Rewrite audio engine: replace BASS with miniaudio

SFX and blip players largely remain the same.

For the music player, we now have to implement network streaming
natively, we no longer have a convenient function that did everything
for us. I introduced QNetworkRequest to download the stream in memory
and signal when it's ready to be decoded and played back. The size is
guarded to prevent the client from accidentally downloading terabytes of
audio.

Delete QFutureWatcher, we no longer need it for concurrency. miniaudio
uses a separate audio thread. Network donwloads and communication with
the track name display are handled by Qt signals.

Also, delete an odd "music.txt" feature. Its purpose was specifying
offsets for loops in a text file per track, but it remained obscure and
unused in practice.

Unsupported:

- Large streams, including unbounded ones (radio). We'll need a ring
  buffer for that, and a mechanism to write to it from the network and
  feed it to the audio thread.

- Effect flags: fade in, fade out, sync pos. Ignored.

- Audio device selection.

1 files changed, 39 insertions, 8 deletions

diff --git a/src/aomusicplayer.h b/src/aomusicplayer.h
index 707d64ad..b45c22fe 100644
--- a/src/aomusicplayer.h
+++ b/src/aomusicplayer.h
@@ -2,17 +2,20 @@
 
 #include "aoapplication.h"
 
-#include <QFutureWatcher>
+#include <QNetworkAccessManager>
+#include <QPointer>
 
-class AOMusicPlayer
+class AOMusicPlayer : public QObject
 {
+  Q_OBJECT
+
 public:
   // 0 = music
   // 1 = ambience
   static constexpr int STREAM_COUNT = 2;
 
   explicit AOMusicPlayer(AOApplication *ao_app);
-  virtual ~AOMusicPlayer();
+  ~AOMusicPlayer();
 
   void setMuted(bool enabled);
 
@@ -21,18 +24,46 @@ public:
   void setStreamVolume(int value, int streamId);
   void setStreamLooping(bool enabled, int streamId);
 
-  QFutureWatcher<QString> m_watcher;
+  void play_from_url(const QString &url, int id, bool looping, int flags);
+  void play_from_file(const QString &path, int id, bool looping, int flags);
 
 private:
+  struct Stream
+  {
+    ma_sound sound;
+    QByteArray buffer;
+    ma_decoder decoder;
+    // I've had use-after-free crashes on `stop` due to QNetworkReply's lifetime
+    // being unclear (specifically, calling `abort` on it). QPointer is a
+    // bandaid fix.
+    QPointer<QNetworkReply> reply;
+    bool has_decoder;
+    enum
+    {
+      standby,
+      playing,
+    } state = standby;
+  };
+
+  // Default flags for music: STREAM decodes incrementally in 2-second chunks,
+  // the other two disable 3D positioning and Doppler effect.
+  const ma_uint32 m_flags = MA_SOUND_FLAG_STREAM | MA_SOUND_FLAG_NO_SPATIALIZATION | MA_SOUND_FLAG_NO_PITCH;
+
   AOApplication *ao_app;
 
+  float m_volume[STREAM_COUNT]{};
   bool m_muted = false;
-
-  int m_volume[STREAM_COUNT]{};
-  HSTREAM m_stream_list[STREAM_COUNT]{};
-  HSYNC m_loop_sync[STREAM_COUNT]{};
+  Stream m_stream[STREAM_COUNT]{};
+  ma_pcm_rb m_audio_ring;
   quint32 m_loop_start[STREAM_COUNT]{};
   quint32 m_loop_end[STREAM_COUNT]{};
 
   bool ensureValidStreamId(int streamId);
+
+  void on_url_download_finished(int id, QNetworkReply *reply, bool looping);
+  void start_playback(int id);
+  void stop(int id);
+
+signals:
+  void track_ready(QString label);
 };