+ FEM: Improve drag and drop for FEM analysis object

src/Gui/Tree.cpp

@@ -390,6 +390,9 @@ QMimeData * TreeWidget::mimeData (const QList<QTreeWidgetItem *> items) const
                 if (!vp->canDragObjects()) {
                     return 0;
                 }
+                else if (!vp->canDragObject(obj)) {
+                    return 0;
+                }
             }
         }
     }
@@ -479,6 +482,12 @@ void TreeWidget::dragMoveEvent(QDragMoveEvent *event)
                 event->ignore();
                 return;
             }
+
+            // let the view provider decide to accept the object or ignore it
+            if (!vp->canDropObject(obj)) {
+                event->ignore();
+                return;
+            }
         }
     }
     else {

src/Gui/ViewProvider.h

@@ -134,7 +134,7 @@ public:
     /** @name Methods used by the Tree
       * If you want to take control over the 
       * appearance of your object in the tree you
-      * can reimplemnt this methods.
+      * can reimplemnt these methods.
      */
     //@{
     /// deliver the icon shown in the tree view
@@ -148,15 +148,32 @@ public:
       */
     virtual std::vector<App::DocumentObject*> claimChildren(void) const
     { return std::vector<App::DocumentObject*>(); }
+    //@}
+
+    /** @name Drag and drop
+     * To enable drag and drop you have to re-implement \ref canDragObjects() and
+     * \ref canDropObjects() to return true. For finer control you can also re-implement
+     * \ref canDragObject() or \ref canDropObject() to filter certain object types, by
+     * default these methods don't filter any types.
+     * To take action of drag and drop the method \ref dragObject() and \ref dropObject()
+     * must be re-implemented, too.
+     */
+    //@{
     /** Check whether children can be removed from the view provider by drag and drop */
     virtual bool canDragObjects() const
     { return false; }
+    /** Check whether the object can be removed from the view provider by drag and drop */
+    virtual bool canDragObject(App::DocumentObject*) const
+    { return true; }
     /** Remove a child from the view provider by drag and drop */
     virtual void dragObject(App::DocumentObject*)
     { }
     /** Check whether objects can be added to the view provider by drag and drop */
     virtual bool canDropObjects() const
     { return false; }
+    /** Check whether the object can be dropped to the view provider by drag and drop */
+    virtual bool canDropObject(App::DocumentObject*) const
+    { return true; }
     /** Add an object to the view provider by drag and drop */
     virtual void dropObject(App::DocumentObject*)
     { }

src/Mod/Fem/Gui/ViewProviderAnalysis.cpp

@@ -25,7 +25,6 @@
 
 #ifndef _PreComp_
 # include <Standard_math.hxx>
-
 #endif
 
 #include "ViewProviderAnalysis.h"
@@ -35,6 +34,9 @@
 
 #include <Mod/Fem/App/FemAnalysis.h>
 #include <Mod/Fem/App/FemMeshObject.h>
+#include <Mod/Fem/App/FemSetObject.h>
+#include <Mod/Fem/App/FemConstraint.h>
+#include <App/MaterialObject.h>
 
 #include "TaskDlgAnalysis.h"
 
@@ -52,7 +54,6 @@ PROPERTY_SOURCE(FemGui::ViewProviderFemAnalysis, Gui::ViewProviderDocumentObject
 ViewProviderFemAnalysis::ViewProviderFemAnalysis()
 {
     sPixmap = "Fem_Analysis";
-
 }
 
 ViewProviderFemAnalysis::~ViewProviderFemAnalysis()
@@ -165,6 +166,22 @@ bool ViewProviderFemAnalysis::canDragObjects() const
     return true;
 }
 
+bool ViewProviderFemAnalysis::canDragObject(App::DocumentObject* obj) const
+{
+    if (!obj)
+        return false;
+    if (obj->getTypeId().isDerivedFrom(Fem::FemMeshObject::getClassTypeId()))
+        return true;
+    else if (obj->getTypeId().isDerivedFrom(Fem::Constraint::getClassTypeId()))
+        return true;
+    else if (obj->getTypeId().isDerivedFrom(Fem::FemSetObject::getClassTypeId()))
+        return true;
+    else if (obj->getTypeId().isDerivedFrom(App::MaterialObject::getClassTypeId()))
+        return true;
+    else
+        return false;
+}
+
 void ViewProviderFemAnalysis::dragObject(App::DocumentObject* obj)
 {
     Fem::FemAnalysis* analyze = static_cast<Fem::FemAnalysis*>(getObject());
@@ -183,10 +200,13 @@ bool ViewProviderFemAnalysis::canDropObjects() const
     return true;
 }
 
+bool ViewProviderFemAnalysis::canDropObject(App::DocumentObject* obj) const
+{
+    return canDragObject(obj);
+}
+
 void ViewProviderFemAnalysis::dropObject(App::DocumentObject* obj)
 {
-    if (!obj || !obj->getTypeId().isDerivedFrom(Fem::FemMeshObject::getClassTypeId()))
-        return;
     Fem::FemAnalysis* analyze = static_cast<Fem::FemAnalysis*>(getObject());
     std::vector<App::DocumentObject*> fem = analyze->Member.getValues();
     fem.push_back(obj);

src/Mod/Fem/Gui/ViewProviderAnalysis.h

@@ -67,10 +67,14 @@ public:
     //@{
     /// Returns true if the view provider generally supports dragging objects
     bool canDragObjects() const;
+    /// Check whether the object can be removed from the view provider by drag and drop
+    bool canDragObject(App::DocumentObject*) const;
     /// Starts to drag the object
     void dragObject(App::DocumentObject*);
     /// Returns true if the view provider generally accepts dropping of objects
     bool canDropObjects() const;
+    /// Check whether the object can be dropped to the view provider by drag and drop
+    bool canDropObject(App::DocumentObject*) const;
     /// If the dropped object type is accepted the object will be added as child
     void dropObject(App::DocumentObject*);
     //@}