Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 979 insertions, 0 deletions

diff --git a/servo/components/style/style_adjuster.rs b/servo/components/style/style_adjuster.rs
new file mode 100644
index 0000000000..da86b2169f
--- /dev/null
+++ b/servo/components/style/style_adjuster.rs
@@ -0,0 +1,979 @@
+/* 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/. */
+
+//! A struct to encapsulate all the style fixups and flags propagations
+//! a computed style needs in order for it to adhere to the CSS spec.
+
+use crate::computed_value_flags::ComputedValueFlags;
+use crate::dom::TElement;
+use crate::properties::longhands::contain::computed_value::T as Contain;
+use crate::properties::longhands::container_type::computed_value::T as ContainerType;
+use crate::properties::longhands::content_visibility::computed_value::T as ContentVisibility;
+use crate::properties::longhands::display::computed_value::T as Display;
+use crate::properties::longhands::float::computed_value::T as Float;
+use crate::properties::longhands::overflow_x::computed_value::T as Overflow;
+use crate::properties::longhands::position::computed_value::T as Position;
+use crate::properties::{self, ComputedValues, StyleBuilder};
+
+/// A struct that implements all the adjustment methods.
+///
+/// NOTE(emilio): If new adjustments are introduced that depend on reset
+/// properties of the parent, you may need tweaking the
+/// `ChildCascadeRequirement` code in `matching.rs`.
+///
+/// NOTE(emilio): Also, if new adjustments are introduced that break the
+/// following invariant:
+///
+///   Given same tag name, namespace, rules and parent style, two elements would
+///   end up with exactly the same style.
+///
+/// Then you need to adjust the lookup_by_rules conditions in the sharing cache.
+pub struct StyleAdjuster<'a, 'b: 'a> {
+    style: &'a mut StyleBuilder<'b>,
+}
+
+#[cfg(feature = "gecko")]
+fn is_topmost_svg_svg_element<E>(e: E) -> bool
+where
+    E: TElement,
+{
+    debug_assert!(e.is_svg_element());
+    if e.local_name() != &*atom!("svg") {
+        return false;
+    }
+
+    let parent = match e.traversal_parent() {
+        Some(n) => n,
+        None => return true,
+    };
+
+    if !parent.is_svg_element() {
+        return true;
+    }
+
+    parent.local_name() == &*atom!("foreignObject")
+}
+
+// https://drafts.csswg.org/css-display/#unbox
+#[cfg(feature = "gecko")]
+fn is_effective_display_none_for_display_contents<E>(element: E) -> bool
+where
+    E: TElement,
+{
+    use crate::Atom;
+
+    const SPECIAL_HTML_ELEMENTS: [Atom; 16] = [
+        atom!("br"),
+        atom!("wbr"),
+        atom!("meter"),
+        atom!("progress"),
+        atom!("canvas"),
+        atom!("embed"),
+        atom!("object"),
+        atom!("audio"),
+        atom!("iframe"),
+        atom!("img"),
+        atom!("video"),
+        atom!("frame"),
+        atom!("frameset"),
+        atom!("input"),
+        atom!("textarea"),
+        atom!("select"),
+    ];
+
+    // https://drafts.csswg.org/css-display/#unbox-svg
+    //
+    // There's a note about "Unknown elements", but there's not a good way to
+    // know what that means, or to get that information from here, and no other
+    // UA implements this either.
+    const SPECIAL_SVG_ELEMENTS: [Atom; 6] = [
+        atom!("svg"),
+        atom!("a"),
+        atom!("g"),
+        atom!("use"),
+        atom!("tspan"),
+        atom!("textPath"),
+    ];
+
+    // https://drafts.csswg.org/css-display/#unbox-html
+    if element.is_html_element() {
+        let local_name = element.local_name();
+        return SPECIAL_HTML_ELEMENTS
+            .iter()
+            .any(|name| &**name == local_name);
+    }
+
+    // https://drafts.csswg.org/css-display/#unbox-svg
+    if element.is_svg_element() {
+        if is_topmost_svg_svg_element(element) {
+            return true;
+        }
+        let local_name = element.local_name();
+        return !SPECIAL_SVG_ELEMENTS
+            .iter()
+            .any(|name| &**name == local_name);
+    }
+
+    // https://drafts.csswg.org/css-display/#unbox-mathml
+    //
+    // We always treat XUL as display: none. We don't use display:
+    // contents in XUL anyway, so should be fine to be consistent with
+    // MathML unless there's a use case for it.
