App/Gui: implement a lightweight weak_ptr like class to work with Document, DocumentObject and ViewProvider

src/App/DocumentObserver.cpp

@@ -257,6 +257,7 @@ Property *DocumentObjectT::getProperty() const {
         return obj->getPropertyByName(property.c_str());
     return 0;
 }
+
 // -----------------------------------------------------------------------------
 
 SubObjectT::SubObjectT()
@@ -387,6 +388,138 @@ std::vector<App::DocumentObject*> SubObjectT::getSubObjectList() const {
 }
 
 // -----------------------------------------------------------------------------
+
+class DocumentWeakPtrT::Private {
+public:
+    Private(App::Document* doc) : _document(doc) {
+        if (doc) {
+            connectApplicationDeletedDocument = App::GetApplication().signalDeleteDocument.connect(boost::bind
+                (&Private::deletedDocument, this, _1));
+        }
+    }
+
+    void deletedDocument(const App::Document& doc) {
+        if (_document == &doc)
+            reset();
+    }
+    void reset() {
+        connectApplicationDeletedDocument.disconnect();
+        _document = nullptr;
+    }
+
+    App::Document* _document;
+    typedef boost::signals2::scoped_connection Connection;
+    Connection connectApplicationDeletedDocument;
+};
+
+DocumentWeakPtrT::DocumentWeakPtrT(App::Document* doc) noexcept
+  : d(new Private(doc))
+{
+}
+
+DocumentWeakPtrT::~DocumentWeakPtrT()
+{
+}
+
+void DocumentWeakPtrT::reset() noexcept
+{
+    d->reset();
+}
+
+bool DocumentWeakPtrT::expired() const noexcept
+{
+    return (d->_document == nullptr);
+}
+
+App::Document* DocumentWeakPtrT::operator->() noexcept
+{
+    return d->_document;
+}
+
+// -----------------------------------------------------------------------------
+
+class DocumentObjectWeakPtrT::Private {
+public:
+    Private(App::DocumentObject* obj) : object(obj), indocument(false) {
+        if (obj) {
+            indocument = true;
+            connectApplicationDeletedDocument = App::GetApplication().signalDeleteDocument.connect(boost::bind
+                (&Private::deletedDocument, this, _1));
+            App::Document* doc = obj->getDocument();
+            connectDocumentCreatedObject = doc->signalNewObject.connect(boost::bind
+                (&Private::createdObject, this, _1));
+            connectDocumentDeletedObject = doc->signalDeletedObject.connect(boost::bind
+                (&Private::deletedObject, this, _1));
+        }
+    }
+    void deletedDocument(const App::Document& doc) {
+        // When deleting document then there is no way to undo it
+        if (object && object->getDocument() == &doc) {
+            reset();
+        }
+    }
+    void createdObject(const App::DocumentObject& obj) {
+        // When undoing the removal
+        if (object == &obj) {
+            indocument = true;
+        }
+    }
+    void deletedObject(const App::DocumentObject& obj) {
+        if (object == &obj) {
+            indocument = false;
+        }
+    }
+    void reset() {
+        connectApplicationDeletedDocument.disconnect();
+        connectDocumentCreatedObject.disconnect();
+        connectDocumentDeletedObject.disconnect();
+        object = nullptr;
+        indocument = false;
+    }
+    App::DocumentObject* get() const {
+        return indocument ? object : nullptr;
+    }
+
+    App::DocumentObject* object;
+    bool indocument;
+    typedef boost::signals2::scoped_connection Connection;
+    Connection connectApplicationDeletedDocument;
+    Connection connectDocumentCreatedObject;
+    Connection connectDocumentDeletedObject;
+};
+
+DocumentObjectWeakPtrT::DocumentObjectWeakPtrT(App::DocumentObject* obj) noexcept
+  : d(new Private(obj))
+{
+}
+
+DocumentObjectWeakPtrT::~DocumentObjectWeakPtrT()
+{
+
+}
+
+App::DocumentObject* DocumentObjectWeakPtrT::_get() const noexcept
+{
+    return d->get();
+}
+
+void DocumentObjectWeakPtrT::reset() noexcept
+{
+    d->reset();
+}
+
+bool DocumentObjectWeakPtrT::expired() const noexcept
+{
+    return !d->indocument;
+}
+
+App::DocumentObject* DocumentObjectWeakPtrT::operator->() noexcept
+{
+    return d->get();
+}
+
+// -----------------------------------------------------------------------------
+
 DocumentObserver::DocumentObserver() : _document(0)
 {
     this->connectApplicationCreatedDocument = App::GetApplication().signalNewDocument.connect(boost::bind

src/App/DocumentObserver.h

@@ -27,6 +27,7 @@
 #include <Base/BaseClass.h>
 #include <boost/signals2.hpp>
 #include <set>
+#include <memory>
 
 namespace App
 {
@@ -144,7 +145,7 @@ private:
     std::string property;
 };
 
