Add basic paragraph function 📑

Allows to change:
- (paragraph) spacing
- leading
- word-spacing

src/library/mod.rs

@@ -9,6 +9,7 @@ mod font;
 mod image;
 mod pad;
 mod page;
+mod par;
 mod shapes;
 mod spacing;
 
@@ -18,6 +19,7 @@ pub use base::*;
 pub use font::*;
 pub use pad::*;
 pub use page::*;
+pub use par::*;
 pub use shapes::*;
 pub use spacing::*;
 
@@ -50,6 +52,7 @@ pub fn new() -> Scope {
     set!(func: "pad", pad);
     set!(func: "page", page);
     set!(func: "pagebreak", pagebreak);
+    set!(func: "paragraph", paragraph);
     set!(func: "rect", rect);
     set!(func: "repr", repr);
     set!(func: "rgb", rgb);

src/library/par.rs

@@ -0,0 +1,41 @@
+use super::*;
+
+/// `paragraph`: Configure paragraphs.
+///
+/// # Named parameters
+/// - Paragraph spacing: `spacing`, of type `linear` relative to current font size.
+/// - Line leading: `leading`, of type `linear` relative to current font size.
+/// - Word spacing: `word-spacing`, of type `linear` relative to current font size.
+///
+/// # Return value
+/// A template that configures paragraph properties. The effect is scoped to the
+/// body if present.
+pub fn paragraph(ctx: &mut EvalContext, args: &mut ValueArgs) -> Value {
+    let spacing = args.get(ctx, "spacing");
+    let leading = args.get(ctx, "leading");
+    let word_spacing = args.get(ctx, "word-spacing");
+    let body = args.find::<ValueTemplate>(ctx);
+
+    Value::template("paragraph", move |ctx| {
+        let snapshot = ctx.state.clone();
+
+        if let Some(spacing) = spacing {
+            ctx.state.par.spacing = spacing;
+        }
+
+        if let Some(leading) = leading {
+            ctx.state.par.leading = leading;
+        }
+
+        if let Some(word_spacing) = word_spacing {
+            ctx.state.par.word_spacing = word_spacing;
+        }
+
+        ctx.push_parbreak();
+
+        if let Some(body) = &body {
+            body.exec(ctx);
+            ctx.state = snapshot;
+        }
+    })
+}

tests/typ/library/paragraph.typ

@@ -0,0 +1,13 @@
+// Test the `paragraph` function.
+
+---
+// Test configuring paragraph properties.
+
+#paragraph(spacing: 10pt, leading: 25%, word-spacing: 1pt)
+
+But, soft! what light through yonder window breaks? It is the east, and Juliet
+is the sun.
+
+---
+// Test that it finishes an existing paragraph.
+Hello #paragraph(word-spacing: 0pt) t h e r e !