Make accent size adjustable (#3077)

crates/typst/src/eval/call.rs

@@ -122,10 +122,13 @@ impl Eval for ast::FuncCall<'_> {
                 let c = sym.get();
                 if let Some(accent) = Symbol::combining_accent(c) {
                     let base = args.expect("base")?;
+                    let size = args.named("size")?;
                     args.finish()?;
-                    return Ok(Value::Content(
-                        AccentElem::new(base, Accent::new(accent)).pack(),
-                    ));
+                    let mut accent = AccentElem::new(base, Accent::new(accent));
+                    if let Some(size) = size {
+                        accent = accent.with_size(size);
+                    }
+                    return Ok(Value::Content(accent.pack()));
                 }
             }
             let mut body = Content::empty();

crates/typst/src/math/accent.rs

@@ -2,8 +2,8 @@ use ttf_parser::GlyphId;
 use unicode_math_class::MathClass;
 
 use crate::diag::{bail, SourceResult};
-use crate::foundations::{cast, elem, Content, NativeElement, Value};
-use crate::layout::{Abs, Em, Frame, Point, Size};
+use crate::foundations::{cast, elem, Content, NativeElement, Resolve, Smart, Value};
+use crate::layout::{Abs, Em, Frame, Length, Point, Rel, Size};
 use crate::math::{
     FrameFragment, GlyphFragment, LayoutMath, MathContext, MathFragment, Scaled,
 };
@@ -56,6 +56,9 @@ pub struct AccentElem {
     /// | Left arrow    | `arrow.l`, `<-` | `←`       |
     #[required]
     pub accent: Accent,
+
+    /// The size of the accent, relative to the width of the base.
+    pub size: Smart<Rel<Length>>,
 }
 
 impl LayoutMath for AccentElem {
@@ -74,12 +77,18 @@ impl LayoutMath for AccentElem {
             _ => (base.width() + base.italics_correction()) / 2.0,
         };
 
+        let width = self
+            .size(ctx.styles())
+            .unwrap_or(Rel::one())
+            .resolve(ctx.styles())
+            .relative_to(base.width());
+
         // Forcing the accent to be at least as large as the base makes it too
         // wide in many case.
         let Accent(c) = self.accent();
         let glyph = GlyphFragment::new(ctx, *c, self.span());
         let short_fall = ACCENT_SHORT_FALL.scaled(ctx);
-        let variant = glyph.stretch_horizontal(ctx, base.width(), short_fall);
+        let variant = glyph.stretch_horizontal(ctx, width, short_fall);
         let accent = variant.frame;
         let accent_attach = match variant.id {
             Some(id) => attachment(ctx, id, variant.italics_correction),

tests/typ/math/accent.typ

@@ -27,3 +27,7 @@ $A^x != hat(A)^x != hat(hat(A))^x$
 ---
 // Test high base.
 $ tilde(integral), tilde(integral)_a^b, tilde(integral_a^b) $
+
+---
+// Test accent size.
+$tilde(sum), tilde(sum, size: #50%), accent(H, hat, size: #200%)$