new action+shortcut M to toggle multi measure rest creation

libmscore/cmd.cpp

@@ -2388,6 +2388,10 @@ void Score::cmd(const QAction* a)
             transposeSemitone(1);
       else if (cmd == "transpose-down")
             transposeSemitone(-1);
+      else if (cmd == "toggle-mmrest") {
+            bool val = !styleB(ST_createMultiMeasureRests);
+            undo(new ChangeStyleVal(this, ST_createMultiMeasureRests, val));
+            }
       else
             qDebug("1unknown cmd <%s>", qPrintable(cmd));
       }

libmscore/undo.cpp

@@ -2502,6 +2502,18 @@ void ChangeStyle::flip()
       style = tmp;
       }
 
+//---------------------------------------------------------
+//   ChangeStyleVal::flip
+//---------------------------------------------------------
+
+void ChangeStyleVal::flip()
+      {
+      QVariant v = score->style(idx);
+      score->style()->set(idx, value);
+      score->setLayoutAll(true);
+      value = v;
+      }
+
 //---------------------------------------------------------
 //   ChangeChordStaffMove
 //---------------------------------------------------------

libmscore/undo.h

@@ -835,6 +835,22 @@ class ChangeStyle : public UndoCommand {
       UNDO_NAME("ChangeStyle");
       };
 
+//---------------------------------------------------------
+//   ChangeStyleVal
+//---------------------------------------------------------
+
+class ChangeStyleVal : public UndoCommand {
+      Score* score;
+      StyleIdx idx;
+      QVariant value;
+
+      void flip();
+
+   public:
+      ChangeStyleVal(Score* s, StyleIdx i, const QVariant& v) : score(s), idx(i), value(v) {}
+      UNDO_NAME("ChangeStyleVal");
+      };
+
 //---------------------------------------------------------
 //   ChangeChordStaffMove
 //---------------------------------------------------------

mscore/actions.cpp

@@ -2461,7 +2461,7 @@ Shortcut Shortcut::sc[] = {
          STATE_NORMAL,
          A_CMD,
          "toggle-mmrest",
-         QT_TRANSLATE_NOOP("action","toggle create multi measure rest"),
+         QT_TRANSLATE_NOOP("action","toggle create multi measure rest")
          ),
       // xml==0  marks end of list
       Shortcut(0, 0, 0, 0)