Auto merge of #25645 - mrobinson:scrollable-overflow-v2, r=SimonSapin

Add support for overflow:scroll and overflow:hidden to layout_2020

This adds clipping and interactive scrolling support, but scrolling from
script is still not functional.

<!-- Please describe your changes on the following line: -->

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #___ (GitHub issue number if applicable)

<!-- Either: -->
- [x] There are tests for these changes OR
- [ ] These changes do not require tests because ___

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

19 files changed, 129 insertions, 63 deletions

diff --git a/components/layout_2020/display_list/mod.rs b/components/layout_2020/display_list/mod.rs
index 96ac84032a9..fa193874892 100644
--- a/components/layout_2020/display_list/mod.rs
+++ b/components/layout_2020/display_list/mod.rs
@@ -9,9 +9,11 @@ use crate::replaced::IntrinsicSizes;
 use embedder_traits::Cursor;
 use euclid::{Point2D, SideOffsets2D, Size2D};
 use gfx::text::glyph::GlyphStore;
+use gfx_traits::{combine_id_with_fragment_type, FragmentType};
 use mitochondria::OnceCell;
 use net_traits::image_cache::UsePlaceholder;
 use std::sync::Arc;
+use style::computed_values::overflow_x::T as ComputedOverflow;
 use style::dom::OpaqueNode;
 use style::properties::ComputedValues;
 use style::values::computed::{BorderStyle, Length, LengthPercentage};
@@ -63,8 +65,6 @@ impl<'a> DisplayListBuilder<'a> {
         wr::CommonItemProperties::new(clip_rect, self.current_space_and_clip)
     }
 
-    // FIXME: use this for the `overflow` property or anything else that clips an entire subtree.
-    #[allow(unused)]
     fn clipping_and_scrolling_scope<R>(&mut self, f: impl FnOnce(&mut Self) -> R) -> R {
         let previous = self.current_space_and_clip;
         let result = f(self);
@@ -256,14 +256,49 @@ impl<'a> BuilderForBoxFragment<'a> {
 
         self.build_background(builder);
         self.build_border(builder);
-        let content_rect = self
-            .fragment
-            .content_rect
-            .to_physical(self.fragment.style.writing_mode, self.containing_block)
-            .translate(self.containing_block.origin.to_vector());
-        for child in &self.fragment.children {
-            child.build_display_list(builder, &content_rect)
-        }
+
+        builder.clipping_and_scrolling_scope(|builder| {
+            let overflow_x = self.fragment.style.get_box().overflow_x;
+            let overflow_y = self.fragment.style.get_box().overflow_y;
+            let original_scroll_and_clip_info = builder.current_space_and_clip;
+            if overflow_x != ComputedOverflow::Visible || overflow_y != ComputedOverflow::Visible {
+                // TODO(mrobinson): We should use the correct fragment type, once we generate
+                // fragments from ::before and ::after generated content selectors.
+                let id = combine_id_with_fragment_type(
+                    self.fragment.tag.id() as usize,
+                    FragmentType::FragmentBody,
+                ) as u64;
+                let external_id = wr::ExternalScrollId(id, builder.wr.pipeline_id);
+
+                let sensitivity = if ComputedOverflow::Hidden == overflow_x &&
+                    ComputedOverflow::Hidden == overflow_y
+                {
+                    wr::ScrollSensitivity::Script
+                } else {
+                    wr::ScrollSensitivity::ScriptAndInputEvents
+                };
+
+                builder.current_space_and_clip = builder.wr.define_scroll_frame(
+                    &original_scroll_and_clip_info,
+                    Some(external_id),
+                    self.fragment.scrollable_overflow().to_webrender(),
+                    *self.padding_rect(),
+                    vec![], // complex_clips
+                    None,   // image_mask
+                    sensitivity,
+                    wr::units::LayoutVector2D::zero(),
+                );
+            }
+
+            let content_rect = self
+                .fragment
+                .content_rect
+                .to_physical(self.fragment.style.writing_mode, self.containing_block)
+                .translate(self.containing_block.origin.to_vector());
+            for child in &self.fragment.children {
+                child.build_display_list(builder, &content_rect)
+            }
+        });
     }
 
     fn build_background(&mut self, builder: &mut DisplayListBuilder) {
diff --git a/components/layout_2020/fragments.rs b/components/layout_2020/fragments.rs
index 37f81978108..c46b332dec5 100644
--- a/components/layout_2020/fragments.rs
+++ b/components/layout_2020/fragments.rs
@@ -3,11 +3,12 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use crate::geom::flow_relative::{Rect, Sides, Vec2};
-use crate::geom::PhysicalRect;
+use crate::geom::{PhysicalPoint, PhysicalRect};
 use gfx::text::glyph::GlyphStore;
 use gfx_traits::print_tree::PrintTree;
 use servo_arc::Arc as ServoArc;
 use std::sync::Arc;
+use style::computed_values::overflow_x::T as ComputedOverflow;
 use style::dom::OpaqueNode;
 use style::logical_geometry::WritingMode;
 use style::properties::ComputedValues;
@@ -39,7 +40,7 @@ pub(crate) struct BoxFragment {
     pub block_margins_collapsed_with_children: CollapsedBlockMargins,
 
