fdo#66811: vcl: fix broken OUString with length STRING_LEN

ImplSalGetUniString was wrongly converted and constructs OUString with
invalid length in WinSalGraphics::CreateFontSubset; this is then
implicitly converted to an empty UniString so the font names are
missing in the PDF files generated on Windows.

(regression from 9e310cc3)

Change-Id: I1603e62cf18f353f3d7de322b9111a173dc6b225

vcl/inc/win/saldata.hxx

@@ -196,7 +196,7 @@ void ImplSalPostDispatchMsg( MSG* pMsg, LRESULT nDispatchResult );
 void ImplSalLogFontToFontW( HDC hDC, const LOGFONTW& rLogFont, Font& rFont );
 
 rtl_TextEncoding ImplSalGetSystemEncoding();
-OUString ImplSalGetUniString( const sal_Char* pStr, xub_StrLen nLen = STRING_LEN );
+OUString ImplSalGetUniString(const sal_Char* pStr, sal_Int32 nLen = -1);
 int ImplSalWICompareAscii( const wchar_t* pStr1, const char* pStr2 );
 
 #define SAL_FRAME_WNDEXTRA          sizeof( DWORD )

vcl/win/source/app/saldata.cxx

@@ -44,9 +44,10 @@ rtl_TextEncoding ImplSalGetSystemEncoding()
 
 // -----------------------------------------------------------------------
 
-OUString ImplSalGetUniString( const sal_Char* pStr, xub_StrLen nLen )
+OUString ImplSalGetUniString(const sal_Char* pStr, sal_Int32 const nLen)
 {
-    return OUString( pStr, nLen, ImplSalGetSystemEncoding(),
+    return OUString( pStr, (-1 == nLen) ? strlen(pStr) : nLen,
+                      ImplSalGetSystemEncoding(),
                       RTL_TEXTTOUNICODE_FLAGS_UNDEFINED_DEFAULT |
                       RTL_TEXTTOUNICODE_FLAGS_MBUNDEFINED_DEFAULT |
                       RTL_TEXTTOUNICODE_FLAGS_INVALID_DEFAULT );

vcl/win/source/gdi/salprn.cxx

@@ -266,7 +266,7 @@ OUString WinSalInstance::GetDefaultPrinter()
         char* pTmp = pBuf;
         while ( *pTmp && (*pTmp != ',') )
             pTmp++;
-        return ImplSalGetUniString( pBuf, (xub_StrLen)(pTmp-pBuf) );
+        return ImplSalGetUniString( pBuf, static_cast<sal_Int32>(pTmp-pBuf) );
     }
     else
         return OUString();