From 63a6b73f9a1a10af2a913b051fb89c7b599a3593 Mon Sep 17 00:00:00 2001
From: Martin Robinson <mrobinson@igalia.com>
Date: Thu, 22 Jun 2023 11:28:26 +0200
Subject: [PATCH] Fix positioning of statically positioned fixed child of
 absolutes

---
 components/layout_2020/positioned.rs                | 11 +++++++++++
 tests/wpt/meta/MANIFEST.json                        | 13 +++++++++++++
 .../hypothetical-dynamic-change-001.html.ini        |  2 --
 .../hypothetical-dynamic-change-002.html.ini        |  2 --
 .../position-fixed-scroll-nested-fixed.html.ini     |  2 --
 .../css/CSS2/abspos/static-fixed-inside-abspos.html | 13 +++++++++++++
 6 files changed, 37 insertions(+), 6 deletions(-)
 delete mode 100644 tests/wpt/meta/css/css-position/hypothetical-dynamic-change-001.html.ini
 delete mode 100644 tests/wpt/meta/css/css-position/hypothetical-dynamic-change-002.html.ini
 delete mode 100644 tests/wpt/meta/css/css-position/position-fixed-scroll-nested-fixed.html.ini
 create mode 100644 tests/wpt/web-platform-tests/css/CSS2/abspos/static-fixed-inside-abspos.html

diff --git a/components/layout_2020/positioned.rs b/components/layout_2020/positioned.rs
index 07831f8dbf8..493c5a1c714 100644
--- a/components/layout_2020/positioned.rs
+++ b/components/layout_2020/positioned.rs
@@ -626,8 +626,19 @@ impl HoistedAbsolutelyPositionedBox {
             )
         };
         positioning_context.layout_collected_children(layout_context, &mut new_fragment);
+
+        // Any hoisted boxes that remain in this positioning context are going to be hoisted
+        // up above this absolutely positioned box. These will necessarily be fixed position
+        // elements, because absolutely positioned elements form containing blocks for all
+        // other elements. If any of them have a static start position though, we need to
+        // adjust it to account for the start corner of this absolute.
+        positioning_context.adjust_static_position_of_hoisted_fragments_with_offset(
+            &new_fragment.content_rect.start_corner,
+        );
+
         for_nearest_containing_block_for_all_descendants
             .extend(positioning_context.for_nearest_containing_block_for_all_descendants);
+
         new_fragment
     }
 }
diff --git a/tests/wpt/meta/MANIFEST.json b/tests/wpt/meta/MANIFEST.json
index d39c79550ed..acbf476370f 100644
--- a/tests/wpt/meta/MANIFEST.json
+++ b/tests/wpt/meta/MANIFEST.json
@@ -31605,6 +31605,19 @@
         {}
        ]
       ],
+      "static-fixed-inside-abspos.html": [
+       "e3c3aa450d42505557b1f3eefd0aee8ea63fa4d6",
+       [
+        null,
+        [
+         [
+          "/css/reference/ref-filled-green-100px-square.xht",
+          "=="
+         ]
+        ],
+        {}
+       ]
+      ],
       "static-inside-inline-block.html": [
        "327e8e6dacdeabb4d2d57ab700d80f966ccde76b",
        [
diff --git a/tests/wpt/meta/css/css-position/hypothetical-dynamic-change-001.html.ini b/tests/wpt/meta/css/css-position/hypothetical-dynamic-change-001.html.ini
deleted file mode 100644
index 334022baff7..00000000000
--- a/tests/wpt/meta/css/css-position/hypothetical-dynamic-change-001.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[hypothetical-dynamic-change-001.html]
-  expected: FAIL
diff --git a/tests/wpt/meta/css/css-position/hypothetical-dynamic-change-002.html.ini b/tests/wpt/meta/css/css-position/hypothetical-dynamic-change-002.html.ini
deleted file mode 100644
index 5541b847967..00000000000
--- a/tests/wpt/meta/css/css-position/hypothetical-dynamic-change-002.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[hypothetical-dynamic-change-002.html]
-  expected: FAIL
diff --git a/tests/wpt/meta/css/css-position/position-fixed-scroll-nested-fixed.html.ini b/tests/wpt/meta/css/css-position/position-fixed-scroll-nested-fixed.html.ini
deleted file mode 100644
index 2903ed8c405..00000000000
--- a/tests/wpt/meta/css/css-position/position-fixed-scroll-nested-fixed.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[position-fixed-scroll-nested-fixed.html]
-  expected: FAIL
diff --git a/tests/wpt/web-platform-tests/css/CSS2/abspos/static-fixed-inside-abspos.html b/tests/wpt/web-platform-tests/css/CSS2/abspos/static-fixed-inside-abspos.html
new file mode 100644
index 00000000000..e3c3aa450d4
--- /dev/null
+++ b/tests/wpt/web-platform-tests/css/CSS2/abspos/static-fixed-inside-abspos.html
@@ -0,0 +1,13 @@
+<!DOCTYPE html>
+<title>Static position fixed inside static position absolute</title>
+<link rel="author" title="Martin Robinson" href="mrobinson@igalia.com">
+<link rel="help" href="https://www.w3.org/TR/CSS22/visudet.html#abs-non-replaced-width" title="10.3.7 Absolutely positioned, non-replaced elements">
+<link rel="match" href="../../reference/ref-filled-green-100px-square.xht">
+
+<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
+
+<div style="display: absolute; width: 100px; height: 100px; background: green;">
+    <div style="position: absolute; width: 50px; height: 50px; margin-left: 50px; margin-top: 50px; background: red;">
+        <div style="position: fixed; width: 50px; height: 50px; background: green;"></div>
+    </div>
+</div>