Better quote selection (#3422)

7 files changed, 75 insertions, 28 deletions

diff --git a/crates/typst/src/foundations/styles.rs b/crates/typst/src/foundations/styles.rs
index 9656fafb..9472e207 100644
--- a/crates/typst/src/foundations/styles.rs
+++ b/crates/typst/src/foundations/styles.rs
@@ -745,3 +745,13 @@ impl<T, const N: usize> Fold for SmallVec<[T; N]> {
         self
     }
 }
+
+/// A type that accumulates depth when folded.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Hash)]
+pub struct Depth(pub usize);
+
+impl Fold for Depth {
+    fn fold(self, outer: Self) -> Self {
+        Self(outer.0 + self.0)
+    }
+}
diff --git a/crates/typst/src/layout/inline/mod.rs b/crates/typst/src/layout/inline/mod.rs
index 3e3b7a76..17407bfa 100644
--- a/crates/typst/src/layout/inline/mod.rs
+++ b/crates/typst/src/layout/inline/mod.rs
@@ -464,15 +464,12 @@ fn collect<'a>(
             Segment::Text(c.len_utf8())
         } else if let Some(elem) = child.to_packed::<SmartQuoteElem>() {
             let prev = full.len();
-            if SmartQuoteElem::enabled_in(styles) {
-                let quotes = SmartQuoteElem::quotes_in(styles);
-                let lang = TextElem::lang_in(styles);
-                let region = TextElem::region_in(styles);
+            if elem.enabled(styles) {
                 let quotes = SmartQuotes::new(
-                    quotes,
-                    lang,
-                    region,
-                    SmartQuoteElem::alternative_in(styles),
+                    elem.quotes(styles),
+                    TextElem::lang_in(styles),
+                    TextElem::region_in(styles),
+                    elem.alternative(styles),
                 );
                 let peeked = iter.peek().and_then(|&child| {
                     let child = if let Some(styled) = child.to_packed::<StyledElem>() {
diff --git a/crates/typst/src/model/list.rs b/crates/typst/src/model/list.rs
index ebd733e3..6de78bbd 100644
--- a/crates/typst/src/model/list.rs
+++ b/crates/typst/src/model/list.rs
@@ -1,7 +1,7 @@
 use crate::diag::{bail, SourceResult};
 use crate::engine::Engine;
 use crate::foundations::{
-    cast, elem, scope, Array, Content, Fold, Func, Packed, Smart, StyleChain, Value,
+    cast, elem, scope, Array, Content, Depth, Func, Packed, Smart, StyleChain, Value,
 };
 use crate::layout::{
     Axes, BlockElem, Cell, CellGrid, Em, Fragment, GridLayouter, HAlignment,
@@ -236,12 +236,3 @@ cast! {
     },
     v: Func => Self::Func(v),
 }
-
-#[derive(Debug, Default, Clone, Copy, PartialEq, Hash)]
-struct Depth(usize);
-
-impl Fold for Depth {
-    fn fold(self, outer: Self) -> Self {
-        Self(outer.0 + self.0)
-    }
-}
diff --git a/crates/typst/src/model/quote.rs b/crates/typst/src/model/quote.rs
index 883f876e..d02208b6 100644
--- a/crates/typst/src/model/quote.rs
+++ b/crates/typst/src/model/quote.rs
@@ -1,12 +1,12 @@
 use crate::diag::SourceResult;
 use crate::engine::Engine;
 use crate::foundations::{
-    cast, elem, Content, Label, NativeElement, Packed, Show, ShowSet, Smart, StyleChain,
-    Styles,
+    cast, elem, Content, Depth, Label, NativeElement, Packed, Show, ShowSet, Smart,
+    StyleChain, Styles,
 };
 use crate::layout::{Alignment, BlockElem, Em, HElem, PadElem, Spacing, VElem};
 use crate::model::{CitationForm, CiteElem};
-use crate::text::{SmartQuoteElem, SpaceElem, TextElem};
+use crate::text::{SmartQuoteElem, SmartQuotes, SpaceElem, TextElem};
 
