AUDIO: Add pure virtual MidiDriver::isOpen() method

This in turn enables modifying MidiDriver_MPU401::close() to allow
it to be called on a midi driver that has not yet been opened.

The specific issue that triggered me to make these changes was a
crash-upon-quit in HUGO, caused by it instantiating a midi driver,
then encountering an error (missing hugo.dat) *before* having
opened the new midi driver; the general cleanup code then tries
to close the (not yet opened) midi driver -> kaboom

Also fixed some engines which were leaking MidiDriver instances.

2 files changed, 5 insertions, 0 deletions

diff --git a/engines/groovie/music.cpp b/engines/groovie/music.cpp
index 011409155c..7651576828 100644
--- a/engines/groovie/music.cpp
+++ b/engines/groovie/music.cpp
@@ -264,6 +264,10 @@ int MusicPlayerMidi::open() {
 	return 0;
 }
 
+bool MusicPlayerMidi::isOpen() const {
+	return _driver && _driver->isOpen();
+}
+
 void MusicPlayerMidi::close() {}
 
 void MusicPlayerMidi::send(uint32 b) {
diff --git a/engines/groovie/music.h b/engines/groovie/music.h
index 5974559c53..e45e130a70 100644
--- a/engines/groovie/music.h
+++ b/engines/groovie/music.h
@@ -95,6 +95,7 @@ public:
 
 	// MidiDriver interface
 	virtual int open();
+	virtual bool isOpen() const;
 	virtual void close();
 	virtual void send(uint32 b);
 	virtual void metaEvent(byte type, byte *data, uint16 length);