[TD]improve handling of View in multiple Pages

src/Mod/TechDraw/App/DrawProjGroupItem.cpp

@@ -349,6 +349,38 @@ void DrawProjGroupItem::unsetupObject()
     DrawViewPart::unsetupObject();
 }
 
+//DPGIs have DPG as parent, not Page, so we need to ask the DPG how many Pages own it.
+int DrawProjGroupItem::countParentPages() const
+{
+    DrawProjGroup* dpg = getPGroup();
+    if (dpg != nullptr) {
+        int count = dpg->countParentPages();
+        return count;
+    }
+    return 0;
+}
+
+DrawPage* DrawProjGroupItem::findParentPage() const
+{
+    DrawProjGroup* dpg = getPGroup();
+    if (dpg != nullptr) {
+        DrawPage* dp = dpg->findParentPage();
+        return dp;
+    }
+    return nullptr;
+}
+
+std::vector<DrawPage*> DrawProjGroupItem::findAllParentPages() const
+{
+    DrawProjGroup* dpg = getPGroup();
+    if (dpg != nullptr) {
+        std::vector<DrawPage*> dps = dpg->findAllParentPages();
+        return dps;
+    }
+    std::vector<DrawPage*> empty;
+    return empty;
+}
+
 PyObject *DrawProjGroupItem::getPyObject(void)
 {
     if (PythonObject.is(Py::_None())) {

src/Mod/TechDraw/App/DrawProjGroupItem.h

@@ -89,6 +89,10 @@ public:
     virtual bool checkFit(void) const override { return true; }
     virtual bool checkFit(DrawPage*) const override { return true; }
 
+    virtual int countParentPages() const override;
+    virtual DrawPage* findParentPage() const override;
+    virtual std::vector<DrawPage*> findAllParentPages() const override;
+
 protected:
     void onChanged(const App::Property* prop) override;
     virtual bool isLocked(void) const override;

src/Mod/TechDraw/App/DrawView.cpp

@@ -246,6 +246,7 @@ void DrawView::onDocumentRestored()
  * in case it is also a child of another duplicate page
  * @return
  */
+//note this won't find parent pages for DrawProjItem since their parent is DrawProjGroup!
 int DrawView::countParentPages() const
 {
     int count = 0;
@@ -260,6 +261,9 @@ int DrawView::countParentPages() const
     return count;
 }
 
+//finds the first DrawPage in this Document that claims to own this DrawView
+//note that it is possible to manipulate the Views property of DrawPage so that
+//more than 1 DrawPage claims a DrawView.
 DrawPage* DrawView::findParentPage() const
 {
     // Get Feature Page
@@ -283,6 +287,33 @@ DrawPage* DrawView::findParentPage() const
     return page;
 }
 
+
+std::vector<DrawPage*> DrawView::findAllParentPages() const
+{
+    // Get Feature Page
+    std::vector<DrawPage*> result;
+    DrawPage *page = 0;
+    DrawViewCollection *collection = 0;
+    std::vector<App::DocumentObject*> parent = getInList();
+    for (std::vector<App::DocumentObject*>::iterator it = parent.begin(); it != parent.end(); ++it) {
+        if ((*it)->getTypeId().isDerivedFrom(DrawPage::getClassTypeId())) {
+            page = static_cast<TechDraw::DrawPage *>(*it);
+        }
+
+        if ((*it)->getTypeId().isDerivedFrom(DrawViewCollection::getClassTypeId())) {
+            collection = static_cast<TechDraw::DrawViewCollection *>(*it);
+            page = collection->findParentPage();
+        }
+
+        if(page) {
+            result.emplace_back(page);
+        }
+    }
+
+    return result;
+}
+
+
 bool DrawView::isInClip()
 {
     std::vector<App::DocumentObject*> parent = getInList();

src/Mod/TechDraw/App/DrawView.h

@@ -23,6 +23,8 @@
 #ifndef _DrawView_h_
 #define _DrawView_h_
 
+#include <Mod/TechDraw/TechDrawGlobal.h>
+
 #include <boost_signals2.hpp>
 
 #include <QCoreApplication>
@@ -85,6 +87,7 @@ public:
     virtual PyObject *getPyObject(void) override;
 
     virtual DrawPage* findParentPage() const;
+    virtual std::vector<DrawPage*> findAllParentPages() const;
     virtual int countParentPages() const;
     virtual QRectF getRect() const;                      //must be overridden by derived class
     virtual double autoScale(void) const;

src/Mod/TechDraw/Gui/MDIViewPage.cpp

@@ -444,6 +444,10 @@ void MDIViewPage::updateTemplate(bool forceUpdate)
 }
 
 //this is time consuming. should only be used when there is a problem.
+//Solve the situation where a DrawView belonging to this DrawPage has no QGraphicsItem in
+//the QGScene for the DrawPage -or-
+//a QGraphics item exists in the DrawPage's QGScene, but there is no corresponding DrawView
+//in the DrawPage.
 void MDIViewPage::fixOrphans(bool force)
 {
     if(!force) {
@@ -471,7 +475,6 @@ void MDIViewPage::fixOrphans(bool force)
             attachView(dv);
         }
     }
-
     // if qView doesn't have a Feature on this Page, delete it
     std::vector<QGIView*> qvss = m_view->getViews();
     // qvss may contain an item and its child item(s) and to avoid to access a deleted item a QPointer is needed
@@ -485,15 +488,41 @@ void MDIViewPage::fixOrphans(bool force)
             continue; // already deleted?
         App::DocumentObject* obj = doc->getObject(qv->getViewName());
         if (obj == nullptr) {
+            //no DrawView anywhere in Document
             m_view->removeQView(qv);
         } else {
-            TechDraw::DrawPage* pp = qv->getViewObject()->findParentPage();
-            /** avoid crash where a view might have more than one parent page
-             * if the user duplicated the page without duplicating dependencies
-             */
+            //DrawView exists in Document.  Does it belong to this DrawPage?
             int numParentPages = qv->getViewObject()->countParentPages();
-            if (thisPage != pp && numParentPages == 0) {
-               m_view->removeQView(qv);
+            if (numParentPages == 0) {
+                //DrawView does not belong to any DrawPage
+                //remove QGItem from QGScene
+                m_view->removeQView(qv);
+            } else if (numParentPages == 1) {
+                //Does DrawView belong to this DrawPage?
+                TechDraw::DrawPage* pp = qv->getViewObject()->findParentPage();
+                if (thisPage != pp) {
+                    //DrawView does not belong to this DrawPage
+                    //remove QGItem from QGScene
+                    m_view->removeQView(qv);
+                }
+            } else if (numParentPages > 1) {
+                //DrawView belongs to multiple DrawPages
+                //this is a problem - not supposed to happen
+                //check if this MDIViewPage corresponds to any parent DrawPage
+                //if not, delete the QGItem
+                Base::Console().Warning("%s belongs to multiple Pages\n", obj->getNameInDocument());
+                std::vector<TechDraw::DrawPage*> pPages = qv->getViewObject()->findAllParentPages();
+                bool found = false;
+                for (auto p: pPages) {
+                    if (thisPage == p) {
+                        found = true;
+                        break;
+                    }
+                }
+                if (!found) {
+                    //none of the parent Pages for View coorespond to this Page
+                    m_view->removeQView(qv);
+                }
             }
         }
     }