Implement shadow dom slots (#35013)

* Implement slot-related algorithms

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

* Hook up slot elements to DOM creation logic

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

* Set a slot assignment mode for servo-internal shadow roots

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

* Assign slots when a slottable's slot attribute changes

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

* Properly compute slot name

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

* ./mach test-tidy

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

* Update <slot> name when name attribute changes

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

* Implement fast path for Node::assign_slottables_for_a_tree

assign_slottables_for_a_tree traverses all descendants of the node
and is potentially very expensive. If the node is not a shadow root
then assigning slottables to it won't have any effect, so we
take a fast path out.

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

* Move slottable data into ElementRareData

This shrinks all element descendants back to their
original size.

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

* Address review comments

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

* Update WPT expectations

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

---------

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

1 files changed, 21 insertions, 1 deletions

diff --git a/components/script/dom/text.rs b/components/script/dom/text.rs
index 2f0e1c66857..3f81f0be6e2 100644
--- a/components/script/dom/text.rs
+++ b/components/script/dom/text.rs
@@ -2,6 +2,8 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use std::cell::RefCell;
+
 use dom_struct::dom_struct;
 use js::rust::HandleObject;
 
@@ -12,10 +14,12 @@ use crate::dom::bindings::codegen::Bindings::TextBinding::TextMethods;
 use crate::dom::bindings::codegen::Bindings::WindowBinding::WindowMethods;
 use crate::dom::bindings::error::{Error, Fallible};
 use crate::dom::bindings::inheritance::Castable;
-use crate::dom::bindings::root::DomRoot;
+use crate::dom::bindings::root::{Dom, DomRoot};
 use crate::dom::bindings::str::DOMString;
 use crate::dom::characterdata::CharacterData;
 use crate::dom::document::Document;
+use crate::dom::globalscope::GlobalScope;
+use crate::dom::htmlslotelement::{HTMLSlotElement, Slottable, SlottableData};
 use crate::dom::node::Node;
 use crate::dom::window::Window;
 use crate::script_runtime::CanGc;
@@ -24,12 +28,14 @@ use crate::script_runtime::CanGc;
 #[dom_struct]
 pub(crate) struct Text {
     characterdata: CharacterData,
+    slottable_data: RefCell<SlottableData>,
 }
 
 impl Text {
     pub(crate) fn new_inherited(text: DOMString, document: &Document) -> Text {
         Text {
             characterdata: CharacterData::new_inherited(text, document),
+            slottable_data: Default::default(),
         }
     }
 
@@ -50,6 +56,10 @@ impl Text {
             can_gc,
         )
     }
+
+    pub(crate) fn slottable_data(&self) -> &RefCell<SlottableData> {
+        &self.slottable_data
+    }
 }
 
 impl TextMethods<crate::DomTypeHolder> for Text {
@@ -119,4 +129,14 @@ impl TextMethods<crate::DomTypeHolder> for Text {
         }
         DOMString::from(text)
     }
+
+    /// <https://dom.spec.whatwg.org/#dom-slotable-assignedslot>
+    fn GetAssignedSlot(&self) -> Option<DomRoot<HTMLSlotElement>> {
+        let cx = GlobalScope::get_cx();
+
+        // > The assignedSlot getter steps are to return the result of
+        // > find a slot given this and with the open flag set.
+        rooted!(in(*cx) let slottable = Slottable::Text(Dom::from_ref(self)));
+        slottable.find_a_slot(true)
+    }
 }