From 61fe4bcaeec743b64ef9e04f992ff41355a6764b Mon Sep 17 00:00:00 2001
From: Abdullah Tahiri <abdullah.tahiri.yo@gmail.com>
Date: Wed, 21 Dec 2016 16:25:19 +0100
Subject: [PATCH] Sketcher: Parabola Arc rules solver constraint

---
 src/Mod/Sketcher/App/Sketch.cpp       | 4 ++--
 src/Mod/Sketcher/App/planegcs/GCS.cpp | 6 ++++++
 src/Mod/Sketcher/App/planegcs/GCS.h   | 3 ++-
 src/Mod/Sketcher/App/planegcs/Geo.cpp | 4 ++--
 4 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/Mod/Sketcher/App/Sketch.cpp b/src/Mod/Sketcher/App/Sketch.cpp
index f5fafeff5..a2f034cb0 100644
--- a/src/Mod/Sketcher/App/Sketch.cpp
+++ b/src/Mod/Sketcher/App/Sketch.cpp
@@ -639,8 +639,8 @@ int Sketch::addArcOfParabola(const Part::GeomArcOfParabola &parabolaSegment, boo
     Geoms.push_back(def);
 
     // arcs require an ArcRules constraint for the end points
-    //if (!fixed)
-    //    GCSsys.addConstraintArcOfParabolaRules(a);
+    if (!fixed)
+        GCSsys.addConstraintArcOfParabolaRules(a);
 
     // return the position of the newly added geometry
     return Geoms.size()-1;
diff --git a/src/Mod/Sketcher/App/planegcs/GCS.cpp b/src/Mod/Sketcher/App/planegcs/GCS.cpp
index 312830ec7..289bfe9d5 100644
--- a/src/Mod/Sketcher/App/planegcs/GCS.cpp
+++ b/src/Mod/Sketcher/App/planegcs/GCS.cpp
@@ -604,6 +604,12 @@ int System::addConstraintArcOfHyperbolaRules(ArcOfHyperbola &a, int tagId)
     return addConstraintCurveValue(a.end,a,a.endAngle, tagId);
 }
 
+int System::addConstraintArcOfParabolaRules(ArcOfParabola &a, int tagId)
+{
+    addConstraintCurveValue(a.start,a,a.startAngle, tagId);
+    return addConstraintCurveValue(a.end,a,a.endAngle, tagId);
+}
+
 int System::addConstraintPointOnArc(Point &p, Arc &a, int tagId)
 {
     return addConstraintP2PDistance(p, a.center, a.rad, tagId);
diff --git a/src/Mod/Sketcher/App/planegcs/GCS.h b/src/Mod/Sketcher/App/planegcs/GCS.h
index e6ee58ac4..981e766f6 100644
--- a/src/Mod/Sketcher/App/planegcs/GCS.h
+++ b/src/Mod/Sketcher/App/planegcs/GCS.h
@@ -184,7 +184,8 @@ namespace GCS
         int addConstraintPointOnHyperbolicArc(Point &p, ArcOfHyperbola &e, int tagId=0);
         int addConstraintArcOfEllipseRules(ArcOfEllipse &a, int tagId=0);
         int addConstraintCurveValue(Point &p, Curve &a, double *u, int tagId=0);
-        int addConstraintArcOfHyperbolaRules(ArcOfHyperbola &a, int tagId=0);        
+        int addConstraintArcOfHyperbolaRules(ArcOfHyperbola &a, int tagId=0);
+	int addConstraintArcOfParabolaRules(ArcOfParabola &a, int tagId=0);
         int addConstraintPointOnArc(Point &p, Arc &a, int tagId=0);
         int addConstraintPerpendicularLine2Arc(Point &p1, Point &p2, Arc &a,
                                                int tagId=0);
diff --git a/src/Mod/Sketcher/App/planegcs/Geo.cpp b/src/Mod/Sketcher/App/planegcs/Geo.cpp
index 5662cfb07..7671e86fa 100644
--- a/src/Mod/Sketcher/App/planegcs/Geo.cpp
+++ b/src/Mod/Sketcher/App/planegcs/Geo.cpp
@@ -539,9 +539,9 @@ DeriVector2 Parabola::Value(double u, double du, double* derivparam)
     f = fv.length(df);
     
     DeriVector2 xdir = fv.getNormalized();
-    DeriVector2 ydir = xdir.rotate90ccw();
+    DeriVector2 ydir = xdir.rotate90cw();
     
-    DeriVector2 dirx = xdir.multD(u,du).multD(u,du).multD(0.25*f,0.5*df); 
+    DeriVector2 dirx = xdir.multD(u,du).multD(u,du).divD(4*f,4*df);
     DeriVector2 diry = ydir.multD(u,du); 
     
     DeriVector2 dir = dirx.sum(diry);