From a35b1eff4ab9a4ba42767bf5f7c2ca15bead10a3 Mon Sep 17 00:00:00 2001
From: Niek van den Berg <njvdberg@xs4all.nl>
Date: Fri, 1 May 2020 09:05:47 +0200
Subject: [PATCH] Fix #283964 - Linked parts for single voices don't work

Corrects recognistion of linked staves with a part and linked staves over
excerpts.
---
 libmscore/edit.cpp  | 45 ++++++++++++++++++++++++++++++++++++---------
 libmscore/score.cpp |  2 +-
 2 files changed, 37 insertions(+), 10 deletions(-)

diff --git a/libmscore/edit.cpp b/libmscore/edit.cpp
index 4cbdf6edf0499..35718e7dc3daf 100644
--- a/libmscore/edit.cpp
+++ b/libmscore/edit.cpp
@@ -4889,17 +4889,44 @@ void Score::undoAddCR(ChordRest* cr, Measure* measure, const Fraction& tick)
 
       Tuplet* t = cr->tuplet();
 
+      // For linked staves the length of staffList is always > 1 since the list contains the staff itself too!
+      const bool linked = ostaff->staffList().length() > 1;
+
       for (const Staff* staff : ostaff->staffList()) {
             QList<int> tracks;
-            int staffIdx = staff->idx();
-            if ((strack & ~3) != staffIdx) // linked staff ?
-                  tracks.append(staffIdx * VOICES + (strack % VOICES));
-            else if (staff->score()->excerpt() && !staff->score()->excerpt()->tracks().isEmpty())
-                  tracks = staff->score()->excerpt()->tracks().values(strack);
-            else if (!staff->score()->excerpt())
-                  tracks.append(staffIdx * VOICES + (strack % VOICES));
-            else
-                  tracks.append(staffIdx * VOICES + cr->voice());
+            if (!staff->score()->excerpt()) {
+                  // On masterScore.
+                  int track = staff->idx() * VOICES + (strack % VOICES);
+                  tracks.append(track);
+                  }
+            else {
+                  QMultiMap<int, int> mapping = staff->score()->excerpt()->tracks();
+                  if (mapping.isEmpty()) {
+                        // This can happen during reading the score and there is
+                        // no Tracklist tag specified.
+                        // TODO solve this in read301.cpp.
+                        tracks.append(strack);
+                        }
+                  else {
+                        // linkedPart : linked staves within same part/instrument.
+                        // linkedScore: linked staves over different scores via excerpts.
+                        const bool linkedPart  = linked && (staff != ostaff) && (staff->score() == ostaff->score());
+                        const bool linkedScore = linked && (staff != ostaff) && (staff->score() != ostaff->score());
+                        for (int track : mapping.values(strack)) {
+                              if (linkedPart && !linkedScore) {
+                                    tracks.append(staff->idx() * VOICES + mapping.value(track));
+                                    }
+                              else if (!linkedPart && linkedScore) {
+                                    if ((track >> 2) != staff->idx())
+                                          track += (staff->idx() - (track >> 2)) * VOICES;
+                                    tracks.append(track);
+                                    }
+                              else {
+                                    tracks.append(track);
+                                    }
+                              }
+                        }
+                  }
 
             for (int ntrack : tracks) {
                   if (ntrack < staff->part()->startTrack() || ntrack >= staff->part()->endTrack())
diff --git a/libmscore/score.cpp b/libmscore/score.cpp
index c4aa5e05a3c8d..a2efc0b247662 100644
--- a/libmscore/score.cpp
+++ b/libmscore/score.cpp
@@ -1910,7 +1910,7 @@ void MasterScore::addExcerpt(Excerpt* ex)
                         }
                   }
             }
-      if (ex->tracks().isEmpty()) {                         // SHOULDN'T HAPPEN, protected in the UI
+      if (ex->tracks().isEmpty()) {      // SHOULDN'T HAPPEN, protected in the UI, but it happens during read-in!!!
             QMultiMap<int, int> tracks;
             for (Staff* s : score->staves()) {
                   const LinkedElements* ls = s->links();