Not all gdt symbols are present in other fonts. To display the symbols correctly, you need the correct font with the same encoding. Thus there is no need to convert character codes. For example, to display Cyrillic characters you should use a Cyrillic font, but no recording is required.
To see all characters in a TTF font on Microsoft® Windows®, you can use the Windows Character Map.
Detailed information about font handling can be found in the Developer's Guide, Font Handling topic.