+    if element.is_mathml_element() || element.is_xul_element() {
+        return true;
+    }
+
+    false
+}
+
+impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
+    /// Trivially constructs a new StyleAdjuster.
+    #[inline]
+    pub fn new(style: &'a mut StyleBuilder<'b>) -> Self {
+        StyleAdjuster { style }
+    }
+
+    /// <https://fullscreen.spec.whatwg.org/#new-stacking-layer>
+    ///
+    ///    Any position value other than 'absolute' and 'fixed' are
+    ///    computed to 'absolute' if the element is in a top layer.
+    ///
+    fn adjust_for_top_layer(&mut self) {
+        if !self.style.in_top_layer() {
+            return;
+        }
+        if !self.style.is_absolutely_positioned() {
+            self.style.mutate_box().set_position(Position::Absolute);
+        }
+        if self.style.get_box().clone_display().is_contents() {
+            self.style.mutate_box().set_display(Display::Block);
+        }
+    }
+
+    /// -webkit-box with line-clamp and vertical orientation gets turned into
+    /// flow-root at computed-value time.
+    ///
+    /// This makes the element not be a flex container, with all that it
+    /// implies, but it should be safe. It matches blink, see
+    /// https://bugzilla.mozilla.org/show_bug.cgi?id=1786147#c10
+    fn adjust_for_webkit_line_clamp(&mut self) {
+        use crate::properties::longhands::_moz_box_orient::computed_value::T as BoxOrient;
+        use crate::values::specified::box_::{DisplayInside, DisplayOutside};
+        let box_style = self.style.get_box();
+        if box_style.clone__webkit_line_clamp().is_none() {
+            return;
+        }
+        let disp = box_style.clone_display();
+        if disp.inside() != DisplayInside::WebkitBox {
+            return;
+        }
+        if self.style.get_xul().clone__moz_box_orient() != BoxOrient::Vertical {
+            return;
+        }
+        let new_display = if disp.outside() == DisplayOutside::Block {
+            Display::FlowRoot
+        } else {
+            debug_assert_eq!(disp.outside(), DisplayOutside::Inline);
+            Display::InlineBlock
+        };
+        self.style
+            .mutate_box()
+            .set_adjusted_display(new_display, false);
+    }
+
+    /// CSS 2.1 section 9.7:
+    ///
+    ///    If 'position' has the value 'absolute' or 'fixed', [...] the computed
+    ///    value of 'float' is 'none'.
+    ///
+    fn adjust_for_position(&mut self) {
+        if self.style.is_absolutely_positioned() && self.style.is_floating() {
+            self.style.mutate_box().set_float(Float::None);
+        }
+    }
+
+    /// Whether we should skip any item-based display property blockification on
+    /// this element.
+    fn skip_item_display_fixup<E>(&self, element: Option<E>) -> bool
+    where
+        E: TElement,
+    {
+        if let Some(pseudo) = self.style.pseudo {
+            return pseudo.skip_item_display_fixup();
+        }
+
+        element.map_or(false, |e| e.skip_item_display_fixup())
+    }
+
+    /// Apply the blockification rules based on the table in CSS 2.2 section 9.7.
+    /// <https://drafts.csswg.org/css2/visuren.html#dis-pos-flo>
+    /// A ::marker pseudo-element with 'list-style-position:outside' needs to
+    /// have its 'display' blockified, unless the ::marker is for an inline
+    /// list-item (for which 'list-style-position:outside' behaves as 'inside').
