Add styling support for Unicode 18.0's LATIN SMALL LIGATURE LONG S WITH DESCENDER S

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-      - uses: dtolnay/rust-toolchain@e814c742d4444ce2f3f6abddea7faf00161ed941 # 1.88.0
+      - uses: dtolnay/rust-toolchain@87eb139fed4b08a67bd1fa429a21d1f5d523e03e # 1.92.0
       - uses: Swatinem/rust-cache@e18b497796c12c097a38f9edb9d0641fb99eee32 # v2
       - run: cargo test --workspace --all-features --no-run
       - run: cargo test --workspace --all-features --no-fail-fast
@@ -25,7 +25,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-      - uses: dtolnay/rust-toolchain@e814c742d4444ce2f3f6abddea7faf00161ed941 # 1.88.0
+      - uses: dtolnay/rust-toolchain@87eb139fed4b08a67bd1fa429a21d1f5d523e03e # 1.92.0
         with:
           components: clippy, rustfmt
       - uses: Swatinem/rust-cache@e18b497796c12c097a38f9edb9d0641fb99eee32 # v2

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "codex"
 version = "0.3.0"
-rust-version = "1.88" # also change in ci.yml
+rust-version = "1.92" # also change in ci.yml
 authors = ["The Typst Project Developers"]
 edition = "2024"
 description = "Human-friendly notation for Unicode symbols."

src/styling.rs

@@ -67,7 +67,8 @@ pub enum MathStyle {
     Bold,
     /// Italic style. May be serif or sans-serif depending on the font.
     ///
-    /// Supported characters: latin, greek, dotless, and the extra ħ (U+0127).
+    /// Supported characters: latin, greek, dotless, and the extra ħ (U+0127)
+    /// and 𝾕 (U+1DF95).
     Italic,
     /// Bold italic style. May be serif or sans-serif depending on the font.
     ///
@@ -265,7 +266,7 @@ impl MathStyle {
             (_, true, None) if is_latin(c) | is_lower_greek(c) => MathStyle::BoldItalic,
             (_, true, None) if is_upper_greek(c) => MathStyle::Bold,
             (_, true, _) if is_digit(c) | matches!(c, 'Ϝ' | 'ϝ') => MathStyle::Bold,
-            (_, _, Some(true) | None) if matches!(c, 'ı' | 'ȷ' | 'ħ') => {
+            (_, _, Some(true) | None) if matches!(c, 'ı' | 'ȷ' | 'ħ' | '𝾕') => {
                 MathStyle::Italic
             }
             (_, _, Some(true) | None) if is_hebrew(c) => MathStyle::Hebrew,
@@ -448,8 +449,8 @@ mod conversions {
 
     /// The character given by adding `delta` to the codepoint of `c`.
     #[inline]
-    fn apply_delta(c: char, delta: u32) -> char {
-        std::char::from_u32((c as u32) + delta).unwrap()
+    fn apply_delta(c: char, delta: i32) -> char {
+        std::char::from_u32((c as u32).strict_add_signed(delta)).unwrap()
     }
 
     pub fn to_bold(c: char) -> char {
@@ -495,6 +496,8 @@ mod conversions {
             // Dotless symbols (U+1D6A4..U+1D6A5)
             'ı' => 0x1D573,
             'ȷ' => 0x1D46E,
+            // Ligature long s (U+1D6A6)
+            '𝾕' => -0x8EF,
             // Italic Greek symbols (U+1D6E2..U+1D714)
             'Α'..='Ρ' => 0x1D351,
             'ϴ' => 0x1D2FF,
@@ -854,7 +857,7 @@ mod conversions {
             'Γ' => 0x1DAB,
             'Π' => 0x1D9F,
             // Double-struck large operator (U+2140)
-            '∑' => return '⅀', // delta is negative
+            '∑' => -0xD1, // delta is negative
 
             // Mathematical Alphanumeric Symbols Block (U+1D400..U+1D7FF)
             // Double-struck symbols (U+1D538..U+1D56B)