Add wxHAS_CONFIG_AS_{REG,FILE}CONFIG symbols

Sometimes it's useful to have some code used only if wxConfig is defined
as wxRegConfig or only if it is defined as wxFileConfig and testing for
these symbols is more clear than testing for the platform (and more
correct, considering that setting wxUSE_CONFIG_NATIVE to 0 may result in
wxFileConfig being used even under Windows).

docs/doxygen/mainpages/const_cpp.h

@@ -168,6 +168,10 @@ Currently the following symbols exist:
     implemented in a generic way, using a critical section.}
 @itemdef{wxHAS_BITMAPTOGGLEBUTTON, Defined in @c wx/tglbtn.h if
     wxBitmapToggleButton class is available in addition to wxToggleButton.}
+@itemdef{wxHAS_CONFIG_AS_FILECONFIG, Defined if wxConfig is defined as
+    wxFileConfig. This constant is available since wxWidgets 3.3.0.}
+@itemdef{wxHAS_CONFIG_AS_REGCONFIG, Defined if wxConfig is defined as
+    wxRegConfig. This constant is available since wxWidgets 3.3.0.}
 @itemdef{wxHAS_CONFIG_TEMPLATE_RW, Defined if the currently used compiler
     supports template Read() and Write() methods in wxConfig.}
 @itemdef{wxHAS_DEPRECATED_ATTR, Defined if C++14 @c [[deprecated]] attribute is

include/wx/config.h

@@ -23,9 +23,11 @@
 #if defined(__WINDOWS__) && wxUSE_CONFIG_NATIVE
     #include "wx/msw/regconf.h"
     #define wxConfig  wxRegConfig
+    #define wxHAS_CONFIG_AS_REGCONFIG
 #else // either we're under Unix or wish to always use config files
     #include "wx/fileconf.h"
     #define wxConfig wxFileConfig
+    #define wxHAS_CONFIG_AS_FILECONFIG
 #endif
 
 #endif // wxUSE_CONFIG

interface/wx/config.h

@@ -57,7 +57,9 @@ enum
     with the registry under Windows or text-based config files under Unix.
     To make writing the portable code even easier, wxWidgets provides a typedef
     wxConfig which is mapped onto the native wxConfigBase implementation on the
-    given platform: i.e. wxRegConfig under Windows and wxFileConfig otherwise.
+    given platform: i.e. wxRegConfig under Windows (in this case
+    `wxHAS_CONFIG_AS_REGCONFIG` preprocessor symbol is defined) and
+    wxFileConfig otherwise (in this case `wxHAS_CONFIG_AS_FILECONFIG` is).
 
     See @ref overview_config for a description of all features of this class.
 

src/common/config.cpp

@@ -56,12 +56,13 @@ bool          wxConfigBase::ms_bAutoCreate = true;
 
 wxConfigBase *wxAppTraitsBase::CreateConfig()
 {
-    return new
+#if defined(wxHAS_CONFIG_AS_REGCONFIG)
-    #if defined(__WINDOWS__) && wxUSE_CONFIG_NATIVE
+    return new wxRegConfig(wxTheApp->GetAppName(), wxTheApp->GetVendorName());
-        wxRegConfig(wxTheApp->GetAppName(), wxTheApp->GetVendorName());
+#elif defined(wxHAS_CONFIG_AS_FILECONFIG)
-    #else // either we're under Unix or wish to use files even under Windows
+    return new wxFileConfig(wxTheApp->GetAppName());
-        wxFileConfig(wxTheApp->GetAppName());
+#else
-    #endif
+    #error No wxConfig implementation defined.
+#endif
 }
 
 // ----------------------------------------------------------------------------