Revert "Address the poor performance of the existing unique-name generation (#17944)"

This reverts commit 83202d8ad6.

# Conflicts:
#	src/Base/Tools.cpp
#	src/Base/Tools.h

src/App/PropertyStandard.cpp

@@ -1385,13 +1385,101 @@ void PropertyString::setValue(const char* newLabel)
         return;
     }
 
+    std::string _newLabel;
+
     std::vector<std::pair<Property*, std::unique_ptr<Property>>> propChanges;
-    std::string label = newLabel;
+    std::string label;
     auto obj = dynamic_cast<DocumentObject*>(getContainer());
     bool commit = false;
 
-    if (obj && this == &obj->Label) {
-        propChanges = obj->onProposedLabelChange(label);
+    if (obj && obj->isAttachedToDocument() && this == &obj->Label
+        && (!obj->getDocument()->testStatus(App::Document::Restoring)
+            || obj->getDocument()->testStatus(App::Document::Importing))
+        && !obj->getDocument()->isPerformingTransaction()) {
+        // allow object to control label change
+
+        static ParameterGrp::handle _hPGrp;
+        if (!_hPGrp) {
+            _hPGrp = GetApplication().GetUserParameter().GetGroup("BaseApp");
+            _hPGrp = _hPGrp->GetGroup("Preferences")->GetGroup("Document");
+        }
+        App::Document* doc = obj->getDocument();
+        if (doc && !_hPGrp->GetBool("DuplicateLabels") && !obj->allowDuplicateLabel()) {
+            std::vector<std::string> objectLabels;
+            std::vector<App::DocumentObject*>::const_iterator it;
+            std::vector<App::DocumentObject*> objs = doc->getObjects();
+            bool match = false;
+            for (it = objs.begin(); it != objs.end(); ++it) {
+                if (*it == obj) {
+                    continue;  // don't compare object with itself
+                }
+                std::string objLabel = (*it)->Label.getValue();
+                if (!match && objLabel == newLabel) {
+                    match = true;
+                }
+                objectLabels.push_back(objLabel);
+            }
+
+            // make sure that there is a name conflict otherwise we don't have to do anything
+            if (match && *newLabel) {
+                label = newLabel;
+                // remove number from end to avoid lengthy names
+                size_t lastpos = label.length() - 1;
+                while (label[lastpos] >= 48 && label[lastpos] <= 57) {
+                    // if 'lastpos' becomes 0 then all characters are digits. In this case we use
+                    // the complete label again
+                    if (lastpos == 0) {
+                        lastpos = label.length() - 1;
+                        break;
+                    }
+                    lastpos--;
+                }
+
+                bool changed = false;
+                label = label.substr(0, lastpos + 1);
+                if (label != obj->getNameInDocument()
+                    && boost::starts_with(obj->getNameInDocument(), label)) {
+                    // In case the label has the same base name as object's
+                    // internal name, use it as the label instead.
+                    const char* objName = obj->getNameInDocument();
+                    const char* c = &objName[lastpos + 1];
+                    for (; *c; ++c) {
+                        if (*c < 48 || *c > 57) {
+                            break;
+                        }
+                    }
+                    if (*c == 0
+                        && std::find(objectLabels.begin(),
+                                     objectLabels.end(),
+                                     obj->getNameInDocument())
+                            == objectLabels.end()) {
+                        label = obj->getNameInDocument();
+                        changed = true;
+                    }
+                }
+                if (!changed) {
+                    label = Base::Tools::getUniqueName(label, objectLabels, 3);
+                }
+            }
+        }
+
+        if (label.empty()) {
+            label = newLabel;
+        }
+        obj->onBeforeChangeLabel(label);
+        newLabel = label.c_str();
+
+        if (!obj->getDocument()->testStatus(App::Document::Restoring)) {
+            // Only update label reference if we are not restoring. When
+            // importing (which also counts as restoring), it is possible the
+            // new object changes its label. However, we cannot update label
+            // references here, because object restoring is not based on
+            // dependency order. It can only be done in afterRestore().
+            //
+            // See PropertyLinkBase::restoreLabelReference() for more details.
+            propChanges = PropertyLinkBase::updateLabelReferences(obj, newLabel);
+        }
+
         if (!propChanges.empty() && !GetApplication().getActiveTransaction()) {
             commit = true;
             std::ostringstream str;
@@ -1401,7 +1489,7 @@ void PropertyString::setValue(const char* newLabel)
     }
 
     aboutToSetValue();
-    _cValue = label;
+    _cValue = newLabel;
     hasSetValue();
 
     for (auto& change : propChanges) {