The Unicode code path in DMDX can either be turned on with the Unicode check box in the main DMDX dialog or a command line switch. Use of the -unicode command line switch overrides the Unicode check box. With the Unicode code path enabled DMDX uses any Unicode \u control words in the RTF file that may be present instead of the ANSI equivalents and marks all regular ANSI characters up by putting \'00 after them so they become Unicode 16 bit characters. Also as of version 22.214.171.124 when the Unicode option is on DMDX can now open files with names using extended characters (both code page and Unicode) and is no longer limited to just ASCII names and through version 126.96.36.199 the contents of the run dialog list box and various error messages also gained the ability display Unicode characters along with code page ones (that DMDX internally converts to Unicode if the Unicode path is on) so if you've got extended characters in your item file even if you don't need the Unicode option it can still beautify and make DMDX's spew more understandable. If you're curious about your machine's ability to display Unicode glyphs or a particular glyph I coded up a displayer for them.
While the Unicode code path through DMDX was initially added to see if we could get DMDX to handle a Tamil font it's also useful with double byte character set code page Asian fonts that have MS Word smart quotes in them. Because DMDX when run with the Unicode code path on is now using the Unicode RTF keywords it can differentiate between Word's smart quotes and normal characters so the smart quote detection is permanently off when the Unicode code path is on. When using legacy operating systems such as Windows XP once the Unicode path was added the problem with the Tamil font then became that Windows GDI didn't render the vowel modifiers in the correct places until we went to the Control Panel Regional and Language options and checked both the Complex right to left font handling and East Asian boxes (neither of which are present or needed in Windows 10, exactly when they went missing is something for the historians to determine). In passing we also noticed in another instance a machine rendering a Hebrew font (so right to left text) where Unicode was off and it was rendering the Hebrew backwards until we installed the right to left language option, no other changes made to DMDX, the Unicode option or the RTF file (again, not an issue in Windows 10 and probably not for some time before that OSes release). Once these options were installed DMDX's displayed output matched Word's and while Word's output may not be not technically correct (certain glyphs were not displayed) I figure once DMDX's output matches Word's my responsibility is pretty much over.
The key indicator that you need to turn the Unicode code path on is getting question marks rendered instead of the desired characters as that's what the Tamil initially looked like. In the past Asian fonts have had ANSI double byte code page alternatives to the Unicode characters, not so the Tamil. From what I've read using a ? as an alternative to Unicode characters instead of some ANSI code page alternative would appear to be a wide spread practice so perhaps others will come across this as well. It used to be that you didn't want to use Unicode all the time as there are files that contain double byte code page font references without any Unicode alternative and when you forced old versions of DMDX to use the Unicode path it took the double code page references as Unicode references and you'd get gibberish rendered (see next paragraph, they should get converted properly with 188.8.131.52 or later). The problem arose because DMDX used to expect you to either use code page values or Unicode values and not a mix of the two. When not using Unicode there's arcane code in the GDI font rendering routines that takes F0 for instance, the code page value for a Vietnamese bar-d and realizes it should use Unicode end point 111 (U+111 if you're a member of the cognoscenti that actually grok all this stuff). Turn DMDX's Unicode renderer on with versions prior to 184.108.40.206 however where it passes 16 bit values to GDI instead of 8 bit ones that F0 gets interpreted as Unicode F0 (an Icelandic eth, not what we want). Sometimes the code page value is the same as the Unicode value, but not always. And you can't just override it by editing the raw RTF and changing \'F0 to \u273 (273 decimal is 111 hex) because next time you run Word it'll go and revert them all back to code page values, I know, I tried (WordPad operates the same way). Maybe there's some way to force Word to use Unicode but I'm not seeing it. I have reports that LibreOffice will leave characters as Unicode, you might have cut and paste through NotePad++ or EditPad to get it right though.
