Remove unknown fonts of document and set charset

var i,j : Integer;
    s : String;
    ca : TWPCHarAttr;
begin
     for i:=0 to WPRichText1.RTFData.RTFProps.FontMaxAnz-1 do
     begin
       s := WPRichText1.RTFData.RTFProps.Fontname[i];
       if Screen.Fonts.IndexOf( s )<0 then
       begin
         WPRichText1.RTFData.RTFProps.Fontname[i] := 'Arial';


         for j:=0 to WPRichText1.RTFData.RTFProps.Attributes.CharAttrCount-1 do
         begin
            WPRichText1.RTFData.RTFProps.Attributes.GetCharAttr(j, ca);
            if ((ca.MaskHash and BitMask[WPAT_CharFont])<>0) and
               (ca.Values[WPAT_CharFont]=i) then
               begin
                 ca.MaskHash := ca.MaskHash and not BitMask[WPAT_CharCharset];
                 ca.Values[WPAT_CharCharset] := 0;
                 WPRichText1.RTFData.RTFProps.Attributes.OverrideCharAttr(j,ca);
               end;
         end;
       end;
     end;
     WPRichText1.ReformatAll(true, true);
exit;