Add microtype options for par

crates/typst-layout/src/inline/line.rs

@@ -488,7 +488,16 @@ pub fn commit(
     let stretchability = line.stretchability();
     if remaining < Abs::zero() && shrinkability > Abs::zero() {
         // Attempt to reduce the length of the line, using shrinkability.
-        justification_ratio = (remaining / shrinkability).max(-1.0);
+        let microjustifiables = line.microjustifiables();
+
+        extra_microjustification = (remaining / microjustifiables as f64)
+            .max(p.config.microtype.max_retract.abs);
+
+        justification_ratio = ((remaining
+            - extra_microjustification * microjustifiables as f64)
+            / shrinkability)
+            .max(-1.0);
+
         remaining = (remaining + shrinkability).min(Abs::zero());
     } else if line.justify && fr.is_zero() {
         // Attempt to increase the length of the line, using stretchability.
@@ -502,8 +511,8 @@ pub fn commit(
 
         if justifiables > 0 && remaining > Abs::zero() {
             // Underfull line, distribute the extra space.
-            extra_microjustification =
+            extra_microjustification = (remaining / microjustifiables as f64)
-                (remaining / microjustifiables as f64).min(p.config.microjustification);
+                .min(p.config.microtype.max_expand.abs);
 
             extra_justification = (remaining
                 - extra_microjustification * microjustifiables as f64)

crates/typst-layout/src/inline/mod.rs

@@ -17,8 +17,8 @@ use typst_library::foundations::{Packed, Resolve, Smart, StyleChain};
 use typst_library::introspection::{Introspector, Locator, LocatorLink, SplitLocator};
 use typst_library::layout::{Abs, AlignElem, Dir, FixedAlignment, Fragment, Size};
 use typst_library::model::{
-    EnumElem, FirstLineIndent, Linebreaks, ListElem, ParElem, ParLine, ParLineMarker,
+    EnumElem, FirstLineIndent, Linebreaks, ListElem, Microtype, ParElem, ParLine,
-    TermsElem,
+    ParLineMarker, TermsElem,
 };
 use typst_library::routines::{Arenas, Pair, RealizationKind, Routines};
 use typst_library::text::{Costs, Lang, TextElem};
@@ -183,13 +183,13 @@ fn configuration(
     situation: Option<ParSituation>,
 ) -> Config {
     let justify = base.justify;
-    let microjustification = ParElem::microjustification_in(shared);
+    let microtype = ParElem::microtype_in(shared);
     let font_size = TextElem::size_in(shared);
     let dir = TextElem::dir_in(shared);
 
     Config {
         justify,
-        microjustification,
+        microtype,
         linebreaks: base.linebreaks.unwrap_or_else(|| {
             if justify {
                 Linebreaks::Optimized
@@ -269,10 +269,8 @@ struct ConfigBase {
 struct Config {
     /// Whether to justify text.
     justify: bool,
-
     /// The maximum allowed kerning adjustment for microjustification.
-    microjustification: Abs,
+    microtype: Microtype,
-
     /// How to determine line breaks.
     linebreaks: Linebreaks,
     /// The indent the first line of a paragraph should have.

crates/typst-layout/src/inline/shaping.rs

@@ -10,6 +10,7 @@ use ttf_parser::Tag;
 use typst_library::engine::Engine;
 use typst_library::foundations::{Smart, StyleChain};
 use typst_library::layout::{Abs, Dir, Em, Frame, FrameItem, Point, Size};
+use typst_library::model::{Microtype, ParElem};
 use typst_library::text::{
     families, features, is_default_ignorable, variant, Font, FontFamily, FontVariant,
     Glyph, Lang, Region, TextEdgeBounds, TextElem, TextItem,
@@ -152,7 +153,7 @@ impl ShapedGlyph {
             || self.c.is_ascii_digit()
     }
 
-    pub fn base_adjustability(&self, style: CjkPunctStyle) -> Adjustability {
+    pub fn base_adjustability(&self, style: CjkPunctStyle, microtype: Microtype) -> Adjustability {
         let width = self.x_advance;
         if self.is_space() {
             Adjustability {
@@ -176,7 +177,10 @@ impl ShapedGlyph {
                 shrinkability: (width / 4.0, width / 4.0),
             }
         } else {
-            Adjustability::default()
+            Adjustability {
+                stretchability: (Em::zero(), microtype.max_expand.em),
+                shrinkability: (Em::zero(), microtype.max_retract.em),
+            }
         }
     }
 
@@ -900,7 +904,7 @@ fn shape_segment<'a>(
                     x_advance,
                     Adjustability::default().stretchability,
                 ),
-                is_microjustifiable: true,
+                is_microjustifiable: false,
                 script,
             });
         } else {
@@ -1034,9 +1038,10 @@ fn track_and_space(ctx: &mut ShapingContext) {
 /// and CJK punctuation adjustments according to Chinese Layout Requirements.
 fn calculate_adjustability(ctx: &mut ShapingContext, lang: Lang, region: Option<Region>) {
     let style = cjk_punct_style(lang, region);
+    let microtype = ParElem::microtype_in(ctx.styles);
 
     for glyph in &mut ctx.glyphs {
-        glyph.adjustability = glyph.base_adjustability(style);
+        glyph.adjustability = glyph.base_adjustability(style, microtype);
     }
 
     let mut glyphs = ctx.glyphs.iter_mut().peekable();

crates/typst-library/src/model/par.rs

@@ -138,16 +138,8 @@ pub struct ParElem {
     #[default(false)]
     pub justify: bool,
 
-    /// The maximum amount of kerning that is allowed to be used to further
+    /// Microtypographical settings that are used during justification.
-    /// justify an existing line. When this value is nonzero, additional
+    pub microtype: Microtype,
-    /// justification will be applied to individual glyphs.
-    ///
-    /// Note that microjustifications are applied only after a line of text has
-    /// been constructed. This means that the layout will *not* be affected by
-    /// microjustifications, but the internal kerning of a line will be.
-    #[resolve]
-    #[default(Em::new(0.0).into())]
-    pub microjustification: Length,
 
     /// How to determine line breaks.
     ///
@@ -238,6 +230,36 @@ impl ParElem {
     type ParLine;
 }
 
+/// Configuration for microtypographical settings to be used during
+/// justification.
+#[derive(Debug, Default, Copy, Clone, PartialEq, Hash)]
+pub struct Microtype {
+    /// How much a glyph is allowed to translate into its neighbor.
+    pub max_retract: Length,
+    /// How much a glyph is allowed to translate away from its neighbor.
+    pub max_expand: Length,
+}
+
+cast! {
+    Microtype,
+    self => Value::Dict(self.into()),
+    mut dict: Dict => {
+        let max_retract = dict.take("max_retract")?.cast()?;
+        let max_expand = dict.take("max_expand")?.cast()?;
+        dict.finish(&["max_retract", "max_expand"])?;
+        Self { max_retract, max_expand }
+    },
+}
+
+impl From<Microtype> for Dict {
+    fn from(microtype: Microtype) -> Self {
+        dict! {
+            "max_retract" => microtype.max_retract,
+            "max_expand" => microtype.max_expand,
+        }
+    }
+}
+
 /// How to determine line breaks in a paragraph.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Cast)]
 pub enum Linebreaks {