Add wxObjectDataPtr::release()

This makes it possible to use wxObjectDataPtr inside functions returning
raw pointers owned by the caller, such as custom GetAttr() in the grid
sample.

include/wx/object.h

@@ -313,6 +313,13 @@ public:
         m_ptr = ptr;
     }
 
+    T* release()
+    {
+        T* const ptr = m_ptr;
+        m_ptr = NULL;
+        return ptr;
+    }
+
     wxObjectDataPtr& operator=(const wxObjectDataPtr &tocopy)
     {
         if (m_ptr)

interface/wx/object.h

@@ -608,6 +608,21 @@ public:
     */
     void reset(T *ptr);
 
+    /**
+        Release the owned pointer, making caller responsible for decrementing
+        its reference count.
+
+        This method should be used only for interoperating with the existing
+        code working with raw pointers, typically when returning a raw pointer
+        from a function.
+
+        After calling this function, this object becomes invalid, i.e. it
+        doesn't hold any valid pointer value any more.
+
+        @since 3.1.4
+    */
+    T* release();
+
     /**
         Conversion to a boolean expression (in a variant which is not
         convertable to anything but a boolean expression).

samples/grid/griddemo.cpp

@@ -1596,41 +1596,34 @@ void GridFrame::OnBugsTable(wxCommandEvent& )
 // ----------------------------------------------------------------------------
 
 MyGridCellAttrProvider::MyGridCellAttrProvider()
+    : m_attrForOddRows(new wxGridCellAttr)
 {
-    m_attrForOddRows = new wxGridCellAttr;
     m_attrForOddRows->SetBackgroundColour(*wxLIGHT_GREY);
 }
 
-MyGridCellAttrProvider::~MyGridCellAttrProvider()
-{
-    m_attrForOddRows->DecRef();
-}
-
 wxGridCellAttr *MyGridCellAttrProvider::GetAttr(int row, int col,
                            wxGridCellAttr::wxAttrKind  kind /* = wxGridCellAttr::Any */) const
 {
-    wxGridCellAttr *attr = wxGridCellAttrProvider::GetAttr(row, col, kind);
+    wxObjectDataPtr<wxGridCellAttr>
+        attr(wxGridCellAttrProvider::GetAttr(row, col, kind));
 
     if ( row % 2 )
     {
         if ( !attr )
         {
             attr = m_attrForOddRows;
-            attr->IncRef();
         }
         else
         {
             if ( !attr->HasBackgroundColour() )
             {
-                wxGridCellAttr *attrNew = attr->Clone();
+                attr = attr->Clone();
-                attr->DecRef();
-                attr = attrNew;
                 attr->SetBackgroundColour(*wxLIGHT_GREY);
             }
         }
     }
 
-    return attr;
+    return attr.release();
 }
 
 void GridFrame::OnVTable(wxCommandEvent& )

samples/grid/griddemo.h

@@ -296,13 +296,12 @@ class MyGridCellAttrProvider : public wxGridCellAttrProvider
 {
 public:
     MyGridCellAttrProvider();
-    virtual ~MyGridCellAttrProvider();
 
     virtual wxGridCellAttr *GetAttr(int row, int col,
                                     wxGridCellAttr::wxAttrKind  kind) const wxOVERRIDE;
 
 private:
-    wxGridCellAttr *m_attrForOddRows;
+    wxObjectDataPtr<wxGridCellAttr> m_attrForOddRows;
 };
 
 // ----------------------------------------------------------------------------