Use C locale for numbers in wx(File)Config.

Using the current locale decimal point in config files results in problems
when moving the files to another machine or even using a different locale on
the same one, so don't do it.

Always write the numbers using C locale and try to read them in C locale too
first, but also try the current locale if we failed for backwards
compatibility and to be tolerant with users who edit their config files by
hand.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64450 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -450,6 +450,7 @@ All:
   resources.
 - Added wxMessageQueue::Clear().
 - Added wxConfig::Read(float *) overload (Terry Farnham).
+- Always use decimal point (and not the current locale separator) in wxConfig.
 
 Unix:
 

interface/wx/config.h

@@ -689,6 +689,14 @@ public:
     /**
         Writes the double value to the config file and returns @true on
         success.
+
+        Notice that if floating point numbers are saved as strings (as is the
+        case with the configuration files used by wxFileConfig), this function
+        uses the C locale for writing out the number, i.e. it will always use a
+        period as the decimal separator, irrespectively of the current locale.
+        This behaviour is new since wxWidgets 2.9.1 as the current locale was
+        used before, but the change should be transparent because both C and
+        current locales are tried when reading the numbers back.
     */
     bool Write(const wxString& key, double value);
     /**

src/common/config.cpp

@@ -233,7 +233,14 @@ bool wxConfigBase::DoReadDouble(const wxString& key, double* val) const
     wxString str;
     if ( Read(key, &str) )
     {
-        return str.ToDouble(val);
+        if ( str.ToCDouble(val) )
+            return true;
+
+        // Previous versions of wxFileConfig wrote the numbers out using the
+        // current locale and not the C one as now, so attempt to parse the
+        // string as a number in the current locale too, for compatibility.
+        if ( str.ToDouble(val) )
+            return true;
     }
 
     return false;
@@ -256,7 +263,10 @@ wxString wxConfigBase::ExpandEnvVars(const wxString& str) const
 
 bool wxConfigBase::DoWriteDouble(const wxString& key, double val)
 {
-    return DoWriteString(key, wxString::Format(wxT("%g"), val));
+    // Notice that we always write out the numbers in C locale and not the
+    // current one. This makes the config files portable between machines using
+    // different locales.
+    return DoWriteString(key, wxString::FromCDouble(val));
 }
 
 bool wxConfigBase::DoWriteBool(const wxString& key, bool value)