servo/components/layout/dom_traversal.rs
Simon Wülker b100a98e1d
Fully support <input type=color> (#36992)
This change adds a shadow-tree widget for `<input type=color>` elements.
It also involves some changes to the way layout interacts with the DOM,
because currently all `input` and `textarea` elements are rendered as
plain text and their descendants are ignored. This obviously doesn't
work for `<input type={color, date, range, etc}>`.


![image](https://github.com/user-attachments/assets/4f16c3b0-1f79-4095-b19d-1153f5853dd5)

<details><summary>HTML used for the screenshot above</summary>

```html
<input type=color>
```

</details>



Testing: I doubt that this affects WPT tests, because the appearance and
behaviour of the widget is almost entirely unspecified.

---------

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>
2025-05-15 17:30:38 +00:00

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/* 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::borrow::Cow;
use std::iter::FusedIterator;
use fonts::ByteIndex;
use html5ever::{LocalName, local_name};
use range::Range;
use script::layout_dom::ServoLayoutNode;
use script_layout_interface::wrapper_traits::{
LayoutNode, ThreadSafeLayoutElement, ThreadSafeLayoutNode,
};
use script_layout_interface::{LayoutElementType, LayoutNodeType};
use selectors::Element as SelectorsElement;
use servo_arc::Arc as ServoArc;
use style::dom::{NodeInfo, TElement, TNode, TShadowRoot};
use style::properties::ComputedValues;
use style::selector_parser::PseudoElement;
use style::values::generics::counters::{Content, ContentItem};
use style::values::specified::Quotes;
use crate::context::LayoutContext;
use crate::dom::{BoxSlot, LayoutBox, NodeExt};
use crate::flow::inline::SharedInlineStyles;
use crate::fragment_tree::{BaseFragmentInfo, FragmentFlags, Tag};
use crate::quotes::quotes_for_lang;
use crate::replaced::ReplacedContents;
use crate::style_ext::{Display, DisplayGeneratingBox, DisplayInside, DisplayOutside};
/// A data structure used to pass and store related layout information together to
/// avoid having to repeat the same arguments in argument lists.
#[derive(Clone)]
pub(crate) struct NodeAndStyleInfo<'dom> {
pub node: ServoLayoutNode<'dom>,
pub pseudo_element_type: Option<PseudoElement>,
pub style: ServoArc<ComputedValues>,
}
impl<'dom> NodeAndStyleInfo<'dom> {
fn new_with_pseudo(
node: ServoLayoutNode<'dom>,
pseudo_element_type: PseudoElement,
style: ServoArc<ComputedValues>,
) -> Self {
Self {
node,
pseudo_element_type: Some(pseudo_element_type),
style,
}
}
pub(crate) fn new(node: ServoLayoutNode<'dom>, style: ServoArc<ComputedValues>) -> Self {
Self {
node,
pseudo_element_type: None,
style,
}
}
pub(crate) fn is_single_line_text_input(&self) -> bool {
self.node.type_id() == LayoutNodeType::Element(LayoutElementType::HTMLInputElement)
}
pub(crate) fn pseudo(
&self,
context: &LayoutContext,
pseudo_element_type: PseudoElement,
) -> Option<Self> {
let style = self
.node
.to_threadsafe()
.as_element()?
.with_pseudo(pseudo_element_type)?
.style(context.shared_context());
Some(NodeAndStyleInfo {
node: self.node,
pseudo_element_type: Some(pseudo_element_type),
style,
})
}
pub(crate) fn get_selected_style(&self) -> ServoArc<ComputedValues> {
self.node.to_threadsafe().selected_style()
}
pub(crate) fn get_selection_range(&self) -> Option<Range<ByteIndex>> {
self.node.to_threadsafe().selection()
}
}
impl<'dom> From<&NodeAndStyleInfo<'dom>> for BaseFragmentInfo {
fn from(info: &NodeAndStyleInfo<'dom>) -> Self {
let node = info.node;
let pseudo = info.pseudo_element_type;
let threadsafe_node = node.to_threadsafe();
let mut flags = FragmentFlags::empty();
// Anonymous boxes should not have a tag, because they should not take part in hit testing.
//
// TODO(mrobinson): It seems that anonymous boxes should take part in hit testing in some
// cases, but currently this means that the order of hit test results isn't as expected for
// some WPT tests. This needs more investigation.
if matches!(
pseudo,
Some(PseudoElement::ServoAnonymousBox) |
Some(PseudoElement::ServoAnonymousTable) |
Some(PseudoElement::ServoAnonymousTableCell) |
Some(PseudoElement::ServoAnonymousTableRow)
) {
return Self::anonymous();
}
if let Some(element) = threadsafe_node.as_html_element() {
if element.is_body_element_of_html_element_root() {