+    /// https://drafts.csswg.org/css-lists-3/#list-style-position-property
+    fn blockify_if_necessary<E>(&mut self, layout_parent_style: &ComputedValues, element: Option<E>)
+    where
+        E: TElement,
+    {
+        let mut blockify = false;
+        macro_rules! blockify_if {
+            ($if_what:expr) => {
+                if !blockify {
+                    blockify = $if_what;
+                }
+            };
+        }
+
+        blockify_if!(self.style.is_root_element);
+        if !self.skip_item_display_fixup(element) {
+            let parent_display = layout_parent_style.get_box().clone_display();
+            blockify_if!(parent_display.is_item_container());
+        }
+
+        let is_item_or_root = blockify;
+
+        blockify_if!(self.style.is_floating());
+        blockify_if!(self.style.is_absolutely_positioned());
+
+        if !blockify {
+            return;
+        }
+
+        let display = self.style.get_box().clone_display();
+        let blockified_display = display.equivalent_block_display(self.style.is_root_element);
+        if display != blockified_display {
+            self.style
+                .mutate_box()
+                .set_adjusted_display(blockified_display, is_item_or_root);
+        }
+    }
+
+    /// Compute a few common flags for both text and element's style.
+    fn set_bits(&mut self) {
+        let box_style = self.style.get_box();
+        let display = box_style.clone_display();
+
+        if !display.is_contents() {
+            if !self
+                .style
+                .get_text()
+                .clone_text_decoration_line()
+                .is_empty()
+            {
+                self.style
+                    .add_flags(ComputedValueFlags::HAS_TEXT_DECORATION_LINES);
+            }
+
+            if self.style.get_effects().clone_opacity() == 0. {
+                self.style
+                    .add_flags(ComputedValueFlags::IS_IN_OPACITY_ZERO_SUBTREE);
+            }
+        }
+
+        if self.style.is_pseudo_element() {
+            self.style
+                .add_flags(ComputedValueFlags::IS_IN_PSEUDO_ELEMENT_SUBTREE);
+        }
+
+        if self.style.is_root_element {
+            self.style
+                .add_flags(ComputedValueFlags::IS_ROOT_ELEMENT_STYLE);
+        }
+
+        if box_style
+            .clone_effective_containment()
+            .contains(Contain::STYLE)
+        {
+            self.style
+                .add_flags(ComputedValueFlags::SELF_OR_ANCESTOR_HAS_CONTAIN_STYLE);
+        }
+
+        if box_style.clone_container_type().is_size_container_type() {
+            self.style
+                .add_flags(ComputedValueFlags::SELF_OR_ANCESTOR_HAS_SIZE_CONTAINER_TYPE);
+        }
+
+        #[cfg(feature = "servo-layout-2013")]
+        {
+            if self.style.get_parent_column().is_multicol() {
+                self.style.add_flags(ComputedValueFlags::CAN_BE_FRAGMENTED);
+            }
+        }
+    }
+
+    /// Adjust the style for text style.
+    ///
+    /// The adjustments here are a subset of the adjustments generally, because
+    /// text only inherits properties.
+    ///
+    /// Note that this, for Gecko, comes through Servo_ComputedValues_Inherit.
+    #[cfg(feature = "gecko")]
+    pub fn adjust_for_text(&mut self) {
+        debug_assert!(!self.style.is_root_element);
+        self.adjust_for_text_combine_upright();
+        self.adjust_for_text_in_ruby();
+        self.set_bits();
+    }
+
+    /// Change writing mode of the text frame for text-combine-upright.
+    ///
+    /// It is safe to look at our own style because we are looking at inherited
+    /// properties, and text is just plain inheritance.
+    ///
+    /// TODO(emilio): we should (Gecko too) revise these adjustments in presence
+    /// of display: contents.
+    ///
+    /// FIXME(emilio): How does this play with logical properties? Doesn't
+    /// mutating writing-mode change the potential physical sides chosen?
+    #[cfg(feature = "gecko")]
+    fn adjust_for_text_combine_upright(&mut self) {
+        use crate::computed_values::text_combine_upright::T as TextCombineUpright;
+        use crate::computed_values::writing_mode::T as WritingMode;
+        use crate::logical_geometry;
+
+        let writing_mode = self.style.get_inherited_box().clone_writing_mode();
+        let text_combine_upright = self.style.get_inherited_text().clone_text_combine_upright();
+
+        if matches!(
+            writing_mode,
+            WritingMode::VerticalRl | WritingMode::VerticalLr
+        ) && text_combine_upright == TextCombineUpright::All
+        {
+            self.style.add_flags(ComputedValueFlags::IS_TEXT_COMBINED);
+            self.style
+                .mutate_inherited_box()
+                .set_writing_mode(WritingMode::HorizontalTb);
+            self.style.writing_mode =
+                logical_geometry::WritingMode::new(self.style.get_inherited_box());
+        }
+    }
+
+    /// Unconditionally propagates the line break suppression flag to text, and
+    /// additionally it applies it if it is in any ruby box.
