servo/components/script/dom/document/documentorshadowroot.rs

/* This Source Code Form is subject to the terms of the Mozilla Public
 * 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::collections::HashSet;
use std::ffi::c_void;
use std::fmt;

use embedder_traits::UntrustedNodeAddress;
use js::rust::HandleValue;
use layout_api::ElementsFromPointFlags;
use rustc_hash::FxBuildHasher;
use script_bindings::codegen::GenericBindings::DocumentBinding::DocumentMethods;
use script_bindings::codegen::GenericBindings::WindowBinding::WindowMethods;
use script_bindings::error::{Error, ErrorResult};
use script_bindings::script_runtime::{CanGc, JSContext};
use servo_arc::Arc;
use servo_config::pref;
use style::media_queries::MediaList;
use style::shared_lock::{SharedRwLock as StyleSharedRwLock, SharedRwLockReadGuard};
use style::stylesheets::scope_rule::ImplicitScopeRoot;
use style::stylesheets::{Stylesheet, StylesheetContents};
use stylo_atoms::Atom;
use webrender_api::units::LayoutPoint;

use crate::dom::Document;
use crate::dom::bindings::cell::DomRefCell;
use crate::dom::bindings::codegen::Bindings::NodeBinding::GetRootNodeOptions;
use crate::dom::bindings::codegen::Bindings::NodeBinding::Node_Binding::NodeMethods;
use crate::dom::bindings::codegen::Bindings::ShadowRootBinding::ShadowRootMethods;
use crate::dom::bindings::conversions::{ConversionResult, SafeFromJSValConvertible};
use crate::dom::bindings::inheritance::Castable;
use crate::dom::bindings::num::Finite;
use crate::dom::bindings::root::{Dom, DomRoot};
use crate::dom::bindings::trace::HashMapTracedValues;
use crate::dom::css::stylesheetlist::StyleSheetListOwner;
use crate::dom::element::Element;
use crate::dom::node::{self, Node, VecPreOrderInsertionHelper};
use crate::dom::shadowroot::ShadowRoot;
use crate::dom::types::{CSSStyleSheet, EventTarget};
use crate::dom::window::Window;
use crate::stylesheet_set::StylesheetSetRef;

/// Stylesheet could be constructed by a CSSOM object CSSStylesheet or parsed
/// from HTML element such as `<style>` or `<link>`.
#[derive(Clone, JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
pub(crate) enum StylesheetSource {
    Element(Dom<Element>),
    Constructed(Dom<CSSStyleSheet>),
}

impl StylesheetSource {
    pub(crate) fn get_cssom_object(&self) -> Option<DomRoot<CSSStyleSheet>> {
        match self {
            StylesheetSource::Element(el) => el.upcast::<Node>().get_cssom_stylesheet(),
            StylesheetSource::Constructed(ss) => Some(ss.as_rooted()),
        }
    }

    pub(crate) fn is_a_valid_owner(&self) -> bool {
        match self {
            StylesheetSource::Element(el) => el.as_stylesheet_owner().is_some(),
            StylesheetSource::Constructed(ss) => ss.is_constructed(),
        }
    }

    pub(crate) fn is_constructed(&self) -> bool {
        matches!(self, StylesheetSource::Constructed(_))
    }
}

#[derive(Clone, JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
pub(crate) struct ServoStylesheetInDocument {
    #[ignore_malloc_size_of = "Stylo"]
    #[no_trace]
    pub(crate) sheet: Arc<Stylesheet>,
    /// The object that owns this stylesheet. For constructed stylesheet, it would be the
    /// CSSOM object itself, and for stylesheet generated by an element, it would be the
    /// html element. This is used to get the CSSOM Stylesheet within a DocumentOrShadowDOM.
    pub(crate) owner: StylesheetSource,
}

// This is necessary because this type is contained within a Stylo type which needs
// Stylo's version of MallocSizeOf.
impl stylo_malloc_size_of::MallocSizeOf for ServoStylesheetInDocument {
    fn size_of(&self, ops: &mut stylo_malloc_size_of::MallocSizeOfOps) -> usize {
        <ServoStylesheetInDocument as malloc_size_of::MallocSizeOf>::size_of(self, ops)
    }
}

impl fmt::Debug for ServoStylesheetInDocument {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        self.sheet.fmt(formatter)
    }
}

impl PartialEq for ServoStylesheetInDocument {
    fn eq(&self, other: &Self) -> bool {
        Arc::ptr_eq(&self.sheet, &other.sheet)
    }
}

impl ::style::stylesheets::StylesheetInDocument for ServoStylesheetInDocument {
    fn enabled(&self) -> bool {
        self.sheet.enabled()
    }

    fn media<'a>(&'a self, guard: &'a SharedRwLockReadGuard) -> Option<&'a MediaList> {
        self.sheet.media(guard)
    }

    fn contents<'a>(&'a self, guard: &'a SharedRwLockReadGuard) -> &'a StylesheetContents {
        self.sheet.contents(guard)
    }

    fn implicit_scope_root(&self) -> Option<ImplicitScopeRoot> {
        None
    }
}

