decoder/Control: Seek() returns Error information

src/decoder/DecoderControl.cxx

@@ -19,6 +19,7 @@
 
 #include "config.h"
 #include "DecoderControl.hxx"
+#include "DecoderError.hxx"
 #include "MusicPipe.hxx"
 #include "DetachedSong.hxx"
 
@@ -105,7 +106,7 @@ DecoderControl::Stop()
 }
 
 bool
-DecoderControl::Seek(SongTime t)
+DecoderControl::Seek(SongTime t, Error &error_r)
 {
 	assert(state != DecoderState::START);
 	assert(state != DecoderState::ERROR);
@@ -116,20 +117,30 @@ DecoderControl::Seek(SongTime t)
 		gcc_unreachable();
 
 	case DecoderState::STOP:
+		/* TODO: if this happens, the caller should be given a
+		   chance to restart the decoder */
+		error_r.Set(decoder_domain, "Decoder is dead");
 		return false;
 
 	case DecoderState::DECODE:
 		break;
 	}
 
-	if (!seekable)
+	if (!seekable) {
+		error_r.Set(decoder_domain, "Not seekable");
 		return false;
+	}
 
 	seek_time = t;
 	seek_error = false;
 	LockSynchronousCommand(DecoderCommand::SEEK);
 
-	return !seek_error;
+	if (seek_error) {
+		error_r.Set(decoder_domain, "Decoder failed to seek");
+		return false;
+	}
+
+	return true;
 }
 
 void

src/decoder/DecoderControl.hxx

@@ -365,7 +365,7 @@ public:
 
 	void Stop();
 
-	bool Seek(SongTime t);
+	bool Seek(SongTime t, Error &error_r);
 
 	void Quit();
 

src/player/Thread.cxx

@@ -605,8 +605,10 @@ Player::SeekDecoder()
 				where = total_time;
 		}
 
-		if (!dc.Seek(where + start_time)) {
+		Error error;
+		if (!dc.Seek(where + start_time, error)) {
 			/* decoder failure */
+			pc.SetError(PlayerError::DECODER, std::move(error));
 			pc.LockCommandFinished();
 			return false;
 		}