On 1 Apr 2017, at 23:30, Kent Karlsson <[email protected]> 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
