Merge pull request #6307 from MarcSabatella/276141-continuous-spacing

fix #276141: no space for lyrics in continuous view

libmscore/system.cpp

@@ -609,7 +609,41 @@ void System::layout2()
                         dist = qMax(dist, sp->gap() + staff->height());
                   }
             if (!fixedSpace) {
-                  qreal d = score()->lineMode() ? 0.0 : ss->skyline().minDistance(System::staff(si2)->skyline());
+#if 1
+                  // check minimum distance to next staff
+                  // note that in continuous view, we normally only have a partial skyline for the system
+                  // a full one is only built when triggering a full layout
+                  // therefore, we don't know the value we get from minDistance will actually be enough
+                  // so we remember the value between layouts and increase it when necessary
+                  // (the first layout on switching to continuous view gives us good initial values)
+                  // the result is space is good to start and grows as needed
+                  // it does not, however, shrink when possible - only by trigger a full layout
+                  // (such as by toggling to page view and back)
+                  qreal d = ss->skyline().minDistance(System::staff(si2)->skyline());
+                  if (score()->lineMode()) {
+                        qreal previousDist = ss->continuousDist();
+                        if (d > previousDist)
+                              ss->setContinuousDist(d);
+                        else
+                              d = previousDist;
+                        }
+#else
+                  // the code above does do a partial skyline comparison in continuous view
+                  // we hope this does not come at too high a performance penalty for large scores
+                  // if necessary, we can replace the code above with this
+                  // the principle is the same, but we skip the skyline calculation on all but full layout
+                  // the result is space between staves is correct to start but does not grow as needed
+                  qreal d;
+                  if (score()->lineMode()) {
+                        d = ss->continuousDist();
+                        if (d < 0.0) {
+                              d = ss->skyline().minDistance(System::staff(si2)->skyline());
+                              ss->setContinuousDist(d);
+                              }
+                        }
+                  else
+                        d = ss->skyline().minDistance(System::staff(si2)->skyline());
+#endif
                   dist = qMax(dist, d + minVerticalDistance);
                   }
 #endif
@@ -1339,6 +1373,10 @@ qreal System::topDistance(int staffIdx, const SkylineLine& s) const
       {
       Q_ASSERT(!vbox());
       Q_ASSERT(!s.isNorth());
+      // in continuous view, we only build a partial skyline for performance reasons
+      // this means we cannot expect the minDistance calculation to produce meaningful results
+      // so just give up on autoplace for spanners in continuous view
+      // (or any other calculations that rely on this value)
       if (score()->lineMode())
             return 0.0;
       return s.minDistance(staff(staffIdx)->skyline().north());
@@ -1352,6 +1390,7 @@ qreal System::bottomDistance(int staffIdx, const SkylineLine& s) const
       {
       Q_ASSERT(!vbox());
       Q_ASSERT(s.isNorth());
+      // see note on topDistance() above
       if (score()->lineMode())
             return 0.0;
       return staff(staffIdx)->skyline().south().minDistance(s);

libmscore/system.h

@@ -48,6 +48,7 @@ class SysStaff {
       QRectF _bbox;                 // Bbox of StaffLines.
       Skyline _skyline;
       qreal _yOff { 0    };         // offset of top staff line within bbox
+      qreal _continuousDist { -1.0 }; // distance for continuous mode
       bool _show  { true };         // derived from Staff or false if empty
                                     // staff is hidden
    public:
@@ -60,6 +61,9 @@ class SysStaff {
       qreal y() const               { return _bbox.y() + _yOff; }
       void setYOff(qreal offset)    { _yOff = offset; }
 
+      qreal continuousDist() const      { return _continuousDist;  }
+      void setContinuousDist(qreal val) { _continuousDist = val;   }
+
       bool show() const             { return _show; }
       void setShow(bool v)          { _show = v; }