flags.insert(FragmentFlags::IS_BODY_ELEMENT_OF_HTML_ELEMENT_ROOT);
}
match element.get_local_name() {
&local_name!("br") => {
flags.insert(FragmentFlags::IS_BR_ELEMENT);
},
&local_name!("table") | &local_name!("th") | &local_name!("td") => {
flags.insert(FragmentFlags::IS_TABLE_TH_OR_TD_ELEMENT);
},
_ => {},
}
if matches!(
element.type_id(),
Some(LayoutNodeType::Element(
LayoutElementType::HTMLInputElement | LayoutElementType::HTMLTextAreaElement
))
) {
flags.insert(FragmentFlags::IS_TEXT_CONTROL);
}
if ThreadSafeLayoutElement::is_root(&element) {
flags.insert(FragmentFlags::IS_ROOT_ELEMENT);
}
};
Self {
tag: Some(Tag::new_pseudo(threadsafe_node.opaque(), pseudo)),
flags,
}
}
}
#[derive(Debug)]
pub(super) enum Contents {
/// Any kind of content that is not replaced, including the contents of pseudo-elements.
NonReplaced(NonReplacedContents),
/// Example: an `<img src=…>` element.
/// <https://drafts.csswg.org/css2/conform.html#replaced-element>
Replaced(ReplacedContents),
}
#[derive(Debug)]
#[allow(clippy::enum_variant_names)]
pub(super) enum NonReplacedContents {
/// Refers to a DOM subtree, plus `::before` and `::after` pseudo-elements.
OfElement,
/// Content of a `::before` or `::after` pseudo-element that is being generated.
/// <https://drafts.csswg.org/css2/generate.html#content>
OfPseudoElement(Vec<PseudoElementContentItem>),
/// Workaround for input and textarea element until we properly implement `display-inside`.
OfTextControl,
}
#[derive(Debug)]
pub(super) enum PseudoElementContentItem {
Text(String),
Replaced(ReplacedContents),
}
pub(super) trait TraversalHandler<'dom> {
fn handle_text(&mut self, info: &NodeAndStyleInfo<'dom>, text: Cow<'dom, str>);
/// Or pseudo-element
fn handle_element(
&mut self,
info: &NodeAndStyleInfo<'dom>,
display: DisplayGeneratingBox,
contents: Contents,
box_slot: BoxSlot<'dom>,
);
/// Notify the handler that we are about to recurse into a `display: contents` element.
fn enter_display_contents(&mut self, _: SharedInlineStyles) {}
/// Notify the handler that we have finished a `display: contents` element.
fn leave_display_contents(&mut self) {}
}
fn traverse_children_of<'dom>(
parent_element: ServoLayoutNode<'dom>,
context: &LayoutContext,
handler: &mut impl TraversalHandler<'dom>,
) {
traverse_eager_pseudo_element(PseudoElement::Before, parent_element, context, handler);
if parent_element.is_text_input() {
let info = NodeAndStyleInfo::new(
parent_element,
parent_element.style(context.shared_context()),
);
let node_text_content = parent_element.to_threadsafe().node_text_content();
if node_text_content.is_empty() {
// The addition of zero-width space here forces the text input to have an inline formatting
// context that might otherwise be trimmed if there's no text. This is important to ensure
// that the input element is at least as tall as the line gap of the caret:
// <https://drafts.csswg.org/css-ui/#element-with-default-preferred-size>.
//
// This is also used to ensure that the caret will still be rendered when the input is empty.
// TODO: Is there a less hacky way to do this?
handler.handle_text(&info, "\u{200B}".into());
} else {
handler.handle_text(&info, node_text_content);
}
} else {
for child in iter_child_nodes(parent_element) {
if child.is_text_node() {
let info = NodeAndStyleInfo::new(child, child.style(context.shared_context()));
handler.handle_text(&info, child.to_threadsafe().node_text_content());
} else if child.is_element() {
traverse_element(child, context, handler);
}
}
}
traverse_eager_pseudo_element(PseudoElement::After, parent_element, context, handler);
}
fn traverse_element<'dom>(
element: ServoLayoutNode<'dom>,
context: &LayoutContext,
handler: &mut impl TraversalHandler<'dom>,
) {
// Clear any existing pseudo-element box slot, because markers are not handled like
// `::before`` and `::after`. They are processed during box tree creation.
element.unset_pseudo_element_box(PseudoElement::Marker);
let replaced = ReplacedContents::for_element(element, context);
let style = element.style(context.shared_context());
match Display::from(style.get_box().display) {
Display::None => element.unset_all_boxes(),
Display::Contents => {
if replaced.is_some() {
// `display: content` on a replaced element computes to `display: none`
// <https://drafts.csswg.org/css-display-3/#valdef-display-contents>
