Define TrackList::GroupChannels()

src/Track.cpp

@@ -38,6 +38,7 @@ and TimeTrack.
 #include "DirManager.h"
 
 #include "Experimental.h"
+#include "InconsistencyException.h"
 
 #include "TrackPanel.h" // for TrackInfo
 
@@ -724,6 +725,58 @@ Track *TrackList::Add(std::shared_ptr<TrackKind> &&t)
 template Track *TrackList::Add<Track>(std::shared_ptr<Track> &&);
 template Track *TrackList::Add<WaveTrack>(std::shared_ptr<WaveTrack> &&);
 
+void TrackList::GroupChannels(
+   Track &track, size_t groupSize, bool resetChannels )
+{
+   // If group size is more than two, for now only the first two channels
+   // are grouped as stereo, and any others remain mono
+   auto list = track.mList.lock();
+   if ( groupSize > 0 && list.get() == this  ) {
+      auto iter = track.mNode.first;
+      auto after = iter;
+      auto end = this->ListOfTracks::end();
+      auto count = groupSize;
+      for ( ; after != end && count--; ++after )
+         ;
+      if ( count == 0 ) {
+         auto unlink = [&] ( Track &tr ) {
+            if ( tr.GetLinked() ) {
+               if ( resetChannels ) {
+                  auto link = tr.GetLink();
+                  if ( link )
+                     link->SetChannel( Track::MonoChannel );
+               }
+               tr.SetLinked( false );
+            }
+            if ( resetChannels )
+               tr.SetChannel( Track::MonoChannel );
+         };
+
+         // Disassociate previous tracks -- at most one
+         auto pLeader = this->FindLeader( &track );
+         if ( *pLeader && *pLeader != &track )
+            unlink( **pLeader );
+         
+         // First disassociate given and later tracks, then reassociate them
+         for ( auto iter2 = iter; iter2 != after; ++iter2 )
+             unlink( **iter2 );
+
+         if ( groupSize > 1 ) {
+            const auto channel = *iter++;
+            channel->SetLinked( true );
+            channel->SetChannel( Track::LeftChannel );
+            (*iter++)->SetChannel( Track::RightChannel );
+            while (iter != after)
+               (*iter++)->SetChannel( Track::MonoChannel );
+         }
+         return;
+      }
+   }
+   // *this does not contain the track or sufficient following channels
+   // or group size is zero
+   throw InconsistencyException{};
+}
+
 auto TrackList::Replace(Track * t, ListOfTracks::value_type &&with) ->
    ListOfTracks::value_type
 {

src/Track.h

@@ -1318,6 +1318,16 @@ public:
    template<typename TrackKind>
    Track *Add(std::shared_ptr<TrackKind> &&t);
 
+   /** \brief Define a group of channels starting at the given track
+   *
+   * @param track and (groupSize - 1) following tracks must be in this
+   * list.  They will be disassociated from any groups they already belong to.
+   * @param groupSize must be at least 1.
+   * @param resetChannels if true, disassociated channels will be marked Mono.
+   */
+   void GroupChannels(
+      Track &track, size_t groupSize, bool resetChannels = true );
+
    /// Replace first track with second track, give back a holder
    /// Give the replacement the same id as the replaced
    ListOfTracks::value_type Replace(Track * t, ListOfTracks::value_type &&with);