     /// The scrollable overflow of this box fragment.
-    pub scrollable_overflow: PhysicalRect<Length>,
+    pub scrollable_overflow_from_children: PhysicalRect<Length>,
 }
 
 pub(crate) struct CollapsedBlockMargins {
@@ -101,15 +102,16 @@ impl Fragment {
     pub fn scrollable_overflow(&self) -> PhysicalRect<Length> {
         // FIXME(mrobinson, bug 25564): We should be using the containing block
         // here to properly convert scrollable overflow to physical geometry.
+        let containing_block = PhysicalRect::zero();
         match self {
-            Fragment::Box(fragment) => fragment.scrollable_overflow.clone(),
+            Fragment::Box(fragment) => fragment.scrollable_overflow_for_parent(&containing_block),
             Fragment::Anonymous(fragment) => fragment.scrollable_overflow.clone(),
             Fragment::Text(fragment) => fragment
                 .rect
-                .to_physical(fragment.parent_style.writing_mode, &PhysicalRect::zero()),
+                .to_physical(fragment.parent_style.writing_mode, &containing_block),
             Fragment::Image(fragment) => fragment
                 .rect
-                .to_physical(fragment.style.writing_mode, &PhysicalRect::zero()),
+                .to_physical(fragment.style.writing_mode, &containing_block),
         }
     }
 }
@@ -125,10 +127,13 @@ impl AnonymousFragment {
     }
 
     pub fn new(rect: Rect<Length>, children: Vec<Fragment>, mode: WritingMode) -> Self {
-        // FIXME(mrobinson, bug 25564): We should be using the containing block
-        // here to properly convert scrollable overflow to physical geometry.
+        let content_origin = rect.start_corner.to_physical(mode);
         let scrollable_overflow = children.iter().fold(PhysicalRect::zero(), |acc, child| {
-            acc.union(&child.scrollable_overflow())
+            acc.union(
+                &child
+                    .scrollable_overflow()
+                    .translate(content_origin.to_vector()),
+            )
         });
         AnonymousFragment {
             rect,
@@ -141,8 +146,9 @@ impl AnonymousFragment {
     pub fn print(&self, tree: &mut PrintTree) {
         tree.new_level(format!(
             "Anonymous\
-                \nrect={:?}",
-            self.rect
+                \nrect={:?}\
+                \nscrollable_overflow={:?}",
+            self.rect, self.scrollable_overflow
         ));
 
         for child in &self.children {
@@ -163,14 +169,10 @@ impl BoxFragment {
         margin: Sides<Length>,
         block_margins_collapsed_with_children: CollapsedBlockMargins,
     ) -> BoxFragment {
-        // FIXME(mrobinson, bug 25564): We should be using the containing block
-        // here to properly convert scrollable overflow to physical geometry.
-        let scrollable_overflow = children.iter().fold(
-            content_rect
-                .inflate(&border)
-                .to_physical(style.writing_mode, &PhysicalRect::zero()),
-            |acc, child| acc.union(&child.scrollable_overflow()),
-        );
+        let scrollable_overflow_from_children =
+            children.iter().fold(PhysicalRect::zero(), |acc, child| {
+                acc.union(&child.scrollable_overflow())
+            });
         BoxFragment {
             tag,
             style,
@@ -180,10 +182,28 @@ impl BoxFragment {
             border,
             margin,
             block_margins_collapsed_with_children,
-            scrollable_overflow,
+            scrollable_overflow_from_children,
         }
     }
 
