Use wxObjectDataPtr to manage wxPrintData::m_nativeData

Remove code allocating and freeing this pointer directly and use
wxObjectDataPtr instead.

This required adding wxRefCounter-like methods to wxPrintData, which
can't inherit from wxRefCounter because it uses a different name for its
field storing the reference counter, which is public and so can't be
renamed without breaking compatibility.

include/wx/cmndata.h

@@ -113,7 +113,7 @@ public:
     void ConvertToNative();
     void ConvertFromNative();
     // Holds the native print data
-    wxPrintNativeDataBase *GetNativeData() const { return m_nativeData; }
+    wxPrintNativeDataBase *GetNativeData() const { return m_nativeData.get(); }
 
 private:
     wxPrintBin      m_bin;
@@ -136,7 +136,7 @@ private:
 
     std::vector<char> m_privData;
 
-    wxPrintNativeDataBase  *m_nativeData;
+    wxObjectDataPtr<wxPrintNativeDataBase> m_nativeData;
 
 private:
     wxDECLARE_DYNAMIC_CLASS(wxPrintData);

include/wx/prntbase.h

@@ -159,8 +159,8 @@ public:
 class WXDLLIMPEXP_CORE wxPrintNativeDataBase: public wxObject
 {
 public:
-    wxPrintNativeDataBase();
-    virtual ~wxPrintNativeDataBase() {}
+    wxPrintNativeDataBase() = default;
+    virtual ~wxPrintNativeDataBase();
 
     virtual bool TransferTo( wxPrintData &data ) = 0;
     virtual bool TransferFrom( const wxPrintData &data ) = 0;
@@ -172,7 +172,14 @@ public:
     virtual bool Ok() const { return IsOk(); }
     virtual bool IsOk() const = 0;
 
-    int  m_ref;
+    // Internal implementation details, do not use.
+
+    // For historical reasons, this class doesn't use wxRefCounter, but provides
+    // the same methods, so that it could still be used with wxObjectDataPtr.
+    void IncRef() { m_ref++; }
+    void DecRef() { if ( !--m_ref) delete this; }
+
+    int  m_ref = 1;
 
 private:
     wxDECLARE_CLASS(wxPrintNativeDataBase);

src/common/cmndata.cpp

@@ -79,7 +79,6 @@ wxPrintData::wxPrintData()
 wxPrintData::wxPrintData(const wxPrintData& printData)
     : wxObject()
 {
-    m_nativeData = nullptr;
     (*this) = printData;
 }
 
@@ -96,12 +95,7 @@ void wxPrintData::SetPrivData( char *privData, int len )
     }
 }
 
-wxPrintData::~wxPrintData()
-{
-    m_nativeData->m_ref--;
-    if (m_nativeData->m_ref == 0)
-        delete m_nativeData;
-}
+wxPrintData::~wxPrintData() = default;
 
 void wxPrintData::ConvertToNative()
 {
@@ -133,16 +127,7 @@ wxPrintData& wxPrintData::operator=(const wxPrintData& data)
     m_printMode = data.m_printMode;
     m_filename = data.m_filename;
 
-    // UnRef old m_nativeData
-    if (m_nativeData)
-    {
-        m_nativeData->m_ref--;
-        if (m_nativeData->m_ref == 0)
-            delete m_nativeData;
-    }
-    // Set Ref new one
-    m_nativeData = data.GetNativeData();
-    m_nativeData->m_ref++;
+    m_nativeData = data.m_nativeData;
 
     m_privData = data.m_privData;
 

src/common/prntbase.cpp

@@ -288,10 +288,7 @@ wxPrintNativeDataBase *wxNativePrintFactory::CreatePrintNativeData()
 
 wxIMPLEMENT_ABSTRACT_CLASS(wxPrintNativeDataBase, wxObject);
 
-wxPrintNativeDataBase::wxPrintNativeDataBase()
-{
-    m_ref = 1;
-}
+wxPrintNativeDataBase::~wxPrintNativeDataBase() = default;
 
 //----------------------------------------------------------------------------
 // wxPrintFactoryModule