+    ///
+    /// This is necessary because its parent may not itself have the flag set
+    /// (e.g. ruby or ruby containers), thus we may not inherit the flag from
+    /// them.
+    #[cfg(feature = "gecko")]
+    fn adjust_for_text_in_ruby(&mut self) {
+        let parent_display = self.style.get_parent_box().clone_display();
+        if parent_display.is_ruby_type() ||
+            self.style
+                .get_parent_flags()
+                .contains(ComputedValueFlags::SHOULD_SUPPRESS_LINEBREAK)
+        {
+            self.style
+                .add_flags(ComputedValueFlags::SHOULD_SUPPRESS_LINEBREAK);
+        }
+    }
+
+    /// <https://drafts.csswg.org/css-writing-modes-3/#block-flow:>
+    ///
+    ///    If a box has a different writing-mode value than its containing
+    ///    block:
+    ///
+    ///        - If the box has a specified display of inline, its display
+    ///          computes to inline-block. [CSS21]
+    ///
+    /// This matches the adjustment that Gecko does, not exactly following
+    /// the spec. See also:
+    ///
+    /// <https://lists.w3.org/Archives/Public/www-style/2017Mar/0045.html>
+    /// <https://github.com/servo/servo/issues/15754>
+    fn adjust_for_writing_mode(&mut self, layout_parent_style: &ComputedValues) {
+        let our_writing_mode = self.style.get_inherited_box().clone_writing_mode();
+        let parent_writing_mode = layout_parent_style.get_inherited_box().clone_writing_mode();
+
+        if our_writing_mode != parent_writing_mode &&
+            self.style.get_box().clone_display() == Display::Inline
+        {
+            // TODO(emilio): Figure out if we can just set the adjusted display
+            // on Gecko too and unify this code path.
+            if cfg!(feature = "servo") {
+                self.style
+                    .mutate_box()
+                    .set_adjusted_display(Display::InlineBlock, false);
+            } else {
+                self.style.mutate_box().set_display(Display::InlineBlock);
+            }
+        }
+    }
+
+    /// This implements an out-of-date spec. The new spec moves the handling of
+    /// this to layout, which Gecko implements but Servo doesn't.
+    ///
+    /// See https://github.com/servo/servo/issues/15229
+    #[cfg(feature = "servo")]
+    fn adjust_for_alignment(&mut self, layout_parent_style: &ComputedValues) {
+        use crate::computed_values::align_items::T as AlignItems;
+        use crate::computed_values::align_self::T as AlignSelf;
+
+        if self.style.get_position().clone_align_self() == AlignSelf::Auto &&
+            !self.style.is_absolutely_positioned()
+        {
+            let self_align = match layout_parent_style.get_position().clone_align_items() {
+                AlignItems::Stretch => AlignSelf::Stretch,
+                AlignItems::Baseline => AlignSelf::Baseline,
+                AlignItems::FlexStart => AlignSelf::FlexStart,
+                AlignItems::FlexEnd => AlignSelf::FlexEnd,
+                AlignItems::Center => AlignSelf::Center,
+            };
+            self.style.mutate_position().set_align_self(self_align);
+        }
+    }
+
+    /// The initial value of border-*-width may be changed at computed value
+    /// time.
+    ///
+    /// This is moved to properties.rs for convenience.
+    fn adjust_for_border_width(&mut self) {
+        properties::adjust_border_width(self.style);
+    }
+
+    /// column-rule-style: none causes a computed column-rule-width of zero
+    /// at computed value time.
