fixed win32 code to not use MB_ERR_INVALID_CHARS on win version where it isn't available; roundtrip check is used instead

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@37830 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/strconv.cpp

@@ -1652,7 +1652,28 @@ public:
         // own wxMBConvUTF7 doesn't detect errors (e.g. lone "+" which is
         // explicitly ill-formed according to RFC 2152) neither so we don't
         // even have any fallback here...
-        int flags = m_CodePage == CP_UTF7 ? 0 : MB_ERR_INVALID_CHARS;
+        //
+        // Moreover, MB_ERR_INVALID_CHARS is only supported on Win 2K SP4 or
+        // Win XP or newer and if it is specified on older versions, conversion
+        // from CP_UTF8 (which can have flags only 0 or MB_ERR_INVALID_CHARS)
+        // fails. So we can only use the flag on newer Windows versions.
+        // Additionally, the flag is not supported by UTF7, symbol and CJK
+        // encodings. See here:
+        //     http://blogs.msdn.com/michkap/archive/2005/04/19/409566.aspx
+        //     http://msdn.microsoft.com/library/en-us/intl/unicode_17si.asp
+        int flags = 0;
+        if ( m_CodePage != CP_UTF7 && m_CodePage != CP_SYMBOL &&
+             m_CodePage < 50000 &&
+             IsAtLeastWin2kSP4() )
+        {
+            flags = MB_ERR_INVALID_CHARS;
+        }
+        else if ( m_CodePage == CP_UTF8 )
+        {
+            // Avoid round-trip in the special case of UTF-8 by using our
+            // own UTF-8 conversion code:
+            return wxMBConvUTF8().MB2WC(buf, psz, n);
+        }
 
         const size_t len = ::MultiByteToWideChar
                              (
@@ -1663,11 +1684,40 @@ public:
                                 buf,            // output string
                                 buf ? n : 0     // size of output buffer
                              );
+        if ( !len )
+        {
+            // function totally failed
+            return (size_t)-1;
+        }
+
+        // if we were really converting and didn't use MB_ERR_INVALID_CHARS,
+        // check if we succeeded, by doing a double trip:
+        if ( !flags && buf )
+        {
+            wxCharBuffer mbBuf(n);
+            if ( ::WideCharToMultiByte
+                   (
+                      m_CodePage,
+                      0,
+                      buf,
+                      -1,
+                      mbBuf.data(),
+                      n,
+                      NULL,
+                      NULL
+                   ) == 0 ||
+                  strcmp(mbBuf, psz) != 0 )
+            {
+                // we didn't obtain the same thing we started from, hence
+                // the conversion was lossy and we consider that it failed
+                return (size_t)-1;
+            }
+        }
 
         // note that it returns count of written chars for buf != NULL and size
         // of the needed buffer for buf == NULL so in either case the length of
         // the string (which never includes the terminating NUL) is one less
-        return len ? len - 1 : (size_t)-1;
+        return len - 1;
     }
 
     size_t WC2MB(char *buf, const wchar_t *pwz, size_t n) const
@@ -1782,6 +1832,29 @@ private:
         return s_isWin98Or2k == 1;
     }
 
+    static bool IsAtLeastWin2kSP4()
+    {
+        static int s_isAtLeastWin2kSP4 = -1;
+
+        if ( s_isAtLeastWin2kSP4 == -1 )
+        {
+            OSVERSIONINFOEX ver;
+
+            memset(&ver, 0, sizeof(ver));
+            ver.dwOSVersionInfoSize = sizeof(ver);
+            GetVersionEx((OSVERSIONINFO*)&ver);
+
+            s_isAtLeastWin2kSP4 =
+              ((ver.dwMajorVersion > 5) || // Vista+
+               (ver.dwMajorVersion == 5 && ver.dwMinorVersion > 0) || // XP/2003
+               (ver.dwMajorVersion == 5 && ver.dwMinorVersion == 0 &&
+               ver.wServicePackMajor >= 4)) // 2000 SP4+
+              ? 1 : 0;
+        }
+
+        return s_isAtLeastWin2kSP4 == 1;
+    }
+
     long m_CodePage;
 };