From 27c4136f58f5911f2048b7f70f62ec0430115d99 Mon Sep 17 00:00:00 2001
From: wmayer <wmayer@users.sourceforge.net>
Date: Sun, 22 Jan 2017 19:07:07 +0100
Subject: [PATCH] TaskTransformedParameters derives from Gui::DocumentObserver
 to handle deletion of view provider when clicking Cancel button

---
 .../Gui/TaskLinearPatternParameters.cpp       |  8 +++----
 .../Gui/TaskTransformedParameters.cpp         | 23 +++++++++++++++----
 .../Gui/TaskTransformedParameters.h           |  7 +++++-
 3 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/src/Mod/PartDesign/Gui/TaskLinearPatternParameters.cpp b/src/Mod/PartDesign/Gui/TaskLinearPatternParameters.cpp
index 2677e54ac..058959780 100644
--- a/src/Mod/PartDesign/Gui/TaskLinearPatternParameters.cpp
+++ b/src/Mod/PartDesign/Gui/TaskLinearPatternParameters.cpp
@@ -370,18 +370,18 @@ unsigned TaskLinearPatternParameters::getOccurrences(void) const
     return ui->spinOccurrences->value();
 }
 
-
 TaskLinearPatternParameters::~TaskLinearPatternParameters()
 {
     //hide the parts coordinate system axis for selection
-    PartDesign::Body * body = PartDesign::Body::findBodyOf ( getObject() );
-    if(body) {
+    PartDesign::Body * body = PartDesign::Body::findBodyOf(getObject());
+    if (body) {
         try {
             App::Origin *origin = body->getOrigin();
             ViewProviderOrigin* vpOrigin;
             vpOrigin = static_cast<ViewProviderOrigin*>(Gui::Application::Instance->getViewProvider(origin));
             vpOrigin->resetTemporaryVisibility();
-        } catch (const Base::Exception &ex) {
+        }
+        catch (const Base::Exception &ex) {
             Base::Console().Error ("%s\n", ex.what () );
         }
     }
diff --git a/src/Mod/PartDesign/Gui/TaskTransformedParameters.cpp b/src/Mod/PartDesign/Gui/TaskTransformedParameters.cpp
index 913926a2d..bf4750260 100644
--- a/src/Mod/PartDesign/Gui/TaskTransformedParameters.cpp
+++ b/src/Mod/PartDesign/Gui/TaskTransformedParameters.cpp
@@ -72,6 +72,12 @@ TaskTransformedParameters::TaskTransformedParameters(ViewProviderTransformed *Tr
       blockUpdate(false)
 {
     selectionMode = none;
+
+    if (TransformedView) {
+        Gui::Document* doc = TransformedView->getDocument();
+        this->attachDocument(doc);
+        this->enableNotifications(DocumentObserver::Delete);
+    }
 }
 
 TaskTransformedParameters::TaskTransformedParameters(TaskMultiTransformParameters *parentTask)
@@ -92,6 +98,12 @@ TaskTransformedParameters::~TaskTransformedParameters()
     Gui::Selection().rmvSelectionGate();
 }
 
+void TaskTransformedParameters::slotDeletedObject(const Gui::ViewProviderDocumentObject& Obj)
+{
+    if (TransformedView == &Obj)
+        TransformedView = nullptr;
+}
+
 bool TaskTransformedParameters::isViewUpdated() const
 {
     return (blockUpdate == false);
@@ -264,17 +276,18 @@ PartDesignGui::ViewProviderTransformed *TaskTransformedParameters::getTopTransfo
 }
 
 PartDesign::Transformed *TaskTransformedParameters::getTopTransformedObject() const {
-	App::DocumentObject *transform = getTopTransformedView()->getObject();
-	assert (transform->isDerivedFrom(PartDesign::Transformed::getClassTypeId()));
-	return static_cast<PartDesign::Transformed*>(transform);
+    App::DocumentObject *transform = getTopTransformedView()->getObject();
+    assert (transform->isDerivedFrom(PartDesign::Transformed::getClassTypeId()));
+    return static_cast<PartDesign::Transformed*>(transform);
 }
 
-
 PartDesign::Transformed *TaskTransformedParameters::getObject() const {
     if (insideMultiTransform)
         return parentTask->getSubFeature();
-    else
+    else if (TransformedView)
         return static_cast<PartDesign::Transformed*>(TransformedView->getObject());
+    else
+        return nullptr;
 }
 
 Part::Feature *TaskTransformedParameters::getBaseObject() const {
diff --git a/src/Mod/PartDesign/Gui/TaskTransformedParameters.h b/src/Mod/PartDesign/Gui/TaskTransformedParameters.h
index e29c07ce8..f6ffdc5d4 100644
--- a/src/Mod/PartDesign/Gui/TaskTransformedParameters.h
+++ b/src/Mod/PartDesign/Gui/TaskTransformedParameters.h
@@ -30,6 +30,7 @@
 
 #include <Gui/TaskView/TaskView.h>
 #include <Gui/Selection.h>
+#include <Gui/DocumentObserver.h>
 
 #include "TaskFeatureParameters.h"
 #include "TaskTransformedMessages.h"
@@ -114,7 +115,9 @@ private:
   Because in the second case there is no ViewProvider, some special methods are required to
   access the underlying FeatureTransformed object in two different ways.
   **/
-class TaskTransformedParameters : public Gui::TaskView::TaskBox, public Gui::SelectionObserver
+class TaskTransformedParameters : public Gui::TaskView::TaskBox,
+                                  public Gui::SelectionObserver,
+                                  public Gui::DocumentObserver
 {
     Q_OBJECT
 
@@ -184,6 +187,8 @@ protected:
     int getUpdateViewTimeout() const;
 
 protected:
+    /** Notifies when the object is about to be removed. */
+    virtual void slotDeletedObject(const Gui::ViewProviderDocumentObject& Obj);
     virtual void changeEvent(QEvent *e) = 0;
     virtual void onSelectionChanged(const Gui::SelectionChanges& msg) = 0;
     virtual void clearButtons()=0;