PartDesign: fix Shapebinder placement

src/Mod/PartDesign/App/ShapeBinder.cpp

@@ -25,6 +25,7 @@
 #ifndef _PreComp_
 #include <cfloat>
 #include <boost/bind.hpp>
+#include <BRep_Builder.hxx>
 #include <BRepBuilderAPI_MakeFace.hxx>
 #endif
 
@@ -75,16 +76,20 @@ App::DocumentObjectExecReturn* ShapeBinder::execute(void) {
         //if we have a link we rebuild the shape, but we change nothing if we are a simple copy
         if (obj) {
             Part::TopoShape shape = ShapeBinder::buildShapeFromReferences(obj, subs);
-            Base::Placement placement(shape.getTransform());
-            Shape.setValue(shape);
+            //now, shape is in object's CS, and includes local Placement of obj but nothing else.
 
             if (TraceSupport.getValue()) {
-                // this is the inverted global placement of the parent group ...
-                placement = this->globalPlacement() * Placement.getValue().inverse();
-                // multiplied with the global placement of the support shape
-                placement = placement.inverse() * obj->globalPlacement();
+                //compute the transform, and apply it to the shape.
+                Base::Placement sourceCS = //full placement of container of obj
+                        obj->globalPlacement() * obj->Placement.getValue().inverse();
+                Base::Placement targetCS = //full placement of container of this shapebinder
+                        this->globalPlacement() * this->Placement.getValue().inverse();
+                Base::Placement transform = targetCS.inverse() * sourceCS;
+                shape.setPlacement(transform * shape.getPlacement());
             }
-            Placement.setValue(placement);
+
+            this->Placement.setValue(shape.getTransform());
+            this->Shape.setValue(shape);
         }
     }
 
@@ -145,24 +150,24 @@ Part::TopoShape ShapeBinder::buildShapeFromReferences( Part::Feature* obj, std::
     if (subs.empty())
         return obj->Shape.getShape();
 
-    //if we use multiple subshapes we build a shape from them by fusing them together
-    Part::TopoShape base;
-    std::vector<TopoDS_Shape> operators;
+    std::vector<TopoDS_Shape> shapes;
     for (std::string sub : subs) {
-        if (base.isNull())
-            base = obj->Shape.getShape().getSubShape(sub.c_str());
-        else
-            operators.push_back(obj->Shape.getShape().getSubShape(sub.c_str()));
+        shapes.push_back(obj->Shape.getShape().getSubShape(sub.c_str()));
     }
 
-    try {
-        if (!operators.empty() && !base.isNull())
-            return base.fuse(operators);
-    }
-    catch (...) {
-        return base;
+    if (shapes.size() == 1){
+        //single subshape. Return directly.
+        return shapes[0];
+    } else {
+        //multiple subshapes. Make a compound.
+        BRep_Builder builder;
+        TopoDS_Compound cmp;
+        builder.MakeCompound(cmp);
+        for(const TopoDS_Shape& sh : shapes){
+            builder.Add(cmp, sh);
+        }
+        return cmp;
     }
-    return base;
 }
 
 void ShapeBinder::handleChangedPropertyType(Base::XMLReader &reader, const char *TypeName, App::Property *prop)