// https://w3c.github.io/webcomponents/spec/shadow/#extensions-to-the-documentorshadowroot-mixin
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
#[derive(Clone, JSTraceable, MallocSizeOf)]
pub(crate) struct DocumentOrShadowRoot {
    window: Dom<Window>,
}

impl DocumentOrShadowRoot {
    pub(crate) fn new(window: &Window) -> Self {
        Self {
            window: Dom::from_ref(window),
        }
    }

    #[expect(unsafe_code)]
    // https://drafts.csswg.org/cssom-view/#dom-document-elementfrompoint
    pub(crate) fn element_from_point(
        &self,
        x: Finite<f64>,
        y: Finite<f64>,
        document_element: Option<DomRoot<Element>>,
        has_browsing_context: bool,
    ) -> Option<DomRoot<Element>> {
        let x = *x as f32;
        let y = *y as f32;
        let viewport = self.window.viewport_details().size;

        if !has_browsing_context {
            return None;
        }

        if x < 0.0 || y < 0.0 || x > viewport.width || y > viewport.height {
            return None;
        }

        let results = self
            .window
            .elements_from_point_query(LayoutPoint::new(x, y), ElementsFromPointFlags::empty());
        let Some(result) = results.first() else {
            return document_element;
        };

        // SAFETY: This is safe because `Self::query_elements_from_point` has ensured that
        // layout has run and any OpaqueNodes that no longer refer to real nodes are gone.
        let address = UntrustedNodeAddress(result.node.0 as *const c_void);
        let node = unsafe { node::from_untrusted_node_address(address) };
        DomRoot::downcast::<Element>(node.clone()).or_else(|| {
            let parent_node = node.GetParentNode()?;
            if let Some(shadow_root) = parent_node.downcast::<ShadowRoot>() {
                Some(shadow_root.Host())
            } else {
                node.GetParentElement()
            }
        })
    }

    #[expect(unsafe_code)]
    // https://drafts.csswg.org/cssom-view/#dom-document-elementsfrompoint
    pub(crate) fn elements_from_point(
        &self,
        x: Finite<f64>,
        y: Finite<f64>,
        document_element: Option<DomRoot<Element>>,
        has_browsing_context: bool,
    ) -> Vec<DomRoot<Element>> {
        let x = *x as f32;
        let y = *y as f32;
        let viewport = self.window.viewport_details().size;

        if !has_browsing_context {
            return vec![];
        }

        // Step 2
        if x < 0.0 || y < 0.0 || x > viewport.width || y > viewport.height {
            return vec![];
        }

        // Step 1 and Step 3
        let nodes = self
            .window
            .elements_from_point_query(LayoutPoint::new(x, y), ElementsFromPointFlags::FindAll);
        let mut elements: Vec<DomRoot<Element>> = nodes
            .iter()
            .flat_map(|result| {
                // SAFETY: This is safe because `Self::query_elements_from_point` has ensured that
                // layout has run and any OpaqueNodes that no longer refer to real nodes are gone.
                let address = UntrustedNodeAddress(result.node.0 as *const c_void);
                let node = unsafe { node::from_untrusted_node_address(address) };
                DomRoot::downcast::<Element>(node)
            })
            .collect();

        // Step 4
        if let Some(root_element) = document_element {
            if elements.last() != Some(&root_element) {
                elements.push(root_element);
            }
        }

        // Step 5
        elements
    }

    /// <https://html.spec.whatwg.org/multipage/#dom-documentorshadowroot-activeelement-dev>
    pub(crate) fn active_element(&self, this: &Node) -> Option<DomRoot<Element>> {
        // Step 1. Let candidate be this's node document's focused area's DOM anchor.
        //
        // Note: When `Document::focused_element` returns `None`, that means that the
        // `Document` / viewport itself is focused.
        let document = self.window.Document();
        let candidate = match document.focused_element() {
            Some(candidate) => DomRoot::upcast::<Node>(candidate),
            None => DomRoot::upcast::<Node>(document.clone()),
        };

