Preserve contained grid row stretch

crates/obscura-render/src/dom.rs

@@ -5374,6 +5374,12 @@ enum ContainerAutoInlineSize {
     StretchedGridItem,
 }
 
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+enum ContainerAutoBlockSize {
+    Intrinsic,
+    StretchedGridItem,
+}
+
 /// Classify how an auto inline-size is resolved. Stretched grid items need
 /// their intrinsic contribution contained without replacing the final auto
 /// size that stretch alignment consumes.
@@ -5455,6 +5461,55 @@ fn container_auto_inline_size(
     }
 }
 
+/// Classify an auto block-size for size containment. A stretched grid item
+/// must keep its auto size so final alignment can fill a definite grid area;
+/// only its intrinsic track contribution is contained.
+fn container_auto_block_size(
+    tree: &DomTree,
+    id: NodeId,
+    style: &crate::LayoutStyle,
+    styles: &HashMap<NodeId, crate::LayoutStyle>,
+) -> ContainerAutoBlockSize {
+    // Absolutely positioned descendants are not grid items. Preserve the
+    // existing contained intrinsic-height behavior until their independent
+    // inset-based fill sizing is modeled explicitly.
+    if matches!(style.position, Some(taffy::Position::Absolute)) {
+        return ContainerAutoBlockSize::Intrinsic;
+    }
+
+    let mut parent = tree.get_node(id).and_then(|node| node.parent);
+    let parent_style = loop {
+        let Some(parent_id) = parent else {
+            return ContainerAutoBlockSize::Intrinsic;
+        };
+        let Some(parent_style) = styles.get(&parent_id) else {
+            return ContainerAutoBlockSize::Intrinsic;
+        };
+        if parent_style.display_contents {
+            parent = tree.get_node(parent_id).and_then(|node| node.parent);
+            continue;
+        }
+        break parent_style;
+    };
+
+    if parent_style.display == crate::Display::Grid
+        && style
+            .align_self
+            .unwrap_or(
+                parent_style
+                    .align_items
+                    .unwrap_or(taffy::AlignItems::STRETCH),
+            )
+            == taffy::AlignSelf::STRETCH
+        && !style.margin_auto[0]
+        && !style.margin_auto[2]
+    {
+        ContainerAutoBlockSize::StretchedGridItem
+    } else {
+        ContainerAutoBlockSize::Intrinsic
+    }
+}
+
 /// Apply the used-size part of `container-type`'s implicit size containment.
 ///
 /// The default contain-intrinsic-size is zero. Fill-available block boxes keep
@@ -5499,7 +5554,14 @@ fn apply_container_size_containment(
         let ratio_transfers_block_size =
             style.aspect_ratio.is_some() && !matches!(style.width, crate::Dimension::Auto);
         if matches!(style.height, crate::Dimension::Auto) && !ratio_transfers_block_size {
-            taffy_style.size.height = taffy::Dimension::length(0.0);
+            match container_auto_block_size(tree, id, style, styles) {
+                ContainerAutoBlockSize::Intrinsic => {
+                    taffy_style.size.height = taffy::Dimension::length(0.0);
+                }
+                ContainerAutoBlockSize::StretchedGridItem => {
+                    taffy_style.intrinsic_size_containment.height = true;
+                }
+            }
         }
     }
 }

crates/obscura-render/tests/layout_test.rs

@@ -1147,6 +1147,63 @@ fn stretched_inline_size_container_has_zero_intrinsic_grid_contribution() {
     );
 }
 
+#[test]
+fn stretched_size_container_has_zero_intrinsic_grid_row_contribution() {
+    // Chromium 140: block-axis size containment removes the tall child's
+    // intrinsic row contribution, but leaves the grid item's auto height
+    // available for final stretch alignment. Padding and border remain inside
+    // the fixed row's stretched 100px border box.
+    let tree = parse_html(
+        r#"
+        <style>
+          html, body { margin: 0 }
+          .grid { display: grid }
+          .item { container-type: size }
+          .child { width: 20px; height: 240px }
+          #fixed-grid {
+            margin-top: 20px;
+            grid-template-rows: 100px;
+          }
+          #fixed-item {
+            padding-block: 10px;
+            border-top: 5px solid black;
+            border-bottom: 5px solid black;
+          }
+        </style>
+        <div id="shrink-grid" class="grid">
+          <div id="shrink-item" class="item">
+            <div id="shrink-child" class="child"></div>
+          </div>
+        </div>
+        <div id="fixed-grid" class="grid">
+          <div id="fixed-item" class="item">
+            <div id="fixed-child" class="child"></div>
+          </div>
+        </div>
+        "#,
+    );
+    let layout = layout_dom(&tree, (800.0, 600.0));
+    let rect = |id| layout.rects[&tree.get_element_by_id(id).unwrap()];
+    let shrink_grid = rect("shrink-grid");
+    let shrink_item = rect("shrink-item");
+    let shrink_child = rect("shrink-child");
+    let fixed_grid = rect("fixed-grid");
+    let fixed_item = rect("fixed-item");
+    let fixed_child = rect("fixed-child");
+    assert!(
+        shrink_grid.height.abs() < 0.01
+            && shrink_item.height.abs() < 0.01
+            && (shrink_child.height - 240.0).abs() < 0.01
+            && (fixed_grid.height - 100.0).abs() < 0.01
+            && (fixed_item.height - 100.0).abs() < 0.01
+            && (fixed_child.y - fixed_item.y - 15.0).abs() < 0.01
+            && (fixed_child.height - 240.0).abs() < 0.01,
+        "contained intrinsic contribution leaked into the grid row: \
+         shrink=({shrink_grid:?}, {shrink_item:?}, {shrink_child:?}) \
+         fixed=({fixed_grid:?}, {fixed_item:?}, {fixed_child:?})"
+    );
+}
+
 #[test]
 fn non_stretched_auto_grid_item_shrink_wraps_inside_grid_area() {
     let tree = parse_html(