diff --git a/src/common/QskIntervalF.cpp b/src/common/QskIntervalF.cpp
index a24e7e0b..3fdce17f 100644
--- a/src/common/QskIntervalF.cpp
+++ b/src/common/QskIntervalF.cpp
@@ -152,6 +152,36 @@ QskIntervalF QskIntervalF::extended( qreal value ) const noexcept
     return QskIntervalF( lower, upper );
 }
 
+void QskIntervalF::spanFromLowerBound( qreal value ) noexcept
+{
+    if ( !isValid() )
+    {
+        m_lowerBound = value;
+        m_upperBound = value;
+    }
+    else
+    {
+        m_lowerBound = value;
+        if ( m_lowerBound > m_upperBound )
+            m_upperBound = m_lowerBound;
+    }
+}
+
+void QskIntervalF::spanFromUpperBound( qreal value ) noexcept
+{
+    if ( !isValid() )
+    {
+        m_lowerBound = value;
+        m_upperBound = value;
+    }
+    else
+    {
+        m_upperBound = value;
+        if ( m_lowerBound > m_upperBound )
+            m_lowerBound = m_upperBound;
+    }
+}
+
 bool QskIntervalF::fuzzyContains( qreal value ) const
 {
     if ( !isValid() )
diff --git a/src/common/QskIntervalF.h b/src/common/QskIntervalF.h
index f8c2074b..8feb31bd 100644
--- a/src/common/QskIntervalF.h
+++ b/src/common/QskIntervalF.h
@@ -35,15 +35,22 @@ class QSK_EXPORT QskIntervalF
     constexpr qreal upperBound() const noexcept;
     void setUpperBound( qreal ) noexcept;
 
+    void spanFromLowerBound( qreal ) noexcept;
+    void spanFromUpperBound( qreal ) noexcept;
+
     constexpr qreal width() const noexcept;
     void setWidth( qreal ) noexcept;
 
     constexpr bool contains( qreal value ) const noexcept;
     constexpr bool contains( const QskIntervalF& ) const noexcept;
 
+    constexpr bool isBoundary( qreal value ) const noexcept;
+
     bool fuzzyContains( qreal value ) const;
     bool fuzzyContains( const QskIntervalF& ) const;
 
+    bool fuzzyIsBoundary( qreal value ) const;
+
     static constexpr QskIntervalF normalized( qreal value1, qreal value2 ) noexcept;
 
     void translate( qreal offset ) noexcept;
@@ -159,6 +166,11 @@ inline constexpr bool QskIntervalF::contains( const QskIntervalF& interval ) con
         && contains( interval.m_upperBound );
 }
 
+inline constexpr bool QskIntervalF::isBoundary( qreal value ) const noexcept
+{
+    return ( value == m_lowerBound ) || ( value == m_upperBound );
+}
+
 inline void QskIntervalF::translate( qreal offset ) noexcept
 {
     m_lowerBound += offset;