+    fn adjust_for_column_rule_width(&mut self) {
+        let column_style = self.style.get_column();
+        if !column_style.clone_column_rule_style().none_or_hidden() {
+            return;
+        }
+        if !column_style.column_rule_has_nonzero_width() {
+            return;
+        }
+        self.style
+            .mutate_column()
+            .set_column_rule_width(crate::Zero::zero());
+    }
+
+    /// outline-style: none causes a computed outline-width of zero at computed
+    /// value time.
+    fn adjust_for_outline_width(&mut self) {
+        let outline = self.style.get_outline();
+        if !outline.clone_outline_style().none_or_hidden() {
+            return;
+        }
+        if !outline.outline_has_nonzero_width() {
+            return;
+        }
+        self.style
+            .mutate_outline()
+            .set_outline_width(crate::Zero::zero());
+    }
+
+    /// CSS overflow-x and overflow-y require some fixup as well in some cases.
+    /// https://drafts.csswg.org/css-overflow-3/#overflow-properties
+    /// "Computed value: as specified, except with `visible`/`clip` computing to
+    /// `auto`/`hidden` (respectively) if one of `overflow-x` or `overflow-y` is
+    /// neither `visible` nor `clip`."
+    fn adjust_for_overflow(&mut self) {
+        let overflow_x = self.style.get_box().clone_overflow_x();
+        let overflow_y = self.style.get_box().clone_overflow_y();
+        if overflow_x == overflow_y {
+            return; // optimization for the common case
+        }
+
+        if overflow_x.is_scrollable() != overflow_y.is_scrollable() {
+            let box_style = self.style.mutate_box();
+            box_style.set_overflow_x(overflow_x.to_scrollable());
+            box_style.set_overflow_y(overflow_y.to_scrollable());
+        }
+    }
+
+    fn adjust_for_contain(&mut self) {
+        let box_style = self.style.get_box();
+        debug_assert_eq!(
+            box_style.clone_contain(),
+            box_style.clone_effective_containment()
+        );
+        let container_type = box_style.clone_container_type();
+        let content_visibility = box_style.clone_content_visibility();
+        if container_type == ContainerType::Normal &&
+            content_visibility == ContentVisibility::Visible
+        {
+            return;
+        }
+        let old_contain = box_style.clone_contain();
+        let mut new_contain = old_contain;
+        match content_visibility {
+            ContentVisibility::Visible => {},
+            // `content-visibility:auto` also applies size containment when content
+            // is not relevant (and therefore skipped). This is checked in
+            // nsIFrame::GetContainSizeAxes.
+            ContentVisibility::Auto => {
+                new_contain.insert(Contain::LAYOUT | Contain::PAINT | Contain::STYLE)
+            },
+            ContentVisibility::Hidden => new_contain
+                .insert(Contain::LAYOUT | Contain::PAINT | Contain::SIZE | Contain::STYLE),
+        }
+        match container_type {
+            ContainerType::Normal => {},
+            // https://drafts.csswg.org/css-contain-3/#valdef-container-type-inline-size:
+            //     Applies layout containment, style containment, and inline-size
+            //     containment to the principal box.
+            ContainerType::InlineSize => {
+                new_contain.insert(Contain::LAYOUT | Contain::STYLE | Contain::INLINE_SIZE)
+            },
+            // https://drafts.csswg.org/css-contain-3/#valdef-container-type-size:
+            //     Applies layout containment, style containment, and size
+            //     containment to the principal box.
+            ContainerType::Size => {
+                new_contain.insert(Contain::LAYOUT | Contain::STYLE | Contain::SIZE)
+            },
+        }
+        if new_contain == old_contain {
+            return;
+        }
+        self.style
+            .mutate_box()
+            .set_effective_containment(new_contain);
+    }
+
+    /// Handles the relevant sections in:
+    ///
+    /// https://drafts.csswg.org/css-display/#unbox-html
+    ///
+    /// And forbidding display: contents in pseudo-elements, at least for now.
+    #[cfg(feature = "gecko")]
+    fn adjust_for_prohibited_display_contents<E>(&mut self, element: Option<E>)
+    where
+        E: TElement,
+    {
+        if self.style.get_box().clone_display() != Display::Contents {
+            return;
+        }
+
+        // FIXME(emilio): ::before and ::after should support display: contents,
+        // see bug 1418138.
