EC_CONVERGING handles colinear lines properly.

include/geometry/seg.h

@@ -244,14 +244,14 @@ public:
      */
     bool Collinear( const SEG& aSeg ) const
     {
-        ecoord qa1 = A.y - B.y;
-        ecoord qb1 = B.x - A.x;
-        ecoord qc1 = -qa1 * A.x - qb1 * A.y;
-        ecoord qa2 = aSeg.A.y - aSeg.B.y;
-        ecoord qb2 = aSeg.B.x - aSeg.A.x;
-        ecoord qc2 = -qa2 * aSeg.A.x - qb2 * aSeg.A.y;
-
-        return ( qa1 == qa2 ) && ( qb1 == qb2 ) && ( qc1 == qc2 );
+        ecoord qa = A.y - B.y;
+        ecoord qb = B.x - A.x;
+        ecoord qc = -qa * A.x - qb * A.y;
+
+        ecoord d1 = std::abs( aSeg.A.x * qa + aSeg.A.y * qb + qc );
+        ecoord d2 = std::abs( aSeg.B.x * qa + aSeg.B.y * qb + qc );
+
+        return ( d1 <= 1 && d2 <= 1 );
     }
 
     /**

pcbnew/tools/edit_points.cpp

@@ -194,7 +194,8 @@ void EC_CIRCLE::Apply( EDIT_POINT& aHandle )
 
 
 EC_CONVERGING::EC_CONVERGING( EDIT_LINE& aLine, EDIT_POINTS& aPoints ) :
-    EDIT_CONSTRAINT<EDIT_POINT>( aLine.GetOrigin() ), m_line( aLine ), m_editPoints( aPoints )
+    EDIT_CONSTRAINT<EDIT_POINT>( aLine.GetOrigin() ),
+    m_colinearConstraint( NULL ), m_line( aLine ), m_editPoints( aPoints )
 {
     // Dragged segment endings
     EDIT_POINT& origin = aLine.GetOrigin();
@@ -209,7 +210,17 @@ EC_CONVERGING::EC_CONVERGING( EDIT_LINE& aLine, EDIT_POINTS& aPoints ) :
     m_endSideConstraint = new EC_LINE( end, nextEnd );
 
     // Store the current vector of the line
-    m_draggedVector = end.GetPosition() - origin.GetPosition() ;
+    m_draggedVector = end.GetPosition() - origin.GetPosition();
+
+    // Check for colinearity
+    SEG originSide( origin.GetPosition(), prevOrigin.GetPosition() );
+    SEG endSide( end.GetPosition(), nextEnd.GetPosition() );
+    SEG dragged( origin.GetPosition(), end.GetPosition() );
+
+    if( dragged.Collinear( originSide ) )
+        m_colinearConstraint = m_originSideConstraint;
+    else if( dragged.Collinear( endSide ) )
+        m_colinearConstraint = m_endSideConstraint;
 }
 
 
@@ -217,18 +228,25 @@ EC_CONVERGING::~EC_CONVERGING()
 {
     delete m_originSideConstraint;
     delete m_endSideConstraint;
+    // m_colinearConstraint should not be freed, it is a pointer to one of the above
 }
 
 
 void EC_CONVERGING::Apply( EDIT_POINT& aHandle )
 {
-    // The dragged segment
-    SEG dragged( m_line.GetPosition(), m_line.GetPosition() + m_draggedVector );
-
     // The dragged segment endpoints
     EDIT_POINT& origin = m_line.GetOrigin();
     EDIT_POINT& end = m_line.GetEnd();
 
+    if( m_colinearConstraint )
+    {
+        m_colinearConstraint->Apply( origin );
+        m_colinearConstraint->Apply( end );
+    }
+
+    // The dragged segment
+    SEG dragged( origin.GetPosition(), origin.GetPosition() + m_draggedVector );
+
     // Do not allow points on the adjacent segments move freely
     m_originSideConstraint->Apply();
     m_endSideConstraint->Apply();

pcbnew/tools/edit_points.h

@@ -622,6 +622,10 @@ private:
     ///> Constraint for end side segment.
     EDIT_CONSTRAINT<EDIT_POINT>* m_endSideConstraint;
 
+    ///> Additional constriant, applied when at least two points are collinear. It is a pointer to
+    ///> m_[origin/end]SideConstraint, so it should not be freed.
+    EDIT_CONSTRAINT<EDIT_POINT>* m_colinearConstraint;
+
     ///> Dragged segment.
     EDIT_LINE& m_line;