+    pub fn scrollable_overflow(&self) -> PhysicalRect<Length> {
+        // FIXME(mrobinson, bug 25564): We should be using the containing block
+        // here to properly convert scrollable overflow to physical geometry.
+        let physical_padding_rect = self
+            .padding_rect()
+            .to_physical(self.style.writing_mode, &PhysicalRect::zero());
+
+        let content_origin = self
+            .content_rect
+            .start_corner
+            .to_physical(self.style.writing_mode);
+        physical_padding_rect.union(
+            &self
+                .scrollable_overflow_from_children
+                .translate(content_origin.to_vector()),
+        )
+    }
+
     pub fn padding_rect(&self) -> Rect<Length> {
         self.content_rect.inflate(&self.padding)
     }
@@ -197,10 +217,17 @@ impl BoxFragment {
             "Box\
                 \ncontent={:?}\
                 \npadding rect={:?}\
-                \nborder rect={:?}",
+                \nborder rect={:?}\
+                \nscrollable_overflow={:?}\
+                \noverflow={:?} / {:?}\
+                \nstyle={:p}",
             self.content_rect,
             self.padding_rect(),
-            self.border_rect()
+            self.border_rect(),
+            self.scrollable_overflow(),
+            self.style.get_box().overflow_x,
+            self.style.get_box().overflow_y,
+            self.style,
         ));
 
         for child in &self.children {
@@ -208,6 +235,41 @@ impl BoxFragment {
         }
         tree.end_level();
     }
+
+    pub fn scrollable_overflow_for_parent(
+        &self,
+        containing_block: &PhysicalRect<Length>,
+    ) -> PhysicalRect<Length> {
+        let mut overflow = self
+            .border_rect()
+            .to_physical(self.style.writing_mode, containing_block);
+
+        if self.style.get_box().overflow_y != ComputedOverflow::Visible &&
+            self.style.get_box().overflow_x != ComputedOverflow::Visible
+        {
+            return overflow;
+        }
+
+        // https://www.w3.org/TR/css-overflow-3/#scrollable
+        // Only include the scrollable overflow of a child box if it has overflow: visible.
+        let scrollable_overflow = self.scrollable_overflow();
+        let bottom_right = PhysicalPoint::new(
+            overflow.max_x().max(scrollable_overflow.max_x()),
+            overflow.max_y().max(scrollable_overflow.max_y()),
+        );
+
+        if self.style.get_box().overflow_y == ComputedOverflow::Visible {
+            overflow.origin.y = overflow.origin.y.min(scrollable_overflow.origin.y);
+            overflow.size.height = bottom_right.y - overflow.origin.y;
+        }
+
+        if self.style.get_box().overflow_x == ComputedOverflow::Visible {
+            overflow.origin.x = overflow.origin.x.min(scrollable_overflow.origin.x);
+            overflow.size.width = bottom_right.x - overflow.origin.x;
+        }
+
+        overflow
+    }
 }
 
