Type: stylistic sets, alternates, titling, figure styles, superscript and subscript

A character style's OpenType features took nine tags. OtFeatures now
also keeps ss01-ss20, salt, titl, pnum, lnum, sups and subs (off by
default, one bit each in `extra`): they are accepted by the type
commands, stored with the style and passed to the shaper, so a font
that has them uses them.

The Affinity import test used ss01 as its example of a feature kept but
not rendered; it now uses cv01 for that (character variants still
aren't rendered) and keeps ss01 as one that is.

Fixes #1607

crates/engine/src/cmd/textedit.rs

@@ -230,7 +230,12 @@ pub(crate) fn features_param(p: &Value, cmd: &str) -> Result<Option<Vec<String>>
     let Some(v) = p.get("features").filter(|v| !v.is_null()) else { return Ok(None) };
     let tags: Vec<&str> = v.as_array().ok_or_else(|| bad(cmd, "features must be a list of tags"))?.iter().filter_map(Value::as_str).collect();
     if let Some(t) = tags.iter().find(|t| !vectorcraft_text::OtFeatures::known_tag(t)) {
-        return Err(bad(cmd, format!("unknown OpenType feature `{t}` (liga, calt, dlig, smcp, frac, onum, tnum, ordn, swsh; prefix - to turn off)")));
+        return Err(bad(
+            cmd,
+            format!(
+                "unknown OpenType feature `{t}` (liga, calt, dlig, smcp, frac, onum, tnum, ordn, swsh, ss01–ss20, salt, titl, pnum, lnum, sups, subs; prefix - to turn off)"
+            ),
+        ));
     }
     Ok(Some(vectorcraft_text::OtFeatures::default().with_tags(tags).to_tags()))
 }

crates/engine/tests/affinity_text.rs

@@ -159,6 +159,8 @@ fn caps_and_feature_overrides_pass_through_to_editable_type() {
                             vec![(tag(b"Feat"), F::U32(u32::from_be_bytes(*b"CAP\x01"))), (tag(b"Valu"), F::I32(1))],
                             vec![(tag(b"Feat"), F::U32(u32::from_be_bytes(*b"liga"))), (tag(b"Valu"), F::I32(0))],
                             vec![(tag(b"Feat"), F::U32(u32::from_be_bytes(*b"ss01"))), (tag(b"Valu"), F::I32(1))],
+                            // Character variants aren't rendered yet (stylistic sets are, #1607).
+                            vec![(tag(b"Feat"), F::U32(u32::from_be_bytes(*b"cv01"))), (tag(b"Valu"), F::I32(1))],
                         ],
                     ),
                 )],
@@ -169,7 +171,7 @@ fn caps_and_feature_overrides_pass_through_to_editable_type() {
     let t = texts(&loaded.doc)[0];
     assert_eq!(t.runs[0].text, "Mixed");
     assert!(t.runs[0].style.all_caps);
-    assert_eq!(t.runs[0].style.features, ["-liga", "ss01"]);
+    assert_eq!(t.runs[0].style.features, ["-liga", "ss01", "cv01"]);
     assert!(loaded.warnings.iter().any(|w| w.contains("retained but not rendered")));
     let restored = vectorcraft_format::load(&vectorcraft_format::save_file(&loaded.doc)).unwrap();
     assert_eq!(texts(&restored)[0], t);

crates/text/src/features.rs

@@ -41,8 +41,19 @@ pub struct OtFeatures {
     pub ordinals: bool,
     /// Swashes (`swsh`).
     pub swash: bool,
+    /// The features of [`EXTRA_FEATURES`] turned on, one bit each (off by default): stylistic
+    /// sets, alternates, titling, proportional and lining figures, superscript and subscript.
+    pub extra: u32,
 }
 
+/// Features beyond the named fields, off unless asked for, each bit `i` of [`OtFeatures::extra`]:
+/// stylistic sets `ss01`–`ss20`, stylistic alternates `salt`, titling `titl`, proportional `pnum`
+/// and lining `lnum` figures, superscript `sups` and subscript `subs`.
+pub const EXTRA_FEATURES: [&str; 26] = [
+    "ss01", "ss02", "ss03", "ss04", "ss05", "ss06", "ss07", "ss08", "ss09", "ss10", "ss11", "ss12", "ss13", "ss14", "ss15", "ss16", "ss17", "ss18",
+    "ss19", "ss20", "salt", "titl", "pnum", "lnum", "sups", "subs",
+];
+
 impl Default for OtFeatures {
     fn default() -> Self {
         Self {
@@ -56,6 +67,7 @@ impl Default for OtFeatures {
             tabular_figures: false,
             ordinals: false,
             swash: false,
+            extra: 0,
         }
     }
 }
@@ -89,13 +101,14 @@ impl OtFeatures {
                 v.push(if on { tag.to_string() } else { format!("-{tag}") });
             }
         }
+        v.extend(EXTRA_FEATURES.iter().enumerate().filter(|(i, _)| self.extra & (1 << i) != 0).map(|(_, t)| t.to_string()));
         v
     }
 
