Master Sync: preallocate buffers in engine thread func.

pickMaster gets called from the engine thread so we have to be careful to
avoid memory allocation.  Preallocating a constant number fixes this.

Also make kMaxNumberOfDecks a proper mixxx-global value, and check against
it when we add decks.  If someone one day invents a skin that uses 6 or 8
decks, this warning will get tripped (but shouldn't break anything
fundamental in Mixxx).

1 files changed, 7 insertions, 0 deletions

diff --git a/src/mixer/playermanager.cpp b/src/mixer/playermanager.cpp
index 5240f71210..d377a9538a 100644
--- a/src/mixer/playermanager.cpp
+++ b/src/mixer/playermanager.cpp
@@ -20,6 +20,7 @@
 #include "soundio/soundmanager.h"
 #include "track/track.h"
 #include "util/assert.h"
+#include "util/defs.h"
 #include "util/logger.h"
 #include "util/stat.h"
 #include "util/sleepableqthread.h"
@@ -268,6 +269,12 @@ void PlayerManager::slotChangeNumDecks(double v) {
     QMutexLocker locker(&m_mutex);
     int num = (int)v;
 
+    VERIFY_OR_DEBUG_ASSERT(num <= kMaxNumberOfDecks) {
+        qWarning() << "Number of decks exceeds the maximum we expect."
+                   << num << "vs" << kMaxNumberOfDecks
+                   << " Please update util/defs.h";
+    }
+
     // Update the soundmanager config even if the number of decks has been
     // reduced.
     m_pSoundManager->setConfiguredDeckCount(num);