[TD]fix misaligned PAT hatch on section

src/Mod/TechDraw/App/DrawGeomHatch.cpp

@@ -238,11 +238,24 @@ std::vector<LineSet>  DrawGeomHatch::getTrimmedLinesSection(DrawViewSection* sou
                                                             double scale )
 {
     std::vector<LineSet> result;
-    TopoDS_Face tFace = f;
-    tFace = TopoDS::Face(GeometryObject::invertGeometry(tFace));
+    gp_Pln p;
+    Base::Vector3d vfc = DrawUtil::getFaceCenter(f);
+    gp_Pnt fc(vfc.x, vfc.y, vfc.z); 
+    double dir = -1.0;
+    if (fc.Z() < 0.0) {
+        dir = -dir;
+    }
+    Base::Vector3d stdZ(0.0, 0.0, 1.0);
+    Base::Vector3d offset = stdZ * p.Distance(fc) * dir;
+
+    //f may be above or below paper plane and must be moved so Common operation in 
+    //getTrimmedLines succeeds
+    TopoDS_Shape moved = TechDraw::moveShape(f,
+                                              offset);
+    TopoDS_Face fMoved = TopoDS::Face(GeometryObject::invertGeometry(moved));
     result = getTrimmedLines(source,
                              lineSets,
-                             tFace,
+                             fMoved,
                              scale );
     return result;
 }

src/Mod/TechDraw/App/DrawUtil.cpp

@@ -774,6 +774,22 @@ bool  DrawUtil::isCrazy(TopoDS_Edge e)
     return result;
 } 
 
+//get 3d position of a face's center
+Base::Vector3d DrawUtil::getFaceCenter(TopoDS_Face f)
+{
+    BRepAdaptor_Surface adapt(f);
+    double u1 = adapt.FirstUParameter();
+    double u2 = adapt.LastUParameter();
+    double mu = (u1 + u2) / 2.0;
+    double v1 = adapt.FirstVParameter();
+    double v2 = adapt.LastVParameter();
+    double mv = (v1 + v2) / 2.0;
+    BRepLProp_SLProps prop(adapt,mu,mv,0,Precision::Confusion());
+    const gp_Pnt gv = prop.Value();
+    Base::Vector3d v(gv.X(), gv.Y(), gv.Z());
+    return v;
+}
+
 // Supplementary mathematical functions
 // ====================================
 

src/Mod/TechDraw/App/DrawUtil.h

@@ -120,6 +120,7 @@ class TechDrawExport DrawUtil {
         static App::Color pyTupleToColor(PyObject* pColor);
         static PyObject* colorToPyTuple(App::Color color);
         static bool isCrazy(TopoDS_Edge e);
+        static Base::Vector3d getFaceCenter(TopoDS_Face f);
 
         // Supplementary mathematical functions
         static int sgn(double x);