+        if self.style.pseudo.is_some() {
+            self.style.mutate_box().set_display(Display::Inline);
+            return;
+        }
+
+        let element = match element {
+            Some(e) => e,
+            None => return,
+        };
+
+        if is_effective_display_none_for_display_contents(element) {
+            self.style.mutate_box().set_display(Display::None);
+        }
+    }
+
+    /// <textarea>'s editor root needs to inherit the overflow value from its
+    /// parent, but we need to make sure it's still scrollable.
+    #[cfg(feature = "gecko")]
+    fn adjust_for_text_control_editing_root(&mut self) {
+        use crate::selector_parser::PseudoElement;
+
+        if self.style.pseudo != Some(&PseudoElement::MozTextControlEditingRoot) {
+            return;
+        }
+
+        let box_style = self.style.get_box();
+        let overflow_x = box_style.clone_overflow_x();
+        let overflow_y = box_style.clone_overflow_y();
+
+        // If at least one is scrollable we'll adjust the other one in
+        // adjust_for_overflow if needed.
+        if overflow_x.is_scrollable() || overflow_y.is_scrollable() {
+            return;
+        }
+
+        let box_style = self.style.mutate_box();
+        box_style.set_overflow_x(Overflow::Auto);
+        box_style.set_overflow_y(Overflow::Auto);
+    }
+
+    /// If a <fieldset> has grid/flex display type, we need to inherit
+    /// this type into its ::-moz-fieldset-content anonymous box.
+    ///
+    /// NOTE(emilio): We don't need to handle the display change for this case
+    /// in matching.rs because anonymous box restyling works separately to the
+    /// normal cascading process.
+    #[cfg(feature = "gecko")]
+    fn adjust_for_fieldset_content(&mut self, layout_parent_style: &ComputedValues) {
+        use crate::selector_parser::PseudoElement;
+
+        if self.style.pseudo != Some(&PseudoElement::FieldsetContent) {
+            return;
+        }
+
+        debug_assert_eq!(self.style.get_box().clone_display(), Display::Block);
+        // TODO We actually want style from parent rather than layout
+        // parent, so that this fixup doesn't happen incorrectly when
+        // when <fieldset> has "display: contents".
+        let parent_display = layout_parent_style.get_box().clone_display();
+        let new_display = match parent_display {
+            Display::Flex | Display::InlineFlex => Some(Display::Flex),
+            Display::Grid | Display::InlineGrid => Some(Display::Grid),
+            _ => None,
+        };
+        if let Some(new_display) = new_display {
+            self.style.mutate_box().set_display(new_display);
+        }
+    }
+
+    /// -moz-center, -moz-left and -moz-right are used for HTML's alignment.
+    ///
+    /// This is covering the <div align="right"><table>...</table></div> case.
+    ///
+    /// In this case, we don't want to inherit the text alignment into the
+    /// table.
+    #[cfg(feature = "gecko")]
+    fn adjust_for_table_text_align(&mut self) {
+        use crate::properties::longhands::text_align::computed_value::T as TextAlign;
+        if self.style.get_box().clone_display() != Display::Table {
+            return;
+        }
+
+        match self.style.get_inherited_text().clone_text_align() {
+            TextAlign::MozLeft | TextAlign::MozCenter | TextAlign::MozRight => {},
+            _ => return,
+        }
+
+        self.style
+            .mutate_inherited_text()
+            .set_text_align(TextAlign::Start)
+    }
+
+    /// Computes the used text decoration for Servo.
+    ///
+    /// FIXME(emilio): This is a layout tree concept, should move away from
+    /// style, since otherwise we're going to have the same subtle bugs WebKit
+    /// and Blink have with this very same thing.
+    #[cfg(feature = "servo")]
+    fn adjust_for_text_decorations_in_effect(&mut self) {
+        use crate::values::computed::text::TextDecorationsInEffect;
+
+        let decorations_in_effect = TextDecorationsInEffect::from_style(&self.style);
+        if self.style.get_inherited_text().text_decorations_in_effect != decorations_in_effect {
+            self.style
+                .mutate_inherited_text()
+                .text_decorations_in_effect = decorations_in_effect;
+        }
+    }
+
+    #[cfg(feature = "gecko")]
+    fn should_suppress_linebreak<E>(
+        &self,
+        layout_parent_style: &ComputedValues,
+        element: Option<E>,
+    ) -> bool
+    where
+        E: TElement,
+    {
+        // Line break suppression should only be propagated to in-flow children.