        // Step 2. Set candidate to the result of retargeting candidate against this.
        //
        // Note: `retarget()` operates on `EventTarget`, but we can be assured that we are
        // only dealing with various kinds of `Node`s here.
        let candidate =
            DomRoot::downcast::<Node>(candidate.upcast::<EventTarget>().retarget(this.upcast()))?;

        // Step 3. If candidate's root is not this, then return null.
        if this != &*candidate.GetRootNode(&GetRootNodeOptions::empty()) {
            return None;
        }

        // Step 4. If candidate is not a Document object, then return candidate.
        if let Some(candidate) = DomRoot::downcast::<Element>(candidate.clone()) {
            return Some(candidate);
        }
        assert!(candidate.is::<Document>());

        // Step 5. If candidate has a body element, then return that body element.
        if let Some(body) = document.GetBody() {
            return Some(DomRoot::upcast(body));
        }

        // Step 6. If candidate's document element is non-null, then return that document element.
        if let Some(document_element) = document.GetDocumentElement() {
            return Some(document_element);
        }

        // Step 7. Return null.
        None
    }

    /// Remove a stylesheet owned by `owner` from the list of document sheets.
    #[cfg_attr(crown, expect(crown::unrooted_must_root))] // Owner needs to be rooted already necessarily.
    pub(crate) fn remove_stylesheet(
        owner: StylesheetSource,
        s: &Arc<Stylesheet>,
        mut stylesheets: StylesheetSetRef<ServoStylesheetInDocument>,
    ) {
        let guard = s.shared_lock.read();

        // FIXME(emilio): Would be nice to remove the clone, etc.
        stylesheets.remove_stylesheet(
            None,
            ServoStylesheetInDocument {
                sheet: s.clone(),
                owner,
            },
            &guard,
        );
    }

    /// Add a stylesheet owned by `owner` to the list of document sheets, in the
    /// correct tree position.
    #[cfg_attr(crown, expect(crown::unrooted_must_root))] // Owner needs to be rooted already necessarily.
    pub(crate) fn add_stylesheet(
        owner: StylesheetSource,
        mut stylesheets: StylesheetSetRef<ServoStylesheetInDocument>,
        sheet: Arc<Stylesheet>,
        insertion_point: Option<ServoStylesheetInDocument>,
        style_shared_lock: &StyleSharedRwLock,
    ) {
        debug_assert!(owner.is_a_valid_owner(), "Wat");

        if owner.is_constructed() && !pref!(dom_adoptedstylesheet_enabled) {
            return;
        }

        let sheet = ServoStylesheetInDocument { sheet, owner };

        let guard = style_shared_lock.read();

        match insertion_point {
            Some(ip) => {
                stylesheets.insert_stylesheet_before(None, sheet, ip, &guard);
            },
            None => {
                stylesheets.append_stylesheet(None, sheet, &guard);
            },
        }
    }

    /// Remove any existing association between the provided id/name and any elements in this document.
    pub(crate) fn unregister_named_element(
        &self,
        id_map: &DomRefCell<HashMapTracedValues<Atom, Vec<Dom<Element>>, FxBuildHasher>>,
        to_unregister: &Element,
        id: &Atom,
    ) {
        debug!(
            "Removing named element {:p}: {:p} id={}",
            self, to_unregister, id
        );
        let mut id_map = id_map.borrow_mut();
        let is_empty = match id_map.get_mut(id) {
            None => false,
            Some(elements) => {
                let position = elements
                    .iter()
                    .position(|element| &**element == to_unregister)
                    .expect("This element should be in registered.");
                elements.remove(position);
                elements.is_empty()
            },
        };
        if is_empty {
            id_map.remove(id);
        }
    }

    /// Associate an element present in this document with the provided id/name.
    pub(crate) fn register_named_element(
        &self,
        id_map: &DomRefCell<HashMapTracedValues<Atom, Vec<Dom<Element>>, FxBuildHasher>>,
        element: &Element,
        id: &Atom,
        root: DomRoot<Node>,
    ) {
        debug!("Adding named element {:p}: {:p} id={}", self, element, id);
        assert!(
            element.upcast::<Node>().is_in_a_document_tree() ||
                element.upcast::<Node>().is_in_a_shadow_tree()
        );
        assert!(!id.is_empty());
        let mut id_map = id_map.borrow_mut();
        let elements = id_map.entry(id.clone()).or_default();
        elements.insert_pre_order(element, &root);
    }

