Track polygon clearance: use the new TransformOvalClearanceToPolygon function, to avoid underestimation of clearance areas.

(issue already found for oval pads)
Add some comments.

common/convert_basic_shapes_to_polygon.cpp

@@ -74,6 +74,12 @@ void TransformOvalClearanceToPolygon( SHAPE_POLY_SET& aCornerBuffer,
     // so, later, we will clamp the polygonal shape with the bounding box
     // of the segment.
     int     radius  = aWidth / 2;
+
+    // Note if we want to compensate the radius reduction of a circle due to
+    // the segment approx, aCorrectionFactor must be calculated like this:
+    // For a circle the min radius is radius * cos( 2PI / s_CircleToSegmentsCount / 2)
+    // aCorrectionFactor is 1 /cos( PI/s_CircleToSegmentsCount  )
+
     radius = radius * aCorrectionFactor;    // make segments outside the circles
 
     // end point is the coordinate relative to aStart

pcbnew/board_items_to_polygon_shape_transform.cpp

@@ -510,8 +510,8 @@ void DRAWSEGMENT::TransformShapeWithClearanceToPolygon( SHAPE_POLY_SET& aCornerB
         break;
 
     case S_SEGMENT:
-        TransformRoundedEndsSegmentToPolygon( aCornerBuffer, m_Start, m_End,
-                                              aCircleToSegmentsCount, linewidth );
+        TransformOvalClearanceToPolygon( aCornerBuffer, m_Start, m_End, linewidth,
+                                         aCircleToSegmentsCount, aCorrectionFactor );
         break;
 
     case S_POLYGON:
@@ -604,10 +604,10 @@ void TRACK::TransformShapeWithClearanceToPolygon( SHAPE_POLY_SET& aCornerBuffer,
         break;
 
     default:
-        TransformRoundedEndsSegmentToPolygon( aCornerBuffer,
-                                              m_Start, m_End,
+        TransformOvalClearanceToPolygon( aCornerBuffer, m_Start, m_End,
+                                         m_Width + ( 2 * aClearanceValue),
                                          aCircleToSegmentsCount,
-                                              m_Width + ( 2 * aClearanceValue) );
+                                         aCorrectionFactor );
         break;
     }
 }

pcbnew/zone_filler.cpp

@@ -282,7 +282,7 @@ void ZONE_FILLER::buildZoneFeatureHoleList( const ZONE_CONTAINER* aZone,
     /* calculates the coeff to compensate radius reduction of holes clearance
      * due to the segment approx.
      * For a circle the min radius is radius * cos( 2PI / s_CircleToSegmentsCount / 2)
-     * s_Correction is 1 /cos( PI/s_CircleToSegmentsCount  )
+     * correctionFactor is 1 /cos( PI/s_CircleToSegmentsCount  )
      */
     correctionFactor = 1.0 / cos( M_PI / (double) segsPerCircle );