 /// Displays a quote alongside an optional attribution.
 ///
@@ -126,6 +126,12 @@ pub struct QuoteElem {
     /// The quote.
     #[required]
     body: Content,
+
+    /// The nesting depth.
+    #[internal]
+    #[fold]
+    #[ghost]
+    depth: Depth,
 }
 
 /// Attribution for a [quote](QuoteElem).
@@ -152,11 +158,27 @@ impl Show for Packed<QuoteElem> {
         let block = self.block(styles);
 
         if self.quotes(styles) == Smart::Custom(true) || !block {
+            let quotes = SmartQuotes::new(
+                SmartQuoteElem::quotes_in(styles),
+                TextElem::lang_in(styles),
+                TextElem::region_in(styles),
+                SmartQuoteElem::alternative_in(styles),
+            );
+
+            // Alternate between single and double quotes.
+            let Depth(depth) = QuoteElem::depth_in(styles);
+            let double = depth % 2 == 0;
+
             // Add zero-width weak spacing to make the quotes "sticky".
             let hole = HElem::hole().pack();
-            let quote = SmartQuoteElem::new().with_double(true).pack();
-            realized =
-                Content::sequence([quote.clone(), hole.clone(), realized, hole, quote]);
+            realized = Content::sequence([
+                TextElem::packed(quotes.open(double)),
+                hole.clone(),
+                realized,
+                hole,
+                TextElem::packed(quotes.close(double)),
+            ])
+            .styled(QuoteElem::set_depth(Depth(1)));
         }
 
         if block {
diff --git a/crates/typst/src/text/smartquote.rs b/crates/typst/src/text/smartquote.rs
index 9e62bea3..0c435f11 100644
--- a/crates/typst/src/text/smartquote.rs
+++ b/crates/typst/src/text/smartquote.rs
@@ -251,7 +251,7 @@ impl<'s> SmartQuotes<'s> {
     }
 
     /// The opening quote.
-    fn open(&self, double: bool) -> &'s str {
+    pub fn open(&self, double: bool) -> &'s str {
         if double {
             self.double_open
         } else {
@@ -260,7 +260,7 @@ impl<'s> SmartQuotes<'s> {
     }
 
     /// The closing quote.
-    fn close(&self, double: bool) -> &'s str {
+    pub fn close(&self, double: bool) -> &'s str {
         if double {
             self.double_close
         } else {
@@ -269,7 +269,7 @@ impl<'s> SmartQuotes<'s> {
     }
 
     /// Which character should be used as a prime.
-    fn prime(&self, double: bool) -> &'static str {
+    pub fn prime(&self, double: bool) -> &'static str {
         if double {
             "″"
         } else {
@@ -278,7 +278,7 @@ impl<'s> SmartQuotes<'s> {
     }
 
     /// Which character should be used as a fallback quote.
-    fn fallback(&self, double: bool) -> &'static str {
+    pub fn fallback(&self, double: bool) -> &'static str {
         if double {
             "\""
         } else {
diff --git a/tests/ref/text/quote-nesting.png b/tests/ref/text/quote-nesting.png
new file mode 100644
index 00000000..fb16002d
--- /dev/null
+++ b/tests/ref/text/quote-nesting.png
diff --git a/tests/typ/text/quote-nesting.typ b/tests/typ/text/quote-nesting.typ
new file mode 100644
index 00000000..381aaa56
--- /dev/null
+++ b/tests/typ/text/quote-nesting.typ
@@ -0,0 +1,27 @@
+// Test quote nesting.
+
+---
+// Test quote selection.
+#set page(width: auto)
+#set text(lang: "en")
+=== EN
+#quote[An apostroph'] \
+#quote[A #quote[nested] quote] \
+#quote[A #quote[very #quote[nested]] quote]
+
+#set text(lang: "de")
+=== DE
+#quote[Satz mit Apostroph'] \
+#quote[Satz mit #quote[Zitat]] \
+#quote[A #quote[very #quote[nested]] quote]
+
+#set smartquote(alternative: true)
+=== DE Alternative
+#quote[Satz mit Apostroph'] \
+#quote[Satz mit #quote[Zitat]] \
+#quote[A #quote[very #quote[nested]] quote]
+
+---
+// With custom quotes.
+#set smartquote(quotes: (single: ("<", ">"), double: ("(", ")")))
+#quote[A #quote[nested] quote]