proper handling of setting and reverting preview mode in PD view provider

src/Mod/PartDesign/Gui/ViewProviderAddSub.cpp

@@ -57,7 +57,6 @@ PROPERTY_SOURCE(PartDesignGui::ViewProviderAddSub,PartDesignGui::ViewProvider)
 
 ViewProviderAddSub::ViewProviderAddSub()
 {
-    
     previewShape = new SoSeparator();
     previewShape->ref();
     previewFaceSet = new PartGui::SoBrepFaceSet();
@@ -66,7 +65,7 @@ ViewProviderAddSub::ViewProviderAddSub()
     previewCoords->ref();
     previewNorm = new SoNormal();
     previewNorm->ref();
-    
+    whichChild = -1;
 }
 
 ViewProviderAddSub::~ViewProviderAddSub()
@@ -275,18 +274,23 @@ void ViewProviderAddSub::updateData(const App::Property* p) {
 }
 
 void ViewProviderAddSub::setPreviewDisplayMode(bool onoff) {
-
-    if(onoff && displayMode!="Shape preview") {
-    
+    // A mask mode is always set, also for hidden objects.
+    // Now when changing to another mask mode this automatically
+    // displays an object and when restoring the previous state it's
+    // not sufficient to only revert the mask mode. Also the child
+    // number of the switch node must be reverted.
+    if (onoff && displayMode!="Shape preview") {
         displayMode = getActiveDisplayMode();
+        whichChild = pcModeSwitch->whichChild.getValue();
         setDisplayMaskMode("Shape preview");
     }
-    
-    if(!onoff) {
+
+    if (!onoff) {
         setDisplayMaskMode(displayMode.c_str());
+        pcModeSwitch->whichChild.setValue(whichChild);
     }
-    
+
     App::DocumentObject* obj = static_cast<PartDesign::Feature*>(getObject())->BaseFeature.getValue();
-    if(obj)
+    if (obj)
         static_cast<PartDesignGui::ViewProvider*>(Gui::Application::Instance->getViewProvider(obj))->makeTemporaryVisible(onoff);
 }