ScopedVclPtr: needs an = operator to make life flow.

Without this, assigning to a ScopedVclPtr instance thus:

    pScopedVclPtr = new Foo();

constructed a new intermediate ScopedVCLPtr, used a default assignment
operator, unhelpfully disposing the new Foo before it could make it to
pScopedVclPtr => add operator, and hide problematic constructors.

Change-Id: Icc0da962938bf115eac0c24a6a76cfeb66ddf23a

include/vcl/vclptr.hxx

@@ -81,7 +81,6 @@ namespace vcl { class Window; }
 template <class reference_type>
 class VclPtr
 {
-
     ::rtl::Reference<reference_type> m_rInnerRef;
 
 public:
@@ -211,7 +210,6 @@ public:
         return (m_rInnerRef < handle.m_rInnerRef);
     }
 
-
     /** Needed to place VclPtr's into STL collection.
      */
     inline bool SAL_CALL operator> (const VclPtr<reference_type> & handle) const
@@ -231,20 +229,28 @@ public:
         : VclPtr<reference_type>()
     {}
 
-
-    /** Constructor...
+    /** Constructor
      */
     inline ScopedVclPtr (reference_type * pBody)
         : VclPtr<reference_type>(pBody)
     {}
 
-
     /** Copy constructor...
      */
     inline ScopedVclPtr (const VclPtr<reference_type> & handle)
         : VclPtr<reference_type>(handle)
     {}
 
+    /**
+       Assignment that releases the last reference.
+     */
+    inline ScopedVclPtr<reference_type>& SAL_CALL operator= (reference_type * pBody)
+    {
+        VclPtr<reference_type>::disposeAndClear();
+        VclPtr<reference_type>::set(pBody);
+        return *this;
+    }
+
     /** Up-casting conversion constructor: Copies interface reference.
 
         Does not work for up-casts to ambiguous bases.  For the special case of
@@ -265,7 +271,11 @@ public:
     {
         VclPtr<reference_type>::disposeAndClear();
     }
-
+private:
+    // Most likely we don't want this default copy-construtor.
+    ScopedVclPtr (const ScopedVclPtr<reference_type> &) SAL_DELETED_FUNCTION;
+    // And certainly we don't want a default assignment operator.
+    ScopedVclPtr<reference_type>& SAL_CALL operator= (const ScopedVclPtr<reference_type> &) SAL_DELETED_FUNCTION;
 };
 
 #endif // INCLUDED_VCL_PTR_HXX

svtools/source/control/tabbar.cxx

@@ -159,6 +159,7 @@ public:
 private:
     void            ImplTrack( const Point& rScreenPos );
 
+    virtual void    dispose() SAL_OVERRIDE;
     virtual void    MouseButtonDown( const MouseEvent& rMEvt ) SAL_OVERRIDE;
     virtual void    Tracking( const TrackingEvent& rTEvt ) SAL_OVERRIDE;
     virtual void    Paint( const Rectangle& rRect ) SAL_OVERRIDE;
@@ -176,6 +177,11 @@ ImplTabSizer::ImplTabSizer( TabBar* pParent, WinBits nWinStyle )
     SetSizePixel(Size(7 * nScaleFactor, 0));
 }
 
+void ImplTabSizer::dispose()
+{
+    vcl::Window::dispose();
+}
+
 void ImplTabSizer::ImplTrack( const Point& rScreenPos )
 {
     TabBar* pParent = GetParent();

vcl/README.lifecycle

@@ -67,6 +67,14 @@ to lingering pointers to freed objects.
 	'dispose' methods, in order to provide a minimal initial
 	behavioral change.
 
+	As such a VclPtr can have three states:
+
+	VclPtr<PushButton> pButton;
+	...
+	assert (pButton == nullptr || !pButton);    // null
+	assert (pButton && !pButton->IsDisposed()); // alive
+	assert (pButton &&  pButton->IsDisposed()); // disposed
+
 ** ScopedVclPtr - making disposes easier
 
 	While replacing existing code with new, it can be a bit

vcl/source/window/window.cxx

@@ -2264,8 +2264,7 @@ vcl::Font Window::GetPointFont() const
 
 void Window::Show( bool bVisible, sal_uInt16 nFlags )
 {
-
-    if ( mpWindowImpl->mbVisible == bVisible )
+    if ( IsDisposed() || mpWindowImpl->mbVisible == bVisible )
         return;
 
     ImplDelData aDogTag( this );