Sketcher: support external reference without subname

Reference without subname deliberately disables geometry topo name
tracking to handling some special cases, such as configuration table
with explicit geometry reference. Whole object selection is only enabled
by holding `Alt` key.

Related #1028

src/Mod/Sketcher/App/SketchObject.cpp

@@ -7529,15 +7529,24 @@ int SketchObject::addExternal(App::DocumentObject *Obj, const char* SubName, boo
     if (!isExternalAllowed(Obj->getDocument(), Obj))
         return -1;
 
-    auto wholeShape = Part::Feature::getTopoShape(Obj);
-    auto shape = wholeShape.getSubTopoShape(SubName, /*silent*/true);
+    Part::TopoShape wholeShape = Part::Feature::getTopoShape(Obj);
+    Part::TopoShape shape;
     TopAbs_ShapeEnum shapeType = TopAbs_SHAPE;
-    if (shape.shapeType(/*silent*/true) != TopAbs_FACE) {
-        if (shape.hasSubShape(TopAbs_FACE))
-            shapeType = TopAbs_FACE;
-        else if (shape.shapeType(/*silent*/true) != TopAbs_EDGE
-                && shape.hasSubShape(TopAbs_EDGE))
-            shapeType = TopAbs_EDGE;
+    if (!SubName && !SubName[0]) {
+        shape = wholeShape.getSubTopoShape(SubName, /*silent*/true);
+        if (shape.shapeType(/*silent*/true) != TopAbs_FACE
+                && shape.shapeType(/*silent*/true) != TopAbs_WIRE) {
+            if (shape.hasSubShape(TopAbs_FACE)) {
+                shapeType = TopAbs_FACE;
+            }
+            else if (shape.hasSubShape(TopAbs_WIRE)) {
+                shapeType = TopAbs_WIRE;
+            }
+            else if (shape.shapeType(/*silent*/true) != TopAbs_EDGE
+                    && shape.hasSubShape(TopAbs_EDGE)) {
+                shapeType = TopAbs_EDGE;
+            }
+        }
     }
 
     if (shapeType != TopAbs_SHAPE) {
@@ -8456,6 +8465,21 @@ void SketchObject::rebuildExternalGeometry(bool defining, bool addIntersection)
                 FC_WARN("Null shape from geometry reference in " << getFullName() << ": " << key);
                 continue;
             }
+            if (refSubShape.ShapeType() != TopAbs_FACE
+                    && refSubShape.ShapeType() != TopAbs_EDGE
+                    && refSubShape.ShapeType() != TopAbs_VERTEX
+                    && refSubShape.ShapeType() != TopAbs_WIRE)
+            {
+                const std::array<TopAbs_ShapeEnum, 4> types = {
+                    TopAbs_FACE, TopAbs_WIRE, TopAbs_EDGE, TopAbs_VERTEX};
+                Part::TopoShape shape(refSubShape);
+                for (auto type : types) {
+                    if (shape.hasSubShape(type)) {
+                        refSubShape = shape.getSubShape(type, 1);
+                        break;
+                    }
+                }
+            }
 
             auto importFace = [&](const TopoDS_Shape &refSubShape) {
                 gp_Pln plane;
@@ -9029,6 +9053,10 @@ void SketchObject::rebuildExternalGeometry(bool defining, bool addIntersection)
                 if (!intersection)
                     importFace(refSubShape);
                 break;
+            case TopAbs_WIRE:
+                for (const auto &s : Part::TopoShape(refSubShape).getSubShapes(TopAbs_EDGE))
+                    importEdge(s);
+                break;
             case TopAbs_EDGE:
                 importEdge(refSubShape);
                 break;

src/Mod/Sketcher/Gui/DrawSketchHandlerExternal.h

@@ -23,6 +23,7 @@
 #ifndef SKETCHERGUI_DrawSketchHandlerExternal_H
 #define SKETCHERGUI_DrawSketchHandlerExternal_H
 
+#include <array>
 #include "GeometryCreationMode.h"
 
 
@@ -42,13 +43,52 @@ class ExternalSelection : public SketcherSelectionFilterGate
     bool allow(App::Document *pDoc, App::DocumentObject *pObj, const char *sSubName) override
     {
         Sketcher::SketchObject *sketch = static_cast<Sketcher::SketchObject*>(object);
+        static const std::array<const char *, 4> allowedTypes = {"Face", "Wire", "Edge", "Vertex"};
 
         this->notAllowedReason = "";
 
-        if (!sSubName || sSubName[0] == '\0') {
-            this->notAllowedReason = QT_TR_NOOP("No element. ");
+        bool checkShape = true;
+        if (sSubName && sSubName[0]) {
+            for (auto type : allowedTypes) {
+                if (boost::starts_with(sSubName, type)) {
+                    checkShape = false;
+                    break;
+                }
+            }
+        }
+        else if (!(QApplication::queryKeyboardModifiers() & Qt::AltModifier)) {
+            this->notAllowedReason = QT_TR_NOOP("Hold Alt key to enable whole object selection.");
             return false;
         }
+
+        if (checkShape) {
+            auto shape = Part::TopoShape(Part::Feature::getShape(pObj));
+            if (shape.isNull()) {
+                this->notAllowedReason = QT_TR_NOOP("No shape. ");
+                return false;
+            }
+            sSubName = nullptr;
+            for (auto type : allowedTypes) {
+                auto shapeType = Part::TopoShape::shapeType(type);
+                if (shape.shapeType() == shapeType) {
+                    sSubName = type;
+                    break;
+                }
+                int count = shape.countSubShapes(shapeType);
+                if (count == 1) {
+                    sSubName = type;
+                    break;
+                }
+                if (count > 1) {
+                    this->notAllowedReason = QT_TR_NOOP("Multiple elements. ");
+                    return false;
+                }
+            }
+            if (!sSubName) {
+                this->notAllowedReason = QT_TR_NOOP("Unknown element. ");
+                return false;
+            }
+        }
 
         if (!ViewProviderSketch::allowFaceExternalPick() && boost::starts_with(sSubName, "Face")) {
             this->notAllowedReason = QT_TR_NOOP("Face picking disabled in the task panel. ");
@@ -260,10 +300,16 @@ class DrawSketchHandlerExternal: public DrawSketchHandler
             if (obj == NULL)
                 throw Base::ValueError("Sketcher: External geometry: Invalid object in selection");
 
+            if (msg.Object.getOldElementName().empty()
+                    && !(QApplication::queryKeyboardModifiers() & Qt::AltModifier)) {
+                return false;
+            }
+
             auto indexedName = Data::IndexedName(msg.Object.getOldElementName().c_str());
             if (intersection ||
                 obj->getTypeId().isDerivedFrom(App::Plane::getClassTypeId()) ||
                 obj->getTypeId().isDerivedFrom(Part::Datum::getClassTypeId()) ||
+                msg.Object.getOldElementName().empty() ||
                 boost::iends_with(indexedName.getType(), "edge") ||
                 boost::iends_with(indexedName.getType(), "vertex") ||
                 boost::iends_with(indexedName.getType(), "face") ||