Add gap and justify parameters to repeat (#4644)

Co-authored-by: Laurenz <laurmaedje@gmail.com>

crates/typst/src/layout/repeat.rs

@@ -5,7 +5,7 @@ use crate::foundations::{
 };
 use crate::introspection::Locator;
 use crate::layout::{
-    Abs, AlignElem, Axes, BlockElem, Frame, Point, Region, Regions, Size,
+    Abs, AlignElem, Axes, BlockElem, Frame, Length, Point, Region, Regions, Size,
 };
 use crate::utils::Numeric;
 
@@ -14,7 +14,7 @@ use crate::utils::Numeric;
 /// This can be useful when implementing a custom index, reference, or outline.
 ///
 /// Space may be inserted between the instances of the body parameter, so be
-/// sure to include negative space if you need the instances to overlap.
+/// sure to adjust the [`justify`]($repeat.justify) parameter accordingly.
 ///
 /// Errors if there no bounds on the available space, as it would create
 /// infinite content.
@@ -35,6 +35,15 @@ pub struct RepeatElem {
     /// The content to repeat.
     #[required]
     pub body: Content,
+
+    /// The gap between each instance of the body.
+    #[default]
+    pub gap: Length,
+
+    /// Whether to increase the gap between instances to completely fill the
+    /// available space.
+    #[default(true)]
+    pub justify: bool,
 }
 
 impl Show for Packed<RepeatElem> {
@@ -56,15 +65,6 @@ fn layout_repeat(
 ) -> SourceResult<Frame> {
     let pod = Regions::one(region.size, Axes::new(false, false));
     let piece = elem.body().layout(engine, locator, styles, pod)?.into_frame();
-
-    let align = AlignElem::alignment_in(styles).resolve(styles);
-
-    let fill = region.size.x;
-    let width = piece.width();
-    let count = (fill / width).floor();
-    let remaining = fill % width;
-    let apart = remaining / (count - 1.0);
-
     let size = Size::new(region.size.x, piece.height());
 
     if !size.is_finite() {
@@ -76,15 +76,30 @@ fn layout_repeat(
         frame.set_baseline(piece.baseline());
     }
 
+    let mut gap = elem.gap(styles).resolve(styles);
+    let fill = region.size.x;
+    let width = piece.width();
+
+    // count * width + (count - 1) * gap = fill, but count is an integer so
+    // we need to round down and get the remainder.
+    let count = ((fill + gap) / (width + gap)).floor();
+    let remaining = (fill + gap) % (width + gap);
+
+    let justify = elem.justify(styles);
+    if justify {
+        gap += remaining / (count - 1.0);
+    }
+
+    let align = AlignElem::alignment_in(styles).resolve(styles);
     let mut offset = Abs::zero();
-    if count == 1.0 {
+    if count == 1.0 || !justify {
         offset += align.x.position(remaining);
     }
 
     if width > Abs::zero() {
         for _ in 0..(count as usize).min(1000) {
             frame.push_frame(Point::with_x(offset), piece.clone());
-            offset += piece.width() + apart;
+            offset += piece.width() + gap;
         }
     }
 

tests/suite/layout/repeat.typ

@@ -42,3 +42,18 @@ A#box(width: 1fr, repeat(rect(width: 6em, height: 0.7em)))B
 // Error: 2:2-2:13 repeat with no size restrictions
 #set page(width: auto)
 #repeat(".")
+
+--- repeat-gap ---
+// Test repeat with custom gap.
+A#box(width: 1fr, repeat(rect(width: 2em, height: 1em), gap: 1em))B
+
+--- repeat-no-justify ---
+// Test repeat with disabled justification.
+#set repeat(justify: false)
+A#box(width: 1fr, repeat(rect(width: 2em, height: 1em), gap: 1em))B
+
+--- repeat-no-justify-align ---
+// Test repeat with alignment and disabled justification.
+#set repeat(justify: false)
+#set align(right)
+A#box(width: 1fr, repeat(rect(width: 2em, height: 1em), gap: 1em))B