fix: implement computeDryBaseline for custom RenderBox subclasses

In Flutter 3.32+, any RenderBox that overrides
computeDistanceToActualBaseline must also override computeDryBaseline.

Add computeDryBaseline to:
- _ListItemRenderObject
- _ListMarkerRenderObject
- _RubyRenderObject
- _TableRenderObject
- _RenderCssSizing (pass correct child constraints)
- _HorizontalMarginRenderObject (pass deflated constraints)
- _ValignBaselineRenderObject (pass deflated constraints + padding)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: daohoangson

packages/core/lib/src/widgets/css_sizing.dart

@@ -219,6 +219,20 @@ class _RenderCssSizing extends RenderProxyBox {
     markNeedsLayout();
   }
 
+  @override
+  double? computeDryBaseline(
+    BoxConstraints constraints,
+    TextBaseline baseline,
+  ) {
+    final scopedChild = child;
+    if (scopedChild == null) {
+      return null;
+    }
+
+    final cc = _applyContraints(constraints);
+    return scopedChild.getDryBaseline(cc, baseline);
+  }
+
   @override
   Size computeDryLayout(BoxConstraints constraints) {
     final scopedChild = child;

packages/core/lib/src/widgets/horizontal_margin.dart

@@ -55,6 +55,21 @@ class _HorizontalMarginRenderObject extends RenderShiftedBox {
 
   double get marginsOrZero => _left.or(0) + _right.or(0);
 
+  @override
+  double? computeDryBaseline(
+    BoxConstraints constraints,
+    TextBaseline baseline,
+  ) {
+    final scopedChild = child;
+    if (scopedChild == null) {
+      return null;
+    }
+
+    final edges = EdgeInsets.only(left: _left.or(0), right: _right.or(0));
+    final cc = constraints.deflate(edges);
+    return scopedChild.getDryBaseline(cc, baseline);
+  }
+
   @override
   Size computeDryLayout(BoxConstraints constraints) =>
       _compute(child, constraints, ChildLayoutHelper.dryLayoutChild);

packages/core/lib/src/widgets/html_list_item.dart

@@ -87,6 +87,23 @@ class _ListItemRenderObject extends RenderBox
   double? computeDistanceToActualBaseline(TextBaseline baseline) =>
       defaultComputeDistanceToFirstActualBaseline(baseline);
 
+  @override
+  double? computeDryBaseline(
+    BoxConstraints constraints,
+    TextBaseline baseline,
+  ) {
+    final child = firstChild;
+    if (child == null) {
+      return null;
+    }
+
+    final childConstraints = constraints.maxWidth.isFinite && textAlign != null
+        ? constraints.tighten(width: constraints.maxWidth)
+        : constraints;
+    // The first child's offset is always Offset.zero in _compute
+    return child.getDryBaseline(childConstraints, baseline);
+  }
+
   @override
   Size computeDryLayout(BoxConstraints constraints) =>
       _compute(firstChild, constraints, ChildLayoutHelper.dryLayoutChild);

packages/core/lib/src/widgets/html_list_marker.dart

@@ -97,6 +97,13 @@ class _ListMarkerRenderObject extends RenderBox {
   double computeDistanceToActualBaseline(TextBaseline baseline) =>
       _textPainter.computeDistanceToActualBaseline(baseline);
 
+  @override
+  double? computeDryBaseline(
+    BoxConstraints constraints,
+    TextBaseline baseline,
+  ) =>
+      _textPainter.computeDistanceToActualBaseline(baseline);
+
   @override
   Size computeDryLayout(BoxConstraints constraints) =>
       constraints.constrain(_textPainter.size);

packages/core/lib/src/widgets/html_ruby.dart

@@ -39,6 +39,37 @@ class _RubyRenderObject extends RenderBox
     return offset.dy + rubyValue;
   }
 
