From 8a100bf6272bd1d22f2d9f952f9dc115c6dd34e4 Mon Sep 17 00:00:00 2001
From: wmayer <wmayer@users.sourceforge.net>
Date: Mon, 23 Jan 2017 22:48:02 +0100
Subject: [PATCH] issue #0002836: Crash in sketcher

---
 .../PartDesign/Gui/TaskPrimitiveParameters.cpp   | 16 +++++++++++++---
 src/Mod/PartDesign/Gui/TaskPrimitiveParameters.h | 10 ++++++++--
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/src/Mod/PartDesign/Gui/TaskPrimitiveParameters.cpp b/src/Mod/PartDesign/Gui/TaskPrimitiveParameters.cpp
index a74e33180..7497dfa44 100644
--- a/src/Mod/PartDesign/Gui/TaskPrimitiveParameters.cpp
+++ b/src/Mod/PartDesign/Gui/TaskPrimitiveParameters.cpp
@@ -220,7 +220,11 @@ TaskBoxPrimitives::TaskBoxPrimitives(ViewProviderPrimitive* vp, QWidget* parent)
         if(i != index)
             ui.widgetStack->widget(i)->setSizePolicy(QSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored));
     }
-    
+
+    Gui::Document* doc = vp->getDocument();
+    this->attachDocument(doc);
+    this->enableNotifications(DocumentObserver::Delete);
+
     //show the parts coordinate system axis for selection
     PartDesign::Body * body = PartDesign::Body::findBodyOf(vp->getObject());
     if(body) {
@@ -241,8 +245,8 @@ TaskBoxPrimitives::TaskBoxPrimitives(ViewProviderPrimitive* vp, QWidget* parent)
 TaskBoxPrimitives::~TaskBoxPrimitives()
 {
     //hide the parts coordinate system axis for selection
-    PartDesign::Body * body = PartDesign::Body::findBodyOf ( vp->getObject() );
-    if(body) {
+    PartDesign::Body * body = vp ? PartDesign::Body::findBodyOf(vp->getObject()) : 0;
+    if (body) {
         try {
             App::Origin *origin = body->getOrigin();
             Gui::ViewProviderOrigin* vpOrigin;
@@ -254,6 +258,12 @@ TaskBoxPrimitives::~TaskBoxPrimitives()
     }
 }
 
+void TaskBoxPrimitives::slotDeletedObject(const Gui::ViewProviderDocumentObject& Obj)
+{
+    if (this->vp == &Obj)
+        this->vp = nullptr;
+}
+
 void TaskBoxPrimitives::onBoxHeightChanged(double v) {
     PartDesign::Box* box = static_cast<PartDesign::Box*>(vp->getObject());
     box->Height.setValue(v);
diff --git a/src/Mod/PartDesign/Gui/TaskPrimitiveParameters.h b/src/Mod/PartDesign/Gui/TaskPrimitiveParameters.h
index 4f605ac9b..073a4d445 100644
--- a/src/Mod/PartDesign/Gui/TaskPrimitiveParameters.h
+++ b/src/Mod/PartDesign/Gui/TaskPrimitiveParameters.h
@@ -26,6 +26,7 @@
 
 #include <Gui/TaskView/TaskView.h>
 #include <Gui/Selection.h>
+#include <Gui/DocumentObserver.h>
 #include <Gui/TaskView/TaskDialog.h>
 
 #include "TaskSketchBasedParameters.h"
@@ -49,7 +50,8 @@ namespace PartDesignGui {
 
 namespace s = boost::signals;
 
-class TaskBoxPrimitives : public Gui::TaskView::TaskBox
+class TaskBoxPrimitives : public Gui::TaskView::TaskBox,
+                          public Gui::DocumentObserver
 {
     Q_OBJECT
 
@@ -98,7 +100,11 @@ public Q_SLOTS:
     void onWedgeX2inChanged(double);
     void onWedgeZ2maxChanged(double);
     void onWedgeZ2inChanged(double);
-    
+
+private:
+    /** Notifies when the object is about to be removed. */
+    virtual void slotDeletedObject(const Gui::ViewProviderDocumentObject& Obj);
+
 private:
     QWidget* proxy;
     Ui_DlgPrimitives ui;