layout: Add incremental box tree construction for table cell (#37850)

This change extends incremental box tree updates to table cells. In
addition, for simplicity this refactors `BoxSlot::take_layout_box()`
into `BoxSlot::take_layout_box_if_undamaged()`.

Testing: This should not change observable behavior and is thus covered
by existing WPT tests.

Signed-off-by: Oriol Brufau <obrufau@igalia.com>
Co-authored-by: Martin Robinson <mrobinson@igalia.com>

components/layout/dom.rs

@@ -181,7 +181,10 @@ impl BoxSlot<'_> {
         }
     }
 
-    pub(crate) fn take_layout_box(&self) -> Option<LayoutBox> {
+    pub(crate) fn take_layout_box_if_undamaged(&self, damage: LayoutDamage) -> Option<LayoutBox> {
+        if damage.has_box_damage() {
+            return None;
+        }
         self.slot.as_ref().and_then(|slot| slot.borrow_mut().take())
     }
 }

components/layout/table/construct.rs

@@ -855,14 +855,11 @@ impl<'dom> TraversalHandler<'dom> for TableBuilderTraversal<'_, 'dom> {
                         unreachable!("Replaced should not have a LayoutInternal display type.");
                     };
 
-                    let old_caption = (!info.damage.has_box_damage())
+                    let old_box = box_slot.take_layout_box_if_undamaged(info.damage);
-                        .then(|| match box_slot.take_layout_box() {
+                    let old_caption = old_box.and_then(|layout_box| match layout_box {
-                            Some(LayoutBox::TableLevelBox(TableLevelBox::Caption(caption))) => {
+                        LayoutBox::TableLevelBox(TableLevelBox::Caption(caption)) => Some(caption),
-                                Some(caption)
-                            },
                         _ => None,
-                        })
+                    });
-                        .flatten();
 
                     let caption = old_caption.unwrap_or_else(|| {
                         let contents = IndependentNonReplacedContents::Flow(
@@ -1006,6 +1003,15 @@ impl<'dom> TraversalHandler<'dom> for TableRowBuilder<'_, '_, 'dom, '_> {
         match display {
             DisplayGeneratingBox::LayoutInternal(internal) => match internal {
                 DisplayLayoutInternal::TableCell => {
+                    self.finish_current_anonymous_cell_if_needed();
+
+                    let old_box = box_slot.take_layout_box_if_undamaged(info.damage);
+                    let old_cell = old_box.and_then(|layout_box| match layout_box {
+                        LayoutBox::TableLevelBox(TableLevelBox::Cell(cell)) => Some(cell),
+                        _ => None,
+                    });
+
+                    let cell = old_cell.unwrap_or_else(|| {
                         // This value will already have filtered out rowspan=0
                         // in quirks mode, so we don't have to worry about that.
                         let (rowspan, colspan) = if info.pseudo_element_type.is_none() {
@@ -1037,14 +1043,14 @@ impl<'dom> TraversalHandler<'dom> for TableRowBuilder<'_, '_, 'dom, '_> {
                             false, /* is_list_item */
                         );
 
-                    self.finish_current_anonymous_cell_if_needed();
+                        ArcRefCell::new(TableSlotCell {
-
-                    let cell = ArcRefCell::new(TableSlotCell {
                             base: LayoutBoxBase::new(info.into(), info.style.clone()),
                             contents,
                             colspan,
                             rowspan,
+                        })
                     });
+
                     self.table_traversal.builder.add_cell(cell.clone());
                     box_slot.set(LayoutBox::TableLevelBox(TableLevelBox::Cell(cell)));
                 },