From 0281cc77f99f17624c88a786678082faa0d36929 Mon Sep 17 00:00:00 2001
From: Roman Pudashkin <r.pudashkin@gmail.com>
Date: Mon, 4 Oct 2021 16:08:40 +0200
Subject: [PATCH 1/2] fixed crash during removing the last staff

---
 src/engraving/libmscore/engravingitem.cpp | 5 ++++-
 src/engraving/libmscore/system.cpp        | 3 ++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/engraving/libmscore/engravingitem.cpp b/src/engraving/libmscore/engravingitem.cpp
index 7f1b082488c53..38e6fec0940d1 100644
--- a/src/engraving/libmscore/engravingitem.cpp
+++ b/src/engraving/libmscore/engravingitem.cpp
@@ -670,8 +670,11 @@ PointF EngravingItem::canvasPos() const
             qFatal("this %s parent %s\n", name(), parent()->name());
         }
         if (measure) {
-            p.ry() += measure->staffLines(vStaffIdx())->y();
+            const StaffLines* lines = measure->staffLines(vStaffIdx());
+            p.ry() += lines ? lines->y() : 0;
+
             system = measure->system();
+
             if (system) {
                 Page* page = system->page();
                 if (page) {
diff --git a/src/engraving/libmscore/system.cpp b/src/engraving/libmscore/system.cpp
index fced0d8eb63d7..448c5c5a658bc 100644
--- a/src/engraving/libmscore/system.cpp
+++ b/src/engraving/libmscore/system.cpp
@@ -1294,9 +1294,10 @@ void System::scanElements(void* data, void (* func)(void*, EngravingItem*), bool
 
 qreal System::staffYpage(int staffIdx) const
 {
-    IF_ASSERT_FAILED(!(_staves.size() <= staffIdx || staffIdx < 0)) {
+    if (staffIdx < 0 || staffIdx >= _staves.size()) {
         return pagePos().y();
     }
+
     return _staves[staffIdx]->y() + y();
 }
 

From 19589da89712175b631b5e1e4b7bcc0b9e49b1aa Mon Sep 17 00:00:00 2001
From: Roman Pudashkin <r.pudashkin@gmail.com>
Date: Tue, 5 Oct 2021 11:56:31 +0200
Subject: [PATCH 2/2] fixed removing spanners (e.g. volta lines) and
 annotations after removing all staves from a score

---
 src/engraving/libmscore/edit.cpp    | 42 ++++++++++++++++++-----------
 src/engraving/libmscore/measure.cpp | 19 +++++++++----
 2 files changed, 41 insertions(+), 20 deletions(-)

diff --git a/src/engraving/libmscore/edit.cpp b/src/engraving/libmscore/edit.cpp
index 01ab8ddacbe96..4234f56a22727 100644
--- a/src/engraving/libmscore/edit.cpp
+++ b/src/engraving/libmscore/edit.cpp
@@ -4965,33 +4965,45 @@ void Score::undoInsertPart(Part* part, int idx)
 
 void Score::undoRemoveStaff(Staff* staff)
 {
-    const int idx = staff->idx();
-    Q_ASSERT(idx >= 0);
+    const int staffIndex = staff->idx();
+    Q_ASSERT(staffIndex >= 0);
 
-    std::vector<Spanner*> toRemove;
-    for (auto i = _spanner.cbegin(); i != _spanner.cend(); ++i) {
-        Spanner* s = i->second;
-        if (s->staffIdx() == idx && (idx != 0 || !s->systemFlag())) {
-            toRemove.push_back(s);
+    auto removingAllowed = [staffIndex, this](const Spanner* spanner) {
+        if (spanner->staffIdx() != staffIndex) {
+            return false;
+        }
+
+        return staffIndex != 0 || _staves.size() == 1 || !spanner->systemFlag();
+    };
+
+    std::vector<Spanner*> spannersToRemove;
+
+    for (auto it = _spanner.cbegin(); it != _spanner.cend(); ++it) {
+        Spanner* spanner = it->second;
+
+        if (removingAllowed(spanner)) {
+            spannersToRemove.push_back(spanner);
         }
     }
-    for (Spanner* s : _unmanagedSpanner) {
-        if (s->staffIdx() == idx && (idx != 0 || !s->systemFlag())) {
-            toRemove.push_back(s);
+
+    for (Spanner* spanner : _unmanagedSpanner) {
+        if (removingAllowed(spanner)) {
+            spannersToRemove.push_back(spanner);
         }
     }
-    for (Spanner* s : toRemove) {
-        s->undoUnlink();
-        undo(new RemoveElement(s));
+
+    for (Spanner* spanner : spannersToRemove) {
+        spanner->undoUnlink();
+        undo(new RemoveElement(spanner));
     }
 
     //
     //    adjust measures
     //
     for (Measure* m = staff->score()->firstMeasure(); m; m = m->nextMeasure()) {
-        m->cmdRemoveStaves(idx, idx + 1);
+        m->cmdRemoveStaves(staffIndex, staffIndex + 1);
         if (m->hasMMRest()) {
-            m->mmRest()->cmdRemoveStaves(idx, idx + 1);
+            m->mmRest()->cmdRemoveStaves(staffIndex, staffIndex + 1);
         }
     }
 
diff --git a/src/engraving/libmscore/measure.cpp b/src/engraving/libmscore/measure.cpp
index 0fb9989055c9a..ceed17b7a5a2a 100644
--- a/src/engraving/libmscore/measure.cpp
+++ b/src/engraving/libmscore/measure.cpp
@@ -1249,6 +1249,14 @@ void Measure::cmdRemoveStaves(int sStaff, int eStaff)
 {
     int sTrack = sStaff * VOICES;
     int eTrack = eStaff * VOICES;
+
+    auto removingAllowed = [this, sStaff, eStaff](const EngravingItem* item) {
+        int staffIndex = item->staffIdx();
+        int staffCount = score()->nstaves();
+
+        return (staffIndex >= sStaff) && (staffIndex < eStaff) && (!item->systemFlag() || staffCount == 1);
+    };
+
     for (Segment* s = first(); s; s = s->next()) {
         for (int track = eTrack - 1; track >= sTrack; --track) {
             EngravingItem* el = s->element(track);
@@ -1257,20 +1265,21 @@ void Measure::cmdRemoveStaves(int sStaff, int eStaff)
                 score()->undo(new RemoveElement(el));
             }
         }
-        foreach (EngravingItem* e, s->annotations()) {
-            int staffIdx = e->staffIdx();
-            if ((staffIdx >= sStaff) && (staffIdx < eStaff) && !e->systemFlag()) {
+
+        for (EngravingItem* e : s->annotations()) {
+            if (removingAllowed(e)) {
                 e->undoUnlink();
                 score()->undo(new RemoveElement(e));
             }
         }
     }
+
     for (EngravingItem* e : el()) {
         if (e->track() == -1) {
             continue;
         }
-        int staffIdx = e->staffIdx();
-        if (staffIdx >= sStaff && (staffIdx < eStaff) && !e->systemFlag()) {
+
+        if (removingAllowed(e)) {
             e->undoUnlink();
             score()->undo(new RemoveElement(e));
         }