Re: Proposal to add standardized variation sequences for chess notation

From: Michael Everson <>
Date: Mon, 3 Apr 2017 23:35:52 +0100

On 3 Apr 2017, at 22:03, Richard Wordingham <> wrote:

> Nobody said the glyphs for use in ordinary text had to be a fixed width.

That’s why there’s a non-variant state and then two “on-square” variant states.

If you want to construct a chessboard using a font, whether it is using an ASCII font or using Unicode characters with variation selectors, the glyphs in that context have to be fixed width (if you want, you know, a square chess board).

> What I am saying is that the glyphs for the two new variants you are proposing need to harmonise with the block elements such as U+2581

No… in a chess font the font designer has to draw those block-element characters differently, to harmonize with the

> That requires uniform width *for those variants*. That is a key part of the glyph family's essence.

In their original usage in graphic terminals, sure. And some people still emulate those, and when they use those characters they draw them for that purpose. In current ASCII-based chess-fonts, a set of characters is used to draw a line (of one kind or another) around the board, and when I looked for Unicode characters to map to these, the block elements were the ones that had the right structure, since they were high and low and left and right in the em square.

> There is no such requirement on the glyphs for normal text use as at present.

There is **in a chess font** if you want to be able to draw a box around the chessboard. All the ASCII-based chess fonts have glyphs for this. In the Danish Skak font (see Figure 3) the eight ASCII characters 9, _, ), |, \, 0, -, and = are used. In my proposal, I use eight Block Element characters. It works, and is flexible enough even to cater to ornate frames.

> If one had a row of squares in flowing text, one would want the row to act like a word. One might have to resort to gluing it together using CGJ or WJ.

What are you on about? I’m talking about making 8×8 tables, not flowing rows of chessboards within a paragraph. I mean, sure, if you wanted to do that, you’d run into line-breaking weirdness, but nobody would do that, and so that weird situation just doesn’t matter.

All I was saying is that SPACE and NBSP aren’t the right characters to use for the light squares on a game board.

>>> Also having variants of U+25A1 and U+25A8 that match the game square filter modifiers seems quite legitimate.
>> Um, wait… What are you proposing NBSP for? I'm confused now. If you like these two characters (and I am glad you do) there’s no need for
>> U+00A0 at all.
> To be pedantic, I said that the proposed variants were legitimate, not that I liked them.

Um, ok. I don’t see that’s helpful in terms of improving or modifying the proposal. I stand by my proposal, which I have implemented successfully, even quickly as with William’s Quest font.

> I'm talking about looking for a U+2654 glyph for ordinary text when all the first font tried has is:
> 2654 FE01; Chesspiece on white; # WHITE CHESS KING
> 2654 FE02; Chesspiece on black; # WHITE CHESS KING
> I must confess I am now wondering what the format 4 cmap should say about U+2654.

I really don’t know about the “format 4 cmap” text. I copied it from a successful VS proposal by Ken Lunde of Adobe. What I used was the liga and rlig tables. I didn’t edit any cmap table per se and don’t know how to do it.

Without any VS character, 2654 just renders like an ordinary white king as drawn in the font. It only goes to a light or dark board-square glyph with the VS.

> Should it give a glyph for U+2654 or not?

Of course. Why wouldn't it? It’s a graphic character.

> I'm also wondering about Windows behaviour. There was a time when Windows 7 only supported variation sequences if they appeared in the cmap 14 subtable.

I don’t know. Older software often doesn’t support this. Quark XPress, which has become a completely awesome typesetting program, used to be terrible at it. Maybe people typesetting chessboards would have to use something other than some apps on Windows 7, or maybe something other than Windows 7 entirely. I can’t use Unicode at all really on Mac OS 9, which I use rom time to time.

>>> If it's looking for an OpenType font for a glyph of the family <U+82A6, U+E0100>,
>> Or any OpenType substitution string.
> Most won't be recognised as needed. If the first font lacks a ligature for <f, i>, fallback won't be used for it. Grapheme clusters and
> variation sequences get special treatment.

I don’t see how anything you’re saying either identifies or tried to solve any actual problem with the proposal. The proposal says “put some substitution tables into your chess font to display a particular glyph” and some apps do that and some don’t. You can’t use VS with apps that don't.

Michael Everson
Received on Mon Apr 03 2017 - 17:36:13 CDT

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