mixer/playerinfo: Make implicit PlayerInfo creation explicit

Until now, the `PlayerInfo` singleton was instantiated implicitly when
it was first accessed. This commit makes the instantiation explicit by
adding a dedicated `PlayerInfo::create()` method.

When running tests directly via `mixxx-test` (i.e. not a via `ctest`),
all tests will be executed in the *same* process. Thus, the singleton
will be instantiated by the first test that accessses the instance, but
stay alive until `mixxx-test` is terminated.

The `PlayerInfo` instance will repeatedly call
`updateCurrentlyPlayingDeck()` through the `timerEvent()` mehtod during
its lifetime. This will access some COs, e.g. `[Master],num_decks`.
Depending on the currently running test, these COs may or may not be
present. When `QCoreApplication::processEvents()` is called, there might
be a `timerEvent()` in the queue and will cause CO access.  If the CO is
*not* present for that test, the test will throw a `DEBUG_ASSERT`.

By making the singleton instantiation more explicit, we can add
`PlayerInfo::create()` and `PlayerInfo::destroy()` calls only to the
constructor/destructor of text fixtures that need it, and ensure that
the timer doesn't cause failed debug assertions in unrelated tests.

This fixes the remaining `DEBUG_ASSERT` issues and paves the way for
merging PR #2911.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/mixer/playerinfo.h b/src/mixer/playerinfo.h
index 9a94eb15a6..5aee4fc06c 100644
--- a/src/mixer/playerinfo.h
+++ b/src/mixer/playerinfo.h
@@ -28,6 +28,7 @@
 class PlayerInfo : public QObject {
     Q_OBJECT
   public:
+    static PlayerInfo& create();
     static PlayerInfo& instance();
     static void destroy();
     TrackPointer getTrackInfo(const QString& group);