Improve type safety by doing a runtime check to make sure the

wxFontMapper really is a wxFontMapper when GUI code asks for it.
Remove some incorrect comments and add some new ones.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@33080 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/fontmap.h

@@ -49,6 +49,8 @@ class WXDLLIMPEXP_CORE wxFontMapper;
 
 class WXDLLIMPEXP_BASE wxFontMapperBase
 {
+    // For IsWxFontMapper()
+    friend class WXDLLIMPEXP_CORE wxFontMapper;
 public:
     // constructtor and such
     // ---------------------
@@ -61,6 +63,8 @@ public:
 
     // return instance of the wxFontMapper singleton
     // wxBase code only cares that it's a wxFontMapperBase
+    // In wxBase, wxFontMapper is only forward declared
+    // so one cannot implicitly cast from it to wxFontMapperBase.
     static wxFontMapperBase *Get();
 
     // set the singleton to 'mapper' instance and return previous one
@@ -156,6 +160,9 @@ protected:
     int NonInteractiveCharsetToEncoding(const wxString& charset);
 
 private:
+    // pseudo-RTTI since we aren't a wxObject.
+    virtual bool IsWxFontMapper();
+
     // the global fontmapper object or NULL
     static wxFontMapper *sm_instance;
 
@@ -252,6 +259,9 @@ protected:
     wxWindow *m_windowParent;
 
 private:
+    // pseudo-RTTI since we aren't a wxObject.
+    virtual bool IsWxFontMapper();
+
     DECLARE_NO_COPY_CLASS(wxFontMapper)
 };
 

src/common/fmapbase.cpp

@@ -199,7 +199,7 @@ class wxFontMapperModule : public wxModule
 public:
     wxFontMapperModule() : wxModule() { }
     virtual bool OnInit() { return true; }
-    virtual void OnExit() { delete wxFontMapperBase::Set(NULL); }
+    virtual void OnExit() { delete (wxFontMapperBase*)wxFontMapperBase::Set(NULL); }
 
     DECLARE_DYNAMIC_CLASS(wxFontMapperModule)
 };
@@ -233,11 +233,10 @@ wxFontMapperBase::~wxFontMapperBase()
 #endif // wxUSE_CONFIG
 }
 
+bool wxFontMapperBase::IsWxFontMapper()
+{   return false; }
+
 /* static */
-// Declared as returning wxFontMapper when wxUSE_GUI=1.  Unfortunately, it's
-// only implemented in wxBase library.  Note that if the last resort
-// is taken and GUI code tries to treat it as a real wxFontMapper
-// then you'd be in trouble.
 wxFontMapperBase *wxFontMapperBase::Get()
 {
     if ( !sm_instance )

src/common/fontmap.cpp

@@ -163,14 +163,17 @@ wxFontMapper::~wxFontMapper()
 {
 }
 
+bool wxFontMapper::IsWxFontMapper()
+{   return true; }
+
 /* static */
-// Declared as returning wxFontMapper when wxUSE_GUI=1.  Unfortunately, it's
-// only implemented in wxBase library.  Note that if the last resort
-// is taken and GUI code tries to treat it as a real wxFontMapper
-// then you'd be in trouble.
 wxFontMapper *wxFontMapper::Get()
 {
-    return (wxFontMapper*)wxFontMapperBase::Get();
+    wxFontMapperBase *fontmapper = wxFontMapperBase::Get();
+    wxASSERT_MSG(fontmapper->IsWxFontMapper(), wxT("GUI code requested a wxFontMapper but we only have a wxFontMapperBase."));
+    // Now return it anyway because there's a chance the GUI code might just
+    // only want to call wxFontMapperBase functions.
+    return (wxFontMapper*)fontmapper;
 }
 
 wxFontEncoding