On Mon, Apr 3, 2017 at 4:47 PM, Richard Wordingham < richard.wording...@ntlworld.com> wrote:
> On Mon, 3 Apr 2017 23:35:52 +0100 > Michael Everson <ever...@evertype.com> wrote: > > > On 3 Apr 2017, at 22:03, Richard Wordingham > > <richard.wording...@ntlworld.com> wrote: > > The relevant text before was, > > "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" > > > > Should it give a glyph for U+2654 or not? > > > Of course. Why wouldn't it? It’s a graphic character. > > What my conceptual example font has is not the sort of glyph one would > want for sentences like "Alice ♙ d4 meets White Queen ♕ (with shawl)". > > > 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. > > I'm trying to work out whether we need a variation sequence for > "chesspiece in a sentence". We need the advice of someone who's worked > on font fallback. > > You don't need substitution tables to be executed if your application > can just look up glyphs for variation sequences. > I haven't worked on font fallback but maybe I can add something to this. Honestly, I'm not sure we need to make a distinction between piece-on-light-square and piece-in-notation at the SVS level. Currently, chess fonts can be (roughly) divided into "diagram fonts" and "notation fonts". A diagram font: - Is fixed-width (at least for the chess figurines themselves) - Centers each figurine in the character cell - Has a means of producing dark squares and on-dark-square equivalents of the figurines, either through separate allocation or a "combining dark square background" mechanism (usually a negative kerning hack) - Usually has board border elements, and may have decimal digits and a subset of the lowercase Basic Latin alphabet for labeling ranks and files A notation font: - May be proportional - Has figurines sitting on the baseline (Neither is *required* for figurine notation. They just look nice.) None of the features required for a diagram font are unacceptable in figurine notation: they are either irrelevant (dark squares, border elements) or acceptable visual variation (fixed width, vertical centering). Most chess fonts are of the diagram type, and figurines from diagram fonts may be (and frequently are) used in figurine notation. A font with figurines sitting on the baseline would not be illegible in diagrams, just a bit clumsy-looking. A proportional-width font would be unacceptable for proper typesetting of a diagram since board spaces would not line up properly, but would likely still be readable. In addition, when figurines for notation and for diagrams are distinguished, they are distinguished above the character level, in runs of like type: rows of a diagram, or lines of figurine notation. This is not unlike proportional vs. tabular digits. A font that supported both could default to fixed-width figurines (the "safer" option) and provide proportional figurines through a stylistic set.