Proposal to add standardized variation sequences for chess notation

[Michael Everson]

On 5 Apr 2017, at 22:13, Kent Karlsson <kent.karlsson14 at telia.com> wrote:
> 
>         Kent, I can’t read this in a plain-text e-mail.
> 
> Well, it was SUPPOSED to be explicit HTML code in the email. It was NOT the intent that the given example was to be
> rendered directly in the email (even if you have HTML emails enabled).

Oh, you misunderstood me. I knew it was raw HTML. I didn’t expect it to render. But it was meaningless code. 

The proposal for standardized variation sequences for chess treats it as text. Whether that text is analogous to ASCII art or not is irrelevant. The proposal solves a problem. giving good visual fallback, and excellent rendering if properly employed. It’s incredibly simple and uses 

> I agree that the HTML code is a bit of a mouthful (and I would also do it a bit differently), and also has the problem
> mentioned in the previous paragraph). Which is why I support your proposal, but with these modifications:
> 
>  - with the extra requirement to have VSs also for the boarder line drawing characters (to make them fit for 
>    drawing chess board boarders, in a general purpose font), and

Look, if that’s the price I’d have to pay to move forward with this I would. I don’t think it’s necessary. I *do* think that the definition of the resulting glyph “suitable for the chess glyphs in this font that supports … 

Oh, here. This is what I would add. 

2581 FE00; Chessboard box drawing; # LOWER ONE EIGHTH BLOCK
258F FE00; Chessboard box drawing; # LEFT ONE EIGHTH BLOCK
2594 FE00; Chessboard box drawing; # UPPER ONE EIGHTH BLOCK
2595 FE00; Chessboard box drawing; # RIGHT ONE EIGHTH BLOCK
2596 FE00; Chessboard box drawing; # QUADRANT LOWER LEFT
2597 FE00; Chessboard box drawing; # QUADRANT LOWER RIGHT
2598 FE00; Chessboard box drawing; # QUADRANT UPPER LEFT
259D FE00; Chessboard box drawing; # QUADRANT UPPER RIGHT

I guess I see your point. It does no harm, especially if the font might possibly be used for graphics terminal emulation. ;-)

>  - some bidi fix [preferably making the box/border drawing characters bidi "L", if possible; otherwise a caveat that
>    if there is an expectation to paste in such a board into an RTL document, bidi controls need be used to LTR the board]).

I don’t know if there is a problem here and am not able to offer a solution if there is. I don’t object to a solution, if there is a problem. 

> Nit: You sometimes seem to have made the line spacing slightly larger (like 2 points) larger than the character width.

Different fonts have different metrics. The Ludus font supports many games, not just chess. 

> Should they not be exactly the same, to get the best (square) display of the chess boards? (Not that it is very visible,
> but a bit.)

I didn’t overcompensate in the proposal document to make absolutely perfect charts; it’s reasonable to know that from font to font control over leading may be necessary.

> I think the "ligatures" approach is a dead end.

I hope others will think so too. 

[1]
>  - As you mention, the fallback will have very different line lengths for the lines of a board display,
>    and thus basically unreadable.

Since the proposal takes as read that chess data should be parseable and plain-text, an approach with better legibility should be considered superior to an approach with poorer legibility. 

[2]
>  - If ZWJ is not needed, one will need two *new* characters that (in some fonts) ligate with chess pieces.
>    No existing character should ever ligate with chess pieces.

I’d agree, for even if there were “ligate with light/dark chess square”, fallback would be illegible per [1] above. 

[3]
>  - If ZWJ is needed, then one can use some existing characters as board squares.

Not sure what you mean, but it’s probably not important since ZWJ is a bad idea and because of [1] above.

[4]
>  - In either case, it is not clear (or obvious) which should come first, a chess piece or a board square.
>    There will surely be mistakes, giving them in the wrong order (not a problem in your proposal).

The one thing about my proposal is that a parser could tell someone if there were a missing VS or the wrong VS, though when you are typesetting with a conformant font, the visual feedback is enough. 

[5]
>  - My personal guesstimate is that there will be much fewer fonts that would implement the ligation
>    (if that approach was to be chosen), than would implement the VS approach you are suggesting.

And THAT's the reason it has been proposed as a standardized sequence. Chess is an important activity and chess literature is vast and should be properly supported by the UCS. 

> Thus I support your proposal, since that gives:
>   - Good fallback (readable, though ugly).
>   - Fairly good display when the VS sequences are interpreted (and the font is otherwise reasonable),
>     and "good" context (line height setting, not too short lines so that auto line breaking is avoided, ...).
>   - Easier to machine parse than the ligatures approach; and MUCH easier to parse than an HTML version.
>   - Easy to convert to (say) HTML for even better display in (say) HTML pages (CAN look much better,
>     and NO dependence on line height setting or line width setting (or bidi direction derivations), but
>     just that the table (for the board) is reasonably done.

Thank you for your consideration of the proposal, and of your support. 

Michael