Add ordering on alignments

include/vrv/horizontalaligner.h

@@ -109,6 +109,14 @@ class Alignment : public Object {
     Fraction GetTime() const { return m_time; }
     ///@}
 
+    /**
+     * @name Weak ordering: for alignments in the same measure it is based on time, otherwise on the measure order
+     */
+    ///@{
+    bool operator==(const Alignment &other) const;
+    std::weak_ordering operator<=>(const Alignment &other) const;
+    ///@}
+
     /**
      * Add the LayerElement to the appropriate AlignmentReference child.
      * Looks at the cross-staff situation (@staff or parent @staff).

src/horizontalaligner.cpp

@@ -542,6 +542,29 @@ bool Alignment::IsSupportedChild(Object *child)
     return true;
 }
 
+bool Alignment::operator==(const Alignment &other) const
+{
+    const Measure *measure = vrv_cast<const Measure *>(this->GetFirstAncestor(MEASURE));
+    const Measure *otherMeasure = vrv_cast<const Measure *>(other.GetFirstAncestor(MEASURE));
+    assert(measure && otherMeasure);
+
+    return (measure == otherMeasure) && (this->GetTime() == other.GetTime());
+}
+
+std::weak_ordering Alignment::operator<=>(const Alignment &other) const
+{
+    const Measure *measure = vrv_cast<const Measure *>(this->GetFirstAncestor(MEASURE));
+    const Measure *otherMeasure = vrv_cast<const Measure *>(other.GetFirstAncestor(MEASURE));
+    assert(measure && otherMeasure);
+
+    if (measure == otherMeasure) {
+        return this->GetTime() <=> other.GetTime();
+    }
+    else {
+        return Object::IsPreOrdered(measure, otherMeasure) ? std::weak_ordering::less : std::weak_ordering::greater;
+    }
+}
+
 bool Alignment::HasAccidVerticalOverlap(const Alignment *otherAlignment, int staffN) const
 {
     if (!otherAlignment) return false;