From ef229b93863b7b1f1f718c4f1fbb755d0136e40d Mon Sep 17 00:00:00 2001
From: Martin Robinson <mrobinson@igalia.com>
Date: Thu, 19 Sep 2024 14:43:29 +0200
Subject: [PATCH] layout: Ensure that `<caption>`'s support `position:
 relative` (#33426)

This change adds support for `position: relative` to table `<caption>`.
In addition to adjusting their position according to inset values, table
captions must also establish containing blocks for descendants that are
absolutely positioned.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>
---
 components/layout_2020/table/layout.rs        | 16 +++++++++---
 tests/wpt/meta/MANIFEST.json                  | 13 ++++++++++
 ...e-caption-is-containing-block-001.html.ini |  2 --
 .../position-relative-table-caption.html.ini  |  2 --
 .../caption-relative-positioning.html         | 26 +++++++++++++++++++
 5 files changed, 52 insertions(+), 7 deletions(-)
 delete mode 100644 tests/wpt/meta/css/CSS2/abspos/table-caption-is-containing-block-001.html.ini
 delete mode 100644 tests/wpt/meta/css/css-position/position-relative-table-caption.html.ini
 create mode 100644 tests/wpt/tests/css/css-tables/caption-relative-positioning.html

diff --git a/components/layout_2020/table/layout.rs b/components/layout_2020/table/layout.rs
index 054d291c593..5b622cbb7b9 100644
--- a/components/layout_2020/table/layout.rs
+++ b/components/layout_2020/table/layout.rs
@@ -13,6 +13,7 @@ use style::computed_values::border_collapse::T as BorderCollapse;
 use style::computed_values::box_sizing::T as BoxSizing;
 use style::computed_values::caption_side::T as CaptionSide;
 use style::computed_values::empty_cells::T as EmptyCells;
+use style::computed_values::position::T as Position;
 use style::computed_values::table_layout::T as TableLayoutMode;
 use style::computed_values::visibility::T as Visibility;
 use style::logical_geometry::WritingMode;
@@ -1642,7 +1643,7 @@ impl<'a> TableLayout<'a> {
             style: containing_block.style,
         };
 
-        let box_fragment = context.layout_in_flow_block_level(
+        let mut box_fragment = context.layout_in_flow_block_level(
             layout_context,
             positioning_context
                 .as_mut()
@@ -1651,7 +1652,8 @@ impl<'a> TableLayout<'a> {
             None, /* sequential_layout_state */
         );
 
-        if let Some(positioning_context) = positioning_context.take() {
+        if let Some(mut positioning_context) = positioning_context.take() {
+            positioning_context.layout_collected_children(layout_context, &mut box_fragment);
             parent_positioning_context.append(positioning_context);
         }
 
@@ -1735,11 +1737,19 @@ impl<'a> TableLayout<'a> {
                 let caption_pbm = caption_fragment
                     .padding_border_margin()
                     .to_logical(table_writing_mode);
+
+                let caption_relative_offset = match caption_fragment.style.clone_position() {
+                    Position::Relative => {
+                        relative_adjustement(&caption_fragment.style, containing_block_for_children)
+                    },
+                    _ => LogicalVec2::zero(),
+                };
+
                 caption_fragment.content_rect = LogicalRect {
                     start_corner: LogicalVec2 {
                         inline: offset_from_wrapper.inline_start + caption_pbm.inline_start,
                         block: current_block_offset + caption_pbm.block_start,
-                    },
+                    } + caption_relative_offset,
                     size: caption_fragment
                         .content_rect
                         .size
diff --git a/tests/wpt/meta/MANIFEST.json b/tests/wpt/meta/MANIFEST.json
index e35446a99bd..f692f8f9baf 100644
--- a/tests/wpt/meta/MANIFEST.json
+++ b/tests/wpt/meta/MANIFEST.json
@@ -240575,6 +240575,19 @@
        {}
       ]
      ],
+     "caption-relative-positioning.html": [
+      "2be1e86bc077f1293ccc9ea851f23123ae679157",
+      [
+       null,
+       [
+        [
+         "/css/reference/ref-filled-green-100px-square.xht",
+         "=="
+        ]
+       ],
+       {}
+      ]
+     ],
      "col-definite-max-size-001.html": [
       "bcd7ca2fd89c26384e26be64dade0e7af0ea4c79",
       [
diff --git a/tests/wpt/meta/css/CSS2/abspos/table-caption-is-containing-block-001.html.ini b/tests/wpt/meta/css/CSS2/abspos/table-caption-is-containing-block-001.html.ini
deleted file mode 100644
index 66d3d601b7f..00000000000
--- a/tests/wpt/meta/css/CSS2/abspos/table-caption-is-containing-block-001.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[table-caption-is-containing-block-001.html]
-  expected: FAIL
diff --git a/tests/wpt/meta/css/css-position/position-relative-table-caption.html.ini b/tests/wpt/meta/css/css-position/position-relative-table-caption.html.ini
deleted file mode 100644
index e37d2b12888..00000000000
--- a/tests/wpt/meta/css/css-position/position-relative-table-caption.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[position-relative-table-caption.html]
-  expected: FAIL
diff --git a/tests/wpt/tests/css/css-tables/caption-relative-positioning.html b/tests/wpt/tests/css/css-tables/caption-relative-positioning.html
new file mode 100644
index 00000000000..2be1e86bc07
--- /dev/null
+++ b/tests/wpt/tests/css/css-tables/caption-relative-positioning.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+    <link rel="author" title="Martin Robinson" href="mailto:mrobinson@igalia.com">
+    <link rel="author" title="Oriol Brufau" href="mailto:obrufau@igalia.com">
+    <title>&lt;caption&gt; elements can be relatively positioned</title>
+    <meta name="assert" content="The caption is positioned relatively to the table wrapper">
+    <link rel="help" href="https://drafts.csswg.org/css2/#relative-positioning">
+    <link rel="match" href="/css/reference/ref-filled-green-100px-square.xht">
+    <style>
+        caption {
+            position: relative;
+            background: green;
+            width: 100px;
+            height: 100px;
+            margin-left: 200px;
+            left: -200px;
+        }
+   </style>
+
+    <p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
+    <div style="width: 100px; background: red;">
+        <table>
+            <caption></caption>
+        </table>
+    </div>
+</html>