 impl TextFragment {
diff --git a/components/style/properties/longhands/box.mako.rs b/components/style/properties/longhands/box.mako.rs
index f5f09f32e6e..fba2fac66dc 100644
--- a/components/style/properties/longhands/box.mako.rs
+++ b/components/style/properties/longhands/box.mako.rs
@@ -131,7 +131,6 @@ ${helpers.single_keyword(
         "Overflow",
         "computed::Overflow::Visible",
         engines="gecko servo-2013 servo-2020",
-        servo_2020_pref="layout.2020.unimplemented",
         logical_group="overflow",
         logical=logical,
         animation_value_type="discrete",
diff --git a/components/style/properties/shorthands/box.mako.rs b/components/style/properties/shorthands/box.mako.rs
index 351b8cec606..c5fe60834ed 100644
--- a/components/style/properties/shorthands/box.mako.rs
+++ b/components/style/properties/shorthands/box.mako.rs
@@ -9,7 +9,7 @@ ${helpers.two_properties_shorthand(
     "overflow-x",
     "overflow-y",
     "specified::Overflow::parse",
-    engines="gecko servo-2013",
+    engines="gecko servo-2013 servo-2020",
     flags="SHORTHAND_IN_GETCS",
     needs_context=False,
     spec="https://drafts.csswg.org/css-overflow/#propdef-overflow",
diff --git a/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-repeat/background-repeat-repeat-x.xht.ini b/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-repeat/background-repeat-repeat-x.xht.ini
deleted file mode 100644
index 717b8f77595..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-repeat/background-repeat-repeat-x.xht.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[background-repeat-repeat-x.xht]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-repeat/background-repeat-repeat-y.xht.ini b/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-repeat/background-repeat-repeat-y.xht.ini
deleted file mode 100644
index 252cadf070d..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-repeat/background-repeat-repeat-y.xht.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[background-repeat-repeat-y.xht]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-size/background-size-contain.xht.ini b/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-size/background-size-contain.xht.ini
deleted file mode 100644
index 9576c2c23bb..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-size/background-size-contain.xht.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[background-size-contain.xht]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-size/background-size-cover.xht.ini b/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-size/background-size-cover.xht.ini
deleted file mode 100644
index c72a601887c..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-size/background-size-cover.xht.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[background-size-cover.xht]
-  expected: FAIL
diff --git a/tests/wpt/mozilla/meta-layout-2020/css/acid2_ref.html.ini b/tests/wpt/mozilla/meta-layout-2020/css/acid2_ref.html.ini
deleted file mode 100644
index acbcb878252..00000000000
--- a/tests/wpt/mozilla/meta-layout-2020/css/acid2_ref.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[acid2_ref.html]
-  expected: FAIL
diff --git a/tests/wpt/mozilla/meta-layout-2020/css/border_radius_clip_a.html.ini b/tests/wpt/mozilla/meta-layout-2020/css/border_radius_clip_a.html.ini
deleted file mode 100644
index 833b04a6a88..00000000000
--- a/tests/wpt/mozilla/meta-layout-2020/css/border_radius_clip_a.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[border_radius_clip_a.html]
-  expected: FAIL
diff --git a/tests/wpt/mozilla/meta-layout-2020/css/css-position-3/position-sticky-bottom.html.ini b/tests/wpt/mozilla/meta-layout-2020/css/css-position-3/position-sticky-bottom.html.ini
deleted file mode 100644
index bbcf4b45799..00000000000
--- a/tests/wpt/mozilla/meta-layout-2020/css/css-position-3/position-sticky-bottom.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[position-sticky-bottom.html]
-  expected: FAIL
diff --git a/tests/wpt/mozilla/meta-layout-2020/css/css-position-3/position-sticky-top.html.ini b/tests/wpt/mozilla/meta-layout-2020/css/css-position-3/position-sticky-top.html.ini
deleted file mode 100644
index 62f8d7a2409..00000000000
--- a/tests/wpt/mozilla/meta-layout-2020/css/css-position-3/position-sticky-top.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[position-sticky-top.html]
-  expected: FAIL
diff --git a/tests/wpt/mozilla/meta-layout-2020/css/overflow_auto.html.ini b/tests/wpt/mozilla/meta-layout-2020/css/overflow_auto.html.ini
deleted file mode 100644
index 7db72e1707c..00000000000
--- a/tests/wpt/mozilla/meta-layout-2020/css/overflow_auto.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[overflow_auto.html]
-  expected: FAIL
diff --git a/tests/wpt/mozilla/meta-layout-2020/css/overflow_position_abs_simple_a.html.ini b/tests/wpt/mozilla/meta-layout-2020/css/overflow_position_abs_simple_a.html.ini
deleted file mode 100644
index 799983ed073..00000000000
--- a/tests/wpt/mozilla/meta-layout-2020/css/overflow_position_abs_simple_a.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[overflow_position_abs_simple_a.html]
-  expected: FAIL
diff --git a/tests/wpt/mozilla/meta-layout-2020/css/overflow_scroll.html.ini b/tests/wpt/mozilla/meta-layout-2020/css/overflow_scroll.html.ini
deleted file mode 100644
index 8744f4c28bd..00000000000
--- a/tests/wpt/mozilla/meta-layout-2020/css/overflow_scroll.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[overflow_scroll.html]
-  expected: FAIL
diff --git a/tests/wpt/mozilla/meta-layout-2020/css/overflow_simple_a.html.ini b/tests/wpt/mozilla/meta-layout-2020/css/overflow_simple_a.html.ini
deleted file mode 100644
index 354afc282c1..00000000000
--- a/tests/wpt/mozilla/meta-layout-2020/css/overflow_simple_a.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[overflow_simple_a.html]
-  expected: FAIL
diff --git a/tests/wpt/mozilla/meta-layout-2020/css/overflow_xy_a.html.ini b/tests/wpt/mozilla/meta-layout-2020/css/overflow_xy_a.html.ini
deleted file mode 100644
index 99413c09f58..00000000000
--- a/tests/wpt/mozilla/meta-layout-2020/css/overflow_xy_a.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[overflow_xy_a.html]
-  expected: FAIL
diff --git a/tests/wpt/mozilla/meta-layout-2020/css/text_overflow_ellipsis.html.ini b/tests/wpt/mozilla/meta-layout-2020/css/text_overflow_ellipsis.html.ini
deleted file mode 100644
index c5aa371e273..00000000000
--- a/tests/wpt/mozilla/meta-layout-2020/css/text_overflow_ellipsis.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[text_overflow_ellipsis.html]
-  expected: FAIL
diff --git a/tests/wpt/mozilla/meta-layout-2020/css/text_overflow_string.html.ini b/tests/wpt/mozilla/meta-layout-2020/css/text_overflow_string.html.ini
deleted file mode 100644
index 9baeea13322..00000000000
--- a/tests/wpt/mozilla/meta-layout-2020/css/text_overflow_string.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[text_overflow_string.html]
-  expected: FAIL