Add column-gap option to math.equation

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

@@ -220,7 +220,7 @@ fn layout_body(
     let mut x = Abs::zero();
 
     for (index, col) in cols.into_iter().enumerate() {
-        let AlignmentResult { points, width: rcol } = alignments(&col);
+        let AlignmentResult { points, width: rcol } = alignments(&col, Abs::zero());
 
         let mut y = Abs::zero();
 

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

@@ -192,7 +192,9 @@ impl MathRun {
     pub fn multiline_frame_builder(self, styles: StyleChain) -> MathRunFrameBuilder {
         let rows: Vec<_> = self.rows();
         let row_count = rows.len();
-        let alignments = alignments(&rows);
+
+        let column_gap = EquationElem::column_gap_in(styles).resolve(styles);
+        let alignments = alignments(&rows, column_gap);
 
         let leading = if EquationElem::size_in(styles) >= MathSize::Text {
             ParElem::leading_in(styles)

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

@@ -118,7 +118,7 @@ pub fn stack(
     baseline: usize,
     alternator: LeftRightAlternator,
 ) -> Frame {
-    let AlignmentResult { points, width } = alignments(&rows);
+    let AlignmentResult { points, width } = alignments(&rows, Abs::zero());
     let rows: Vec<_> = rows
         .into_iter()
         .map(|row| row.into_line_frame(&points, alternator))
@@ -149,7 +149,7 @@ pub fn stack(
 }
 
 /// Determine the positions of the alignment points, according to the input rows combined.
-pub fn alignments(rows: &[MathRun]) -> AlignmentResult {
+pub fn alignments(rows: &[MathRun], gap: Abs) -> AlignmentResult {
     let mut widths = Vec::<Abs>::new();
 
     let mut pending_width = Abs::zero();
@@ -159,6 +159,9 @@ pub fn alignments(rows: &[MathRun]) -> AlignmentResult {
 
         for fragment in row.iter() {
             if matches!(fragment, MathFragment::Align) {
+                if alignment_index > 0 && alignment_index % 2 == 0 {
+                    width += gap;
+                }
                 if alignment_index < widths.len() {
                     widths[alignment_index].set_max(width);
                 } else {

crates/typst-library/src/math/equation.rs

@@ -11,13 +11,15 @@ use crate::foundations::{
 };
 use crate::introspection::{Count, Counter, CounterUpdate, Locatable};
 use crate::layout::{
-    AlignElem, Alignment, BlockElem, InlineElem, OuterHAlignment, SpecificAlignment,
-    VAlignment,
+    AlignElem, Alignment, BlockElem, Em, InlineElem, Length, OuterHAlignment,
+    SpecificAlignment, VAlignment,
 };
 use crate::math::{MathSize, MathVariant};
 use crate::model::{Numbering, Outlinable, ParLine, Refable, Supplement};
 use crate::text::{FontFamily, FontList, FontWeight, LocalName, TextElem};
 
+const DEFAULT_COL_GAP: Em = Em::new(1.5);
+
 /// A mathematical equation.
 ///
 /// Can be displayed inline with text or as a separate block. An equation
@@ -101,6 +103,17 @@ pub struct EquationElem {
     /// ```
     pub supplement: Smart<Option<Supplement>>,
 
+    /// The gap between columns.
+    ///
+    /// ```example
+    /// #set math.equation(column-gap: 3em)
+    /// $ 4   &= 4 & &"yes" \
+    ///   0   &= 0 & &"no" \
+    ///   1+1 &= 2 & &"maybe" $
+    /// ```
+    #[default(DEFAULT_COL_GAP.into())]
+    pub column_gap: Length,
+
     /// The contents of the equation.
     #[required]
     pub body: Content,
@@ -185,6 +198,7 @@ impl Show for Packed<EquationElem> {
 impl ShowSet for Packed<EquationElem> {
     fn show_set(&self, styles: StyleChain) -> Styles {
         let mut out = Styles::new();
+        out.set(EquationElem::set_column_gap(self.column_gap(styles)));
         if self.block(styles) {
             out.set(AlignElem::set_alignment(Alignment::CENTER));
             out.set(BlockElem::set_breakable(false));

tests/suite/math/alignment.typ

@@ -28,6 +28,7 @@ $
 
 --- math-align-toggle ---
 // Test #460 equations.
+#set math.equation(column-gap: 0em)
 $
 a &=b & quad c&=d \
 e &=f & g&=h

tests/suite/math/call.typ

@@ -205,6 +205,7 @@ $ sin(#1) $
 // attach, etc.)
 //
 // This is not good, so this test should fail and be updated once it is fixed.
+#set math.equation(column-gap: 0em)
 #let id(body) = body
 #let bx(body) = box(body, stroke: blue+0.5pt, inset: (x:2pt, y:3pt))
 #let eq(body) = math.equation(body)

tests/suite/math/equation.typ

@@ -54,6 +54,32 @@ This is big: $sum_(i=0)^n$
 #eq(start)
 #eq(end)
 
+--- math-equation-align-columns-1 ---
+// Test columns in equations.
+#set page(width: auto)
+$     sum a &<= &     sum b &<= &     &sum c \
+  log sum a &<= & log sum b &<= & log &sum c $
+
+#math.equation(block: true, column-gap: 0em, $
+      sum a &<= &     sum b &<= &     &sum c \
+  log sum a &<= & log sum b &<= & log &sum c
+$)
+
+--- math-equation-align-columns-2 ---
+// Test columns in equations.
+#set page(width: auto)
+#set math.equation(column-gap: 1em)
+#block(stroke: black + 1pt, $
+  &&       x & = y  && & a   & = b + c && && && \
+  && -4 + 5x & = -2 && & a b & = c b   && && &&
+$)
+
+--- math-equation-align-column-gap ---
+// Test column-gap in equations.
+#set math.equation(column-gap: 4em)
+$ a &=b & c&=d \
+  e &=f & g&=h $
+
 --- math-equation-number-align ---
 #set math.equation(numbering: "(1)")
 

tests/suite/math/multiline.typ

@@ -17,6 +17,15 @@ $ x + 1 &= a^2 + b^2 \
 $ a + b &= 2 + 3 &= 5 \
       b &= c     &= 3 $
 
+--- math-align-columns ---
+// Test columns created with alignment points.
+$ A &= B &= C \
+  D &= E &= F $
+$ A &= B B B B &= C \
+  D &= E       &= F $
+$ A &= B & &= C \
+  D &= E & &= F $
+
 --- math-align-cases ---
 // Test in case distinction.
 $ f := cases(
@@ -55,6 +64,12 @@ $
 $
 Multiple trailing line breaks.
 
+--- math-multiline-line-spacing ---
+// Test modifying spacing between lines.
+#set par(leading: 2em)
+$ a &=b & c&=d \
+  e &=f & g&=h $
+
 --- math-linebreaking-after-binop-and-rel ---
 // Basic breaking after binop, rel
 #let hrule(x) = box(line(length: x))
@@ -110,6 +125,7 @@ Nothing: $ $, just empty.
 --- math-pagebreaking ---
 // Test breaking of equations at page boundaries.
 #set page(height: 5em)
+#set math.equation(column-gap: 0em)
 #show math.equation: set block(breakable: true)
 
 $ a &+ b + & c \
@@ -121,7 +137,7 @@ $ a &+ b + & c \
 --- math-pagebreaking-numbered ---
 // Test breaking of equations with numbering.
 #set page(height: 5em)
-#set math.equation(numbering: "1")
+#set math.equation(column-gap: 0em, numbering: "1")
 #show math.equation: set block(breakable: true)
 
 $ a &+ b + & c \