Gui: Improve transform UI responsivness

This introduces much faster CenterOfMassProvider#supports method that
can be used as cheap pre-check to see if the object supplied could have
the center of mass and so delay the domputation to a moment where it is
actually needed.

src/Mod/Part/App/Services.cpp

@@ -45,7 +45,7 @@ Base::Placement AttacherSubObjectPlacement::calculate(
 
 std::optional<Base::Vector3d> PartCenterOfMass::ofDocumentObject(App::DocumentObject* object) const
 {
-    if (const auto feature = dynamic_cast<Part::Feature*>(object)) {
+    if (const auto* feature = freecad_cast<Part::Feature*>(object)) {
         const auto shape = feature->Shape.getShape();
 
         if (const auto cog = shape.centerOfGravity()) {
@@ -57,3 +57,8 @@ std::optional<Base::Vector3d> PartCenterOfMass::ofDocumentObject(App::DocumentOb
 
     return {};
 }
+
+bool PartCenterOfMass::supports(App::DocumentObject* object) const
+{
+    return object->isDerivedFrom<Part::Feature>();
+}

src/Mod/Part/App/Services.h

@@ -42,6 +42,7 @@ class PartCenterOfMass final: public App::CenterOfMassProvider
 {
 public:
     std::optional<Base::Vector3d> ofDocumentObject(App::DocumentObject* object) const override;
+    bool supports(App::DocumentObject* object) const override;
 };
 
 #endif  // PART_SERVICES_H