr;
 
+bool AudioDriverJavaScript::is_available() {
+	return EM_ASM_INT({
+		if (!(window.AudioContext || window.webkitAudioContext)) {
+			return 0;
+		}
+		return 1;
+	}) != 0;
+}
+
 const char *AudioDriverJavaScript::get_name() const {
 	return "JavaScript";
 }
@@ -207,12 +216,14 @@ void AudioDriverJavaScript::finish_async() {
 
 	/* clang-format off */
 	EM_ASM({
-		var ref = Module.IDHandler.get($0);
+		const id = $0;
+		var ref = Module.IDHandler.get(id);
 		Module.async_finish.push(new Promise(function(accept, reject) {
 			if (!ref) {
-				console.log("Ref not found!", $0, Module.IDHandler);
+				console.log("Ref not found!", id, Module.IDHandler);
 				setTimeout(accept, 0);
 			} else {
+				Module.IDHandler.remove(id);
 				const context = ref['context'];
 				// Disconnect script and input.
 				ref['script'].disconnect();
@@ -226,7 +237,6 @@ void AudioDriverJavaScript::finish_async() {
 				});
 			}
 		}));
-		Module.IDHandler.remove($0);
 	}, id);
 	/* clang-format on */
 }
@@ -293,9 +303,5 @@ Error AudioDriverJavaScript::capture_stop() {
 }
 
 AudioDriverJavaScript::AudioDriverJavaScript() {
-	_driver_id = 0;
-	internal_buffer = nullptr;
-	buffer_length = 0;
-
 	singleton = this;
 }

platform/javascript/audio_driver_javascript.h

@@ -34,12 +34,13 @@
 #include "servers/audio_server.h"
 
 class AudioDriverJavaScript : public AudioDriver {
-	float *internal_buffer;
+	float *internal_buffer = nullptr;
 
-	int _driver_id;
-	int buffer_length;
+	int _driver_id = 0;
+	int buffer_length = 0;
 
 public:
+	static bool is_available();
 	void mix_to_js();
 	void process_capture(float sample);
 

platform/javascript/javascript_main.cpp

@@ -63,10 +63,17 @@ void main_loop_callback() {
 	}
 	if (os->main_loop_iterate()) {
 		emscripten_cancel_main_loop(); // Cancel current loop and wait for finalize_async.
+		/* clang-format off */
 		EM_ASM({
 			// This will contain the list of operations that need to complete before cleanup.
-			Module.async_finish = [];
+			Module.async_finish = [
+				// Always contains at least one async promise, to avoid firing immediately if nothing is added.
+				new Promise(function(accept, reject) {
+					setTimeout(accept, 0);
+				})
+			];
 		});
+		/* clang-format on */
 		os->get_main_loop()->finish();
 		os->finalize_async(); // Will add all the async finish functions.
 		EM_ASM({

platform/javascript/os_javascript.cpp

@@ -77,7 +77,9 @@ void OS_JavaScript::initialize() {
 }
 
 void OS_JavaScript::resume_audio() {
-	audio_driver_javascript.resume();
+	if (audio_driver_javascript) {
+		audio_driver_javascript->resume();
+	}
 }
 
 void OS_JavaScript::set_main_loop(MainLoop *p_main_loop) {
@@ -125,11 +127,17 @@ void OS_JavaScript::delete_main_loop() {
 
 void OS_JavaScript::finalize_async() {
 	finalizing = true;
-	audio_driver_javascript.finish_async();
+	if (audio_driver_javascript) {
+		audio_driver_javascript->finish_async();
+	}
 }
 
 void OS_JavaScript::finalize() {
 	delete_main_loop();
+	if (audio_driver_javascript) {
+		memdelete(audio_driver_javascript);
+		audio_driver_javascript = nullptr;
+	}
 }
 
 // Miscellaneous
@@ -238,7 +246,10 @@ void OS_JavaScript::initialize_joypads() {
 }
 
 OS_JavaScript::OS_JavaScript() {
-	AudioDriverManager::add_driver(&audio_driver_javascript);
+	if (AudioDriverJavaScript::is_available()) {
+		audio_driver_javascript = memnew(AudioDriverJavaScript);
+		AudioDriverManager::add_driver(audio_driver_javascript);
+	}
 
 	Vector<Logger *> loggers;
 	loggers.push_back(memnew(StdLogger));

platform/javascript/os_javascript.h

@@ -40,7 +40,7 @@
 
 class OS_JavaScript : public OS_Unix {
 	MainLoop *main_loop = nullptr;
-	AudioDriverJavaScript audio_driver_javascript;
+	AudioDriverJavaScript *audio_driver_javascript = nullptr;
 
 	bool finalizing = false;
 	bool idb_available = false;