Matrix baseline alignment

library/src/math/matrix.rs

@@ -249,38 +249,40 @@ fn layout_mat_body(ctx: &mut MathContext, rows: &[Vec<Content>]) -> SourceResult
         return Ok(Frame::new(Size::zero()));
     }
 
-    let mut rcols = vec![Abs::zero(); ncols];
-    let mut rrows = vec![Abs::zero(); nrows];
+    let mut widths = vec![Abs::zero(); ncols];
+    let mut ascents = vec![Abs::zero(); nrows];
+    let mut descents = vec![Abs::zero(); nrows];
 
     ctx.style(ctx.style.for_denominator());
     let mut cols = vec![vec![]; ncols];
-    for (row, rrow) in rows.iter().zip(&mut rrows) {
-        for ((cell, rcol), col) in row.iter().zip(&mut rcols).zip(&mut cols) {
+    for ((row, ascent), descent) in rows.iter().zip(&mut ascents).zip(&mut descents) {
+        for ((cell, rcol), col) in row.iter().zip(&mut widths).zip(&mut cols) {
             let cell = ctx.layout_row(cell)?;
             rcol.set_max(cell.width());
-            rrow.set_max(cell.height());
+            ascent.set_max(cell.ascent());
+            descent.set_max(cell.descent());
             col.push(cell);
         }
     }
     ctx.unstyle();
 
-    let width = rcols.iter().sum::<Abs>() + col_gap * (ncols - 1) as f64;
-    let height = rrows.iter().sum::<Abs>() + row_gap * (nrows - 1) as f64;
+    let width = widths.iter().sum::<Abs>() + col_gap * (ncols - 1) as f64;
+    let height = ascents.iter().sum::<Abs>()
+        + descents.iter().sum::<Abs>()
+        + row_gap * (nrows - 1) as f64;
     let size = Size::new(width, height);
 
     let mut frame = Frame::new(size);
     let mut x = Abs::zero();
-    for (col, &rcol) in cols.into_iter().zip(&rcols) {
+    for (col, &rcol) in cols.into_iter().zip(&widths) {
         let points = alignments(&col);
         let mut y = Abs::zero();
-        for (cell, &rrow) in col.into_iter().zip(&rrows) {
+        for ((cell, &ascent), &descent) in col.into_iter().zip(&ascents).zip(&descents) {
             let cell = cell.to_aligned_frame(ctx, &points, Align::Center);
-            let pos = Point::new(
-                x + (rcol - cell.width()) / 2.0,
-                y + (rrow - cell.height()) / 2.0,
-            );
+            let pos =
+                Point::new(x + (rcol - cell.width()) / 2.0, y + ascent - cell.ascent());
             frame.push_frame(pos, cell);
-            y += rrow + row_gap;
+            y += ascent + descent + row_gap;
         }
         x += rcol + col_gap;
     }

library/src/math/row.rs

@@ -17,8 +17,15 @@ impl MathRow {
     }
 
     pub fn height(&self) -> Abs {
-        let (ascent, descent) = self.extent();
-        ascent + descent
+        self.ascent() + self.descent()
+    }
+
+    pub fn ascent(&self) -> Abs {
+        self.0.iter().map(MathFragment::ascent).max().unwrap_or_default()
+    }
+
+    pub fn descent(&self) -> Abs {
+        self.0.iter().map(MathFragment::descent).max().unwrap_or_default()
     }
 
     pub fn push(
@@ -124,7 +131,8 @@ impl MathRow {
     }
 
     fn to_line_frame(self, ctx: &MathContext, points: &[Abs], align: Align) -> Frame {
-        let (ascent, descent) = self.extent();
+        let ascent = self.ascent();
+        let descent = self.descent();
         let size = Size::new(Abs::zero(), ascent + descent);
         let mut frame = Frame::new(size);
         let mut x = Abs::zero();
@@ -161,12 +169,6 @@ impl MathRow {
         frame.size_mut().x = x;
         frame
     }
-
-    fn extent(&self) -> (Abs, Abs) {
-        let ascent = self.0.iter().map(MathFragment::ascent).max().unwrap_or_default();
-        let descent = self.0.iter().map(MathFragment::descent).max().unwrap_or_default();
-        (ascent, descent)
-    }
 }
 
 impl<T> From<T> for MathRow

tests/typ/math/matrix.typ

@@ -13,12 +13,20 @@ $mat() dot
 
 ---
 // Test sparse matrix.
-$mat(
+$ mat(
   1, 2, ..., 10;
   2, 2, ..., 10;
   dots.v, dots.v, dots.down, dots.v;
   10, 10, ..., 10;
-)$
+) $
+
+---
+// Test baseline alignment.
+$ mat(
+    a, b^2;
+    sum_(x \ y) x, a^(1/2);
+    zeta, alpha;
+  ) $
 
 ---
 // Test alternative delimiter.