So push came to shove and in version 220.127.116.11 of DMDX we finally added code to convert code page references to Unicode 16 bit words, which works fine when there's a code page reference DMDX can recognize in the RTF font specification, which is neither guaranteed nor error free (our table is not complete, in fact it may not be possible to build a complete one as for instance I can't find a clear Japanese code page definition given that there are three possible different choices that I have no way of choosing between without a concrete example) so conversions are by no means guaranteed. If you come up with a font that doesn't work you're more than welcome to contact me and I'll see if I can add your code page to the table DMDX uses. This could also fail if double byte character set code page characters were used however as of 18.104.22.168 DMDX currently now looks up two bytes if they occur next to each other. It appears that editors like Word use Unicode instead of double byte code page references, WordPad, not so much. I'm guessing that with the 22.214.171.124 modifications leaving the Unicode option on all the time is getting pretty close to realistic -- of course text in the diagnostics and run dialog list box became a bit tougher to read with versions of DMDX prior to 126.96.36.199, however there I've written code to convert items to UTF-8 that DMDX can now render. Prior to 188.8.131.52 if you looked at the diagnostic output you'd see what Unicode 16 bit values the double byte character set code page values had been converted to, now however if you want to see what translations were applied you'll have to look at rtfparsed.itm that contains the original markup. Some of them can be translated to two 16 bit words (and of course each 16 bit word is encoded as two 8 bit \'xx RTF control words, low byte first). Also note that in the Unicode mark up you get to see the RTF text formatting control words that are removed for the diagnostics display.
Macros will require a little extra attention when the Unicode code path is on. This is because regions outside of text segments are still ANSI coded 8 bit characters just like they ever were, only inside text segments is Unicode found and it's not real Unicode but instead marked up RTF hex sequences. So the text segment "~M" with the Unicode path turned on gets marked up to "~\'00M\'00". The macro code is smart enough that it will detect macros used outside of quotes and leave them as ANSI sequences and also detect if a macro is used within quotes and mark the macro body up with \'00 correctly. The problem comes if you want to have special Unicode characters in the macro body as the RTF parser is going to strip them out as they won't be in quotes. And you can't use the double quote as a macro delimiter if there's already another text segment as it will get flagged as a frame with multiple text segments. So this would fail:
The solution is to use the keyword version of the macro definition (that I suspect never worked till I fixed it in 184.108.40.206) where the text segment is within the keyword and won't get flagged as multiple text segments:
But care is still needed as use of macro U outside any text segment will freak things out totally as there's no code that strips Unicode sequences out of a macro body when used outside quotes (if it's a real problem I'll add the code but I can't see someone wanting it and only mention it for completeness' sake).
NOTE:- When using versions of DMDX prior to 220.127.116.11 and the Unicode code path was active text in an item's double quote delimited text segments displayed in the diagnostics would be marked up Unicode with \'00 control words, as of 18.104.22.168 they are removed and as of version 22.214.171.124 the rendered diagnostics should look the same as when the Unicode path is off -- unless of course you had actual Unicode characters in there... So given the following example item file:
<fd 100> <cr> <nfb>
0 "Unicode syntax demo";
0 "this will work" <md U"வேறுபாடு">;
0 <xyjustification center> "Hello World",
"مرحبا بالعالم" <xy .125, .125>, "Chào thế giới" <xy .375, .125>,
"नमस्ते दुनिया" <xy .625, .125>, "Привет, мир" <xy .875, .125>,
"ওহে বিশ্ব" <xy .125, .250>, "ಹಲೋ ವರ್ಲ್ಡ್" <xy .875, .250>,
"你好，世界" <xy .125, .375>, "سلام دنیا" <xy .875, .375>,
"សួស្តីពិភពលោក" <xy .125, .500>, "салам дүйнө" <xy .875, .500>,
"สวัสดีชาวโลก" <xy .125, .625>, "హలో వరల్డ్" <xy .875, .625>,
"هيلو ورلڊ" <xy .125, .750>, "ሰላም ልዑል" <xy .875, .750>,
"Γειά σου Κόσμε" <xy .125, .875>, "こんにちは世界" <xy .375, .875>,
"שלום עולם" <xy .625, .875>, "안녕하세요 월드" <xy .875, .875>;
0 "done" ;
A syntax check in version 126.96.36.199 would have looked like this under Windows 7:
Using my debug build of 188.8.131.52 you get this: