From d9a7d92660515db325f8dd786d31d43951aba2e4 Mon Sep 17 00:00:00 2001
From: mpv <mpv@opencascade.com>
Date: Thu, 23 Jun 2016 20:25:05 +0300
Subject: [PATCH] Fix for issue #1594

---
 src/SketchPlugin/SketchPlugin_Arc.cpp | 31 ++++++++++++++++++---------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/src/SketchPlugin/SketchPlugin_Arc.cpp b/src/SketchPlugin/SketchPlugin_Arc.cpp
index 9825ce9c2..7cf3c0ddf 100644
--- a/src/SketchPlugin/SketchPlugin_Arc.cpp
+++ b/src/SketchPlugin/SketchPlugin_Arc.cpp
@@ -213,19 +213,30 @@ AISObjectPtr SketchPlugin_Arc::getAISObject(AISObjectPtr thePrevious)
               std::shared_ptr<GeomDataAPI_Point2D> aPassedAttr = 
                 std::dynamic_pointer_cast<GeomDataAPI_Point2D>(data()->attribute(PASSED_POINT_ID()));
               if (!aPassedAttr->isInitialized()) { // calculate the appropriate center for the presentation
-                std::shared_ptr<GeomAPI_XY> aDir = 
-                  aEndAttr->pnt()->xy()->decreased(aStartAttr->pnt()->xy())->multiplied(0.5);
-                double x = aDir->x();
-                double y = aDir->y();
-                aDir->setX(x - y);
-                aDir->setY(y + x);
-                std::shared_ptr<GeomAPI_XY> aCenterXY = aStartAttr->pnt()->xy()->added(aDir);
-                aCenter = aSketch->to3D(aCenterXY->x(), aCenterXY->y());
+                // check that center is bad for the current start and end and must be recomputed
+                std::shared_ptr<GeomAPI_Circ2d> aCircleForArc(new GeomAPI_Circ2d(
+                  aCenterAttr->pnt(), aStartAttr->pnt()));
+                std::shared_ptr<GeomAPI_Pnt2d> aProjection = aCircleForArc->project(aEndAttr->pnt());
+                if (!aProjection.get() || aEndAttr->pnt()->distance(aProjection) > tolerance) {
+                  std::shared_ptr<GeomAPI_XY> aDir = 
+                    aEndAttr->pnt()->xy()->decreased(aStartAttr->pnt()->xy())->multiplied(0.5);
+                  double x = aDir->x();
+                  double y = aDir->y();
+                  aDir->setX(x - y);
+                  aDir->setY(y + x);
+                  std::shared_ptr<GeomAPI_XY> aCenterXY = aStartAttr->pnt()->xy()->added(aDir);
+                  aCenter = aSketch->to3D(aCenterXY->x(), aCenterXY->y());
+                }
               }
             }
+            AttributeBooleanPtr isInversed =
+              std::dynamic_pointer_cast<ModelAPI_AttributeBoolean>(attribute(INVERSED_ID()));
+
+            std::shared_ptr<GeomAPI_Shape> aCircleShape = 
+              (isInversed->isInitialized() && isInversed->value()) ?
+                GeomAlgoAPI_EdgeBuilder::lineCircleArc(aCenter, aEndPoint, aStartPoint, aNormal) :
+                GeomAlgoAPI_EdgeBuilder::lineCircleArc(aCenter, aStartPoint, aEndPoint, aNormal);
 
-            std::shared_ptr<GeomAPI_Shape> aCircleShape = GeomAlgoAPI_EdgeBuilder::lineCircleArc(
-                                                            aCenter, aStartPoint, aEndPoint, aNormal);
             if (aCircleShape)
               aShapes.push_back(aCircleShape);
           }
-- 
2.39.2