Re: Proposal to add standardized variation sequences for chess notation

On 1 Apr 2017, at 23:30, Kent Karlsson <kent.karlsson14_at_telia.com> wrote:

> 2654 FE00; Chesspiece on white; # WHITE CHESS KING
>
> Why do the ones with white background need a variation selector?

Because for the typesetting to work the glyph has to have the same precise square metrics as the ones on the black square (it is not a “background”), and the chess characters when used as ordinary symbols in text need not have such metrics. (And do not, in most fonts.)

> 25A1 FE00; White chessboard square; # WHITE SQUARE
> 25A8 FE01; Black chessboard square; # SQUARE WITH UPPER RIGHT TO LOWER LEFT FILL
>
> I see that you want a fallback in case the variation selectors aren’t supported;

I am not sure what you mean. If the variation selector isn’t supported then the glyph will not have metrics suitable for setting a chessboard.

> but isn't the convention that one "always" start with FE00 for each character that may have variation selectors applied?

I don’t know what you mean by this. As shown in Figure 2, a white knight for instance may occur on its own, or may occur on a white board square or on a black board square. I don’t think the first need differentiation, which is why the variation sequences apply only to the on—board-square glyphs.

> So in this case, one would only need variation selector FE00; if applied to 25A1 or 25A8 giving the chess board variety, if applied to a chess piece character, gives "checkered" ("black") background (without, one gets the white background).

No, a chesspiece symbol can (and nearly always does) appear on its own in text without square metrics. “Being on a white square” is a specific glyph state, different from “being a symbol on its own”.

> Why not use 25A0 BLACK SQUARE with the variation selector? (I know that it would not entirely black with the variation selector (if not fallback).)

Because the conventional international shading for a black square is the /// one, and using that facilitates legibility in environments where OpenType features are not enabled even if the VS characters are present.

> I mean, there is no absolute LOGICAL NEED to draw the "black” background as WITH UPPER RIGHT TO LOWER LEFT FILL, it could go the other direction or be just "gray" (or for that matter medium blue...); font maker choice.

Since it doesn’t “matter" what character is used I chose the one which is most typical, and stand by that choice.

All the best,
Michael Everson

> Kind regards
> /Kent K
Received on Sat Apr 01 2017 - 18:33:39 CDT