+        if self.style.is_floating() || self.style.is_absolutely_positioned() {
+            return false;
+        }
+        let parent_display = layout_parent_style.get_box().clone_display();
+        if layout_parent_style
+            .flags
+            .contains(ComputedValueFlags::SHOULD_SUPPRESS_LINEBREAK)
+        {
+            // Line break suppression is propagated to any children of
+            // line participants.
+            if parent_display.is_line_participant() {
+                return true;
+            }
+        }
+        match self.style.get_box().clone_display() {
+            // Ruby base and text are always non-breakable.
+            Display::RubyBase | Display::RubyText => true,
+            // Ruby base container and text container are breakable.
+            // Non-HTML elements may not form ruby base / text container because
+            // they may not respect ruby-internal display values, so we can't
+            // make them escaped from line break suppression.
+            // Note that, when certain HTML tags, e.g. form controls, have ruby
+            // level container display type, they could also escape from the
+            // line break suppression flag while they shouldn't. However, it is
+            // generally fine as far as they can't break the line inside them.
+            Display::RubyBaseContainer | Display::RubyTextContainer
+                if element.map_or(true, |e| e.is_html_element()) =>
+            {
+                false
+            },
+            // Anything else is non-breakable if and only if its layout parent
+            // has a ruby display type, because any of the ruby boxes can be
+            // anonymous.
+            _ => parent_display.is_ruby_type(),
+        }
+    }
+
+    /// Do ruby-related style adjustments, which include:
+    /// * propagate the line break suppression flag,
+    /// * inlinify block descendants,
+    /// * suppress border and padding for ruby level containers,
+    /// * correct unicode-bidi.
+    #[cfg(feature = "gecko")]
+    fn adjust_for_ruby<E>(&mut self, layout_parent_style: &ComputedValues, element: Option<E>)
+    where
+        E: TElement,
+    {
+        use crate::properties::longhands::unicode_bidi::computed_value::T as UnicodeBidi;
+
+        let self_display = self.style.get_box().clone_display();
+        // Check whether line break should be suppressed for this element.
+        if self.should_suppress_linebreak(layout_parent_style, element) {
+            self.style
+                .add_flags(ComputedValueFlags::SHOULD_SUPPRESS_LINEBREAK);
+            // Inlinify the display type if allowed.
+            if !self.skip_item_display_fixup(element) {
+                let inline_display = self_display.inlinify();
+                if self_display != inline_display {
+                    self.style
+                        .mutate_box()
+                        .set_adjusted_display(inline_display, false);
+                }
+            }
+        }
+        // Suppress border and padding for ruby level containers.
+        // This is actually not part of the spec. It is currently unspecified
+        // how border and padding should be handled for ruby level container,
+        // and suppressing them here make it easier for layout to handle.
+        if self_display.is_ruby_level_container() {
+            self.style.reset_border_struct();
+            self.style.reset_padding_struct();
+        }
+
+        // Force bidi isolation on all internal ruby boxes and ruby container
+        // per spec https://drafts.csswg.org/css-ruby-1/#bidi
+        if self_display.is_ruby_type() {
+            let new_value = match self.style.get_text().clone_unicode_bidi() {
+                UnicodeBidi::Normal | UnicodeBidi::Embed => Some(UnicodeBidi::Isolate),
+                UnicodeBidi::BidiOverride => Some(UnicodeBidi::IsolateOverride),
+                _ => None,
+            };
+            if let Some(new_value) = new_value {
+                self.style.mutate_text().set_unicode_bidi(new_value);
+            }
+        }
+    }
+
+    /// Computes the RELEVANT_LINK_VISITED flag based on the parent style and on
+    /// whether we're a relevant link.
+    ///
+    /// NOTE(emilio): We don't do this for text styles, which is... dubious, but
+    /// Gecko doesn't seem to do it either. It's extremely easy to do if needed
+    /// though.