-class AppExport SubObjectT: public DocumentObjectT
+class AppExport SubObjectT : public DocumentObjectT
 {
 public:
     /*! Constructor */
@@ -205,6 +206,82 @@ private:
     std::string subname;
 };
 
+/**
+ * @brief The DocumentWeakPtrT class
+ */
+class AppExport DocumentWeakPtrT
+{
+public:
+    DocumentWeakPtrT(App::Document*) noexcept;
+    ~DocumentWeakPtrT();
+
+    /*!
+     * \brief reset
+     * Releases the reference to the managed object. After the call *this manages no object.
+     */
+    void reset() noexcept;
+    /*!
+     * \brief expired
+     * \return true if the managed object has already been deleted, false otherwise.
+     */
+    bool expired() const noexcept;
+    /*!
+     * \brief operator ->
+     * \return pointer to the document
+     */
+    App::Document* operator->() noexcept;
+
+private:
+    // disable
+    DocumentWeakPtrT(const DocumentWeakPtrT&);
+    DocumentWeakPtrT& operator=(const DocumentWeakPtrT&);
+
+    class Private;
+    std::unique_ptr<Private> d;
+};
+
+/**
+ * @brief The DocumentObjectWeakPtrT class
+ */
+class AppExport DocumentObjectWeakPtrT
+{
+public:
+    DocumentObjectWeakPtrT(App::DocumentObject*) noexcept;
+    ~DocumentObjectWeakPtrT();
+
+    /*!
+     * \brief reset
+     * Releases the reference to the managed object. After the call *this manages no object.
+     */
+    void reset() noexcept;
+    /*!
+     * \brief expired
+     * \return true if the managed object has already been deleted, false otherwise.
+     */
+    bool expired() const noexcept;
+    /*!
+     * \brief operator ->
+     * \return pointer to the document
+     */
+    App::DocumentObject* operator->() noexcept;
+    /*! Get a pointer to the object or 0 if it doesn't exist any more or the type doesn't match. */
+    template<typename T>
+    inline T* get() const noexcept
+    {
+        return Base::freecad_dynamic_cast<T>(_get());
+    }
+
+private:
+    App::DocumentObject* _get() const noexcept;
+    // disable
+    DocumentObjectWeakPtrT(const DocumentObjectWeakPtrT&);
+    DocumentObjectWeakPtrT& operator=(const DocumentObjectWeakPtrT&);
+
+private:
+    class Private;
+    std::unique_ptr<Private> d;
+};
+
 /**
  * The DocumentObserver class simplfies the step to write classes that listen
  * to what happens inside a document.

