ProjectTempoListener.cpp

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#include "ClientData.h"
#include "Observer.h"
#include "Project.h"
#include "ProjectTimeSignature.h"
#include "TempoChange.h"
#include "Track.h"
 
#include <cassert>
 
#include "ViewInfo.h"
 
class ProjectTempoListener final : public ClientData::Base
{
public:
   ProjectTempoListener(AudacityProject& project, TrackList& trackList);
   void OnProjectTempoChange(double newTempo);
 
private:
   AudacityProject& mProject;
   ViewInfo& mViewInfo;
   double mTempo { 0 };
   TrackList& mTrackList;
   Observer::Subscription mTrackListSubstription;
   Observer::Subscription mProjectTimeSignatureSubscription;
};
 
static const AttachedProjectObjects::RegisteredFactory key {
   [](AudacityProject& project) {
      return std::make_shared<ProjectTempoListener>(
         project, TrackList::Get(project));
   }
};
 
ProjectTempoListener::ProjectTempoListener(
   AudacityProject& project, TrackList& trackList)
    : mProject { project }
    , mViewInfo { ViewInfo::Get(project) }
    , mTempo { ProjectTimeSignature::Get(project).GetTempo() }
    , mTrackList { trackList }
    , mTrackListSubstription { trackList.Subscribe(
         [this](const TrackListEvent& event) {
            if (event.mType == TrackListEvent::ADDITION)
            {
               const auto tempo = ProjectTimeSignature::Get(mProject).GetTempo();
               if (const auto track = event.mpTrack.lock())
                  DoProjectTempoChange(*track, tempo);
            }
         }) }
{
   mProjectTimeSignatureSubscription =
      ProjectTimeSignature::Get(project).Subscribe(
         [this](const TimeSignatureChangedMessage& event) {
            OnProjectTempoChange(event.newTempo);
         });
   assert(mTrackList.empty()); // No need to call `OnProjectTempoChange` yet ...
}
 
void ProjectTempoListener::OnProjectTempoChange(double newTempo)
{
   for (auto track : mTrackList)
      DoProjectTempoChange(*track, newTempo);
   
   if(!mViewInfo.playRegion.Empty() && mTempo > 0 && newTempo > 0)
   {
      const auto tempoRate = mTempo / newTempo;
      mViewInfo.playRegion.SetTimes(
         mViewInfo.playRegion.GetStart() * tempoRate,
         mViewInfo.playRegion.GetEnd() * tempoRate
      );
   }
   mTempo = newTempo;
}