Proposal to add standardized variation sequences for chess notation
richard.wordingham at ntlworld.com
Tue Apr 4 22:50:56 CDT 2017
On Wed, 5 Apr 2017 01:02:32 +0100
Michael Everson <everson at evertype.com> wrote:
> On 4 Apr 2017, at 18:54, Richard Wordingham
> <richard.wordingham at ntlworld.com> wrote:
> > On Tue, 4 Apr 2017 01:30:05 +0100
> > Michael Everson <everson at evertype.com> wrote:
> >>> I'm trying to work out whether we need a variation sequence for
> >>> "chesspiece in a sentence”.
> >> Of course! Haven’t you ever seen chess problem texts? Check out
> >> the Fairy Chess proposal for encoding additional characters.
> >> Plenty of examples there.
> > Your examples did not have to contend with the possibility of fonts
> > that only support the variants for drawing chessboards.
> Um, what?
> Why would anyone make a font that supports the variants for drawing
> chessboards (which require the encoded characters 2654..265F) not put
> in glyphs for those?
A stop-gap font based on poor glyphs comes to mind.
> FontLab is the program I use to add OpenType features to my fonts,
> and if I try to add a sequence like 2654 + FE00 and the font doesn’t
> have a 2654, if flags it as an error and insists that the character
> appear in the font. OK, someone could be perverse and not add glyphs
> to those code positions, but…
Is this a sequence for the GSUB table or for the cmap table? The font
I have in mind would have no entry for U+2654 in its cmap format 4
subtable but would, following the proposal you put up on Saturday, have
entries for <U+2654, U+FE00> and <U+2654, U+FE01> in its cmap format 14
subtable. This approach is entirely consistent with the conception of
variation sequences as pseudo-encoding. I could make such a font (for
one chesspiece), but it would take at least an evening.
Now, I have sought advice on the OpenType list, and have received the
opinion of one person, to wit that if I have a glyph mapping for
<U+2654, U+FE00>, I am obliged to have a genuine mapping for U+2654,
i.e. not a map to .notdef.
On the basis of this advice, the font writer therefore has three choices
- expose his poor, possibly proportionally spaced glyphs for use as
default U+2654 (probably the best choice), make the glyph for <U+2654
U+FE00> the default glyph (not a disastrous choice), or make the glyph
for <U+2654, U+FE01> the default glyph (a malevolent choice in my view).
If one has no control over the fallback sequence for glyphs, arguably
the situation for truly 'plain text', then the escape root for plain
text is to have the font with good chess glyphs for use in running
text declare that it has the glyph for such use. That requires the
definition of a variation sequence to force the choice of suitable
glyph. Now, having to use variation sequences for chess pieces in plain
text is unfortunate, but should also work with existing fonts
supporting chess pieces. There would be transitional effects as
existing fonts were modified to declare that they supported this
variation sequence - the effects of font fallback would vary as the new
fonts were added to the system.
> But nobody making a chess font with actual support for chess would do
Note that the font I have in mind is just supporting chessboards.
The idea would be that other fonts would be used for high quality
> Nothing prevents someone from drawing the 16 Myanmar base characters
> with rings at the ends of their glyphs even though now VS are being
> recommended for that presentation. Is it legitimate to do that? Of
> course it is.
You seem to be declaring that it would not be wrong for chess piece
characters in running text to be automatically depicted with dark chess
> Can you identify an actual problem?
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