Fix: properly know when a player is deleted from inside the stream.

This eliminates crashes that happen because stream playbacks will call
_mix() for some reason even after their audio player is stopped and
deleted.

src/player.cpp

@@ -100,6 +100,11 @@ SteamAudioPlayer::~SteamAudioPlayer() {
 	iplAudioBufferFree(gs->ctx, &local_state.bufs.mono);
 	iplAudioBufferFree(gs->ctx, &local_state.bufs.refl_ambi);
 	iplAudioBufferFree(gs->ctx, &local_state.bufs.refl_out);
+
+	if (!pb.is_null()) {
+		auto playback = dynamic_cast<SteamAudioStreamPlayback *>(pb.ptr());
+		playback->parent = nullptr;
+	}
 }
 
 LocalSteamAudioState *SteamAudioPlayer::get_local_state() {
@@ -198,9 +203,9 @@ void SteamAudioPlayer::_ready() {
 	// The stream might be actually instantiated before Player::_ready().
 	// If so, transfer the necessary data directly to it.
 	if (this->is_playing() && !get_stream_playback().is_null()) {
-		auto pb = dynamic_cast<SteamAudioStreamPlayback *>(get_stream_playback().ptr());
-		pb->parent = this;
-		pb->set_stream(sub_stream);
+		auto playback = dynamic_cast<SteamAudioStreamPlayback *>(get_stream_playback().ptr());
+		playback->parent = this;
+		playback->set_stream(sub_stream);
 	}
 }
 
@@ -216,6 +221,10 @@ void SteamAudioPlayer::_process(double delta) {
 	if (Engine::get_singleton()->is_editor_hint() && sub_stream.ptr() != get_stream().ptr()) {
 		set_stream(sub_stream);
 	}
+
+	if (is_playing() && !get_stream_playback().is_null()) {
+		pb = get_stream_playback();
+	}
 }
 
 Ref<AudioStream> SteamAudioPlayer::get_sub_stream() { return sub_stream; }

src/player.hpp

@@ -14,6 +14,10 @@ class SteamAudioPlayer : public AudioStreamPlayer3D {
 	GDCLASS(SteamAudioPlayer, AudioStreamPlayer3D);
 
 private:
+	// This ref is kept because at destruction we can't get the playback
+	// since the player has stopped (even though the playback still mixes...)
+	Ref<AudioStreamPlayback> pb;
+
 	Ref<AudioStream> sub_stream;
 	// TODO: we can probably move these values inside local state
 	// for cleanup and the ability to adjust them at runtime

src/steam_audio.hpp

@@ -6,7 +6,7 @@
 #include <godot_cpp/classes/audio_stream_player3d.hpp>
 #include <godot_cpp/classes/node3d.hpp>
 #include <godot_cpp/core/class_db.hpp>
-#include <mutex>
+#include <shared_mutex>
 
 using namespace godot;
 
@@ -78,7 +78,7 @@ struct LocalSteamAudioState {
 	LocalSteamAudioBuffers bufs;
 	SteamAudioEffects fx;
 	SteamAudioSourceConfig cfg;
-	std::mutex mux;
+	std::shared_mutex mux;
 };
 
 inline int ambisonic_channels_from(int order) {

src/stream.cpp

@@ -33,7 +33,6 @@ SteamAudioStreamPlayback::~SteamAudioStreamPlayback() {}
 
 int32_t SteamAudioStreamPlayback::_mix(AudioFrame *buffer, double rate_scale, int32_t frames) {
 	if (parent == nullptr) {
-		SteamAudio::log(SteamAudio::log_error, "mixing: ERROR, parent is null!");
 		return frames;
 	}
 
@@ -58,6 +57,15 @@ int32_t SteamAudioStreamPlayback::_mix(AudioFrame *buffer, double rate_scale, in
 	}
 	std::unique_lock lock(ls->mux);
 
+	// Some extra checks because at this point parent may have been deleted
+	if (parent == nullptr) {
+		return frames;
+	}
+	ls = parent->get_local_state();
+	if (ls == nullptr || !ls->src.player) {
+		return frames;
+	}
+
 	PackedVector2Array mixed_frames = stream_playback->get_raw_audio(rate_scale, frames);
 	frames = int(mixed_frames.size());