element.unset_all_boxes()
} else {
let shared_inline_styles: SharedInlineStyles =
(&NodeAndStyleInfo::new(element, style)).into();
element
.element_box_slot()
.set(LayoutBox::DisplayContents(shared_inline_styles.clone()));
handler.enter_display_contents(shared_inline_styles);
traverse_children_of(element, context, handler);
handler.leave_display_contents();
}
},
Display::GeneratingBox(display) => {
let contents = if let Some(replaced) = replaced {
Contents::Replaced(replaced)
} else if matches!(
element.type_id(),
LayoutNodeType::Element(
LayoutElementType::HTMLInputElement | LayoutElementType::HTMLTextAreaElement
)
) {
NonReplacedContents::OfTextControl.into()
} else {
NonReplacedContents::OfElement.into()
};
let display = display.used_value_for_contents(&contents);
let box_slot = element.element_box_slot();
let info = NodeAndStyleInfo::new(element, style);
handler.handle_element(&info, display, contents, box_slot);
},
}
}
fn traverse_eager_pseudo_element<'dom>(
pseudo_element_type: PseudoElement,
node: ServoLayoutNode<'dom>,
context: &LayoutContext,
handler: &mut impl TraversalHandler<'dom>,
) {
assert!(pseudo_element_type.is_eager());
// First clear any old contents from the node.
node.unset_pseudo_element_box(pseudo_element_type);
let Some(element) = node.to_threadsafe().as_element() else {
return;
};
let Some(pseudo_element) = element.with_pseudo(pseudo_element_type) else {
return;
};
let style = pseudo_element.style(context.shared_context());
if style.ineffective_content_property() {
return;
}
let info = NodeAndStyleInfo::new_with_pseudo(node, pseudo_element_type, style);
match Display::from(info.style.get_box().display) {
Display::None => {},
Display::Contents => {
let items = generate_pseudo_element_content(&info.style, node, context);
let box_slot = node.pseudo_element_box_slot(pseudo_element_type);
let shared_inline_styles: SharedInlineStyles = (&info).into();
box_slot.set(LayoutBox::DisplayContents(shared_inline_styles.clone()));
handler.enter_display_contents(shared_inline_styles);
traverse_pseudo_element_contents(&info, context, handler, items);
handler.leave_display_contents();
},
Display::GeneratingBox(display) => {
let items = generate_pseudo_element_content(&info.style, node, context);
let box_slot = node.pseudo_element_box_slot(pseudo_element_type);
let contents = NonReplacedContents::OfPseudoElement(items).into();
handler.handle_element(&info, display, contents, box_slot);
},
}
}
fn traverse_pseudo_element_contents<'dom>(
info: &NodeAndStyleInfo<'dom>,
context: &LayoutContext,
handler: &mut impl TraversalHandler<'dom>,
items: Vec<PseudoElementContentItem>,
) {
let mut anonymous_info = None;
for item in items {
match item {
PseudoElementContentItem::Text(text) => handler.handle_text(info, text.into()),
PseudoElementContentItem::Replaced(contents) => {
let anonymous_info = anonymous_info.get_or_insert_with(|| {
info.pseudo(context, PseudoElement::ServoAnonymousBox)
.unwrap_or_else(|| info.clone())
});
let display_inline = DisplayGeneratingBox::OutsideInside {
outside: DisplayOutside::Inline,
inside: DisplayInside::Flow {
is_list_item: false,
},
};
// `display` is not inherited, so we get the initial value
debug_assert!(
Display::from(anonymous_info.style.get_box().display) ==
Display::GeneratingBox(display_inline)
);
handler.handle_element(
anonymous_info,
display_inline,
Contents::Replaced(contents),
// We dont keep pointers to boxes generated by contents of pseudo-elements
BoxSlot::dummy(),
)
},
}
}
}
impl Contents {
/// Returns true iff the `try_from` impl below would return `Err(_)`
pub fn is_replaced(&self) -> bool {
matches!(self, Contents::Replaced(_))
}
}
impl From<NonReplacedContents> for Contents {
fn from(non_replaced_contents: NonReplacedContents) -> Self {
Contents::NonReplaced(non_replaced_contents)
}
}
impl std::convert::TryFrom<Contents> for NonReplacedContents {
type Error = &'static str;
fn try_from(contents: Contents) -> Result<Self, Self::Error> {
match contents {
Contents::NonReplaced(non_replaced_contents) => Ok(non_replaced_contents),
Contents::Replaced(_) => {
Err("Tried to covnert a `Contents::Replaced` into `NonReplacedContent`")
},
}
}
}
impl NonReplacedContents {
pub(crate) fn traverse<'dom>(
self,
context: &LayoutContext,
info: &NodeAndStyleInfo<'dom>,
handler: &mut impl TraversalHandler<'dom>,
) {
match self {
