Support first-line-indent for every paragraph (#5768)

crates/typst-layout/src/flow/collect.rs

@@ -23,6 +23,7 @@ use typst_library::World;
 use typst_utils::SliceExt;
 
 use super::{layout_multi_block, layout_single_block, FlowMode};
+use crate::inline::ParSituation;
 use crate::modifiers::layout_and_modify;
 
 /// Collects all elements of the flow into prepared children. These are much
@@ -46,7 +47,7 @@ pub fn collect<'a>(
         base,
         expand,
         output: Vec::with_capacity(children.len()),
-        last_was_par: false,
+        par_situation: ParSituation::First,
     }
     .run(mode)
 }
@@ -60,7 +61,7 @@ struct Collector<'a, 'x, 'y> {
     expand: bool,
     locator: SplitLocator<'a>,
     output: Vec<Child<'a>>,
-    last_was_par: bool,
+    par_situation: ParSituation,
 }
 
 impl<'a> Collector<'a, '_, '_> {
@@ -123,8 +124,7 @@ impl<'a> Collector<'a, '_, '_> {
             styles,
             self.base,
             self.expand,
-            false,
+            None,
-            false,
         )?
         .into_frames();
 
@@ -165,7 +165,7 @@ impl<'a> Collector<'a, '_, '_> {
             styles,
             self.base,
             self.expand,
-            self.last_was_par,
+            self.par_situation,
         )?
         .into_frames();
 
@@ -175,7 +175,7 @@ impl<'a> Collector<'a, '_, '_> {
         self.lines(lines, styles);
 
         self.output.push(Child::Rel(spacing.into(), 4));
-        self.last_was_par = true;
+        self.par_situation = ParSituation::Consecutive;
 
         Ok(())
     }
@@ -272,7 +272,7 @@ impl<'a> Collector<'a, '_, '_> {
         };
 
         self.output.push(spacing(elem.below(styles)));
-        self.last_was_par = false;
+        self.par_situation = ParSituation::Other;
     }
 
     /// Collects a placed element into a [`PlacedChild`].

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

@@ -5,6 +5,7 @@ use typst_library::layout::{
     Abs, AlignElem, BoxElem, Dir, Fr, Frame, HElem, InlineElem, InlineItem, Sizing,
     Spacing,
 };
+use typst_library::model::{EnumElem, ListElem, TermsElem};
 use typst_library::routines::Pair;
 use typst_library::text::{
     is_default_ignorable, LinebreakElem, SmartQuoteElem, SmartQuoter, SmartQuotes,
@@ -124,26 +125,33 @@ pub fn collect<'a>(
     locator: &mut SplitLocator<'a>,
     styles: StyleChain<'a>,
     region: Size,
-    consecutive: bool,
+    situation: Option<ParSituation>,
-    paragraph: bool,
 ) -> SourceResult<(String, Vec<Segment<'a>>, SpanMapper)> {
     let mut collector = Collector::new(2 + children.len());
     let mut quoter = SmartQuoter::new();
 
     let outer_dir = TextElem::dir_in(styles);
 
-    if paragraph && consecutive {
+    if let Some(situation) = situation {
         let first_line_indent = ParElem::first_line_indent_in(styles);
-        if !first_line_indent.is_zero()
+        if !first_line_indent.amount.is_zero()
+            && match situation {
+                // First-line indent for the first paragraph after a list bullet
+                // just looks bad.
+                ParSituation::First => first_line_indent.all && !in_list(styles),
+                ParSituation::Consecutive => true,
+                ParSituation::Other => first_line_indent.all,
+            }
             && AlignElem::alignment_in(styles).resolve(styles).x
                 == outer_dir.start().into()
         {
-            collector.push_item(Item::Absolute(first_line_indent.resolve(styles), false));
+            collector.push_item(Item::Absolute(
+                first_line_indent.amount.resolve(styles),
+                false,
+            ));
             collector.spans.push(1, Span::detached());
         }
-    }
 
-    if paragraph {
         let hang = ParElem::hanging_indent_in(styles);
         if !hang.is_zero() {
             collector.push_item(Item::Absolute(-hang, false));
@@ -257,6 +265,16 @@ pub fn collect<'a>(
     Ok((collector.full, collector.segments, collector.spans))
 }
 
+/// Whether we have a list ancestor.
+///
+/// When we support some kind of more general ancestry mechanism, this can
+/// become more elegant.
+fn in_list(styles: StyleChain) -> bool {
+    ListElem::depth_in(styles).0 > 0
+        || !EnumElem::parents_in(styles).is_empty()
+        || TermsElem::within_in(styles)
+}
+
 /// Collects segments.
 struct Collector<'a> {
     full: String,

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

@@ -42,7 +42,7 @@ pub fn layout_par(
     styles: StyleChain,
     region: Size,
     expand: bool,
-    consecutive: bool,
+    situation: ParSituation,
 ) -> SourceResult<Fragment> {
     layout_par_impl(
         elem,
@@ -56,7 +56,7 @@ pub fn layout_par(
         styles,
         region,
         expand,
-        consecutive,
+        situation,
     )
 }
 
