[TD]Allow non-shape views to have children (#20768) (#21099)

* [TD]Allow non-shape views to have children (#20768)

* Update src/Mod/TechDraw/App/DrawView.cpp

Review comment

Co-authored-by: Benjamin Nauck <benjamin@nauck.se>

* Update src/Mod/TechDraw/App/DrawView.cpp

review comment

Co-authored-by: Benjamin Nauck <benjamin@nauck.se>

* Update src/Mod/TechDraw/Gui/ViewProviderDrawingView.cpp

review comment

Co-authored-by: Benjamin Nauck <benjamin@nauck.se>

* Update src/Mod/TechDraw/Gui/ViewProviderDrawingView.cpp

review comment

Co-authored-by: Benjamin Nauck <benjamin@nauck.se>

---------

Co-authored-by: Benjamin Nauck <benjamin@nauck.se>

src/Mod/TechDraw/App/DrawView.cpp

@@ -439,6 +439,26 @@ DrawView *DrawView::claimParent() const
     return getCollection();
 }
 
+//! return *unique* list of DrawView derived items which consider this DVP to be their 'owner'
+//! if a dimension has two references to this dvp, it will appear twice in the inlist, so we need to
+//! pick out duplicates.
+std::vector<DrawView*> DrawView::getUniqueChildren() const
+{
+    std::vector<DrawView*> result;
+    auto children = getInList();
+    std::sort(children.begin(), children.end(), std::less<>());
+    auto newEnd = std::unique(children.begin(), children.end());
+    children.erase(newEnd, children.end());
+    for (auto& child : children) {
+        auto* childDV = freecad_cast<DrawView*>(child);
+        if (childDV && childDV->claimParent() == this) {
+            result.push_back(childDV);
+        }
+    }
+    return result;
+}
+
+
 DrawViewClip* DrawView::getClipGroup()
 {
     for (auto* obj : getInList()) {

src/Mod/TechDraw/App/DrawView.h

@@ -87,6 +87,7 @@ public:
     virtual DrawPage* findParentPage() const;
     virtual std::vector<DrawPage*> findAllParentPages() const;
     virtual DrawView *claimParent() const;
+    std::vector<TechDraw::DrawView*> getUniqueChildren() const;
 
     virtual int countParentPages() const;
     virtual QRectF getRect() const;                      //must be overridden by derived class

src/Mod/TechDraw/Gui/ViewProviderDrawingView.cpp

@@ -39,6 +39,8 @@
 
 #include <Mod/TechDraw/App/DrawPage.h>
 #include <Mod/TechDraw/App/DrawView.h>
+#include <Mod/TechDraw/App/DrawViewBalloon.h>
+#include <Mod/TechDraw/App/DrawViewDimension.h>
 #include <Mod/TechDraw/App/Preferences.h>
 
 #include "ViewProviderDrawingView.h"
@@ -477,3 +479,55 @@ TechDraw::DrawView* ViewProviderDrawingView::getViewObject() const
 {
     return dynamic_cast<TechDraw::DrawView*>(pcObject);
 }
+
+
+//! it can happen that child graphic items can lose their parent item if the
+//! the parent is deleted, then undo is invoked.  The linkages on the App side are
+//! handled by the undo mechanism, but the QGraphicsScene parentage is not reset.
+void ViewProviderDrawingView::fixSceneDependencies()
+{
+    Base::Console().Message("VPDV::fixSceneDependencies()\n");
+    auto page = getViewProviderPage();
+    if (!page) {
+        return;
+    }
+
+    auto scene = page->getQGSPage();
+    auto ourQView = getQView();
+
+    // this is the logic for items other than Dimensions and Balloons
+    auto children = getViewObject()->getUniqueChildren();
+    for (auto& child : children) {
+        if (child->isDerivedFrom<DrawViewDimension>() ||
+            child->isDerivedFrom<DrawViewBalloon>() ) {
+            // these are handled by ViewProviderViewPart
+            continue;
+        }
+        auto* childQView = scene->findQViewForDocObj(child);
+        auto* childGraphicParent = scene->findParent(childQView);
+        if (childGraphicParent != ourQView) {
+            scene->addItemToParent(childQView, ourQView);
+        }
+    }
+}
+
+
+std::vector<App::DocumentObject*> ViewProviderDrawingView::claimChildren() const
+{
+    std::vector<App::DocumentObject*> temp;
+    const std::vector<App::DocumentObject *> &potentialChildren = getViewObject()->getInList();
+    try {
+      for(auto& child : potentialChildren) {
+          auto* view = freecad_cast<DrawView *>(child);
+          if (view && view->claimParent() == getViewObject()) {
+              temp.push_back(view);
+              continue;
+          }
+      }
+    }
+    catch (...) {
+        return {};
+    }
+    return temp;
+}
+

src/Mod/TechDraw/Gui/ViewProviderDrawingView.h

@@ -99,6 +99,10 @@ public:
 
     const char* whoAmI() const;
 
+    virtual void fixSceneDependencies();
+    std::vector<App::DocumentObject*> claimChildren() const override;
+
+
 private:
     void multiParentPaint(std::vector<TechDraw::DrawPage*>& pages);
     void singleParentPaint(const TechDraw::DrawView* dv);