Fix HTML export of table with gutter (#5920)

2 files changed, 17 insertions, 6 deletions

diff --git a/crates/typst-library/src/layout/grid/resolve.rs b/crates/typst-library/src/layout/grid/resolve.rs
index f6df57a3..762f94ed 100644
--- a/crates/typst-library/src/layout/grid/resolve.rs
+++ b/crates/typst-library/src/layout/grid/resolve.rs
@@ -1526,11 +1526,7 @@ impl<'a> CellGrid<'a> {
         self.entry(x, y).map(|entry| match entry {
             Entry::Cell(_) => Axes::new(x, y),
             Entry::Merged { parent } => {
-                let c = if self.has_gutter {
-                    1 + self.cols.len() / 2
-                } else {
-                    self.cols.len()
-                };
+                let c = self.non_gutter_column_count();
                 let factor = if self.has_gutter { 2 } else { 1 };
                 Axes::new(factor * (*parent % c), factor * (*parent / c))
             }
@@ -1602,6 +1598,21 @@ impl<'a> CellGrid<'a> {
             cell.rowspan.get()
         }
     }
+
+    #[inline]
+    pub fn non_gutter_column_count(&self) -> usize {
+        if self.has_gutter {
+            // Calculation: With gutters, we have
+            // 'cols = 2 * (non-gutter cols) - 1', since there is a gutter
+            // column between each regular column. Therefore,
+            // 'floor(cols / 2)' will be equal to
+            // 'floor(non-gutter cols - 1/2) = non-gutter-cols - 1',
+            // so 'non-gutter cols = 1 + floor(cols / 2)'.
+            1 + self.cols.len() / 2
+        } else {
+            self.cols.len()
+        }
+    }
 }
 
 /// Given a cell's requested x and y, the vector with the resolved cell
diff --git a/crates/typst-library/src/model/table.rs b/crates/typst-library/src/model/table.rs
index 82c1cc08..6f4461bd 100644
--- a/crates/typst-library/src/model/table.rs
+++ b/crates/typst-library/src/model/table.rs
@@ -282,7 +282,7 @@ fn show_cell_html(tag: HtmlTag, cell: &Cell, styles: StyleChain) -> Content {
 
 fn show_cellgrid_html(grid: CellGrid, styles: StyleChain) -> Content {
     let elem = |tag, body| HtmlElem::new(tag).with_body(Some(body)).pack();
-    let mut rows: Vec<_> = grid.entries.chunks(grid.cols.len()).collect();
+    let mut rows: Vec<_> = grid.entries.chunks(grid.non_gutter_column_count()).collect();
 
     let tr = |tag, row: &[Entry]| {
         let row = row