    /// Inner part of adopted stylesheet. We are setting it by, assuming it is a FrozenArray
    /// instead of an ObservableArray. Thus, it would have a completely different workflow
    /// compared to the spec. The workflow here is actually following Gecko's implementation
    /// of AdoptedStylesheet before the implementation of ObservableArray.
    ///
    /// The main purpose from this function is to set the `&mut adopted_stylesheet` to match
    /// `incoming_stylesheet` and update the corresponding Styleset in a Document or a ShadowRoot.
    /// In case of duplicates, the setter will respect the last duplicates.
    ///
    /// <https://drafts.csswg.org/cssom/#dom-documentorshadowroot-adoptedstylesheets>
    // TODO: Handle duplicated adoptedstylesheet correctly, Stylo is preventing duplicates inside a
    //       Stylesheet Set. But this is not ideal. https://bugzilla.mozilla.org/show_bug.cgi?id=1978755
    fn set_adopted_stylesheet(
        adopted_stylesheets: &mut Vec<Dom<CSSStyleSheet>>,
        incoming_stylesheets: &[Dom<CSSStyleSheet>],
        owner: &StyleSheetListOwner,
    ) -> ErrorResult {
        if !pref!(dom_adoptedstylesheet_enabled) {
            return Ok(());
        }

        let owner_doc = match owner {
            StyleSheetListOwner::Document(doc) => doc,
            StyleSheetListOwner::ShadowRoot(root) => root.owner_doc(),
        };

        for sheet in incoming_stylesheets.iter() {
            // > If value’s constructed flag is not set, or its constructor document is not equal
            // > to this DocumentOrShadowRoot’s node document, throw a "NotAllowedError" DOMException.
            if !sheet.constructor_document_matches(owner_doc) {
                return Err(Error::NotAllowed(None));
            }
        }

        // The set to check for the duplicates when removing the old stylesheets.
        let mut stylesheet_remove_set = HashSet::with_capacity(adopted_stylesheets.len());

        // Remove the old stylesheets from the StyleSet. This workflow is limited by utilities
        // Stylo StyleSet given to us.
        // TODO(stevennovaryo): we could optimize this by maintaining the longest common prefix
        //                      but we should consider the implementation of ObservableArray as well.
        for sheet_to_remove in adopted_stylesheets.iter() {
            // Check for duplicates, only proceed with the removal if the stylesheet is not removed yet.
            if stylesheet_remove_set.insert(sheet_to_remove) {
                owner.remove_stylesheet(
                    StylesheetSource::Constructed(sheet_to_remove.clone()),
                    &sheet_to_remove.style_stylesheet(),
                );
                sheet_to_remove.remove_adopter(owner);
            }
        }

        // The set to check for the duplicates when adding a new stylesheet.
        let mut stylesheet_add_set = HashSet::with_capacity(incoming_stylesheets.len());

        // Readd all stylesheet to the StyleSet. This workflow is limited by the utilities
        // Stylo StyleSet given to us.
        for sheet in incoming_stylesheets.iter() {
            // Check for duplicates.
            if !stylesheet_add_set.insert(sheet) {
                // The idea is that this case is rare, so we pay the price of removing the
                // old sheet from the styles and append it later rather than the other way
                // around.
                owner.remove_stylesheet(
                    StylesheetSource::Constructed(sheet.clone()),
                    &sheet.style_stylesheet(),
                );
            } else {
                sheet.add_adopter(owner.clone());
            }

            owner.append_constructed_stylesheet(sheet);
        }

        *adopted_stylesheets = incoming_stylesheets.to_vec();

        Ok(())
    }

    /// Set adoptedStylesheet given a js value by converting and passing the converted
    /// values to the inner [DocumentOrShadowRoot::set_adopted_stylesheet].
    pub(crate) fn set_adopted_stylesheet_from_jsval(
        context: JSContext,
        adopted_stylesheets: &mut Vec<Dom<CSSStyleSheet>>,
        incoming_value: HandleValue,
        owner: &StyleSheetListOwner,
        can_gc: CanGc,
    ) -> ErrorResult {
        let maybe_stylesheets =
            Vec::<DomRoot<CSSStyleSheet>>::safe_from_jsval(context, incoming_value, (), can_gc);

        match maybe_stylesheets {
            Ok(ConversionResult::Success(stylesheets)) => {
                rooted_vec!(let stylesheets <- stylesheets.iter().map(|s| s.as_traced()));

                DocumentOrShadowRoot::set_adopted_stylesheet(
                    adopted_stylesheets,
                    &stylesheets,
                    owner,
                )
            },
            Ok(ConversionResult::Failure(msg)) => Err(Error::Type(msg.into_owned())),
            Err(_) => Err(Error::Type(
                c"The provided value is not a sequence of 'CSSStylesheet'.".to_owned(),
            )),
        }
    }
}