Fix off-by-one error in distance check for arcs

libs/kimath/include/geometry/circle.h

@@ -74,6 +74,18 @@ public:
      */
     VECTOR2I NearestPoint( const VECTOR2I& aP ) const;
 
+    /**
+     * Compute the point (floating point version) on the circumference of the circle that
+     * is the closest to aP.
+     *
+     * In other words: finds the intersection point of this circle and a line that passes through
+     * both this circle's center and aP.
+     *
+     * @param aP.
+     * @return nearest point to aP.
+     */
+    VECTOR2D NearestPoint( const VECTOR2D& aP ) const;
+
     /**
      * Compute the intersection points between this circle and \a aCircle.
      *

libs/kimath/src/geometry/circle.cpp

@@ -206,6 +206,18 @@ VECTOR2I CIRCLE::NearestPoint( const VECTOR2I& aP ) const
 }
 
 
+VECTOR2D CIRCLE::NearestPoint( const VECTOR2D& aP ) const
+{
+    VECTOR2D vec = aP - Center;
+
+    // Handle special case where aP is equal to this circle's center
+    if( vec.x == 0 && vec.y == 0 )
+        vec.x = 1; // Arbitrary, to ensure the return value is always on the circumference
+
+    return vec.Resize( Radius ) + Center;
+}
+
+
 std::vector<VECTOR2I> CIRCLE::Intersect( const CIRCLE& aCircle ) const
 {
     // From https://mathworld.wolfram.com/Circle-CircleIntersection.html

libs/kimath/src/geometry/shape_arc.cpp

@@ -432,8 +432,8 @@ bool SHAPE_ARC::Collide( const VECTOR2I& aP, int aClearance, int* aActual,
     VECTOR2L  center = GetCenter();
     double    radius = ( center - m_start ).EuclideanNorm();
     CIRCLE    fullCircle( center, radius );
-    VECTOR2I  nearestPt = fullCircle.NearestPoint( aP );
-    int       dist = ( nearestPt - aP ).EuclideanNorm();
+    VECTOR2D  nearestPt = fullCircle.NearestPoint( VECTOR2D( aP ) );
+    int       dist = nearestPt.Distance( aP );
     EDA_ANGLE angleToPt( aP - fullCircle.Center ); // Angle from center to the point
 
     if( !dist )