src/Gui/DocumentObserver.cpp

@@ -199,6 +199,137 @@ std::string ViewProviderT::getObjectPython() const
 
 // -----------------------------------------------------------------------------
 
+class DocumentWeakPtrT::Private {
+public:
+    Private(Gui::Document* doc) : _document(doc) {
+        if (doc) {
+            connectApplicationDeletedDocument = doc->signalDeleteDocument.connect(boost::bind
+                (&Private::deletedDocument, this, _1));
+        }
+    }
+
+    void deletedDocument(const Gui::Document& doc) {
+        if (_document == &doc)
+            reset();
+    }
+    void reset() {
+        connectApplicationDeletedDocument.disconnect();
+        _document = nullptr;
+    }
+
+    Gui::Document* _document;
+    typedef boost::signals2::scoped_connection Connection;
+    Connection connectApplicationDeletedDocument;
+};
+
+DocumentWeakPtrT::DocumentWeakPtrT(Gui::Document* doc) noexcept
+  : d(new Private(doc))
+{
+}
+
+DocumentWeakPtrT::~DocumentWeakPtrT()
+{
+}
+
+void DocumentWeakPtrT::reset() noexcept
+{
+    d->reset();
+}
+
+bool DocumentWeakPtrT::expired() const noexcept
+{
+    return (d->_document == nullptr);
+}
+
+Gui::Document* DocumentWeakPtrT::operator->() noexcept
+{
+    return d->_document;
+}
+
+// -----------------------------------------------------------------------------
+
+class ViewProviderWeakPtrT::Private {
+public:
+    Private(ViewProviderDocumentObject* obj) : object(obj), indocument(false) {
+        if (obj) {
+            indocument = true;
+            Gui::Document* doc = obj->getDocument();
+            connectApplicationDeletedDocument = doc->signalDeleteDocument.connect(boost::bind
+                (&Private::deletedDocument, this, _1));
+            connectDocumentCreatedObject = doc->signalNewObject.connect(boost::bind
+                (&Private::createdObject, this, _1));
+            connectDocumentDeletedObject = doc->signalDeletedObject.connect(boost::bind
+                (&Private::deletedObject, this, _1));
+        }
+    }
+    void deletedDocument(const Gui::Document& doc) {
+        // When deleting document then there is no way to undo it
+        if (object && object->getDocument() == &doc) {
+            reset();
+        }
+    }
+    void createdObject(const Gui::ViewProvider& obj) {
+        // When undoing the removal
+        if (object == &obj) {
+            indocument = true;
+        }
+    }
+    void deletedObject(const Gui::ViewProvider& obj) {
+        if (object == &obj) {
+            indocument = false;
+        }
+    }
+    void reset() {
+        connectApplicationDeletedDocument.disconnect();
+        connectDocumentCreatedObject.disconnect();
+        connectDocumentDeletedObject.disconnect();
+        object = nullptr;
+        indocument = false;
+    }
+    ViewProviderDocumentObject* get() const {
+        return indocument ? object : nullptr;
+    }
+
+    Gui::ViewProviderDocumentObject* object;
+    bool indocument;
+    typedef boost::signals2::scoped_connection Connection;
+    Connection connectApplicationDeletedDocument;
+    Connection connectDocumentCreatedObject;
+    Connection connectDocumentDeletedObject;
+};
+
+ViewProviderWeakPtrT::ViewProviderWeakPtrT(ViewProviderDocumentObject* obj) noexcept
+  : d(new Private(obj))
+{
+}
+
+ViewProviderWeakPtrT::~ViewProviderWeakPtrT()
+{
+
+}
+
+ViewProviderDocumentObject* ViewProviderWeakPtrT::_get() const noexcept
+{
+    return d->get();
+}
+
+void ViewProviderWeakPtrT::reset() noexcept
+{
+    d->reset();
+}
+
+bool ViewProviderWeakPtrT::expired() const noexcept
+{
+    return !d->indocument;
+}
+
+ViewProviderDocumentObject* ViewProviderWeakPtrT::operator->() noexcept
+{
+    return d->get();
+}
+
+// -----------------------------------------------------------------------------
+
 DocumentObserver::DocumentObserver()
 {
 }

src/Gui/DocumentObserver.h

@@ -118,6 +118,82 @@ private:
     std::string object;
 };
 
+/**
+ * @brief The DocumentWeakPtrT class
+ */
+class GuiExport DocumentWeakPtrT
+{
+public:
+    DocumentWeakPtrT(Gui::Document*) noexcept;
+    ~DocumentWeakPtrT();
+
+    /*!
+     * \brief reset
+     * Releases the reference to the managed object. After the call *this manages no object.
+     */
+    void reset() noexcept;
+    /*!
+     * \brief expired
+     * \return true if the managed object has already been deleted, false otherwise.
+     */
+    bool expired() const noexcept;
+    /*!
+     * \brief operator ->
+     * \return pointer to the document
+     */
+    Gui::Document* operator->() noexcept;
+
+private:
+    // disable
+    DocumentWeakPtrT(const DocumentWeakPtrT&);
+    DocumentWeakPtrT& operator=(const DocumentWeakPtrT&);
+
+    class Private;
+    std::unique_ptr<Private> d;
+};
+
+/**
+ * @brief The ViewProviderWeakPtrT class
+ */
+class AppExport ViewProviderWeakPtrT
+{
+public:
+    ViewProviderWeakPtrT(ViewProviderDocumentObject*) noexcept;
+    ~ViewProviderWeakPtrT();
+
+    /*!
+     * \brief reset
+     * Releases the reference to the managed object. After the call *this manages no object.
+     */
+    void reset() noexcept;
+    /*!
+     * \brief expired
+     * \return true if the managed object has already been deleted, false otherwise.
+     */
+    bool expired() const noexcept;
+    /*!
+     * \brief operator ->
+     * \return pointer to the document
+     */
+    ViewProviderDocumentObject* operator->() noexcept;
+    /*! Get a pointer to the object or 0 if it doesn't exist any more or the type doesn't match. */
+    template<typename T>
+    inline T* get() const noexcept
+    {
+        return Base::freecad_dynamic_cast<T>(_get());
+    }
+
+private:
+    ViewProviderDocumentObject* _get() const noexcept;
+    // disable
+    ViewProviderWeakPtrT(const ViewProviderWeakPtrT&);
+    ViewProviderWeakPtrT& operator=(const ViewProviderWeakPtrT&);
+
+private:
+    class Private;
+    std::unique_ptr<Private> d;
+};
+
 /**
  * The DocumentObserver class simplifies the step to write classes that listen
  * to what happens inside a document.