geometry: SEG::NearestPoint(SEG) now returns points only on (this) segment

libs/kimath/src/geometry/seg.cpp

@@ -36,10 +36,26 @@ int sgn( T aVal )
 
 SEG::ecoord SEG::SquaredDistance( const SEG& aSeg ) const
 {
-    VECTOR2I closestOnRef = NearestPoint( aSeg );
-    VECTOR2I closestOnASeg = aSeg.NearestPoint( *this );
+    // fixme: rather inefficient....
+    if( Intersect( aSeg ) )
+        return 0;
 
-    return ( closestOnRef - closestOnASeg ).SquaredEuclideanNorm();
+    const VECTOR2I pts[4] =
+    {
+        aSeg.NearestPoint( A ) - A,
+        aSeg.NearestPoint( B ) - B,
+        NearestPoint( aSeg.A ) - aSeg.A,
+        NearestPoint( aSeg.B ) - aSeg.B
+    };
+
+    ecoord m = VECTOR2I::ECOORD_MAX;
+  
+    for( int i = 0; i < 4; i++ )
+    {
+        m = std::min( m, pts[i].SquaredEuclideanNorm() );
+    }
+
+    return m;
 }
 
 
@@ -48,15 +64,40 @@ const VECTOR2I SEG::NearestPoint( const SEG& aSeg ) const
     if( OPT_VECTOR2I p = Intersect( aSeg ) )
         return *p;
 
-    VECTOR2I nearestA = NearestPoint( aSeg.A );
-    VECTOR2I deltaA = nearestA - aSeg.A;
-    VECTOR2I nearestB = NearestPoint( aSeg.B );
-    VECTOR2I deltaB = nearestB - aSeg.B;
+    const VECTOR2I pts_origin[4] =
+    {
+            aSeg.NearestPoint( A ),
+            aSeg.NearestPoint( B ),
+            NearestPoint( aSeg.A ),
+            NearestPoint( aSeg.B )
+    };
+
+
+    const VECTOR2I* pts_out[4] =
+    {
+            &A,
+            &B,
+            &pts_origin[2],
+            &pts_origin[3]
+    };
+
+    const ecoord pts_dist[4] =
+    {
+            ( pts_origin[0] - A ).SquaredEuclideanNorm(),
+            ( pts_origin[1] - B ).SquaredEuclideanNorm(),
+            ( pts_origin[2] - aSeg.A ).SquaredEuclideanNorm(),
+            ( pts_origin[3] - aSeg.B ).SquaredEuclideanNorm()
+    };
+
+    int min_i = 0;
+ 
+    for( int i = 0; i < 4; i++ )
+    {
+        if( pts_dist[i] < pts_dist[min_i] )
+            min_i = i;
+    }
 
-    if( deltaA.SquaredEuclideanNorm() < deltaB.SquaredEuclideanNorm() )
-        return nearestA;
-    else
-        return nearestB;
+    return *pts_out[min_i];
 }