NonReplacedContents::OfElement | NonReplacedContents::OfTextControl => {
traverse_children_of(info.node, context, handler)
},
NonReplacedContents::OfPseudoElement(items) => {
traverse_pseudo_element_contents(info, context, handler, items)
},
}
}
}
fn get_quote_from_pair<I, S>(item: &ContentItem<I>, opening: &S, closing: &S) -> String
where
S: ToString + ?Sized,
{
match item {
ContentItem::OpenQuote => opening.to_string(),
ContentItem::CloseQuote => closing.to_string(),
_ => unreachable!("Got an unexpected ContentItem type when processing quotes."),
}
}
/// <https://www.w3.org/TR/CSS2/generate.html#propdef-content>
fn generate_pseudo_element_content(
pseudo_element_style: &ComputedValues,
element: ServoLayoutNode<'_>,
context: &LayoutContext,
) -> Vec<PseudoElementContentItem> {
match &pseudo_element_style.get_counters().content {
Content::Items(items) => {
let mut vec = vec![];
for item in items.items.iter() {
match item {
ContentItem::String(s) => {
vec.push(PseudoElementContentItem::Text(s.to_string()));
},
ContentItem::Attr(attr) => {
let element = element
.to_threadsafe()
.as_element()
.expect("Expected an element");
// From
// <https://html.spec.whatwg.org/multipage/#case-sensitivity-of-the-css-%27attr%28%29%27-function>
//
// > CSS Values and Units leaves the case-sensitivity of attribute names for
// > the purpose of the `attr()` function to be defined by the host language.
// > [[CSSVALUES]].
// >
// > When comparing the attribute name part of a CSS `attr()`function to the
// > names of namespace-less attributes on HTML elements in HTML documents,
// > the name part of the CSS `attr()` function must first be converted to
// > ASCII lowercase. The same function when compared to other attributes must
// > be compared according to its original case. In both cases, to match the
// > values must be identical to each other (and therefore the comparison is
// > case sensitive).
let attr_name = match element.is_html_element_in_html_document() {
true => &*attr.attribute.to_ascii_lowercase(),
false => &*attr.attribute,
};
let attr_val =
element.get_attr(&attr.namespace_url, &LocalName::from(attr_name));
vec.push(PseudoElementContentItem::Text(
attr_val.map_or("".to_string(), |s| s.to_string()),
));
},
ContentItem::Image(image) => {
if let Some(replaced_content) =
ReplacedContents::from_image(element, context, image)
{
vec.push(PseudoElementContentItem::Replaced(replaced_content));
}
},
ContentItem::OpenQuote | ContentItem::CloseQuote => {
// TODO(xiaochengh): calculate quote depth
let maybe_quote = match &pseudo_element_style.get_list().quotes {
Quotes::QuoteList(quote_list) => {
quote_list.0.first().map(|quote_pair| {
get_quote_from_pair(
item,
&*quote_pair.opening,
&*quote_pair.closing,
)
})
},
Quotes::Auto => {
let lang = &pseudo_element_style.get_font()._x_lang;
let quotes = quotes_for_lang(lang.0.as_ref(), 0);
Some(get_quote_from_pair(item, &quotes.opening, &quotes.closing))
},
};
if let Some(quote) = maybe_quote {
vec.push(PseudoElementContentItem::Text(quote));
}
},
ContentItem::Counter(_, _) |
ContentItem::Counters(_, _, _) |
ContentItem::NoOpenQuote |
ContentItem::NoCloseQuote => {
// TODO: Add support for counters and quotes.
},
}
}
vec
},
Content::Normal | Content::None => unreachable!(),
}
}
pub enum ChildNodeIterator<'dom> {
/// Iterating over the children of a node
Node(Option<ServoLayoutNode<'dom>>),
/// Iterating over the assigned nodes of a `HTMLSlotElement`
Slottables(<Vec<ServoLayoutNode<'dom>> as IntoIterator>::IntoIter),
}
pub(crate) fn iter_child_nodes(parent: ServoLayoutNode<'_>) -> ChildNodeIterator<'_> {
if let Some(element) = parent.as_element() {
if let Some(shadow) = element.shadow_root() {
return iter_child_nodes(shadow.as_node());
};
let slotted_nodes = element.slotted_nodes();
if !slotted_nodes.is_empty() {
#[allow(clippy::unnecessary_to_owned)] // Clippy is wrong.
return ChildNodeIterator::Slottables(slotted_nodes.to_owned().into_iter());
}
}
let first = parent.first_child();
ChildNodeIterator::Node(first)
}
impl<'dom> Iterator for ChildNodeIterator<'dom> {
type Item = ServoLayoutNode<'dom>;
fn next(&mut self) -> Option<Self::Item> {
match self {
Self::Node(node) => {
let old = *node;
*node = old?.next_sibling();
old
},
Self::Slottables(slots) => slots.next(),
}
}
}
impl FusedIterator for ChildNodeIterator<'_> {}