From b026dae8ac244be8b9682b119c5bf13e53d1cdb7 Mon Sep 17 00:00:00 2001
From: Manish Goregaokar <manishsmail@gmail.com>
Date: Mon, 27 Jul 2020 23:15:46 -0700
Subject: [PATCH] Only apply clip() to positioned elements

---
 .../display_list/stacking_context.rs          | 29 +++++++++++--------
 .../clip-not-absolute-positioned-001.html.ini |  2 --
 .../clip-not-absolute-positioned-002.html.ini |  2 --
 .../clip-not-absolute-positioned-003.html.ini |  2 --
 .../clip-not-absolute-positioned-004.html.ini |  2 --
 5 files changed, 17 insertions(+), 20 deletions(-)
 delete mode 100644 tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-001.html.ini
 delete mode 100644 tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-002.html.ini
 delete mode 100644 tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-003.html.ini
 delete mode 100644 tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-004.html.ini

diff --git a/components/layout_2020/display_list/stacking_context.rs b/components/layout_2020/display_list/stacking_context.rs
index 5c95b3168dc..a76b607fa6d 100644
--- a/components/layout_2020/display_list/stacking_context.rs
+++ b/components/layout_2020/display_list/stacking_context.rs
@@ -715,19 +715,24 @@ impl BoxFragment {
         builder: &mut StackingContextBuilder,
         containing_block_info: &ContainingBlockInfo,
     ) {
-        let clip = self.style.get_effects().clip;
-        if let ClipRectOrAuto::Rect(r) = clip {
-            let border_rect = self
-                .border_rect()
-                .to_physical(self.style.writing_mode, &containing_block_info.rect);
-            let clip_rect = r
-                .for_border_rect(border_rect)
-                .translate(containing_block_info.rect.origin.to_vector())
-                .to_webrender();
+        let position = self.style.get_box().position;
+        // https://drafts.csswg.org/css2/#clipping
+        // The clip property applies only to absolutely positioned elements
+        if position == ComputedPosition::Absolute || position == ComputedPosition::Fixed {
+            let clip = self.style.get_effects().clip;
+            if let ClipRectOrAuto::Rect(r) = clip {
+                let border_rect = self
+                    .border_rect()
+                    .to_physical(self.style.writing_mode, &containing_block_info.rect);
+                let clip_rect = r
+                    .for_border_rect(border_rect)
+                    .translate(containing_block_info.rect.origin.to_vector())
+                    .to_webrender();
 
-            let parent = builder.current_space_and_clip;
-            builder.current_space_and_clip.clip_id =
-                builder.wr.define_clip_rect(&parent, clip_rect);
+                let parent = builder.current_space_and_clip;
+                builder.current_space_and_clip.clip_id =
+                    builder.wr.define_clip_rect(&parent, clip_rect);
+            }
         }
     }
 
diff --git a/tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-001.html.ini b/tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-001.html.ini
deleted file mode 100644
index 57f7fa26349..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-001.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[clip-not-absolute-positioned-001.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-002.html.ini b/tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-002.html.ini
deleted file mode 100644
index 118d113a23f..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-002.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[clip-not-absolute-positioned-002.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-003.html.ini b/tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-003.html.ini
deleted file mode 100644
index e0b8b1aa04f..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-003.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[clip-not-absolute-positioned-003.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-004.html.ini b/tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-004.html.ini
deleted file mode 100644
index 99b0e02d4a4..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-masking/clip/clip-not-absolute-positioned-004.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[clip-not-absolute-positioned-004.html]
-  expected: FAIL