+  @override
+  double? computeDryBaseline(
+    BoxConstraints constraints,
+    TextBaseline baseline,
+  ) {
+    final ruby = firstChild;
+    if (ruby == null) {
+      return null;
+    }
+
+    final rubyConstraints = constraints.loosen();
+    final rubySize = ruby.getDryLayout(rubyConstraints);
+    final rubyBaseline = ruby.getDryBaseline(rubyConstraints, baseline);
+    if (rubyBaseline == null) {
+      return null;
+    }
+
+    final rt = (ruby.parentData! as _RubyParentData).nextSibling;
+    final rtHeight = rt != null
+        ? rt
+            .getDryLayout(
+              rubyConstraints.copyWith(
+                maxHeight: rubyConstraints.maxHeight - rubySize.height,
+              ),
+            )
+            .height
+        : 0.0;
+
+    return rtHeight + rubyBaseline;
+  }
+
   @override
   Size computeDryLayout(BoxConstraints constraints) =>
       _compute(firstChild, constraints, ChildLayoutHelper.dryLayoutChild);

packages/core/lib/src/widgets/html_table.dart

@@ -836,6 +836,40 @@ class _TableRenderObject extends RenderBox
     return result;
   }
 
+  @override
+  double? computeDryBaseline(
+    BoxConstraints constraints,
+    TextBaseline baseline,
+  ) {
+    double? result;
+
+    var child = firstChild;
+    while (child != null) {
+      final data = child.parentData! as _TableCellData;
+
+      if (data.rowStart == 0) {
+        // only compute cells in the first row
+        // use the child's dry baseline with loosened constraints
+        // since exact cell constraints require full table layout
+        final candidate = child.getDryBaseline(constraints.loosen(), baseline);
+        if (candidate != null) {
+          final adjusted = candidate + paddingTop + rowGap;
+          if (result != null) {
+            if (adjusted < result) {
+              result = adjusted;
+            }
+          } else {
+            result = adjusted;
+          }
+        }
+      }
+
+      child = data.nextSibling;
+    }
+
+    return result;
+  }
+
   @override
   Size computeDryLayout(BoxConstraints constraints) =>
       _TableRenderLayouter.dry(this, constraints).compute(firstChild).totalSize;

packages/core/lib/src/widgets/valign_baseline.dart

@@ -121,6 +121,25 @@ class _ValignBaselineRenderObject extends RenderProxyBox {
   double? _baselineWithOffset;
   var _paddingTop = 0.0;
 
+  @override
+  double? computeDryBaseline(
+    BoxConstraints constraints,
+    TextBaseline baseline,
+  ) {
+    final scopedChild = child;
+    if (scopedChild == null) {
+      return null;
+    }
+
+    final cc = constraints.loosen().deflate(EdgeInsets.only(top: _paddingTop));
+    final childBaseline = scopedChild.getDryBaseline(cc, baseline);
+    if (childBaseline == null) {
+      return null;
+    }
+
+    return childBaseline + _paddingTop;
+  }
+
   @override
   Size computeDryLayout(BoxConstraints constraints) =>
       _compute(child, constraints, ChildLayoutHelper.dryLayoutChild);

packages/core/test/tag_table_test.dart

@@ -829,15 +829,18 @@ Future<void> main() async {
     testWidgets('computeDryBaseline', (tester) async {
       final key = GlobalKey();
       await tester.pumpWidget(
-        HtmlTable(
-          key: key,
-          children: const [
-            HtmlTableCell(
-              columnStart: 0,
-              rowStart: 0,
-              child: Text('Cell'),
-            ),
-          ],
+        Directionality(
+          textDirection: TextDirection.ltr,
+          child: HtmlTable(
+            key: key,
+            children: const [
+              HtmlTableCell(
+                columnStart: 0,
+                rowStart: 0,
+                child: Text('Cell'),
+              ),
+            ],
+          ),
         ),
       );
       await tester.pumpAndSettle();