@@ -75,7 +75,7 @@ fn layout_par_impl(
     styles: StyleChain,
     region: Size,
     expand: bool,
-    consecutive: bool,
+    situation: ParSituation,
 ) -> SourceResult<Fragment> {
     let link = LocatorLink::new(locator);
     let mut locator = Locator::link(&link).split();
@@ -105,8 +105,7 @@ fn layout_par_impl(
         styles,
         region,
         expand,
-        true,
+        Some(situation),
-        consecutive,
     )
 }
 
@@ -119,16 +118,15 @@ pub fn layout_inline<'a>(
     styles: StyleChain<'a>,
     region: Size,
     expand: bool,
-    paragraph: bool,
+    par: Option<ParSituation>,
-    consecutive: bool,
 ) -> SourceResult<Fragment> {
     // Collect all text into one string for BiDi analysis.
     let (text, segments, spans) =
-        collect(children, engine, locator, styles, region, consecutive, paragraph)?;
+        collect(children, engine, locator, styles, region, par)?;
 
     // Perform BiDi analysis and performs some preparation steps before we
     // proceed to line breaking.
-    let p = prepare(engine, children, &text, segments, spans, styles, paragraph)?;
+    let p = prepare(engine, children, &text, segments, spans, styles, par)?;
 
     // Break the text into lines.
     let lines = linebreak(engine, &p, region.x - p.hang);
@@ -136,3 +134,17 @@ pub fn layout_inline<'a>(
     // Turn the selected lines into frames.
     finalize(engine, &p, &lines, styles, region, expand, locator)
 }
+
+/// Distinguishes between a few different kinds of paragraphs.
+///
+/// In the form `Option<ParSituation>`, `None` implies that we are creating an
+/// inline layout that isn't a semantic paragraph.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub enum ParSituation {
+    /// The paragraph is the first thing in the flow.
+    First,
+    /// The paragraph follows another paragraph.
+    Consecutive,
+    /// Any other kind of paragraph.
+    Other,
+}

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

@@ -85,7 +85,7 @@ pub fn prepare<'a>(
     segments: Vec<Segment<'a>>,
     spans: SpanMapper,
     styles: StyleChain<'a>,
-    paragraph: bool,
+    situation: Option<ParSituation>,
 ) -> SourceResult<Preparation<'a>> {
     let dir = TextElem::dir_in(styles);
     let default_level = match dir {
@@ -130,7 +130,11 @@ pub fn prepare<'a>(
     }
 
     // Only apply hanging indent to real paragraphs.
-    let hang = if paragraph { ParElem::hanging_indent_in(styles) } else { Abs::zero() };
+    let hang = if situation.is_some() {
+        ParElem::hanging_indent_in(styles)
+    } else {
+        Abs::zero()
+    };
 
     Ok(Preparation {
         text,

crates/typst-layout/src/math/text.rs

@@ -107,8 +107,7 @@ fn layout_inline_text(
             styles,
             Size::splat(Abs::inf()),
             false,
-            false,
+            None,
-            false,
         )?
         .into_frame();
 

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

@@ -3,8 +3,8 @@ use typst_utils::singleton;
 use crate::diag::{bail, SourceResult};
 use crate::engine::Engine;
 use crate::foundations::{
-    elem, scope, Args, Cast, Construct, Content, NativeElement, Packed, Smart,
+    cast, dict, elem, scope, Args, Cast, Construct, Content, Dict, NativeElement, Packed,
-    Unlabellable,
+    Smart, Unlabellable, Value,
 };
 use crate::introspection::{Count, CounterUpdate, Locatable};
 use crate::layout::{Em, HAlignment, Length, OuterHAlignment};
@@ -163,16 +163,56 @@ pub struct ParElem {
 
