From a971dd5bb42f742199155acbd74822f0f2afc7f0 Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@audacityteam.org>
Date: Sat, 23 Sep 2017 21:23:34 -0400
Subject: [PATCH] Detect whether ALSA is the portaudio host (possible only on
 Linux)

---
 src/AudioIO.cpp | 9 +++++++--
 src/AudioIO.h   | 2 ++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/AudioIO.cpp b/src/AudioIO.cpp
index 51adc3e10..66eae0bc3 100644
--- a/src/AudioIO.cpp
+++ b/src/AudioIO.cpp
@@ -1678,6 +1678,12 @@ int AudioIO::StartStream(const ConstWaveTrackArray &playbackTracks,
          wxMilliSleep( 50 );
    }
 
+#ifdef __WXGTK__
+   // Detect whether ALSA is the chosen host, and do the various involved MIDI
+   // timing compensations only then.
+   mUsingAlsa = (gPrefs->Read(wxT("/AudioIO/Host"), wxT("")) == "ALSA");
+#endif
+
    gPrefs->Read(wxT("/AudioIO/SWPlaythrough"), &mSoftwarePlaythrough, false);
    gPrefs->Read(wxT("/AudioIO/SoundActivatedRecord"), &mPauseRec, false);
    int silenceLevelDB;
@@ -2033,8 +2039,7 @@ int AudioIO::StartStream(const ConstWaveTrackArray &playbackTracks,
       // (Which we should be able to determine from fields of
       // PaStreamCallbackTimeInfo, but that seems not to work as documented with
       // ALSA.)
-      wxString hostName = gPrefs->Read(wxT("/AudioIO/Host"), wxT(""));
-      if (hostName == "ALSA")
+      if (mUsingAlsa)
          // Perhaps we should do this only if also playing MIDI ?
          PaAlsa_EnableRealtimeScheduling( mPortStreamV19, 1 );
 #endif
diff --git a/src/AudioIO.h b/src/AudioIO.h
index e83587263..609e649ff 100644
--- a/src/AudioIO.h
+++ b/src/AudioIO.h
@@ -727,6 +727,8 @@ private:
 
    const TimeTrack *mTimeTrack;
 
+   bool mUsingAlsa { false };
+
    // For cacheing supported sample rates
    static int mCachedPlaybackIndex;
    static wxArrayLong mCachedPlaybackRates;