     /// Is `tag` (optionally prefixed with `-` or `+`) one this set understands?
     pub fn known_tag(tag: &str) -> bool {
         let t = tag.trim_start_matches(['-', '+']);
-        matches!(t, "liga" | "calt" | "dlig" | "smcp" | "frac" | "onum" | "tnum" | "ordn" | "swsh")
+        matches!(t, "liga" | "calt" | "dlig" | "smcp" | "frac" | "onum" | "tnum" | "ordn" | "swsh") || EXTRA_FEATURES.contains(&t)
     }
 
     /// This set with `tags` applied on top.
@@ -116,7 +129,15 @@ impl OtFeatures {
                 "tnum" => o.tabular_figures = on,
                 "ordn" => o.ordinals = on,
                 "swsh" => o.swash = on,
-                _ => {}
+                _ => {
+                    if let Some(i) = EXTRA_FEATURES.iter().position(|e| *e == t) {
+                        if on {
+                            o.extra |= 1 << i;
+                        } else {
+                            o.extra &= !(1 << i);
+                        }
+                    }
+                }
             }
         }
         self
@@ -155,6 +176,11 @@ impl OtFeatures {
                 v.push(f(tag, true));
             }
         }
+        for (i, tag) in EXTRA_FEATURES.iter().enumerate() {
+            if let (true, Ok(t)) = (s.extra & (1 << i) != 0, <[u8; 4]>::try_from(tag.as_bytes())) {
+                v.push(f(&t, true));
+            }
+        }
         if self.vertical {
             // Not `vrt2`: its glyphs are already turned on their side, and the layout turns Latin
             // and digits itself (they would lie upside down, and tate-chu-yoko break).
@@ -230,6 +256,22 @@ pub fn explicit_ligatures<S: AsRef<str>>(features: &[S]) -> bool {
 #[cfg(test)]
 mod tests {
     use super::*;
+
+    /// #1607: stylistic sets, alternates, titling, figure styles and superscript/subscript are
+    /// known, round-trip through the stored tags and reach the shaper.
+    #[test]
+    fn extra_features_are_kept_and_shaped() {
+        for t in ["ss01", "ss20", "-ss07", "salt", "titl", "pnum", "lnum", "sups", "subs"] {
+            assert!(OtFeatures::known_tag(t), "{t}");
+        }
+        assert!(!OtFeatures::known_tag("ss21"));
+        let o = OtFeatures::from_tags(["ss03", "pnum", "sups", "-liga"]);
+        assert_eq!(o.to_tags(), vec!["-liga", "ss03", "pnum", "sups"]);
+        assert_eq!(OtFeatures::from_tags(["ss03", "-ss03"]).to_tags(), Vec::<String>::new(), "turned off again");
+        let st = CharStyle { features: vec!["ss05".into(), "titl".into()], ..CharStyle::default() };
+        let tags: Vec<String> = OtFeatures::default().resolve(&st).iter().filter(|f| f.value == 1).map(|f| f.tag.to_string()).collect();
+        assert!(tags.contains(&"ss05".to_string()) && tags.contains(&"titl".to_string()), "{tags:?}");
+    }
     use crate::{FontDb, layout};
     use vectorcraft_doc::TextObject;
     use vectorcraft_geom::Point;

crates/text/src/lib.rs

@@ -26,7 +26,7 @@ pub mod test_fonts;
 pub mod thread;
 
 pub use craft_fonts::{CRAFT_FONTS, CraftFont, WEB_FONTS, WebFont};
-pub use features::{LIGATURE_TRACKING_LIMITS, OtFeatures, explicit_ligatures, ligatures_suppressed_by};
+pub use features::{EXTRA_FEATURES, LIGATURE_TRACKING_LIMITS, OtFeatures, explicit_ligatures, ligatures_suppressed_by};
 pub use fontdb::{
     FALLBACK_FAMILY, FontClass, FontDb, FontFace, FontMatch, FontTraits, IcfMargins, PlatformFontFiles, WantedFont, WantedFonts, app_font_dir,
     is_font_file, is_suitcase, set_app_font_dir, set_platform_font_files, set_user_font_dirs, style_weight, system_font_dirs, user_font_dirs,