skip layout of redundant gutter at the top of footer

crates/typst-layout/src/grid/layouter.rs

@@ -232,7 +232,7 @@ pub(super) enum Row {
 
 impl Row {
     /// Returns the `y` index of this row.
-    fn index(&self) -> usize {
+    pub(super) fn index(&self) -> usize {
         match self {
             Self::Frame(_, y, _) => *y,
             Self::Fr(_, y, _) => *y,

crates/typst-layout/src/grid/repeated.rs

@@ -679,9 +679,23 @@ impl<'a> GridLayouter<'a> {
         let footer_len = footer.range.end - footer.range.start;
         self.unbreakable_rows_left += footer_len;
 
-        // TODO(subfooters): also consider omitted gutter before the footer
-        // when there is a header right before it taking it.
-        for y in footer.range.clone() {
+        let footer_start = if self.grid.is_gutter_track(footer.range.start)
+            && self
+                .current
+                .lrows
+                .last()
+                .is_none_or(|r| self.grid.is_gutter_track(r.index()))
+        {
+            // Skip gutter at the top of footer if there's already a gutter
+            // from a repeated header right before it in the current region.
+            // Normally, that shouldn't happen as it indicates we have a widow,
+            // but we can't fully prevent widows anyway.
+            footer.range.start + 1
+        } else {
+            footer.range.start
+        };
+
+        for y in footer_start..footer.range.end {
             self.layout_row_with_state(
                 y,
                 engine,

tests/suite/layout/grid/footers.typ

@@ -41,6 +41,20 @@
   )
 )
 
+--- grid-footer-gutter-short-lived ---
+// Gutter, no repetition, short-lived
+#set page(height: 6em)
+#set text(6pt)
+#set table(inset: 2pt, stroke: 0.5pt)
+#table(
+  gutter: 2pt,
+  align: center + horizon,
+  table.header([a]),
+  table.footer([b]),
+  table.footer([c]),
+  [d],
+)
+
 --- grid-cell-override-in-header-and-footer ---
 #table(
   table.header(table.cell(stroke: red)[Hello]),