     /// The indent the first line of a paragraph should have.
     ///
-    /// Only the first line of a consecutive paragraph will be indented (not
+    /// By default, only the first line of a consecutive paragraph will be
-    /// the first one in a block or on the page).
+    /// indented (not the first one in the document or container, and not
+    /// paragraphs immediately following other block-level elements).
+    ///
+    /// If you want to indent all paragraphs instead, you can pass a dictionary
+    /// containing the `amount` of indent as a length and the pair
+    /// `{all: true}`. When `all` is omitted from the dictionary, it defaults to
+    /// `{false}`.
     ///
     /// By typographic convention, paragraph breaks are indicated either by some
-    /// space between paragraphs or by indented first lines. Consider reducing
+    /// space between paragraphs or by indented first lines. Consider
-    /// the [paragraph spacing]($block.spacing) to the [`leading`]($par.leading)
+    /// - reducing the [paragraph `spacing`]($par.spacing) to the
-    /// when using this property (e.g. using `[#set par(spacing: 0.65em)]`).
+    ///   [`leading`]($par.leading) using `{set par(spacing: 0.65em)}`
-    pub first_line_indent: Length,
+    /// - increasing the [block `spacing`]($block.spacing) (which inherits the
+    ///   paragraph spacing by default) to the original paragraph spacing using
+    ///   `{set block(spacing: 1.2em)}`
+    ///
+    /// ```example
+    /// #set block(spacing: 1.2em)
+    /// #set par(
+    ///   first-line-indent: 1.5em,
+    ///   spacing: 0.65em,
+    /// )
+    ///
+    /// The first paragraph is not affected
+    /// by the indent.
+    ///
+    /// But the second paragraph is.
+    ///
+    /// #line(length: 100%)
+    ///
+    /// #set par(first-line-indent: (
+    ///   amount: 1.5em,
+    ///   all: true,
+    /// ))
+    ///
+    /// Now all paragraphs are affected
+    /// by the first line indent.
+    ///
+    /// Even the first one.
+    /// ```
+    pub first_line_indent: FirstLineIndent,
 
     /// The indent that all but the first line of a paragraph should have.
+    ///
+    /// ```example
+    /// #set par(hanging-indent: 1em)
+    ///
+    /// #lorem(15)
+    /// ```
     #[resolve]
     pub hanging_indent: Length,
 
@@ -199,6 +239,36 @@ pub enum Linebreaks {
     Optimized,
 }
 
+/// Configuration for first line indent.
+#[derive(Debug, Default, Copy, Clone, PartialEq, Hash)]
+pub struct FirstLineIndent {
+    /// The amount of indent.
+    pub amount: Length,
+    /// Whether to indent all paragraphs, not just consecutive ones.
+    pub all: bool,
+}
+
+cast! {
+    FirstLineIndent,
+    self => Value::Dict(self.into()),
+    amount: Length => Self { amount, all: false },
+    mut dict: Dict => {
+        let amount = dict.take("amount")?.cast()?;
+        let all = dict.take("all").ok().map(|v| v.cast()).transpose()?.unwrap_or(false);
+        dict.finish(&["amount", "all"])?;
+        Self { amount, all }
+    },
+}
+
+impl From<FirstLineIndent> for Dict {
+    fn from(indent: FirstLineIndent) -> Self {
+        dict! {
+            "amount" => indent.amount,
+            "all" => indent.all,
+        }
+    }
+}
+
 /// A paragraph break.
 ///
 /// This starts a new paragraph. Especially useful when used within code like

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

@@ -105,6 +105,11 @@ pub struct TermsElem {
     /// ```
     #[variadic]
     pub children: Vec<Packed<TermItem>>,
+
+    /// Whether we are currently within a term list.
+    #[internal]
+    #[ghost]
+    pub within: bool,
 }
 
 #[scope]
@@ -180,7 +185,8 @@ impl Show for Packed<TermsElem> {
             .with_spacing(Some(gutter.into()))
             .pack()
             .spanned(span)
-            .padded(padding);
+            .padded(padding)
+            .styled(TermsElem::set_within(true));
 
         if tight {
             let leading = ParElem::leading_in(styles);

tests/suite/model/par.typ

@@ -156,6 +156,57 @@ starts a paragraph, also with indent.
 
 ثم يصبح النص رطبًا وقابل للطرق ويبدو المستند رائعًا.
 
+--- par-first-line-indent-all ---
+#set par(
+  first-line-indent: (amount: 12pt, all: true),
+  spacing: 5pt,
+  leading: 5pt,
+)
+#set block(spacing: 1.2em)
+#show heading: set text(size: 10pt)
+
+= Heading
+All paragraphs are indented.
+
+Even the first.
+
+--- par-first-line-indent-all-list ---
+#show list.where(tight: false): set list(spacing: 1.2em)
+#set par(
+  first-line-indent: (amount: 12pt, all: true),
+  spacing: 5pt,
+  leading: 5pt,
+)
+
+- A #parbreak() B #line(length: 100%) C
+
+- D
+
+--- par-first-line-indent-all-enum ---
+#show enum.where(tight: false): set enum(spacing: 1.2em)
+#set par(
+  first-line-indent: (amount: 12pt, all: true),
+  spacing: 5pt,
+  leading: 5pt,
+)
+
++ A #parbreak() B #line(length: 100%) C
+
++ D
+
+--- par-first-line-indent-all-terms ---
+#show terms.where(tight: false): set terms(spacing: 1.2em)
+#set terms(hanging-indent: 10pt)
+#set par(
+  first-line-indent: (amount: 12pt, all: true),
+  spacing: 5pt,
+  leading: 5pt,
+)
+
+/ Term A: B \ C #parbreak() D #line(length: 100%) E
+
+/ Term F: G
+
 --- par-spacing-and-first-line-indent ---
 // This is madness.
 #set par(first-line-indent: 12pt)