Core: Tree: Allow reordering in root and groups allowing it (parts, groups

src/Gui/Tree.h

@@ -140,6 +140,18 @@ protected:
     void dragLeaveEvent(QDragLeaveEvent * event) override;
     void dragMoveEvent(QDragMoveEvent *event) override;
     void dropEvent(QDropEvent *event) override;
+    struct TargetItemInfo {
+        QTreeWidgetItem* targetItem = nullptr; //target may be the parent of underMouse
+        QTreeWidgetItem* underMouseItem = nullptr;
+        App::Document* targetDoc = nullptr;
+        QPoint pos;
+        bool inBottomHalf = false;
+        bool inThresholdZone = false;
+    };
+    TargetItemInfo getTargetInfo(QEvent* ev);
+    bool dropInObject(QDropEvent* event, TargetItemInfo& targetInfo, std::vector<std::pair<DocumentObjectItem*, std::vector<std::string> > > items);
+    bool dropInDocument(QDropEvent* event, TargetItemInfo& targetInfo, std::vector<std::pair<DocumentObjectItem*, std::vector<std::string> > > items);
+    void sortDroppedObjects(TargetItemInfo& targetInfo, std::vector<App::DocumentObject*> draggedObjects);
     //@}
     bool event(QEvent *e) override;
     void keyPressEvent(QKeyEvent *event) override;
@@ -291,6 +303,7 @@ public:
     void setData(int column, int role, const QVariant & value) override;
     void populateItem(DocumentObjectItem *item, bool refresh=false, bool delayUpdate=true);
     bool populateObject(App::DocumentObject *obj);
+    void sortObjectItems();
     void selectAllInstances(const ViewProviderDocumentObject &vpd);
     bool showItem(DocumentObjectItem *item, bool select, bool force=false);
     void updateItemsVisibility(QTreeWidgetItem *item, bool show);
@@ -439,10 +452,14 @@ public:
     int isParentGroup() const;
 
     DocumentObjectItem *getParentItem() const;
+    DocumentObjectItem *getNextSibling() const;
+    DocumentObjectItem *getPreviousSibling() const;
     TreeWidget *getTree() const;
 
 private:
     void setCheckState(bool checked);
+    void getExpandedSnapshot(std::vector<bool>& snapshot) const;
+    void applyExpandedSnapshot(const std::vector<bool>& snapshot, std::vector<bool>::const_iterator& from);
 
     QBrush bgBrush;
     DocumentItem *myOwner;

src/Gui/ViewProvider.h

@@ -310,6 +310,8 @@ public:
      * */
     virtual bool canDropObjectEx(App::DocumentObject *obj, App::DocumentObject *owner,
             const char *subname, const std::vector<std::string> &elements) const;
+    /* Check whether the object accept reordering of its children during drop.*/
+    virtual bool acceptReorderingObjects() const { return false; };
 
     /// return a subname referencing the sub-object holding the dropped objects
     virtual std::string getDropPrefix() const { return {}; }

src/Gui/ViewProviderDocumentObject.cpp

@@ -77,6 +77,8 @@ ViewProviderDocumentObject::ViewProviderDocumentObject()
             "Element: On top only if some sub-element of the object is selected");
     OnTopWhenSelected.setEnums(OnTopEnum);
 
+    ADD_PROPERTY_TYPE(TreeRank, (-1), dogroup, App::Prop_Hidden, "Tree view item ordering key");
+
     sPixmap = "Feature";
 }
 

src/Gui/ViewProviderDocumentObject.h

@@ -64,6 +64,9 @@ public:
     App::PropertyEnumeration OnTopWhenSelected;
     App::PropertyEnumeration SelectionStyle;
 
+    // Hidden properties
+    App::PropertyInteger TreeRank;
+
     virtual void attach(App::DocumentObject *pcObject);
     virtual void reattach(App::DocumentObject *);
     void update(const App::Property*) override;

src/Gui/ViewProviderDocumentObjectGroup.h

@@ -48,6 +48,9 @@ public:
     /// deliver the icon shown in the tree view
     QIcon getIcon() const override;
 
+    /* Check whether the object accept reordering of its children during drop.*/
+    bool acceptReorderingObjects() const override { return true; };
+
 protected:
     void getViewProviders(std::vector<ViewProviderDocumentObject*>&) const;
 

src/Gui/ViewProviderGroupExtension.cpp

@@ -80,8 +80,8 @@ bool ViewProviderGroupExtension::extensionCanDropObject(App::DocumentObject* obj
 
     auto* group = getExtendedViewProvider()->getObject()->getExtensionByType<App::GroupExtension>();
 
-    //we cannot drop thing of this group into it again
-    if (group->hasObject(obj))
+    //we cannot drop thing of this group into it again if it does not allow reorder
+    if (group->hasObject(obj) && !getExtendedViewProvider()->acceptReorderingObjects())
         return false;
 
     if (group->allowObject(obj))

src/Gui/ViewProviderPart.h

@@ -50,6 +50,9 @@ public:
     /// override from ViewProvider.h
     QIcon getIcon() const override;
 
+    /* Check whether the object accept reordering of its children during drop.*/
+    bool acceptReorderingObjects() const override { return true; };
+
 protected:
     /// get called by the container whenever a property has been changed
     void onChanged(const App::Property* prop) override;