+    ///
+    /// FIXME(emilio): This isn't technically a style adjustment thingie, could
+    /// it move somewhere else?
+    fn adjust_for_visited<E>(&mut self, element: Option<E>)
+    where
+        E: TElement,
+    {
+        if !self.style.has_visited_style() {
+            return;
+        }
+
+        let is_link_element = self.style.pseudo.is_none() && element.map_or(false, |e| e.is_link());
+
+        if !is_link_element {
+            return;
+        }
+
+        if element.unwrap().is_visited_link() {
+            self.style
+                .add_flags(ComputedValueFlags::IS_RELEVANT_LINK_VISITED);
+        } else {
+            // Need to remove to handle unvisited link inside visited.
+            self.style
+                .remove_flags(ComputedValueFlags::IS_RELEVANT_LINK_VISITED);
+        }
+    }
+
+    /// Resolves "justify-items: legacy" based on the inherited style if needed
+    /// to comply with:
+    ///
+    /// <https://drafts.csswg.org/css-align/#valdef-justify-items-legacy>
+    #[cfg(feature = "gecko")]
+    fn adjust_for_justify_items(&mut self) {
+        use crate::values::specified::align;
+        let justify_items = self.style.get_position().clone_justify_items();
+        if justify_items.specified.0 != align::AlignFlags::LEGACY {
+            return;
+        }
+
+        let parent_justify_items = self.style.get_parent_position().clone_justify_items();
+
+        if !parent_justify_items
+            .computed
+            .0
+            .contains(align::AlignFlags::LEGACY)
+        {
+            return;
+        }
+
+        if parent_justify_items.computed == justify_items.computed {
+            return;
+        }
+
+        self.style
+            .mutate_position()
+            .set_computed_justify_items(parent_justify_items.computed);
+    }
+
+    /// If '-webkit-appearance' is 'menulist' on a <select> element then
+    /// the computed value of 'line-height' is 'normal'.
+    ///
+    /// https://github.com/w3c/csswg-drafts/issues/3257
+    #[cfg(feature = "gecko")]
+    fn adjust_for_appearance<E>(&mut self, element: Option<E>)
+    where
+        E: TElement,
+    {
+        use crate::properties::longhands::appearance::computed_value::T as Appearance;
+        use crate::properties::longhands::line_height::computed_value::T as LineHeight;
+
+        let box_ = self.style.get_box();
+        let appearance = match box_.clone_appearance() {
+            Appearance::Auto => box_.clone__moz_default_appearance(),
+            a => a,
+        };
+
+        if appearance == Appearance::Menulist {
+            if self.style.get_inherited_text().clone_line_height() == LineHeight::normal() {
+                return;
+            }
+            if self.style.pseudo.is_some() {
+                return;
+            }
+            let is_html_select_element = element.map_or(false, |e| {
+                e.is_html_element() && e.local_name() == &*atom!("select")
+            });
+            if !is_html_select_element {
+                return;
+            }
+            self.style
+                .mutate_inherited_text()
+                .set_line_height(LineHeight::normal());
+        }
+    }
+
+    /// A legacy ::marker (i.e. no 'content') without an author-specified 'font-family'
+    /// and 'list-style-type:disc|circle|square|disclosure-closed|disclosure-open'
+    /// is assigned 'font-family:-moz-bullet-font'. (This is for <ul><li> etc.)
+    /// We don't want synthesized italic/bold for this font, so turn that off too.
+    /// Likewise for 'letter/word-spacing' -- unless the author specified it then reset
+    /// them to their initial value because traditionally we never added such spacing
+    /// between a legacy bullet and the list item's content, so we keep that behavior
+    /// for web-compat reasons.
+    /// We intentionally don't check 'list-style-image' below since we want it to use
+    /// the same font as its fallback ('list-style-type') in case it fails to load.
+    #[cfg(feature = "gecko")]
+    fn adjust_for_marker_pseudo(&mut self) {
+        use crate::values::computed::counters::Content;
+        use crate::values::computed::font::{FontFamily, FontSynthesis};
+        use crate::values::computed::text::{LetterSpacing, WordSpacing};
+
+        let is_legacy_marker = self.style.pseudo.map_or(false, |p| p.is_marker()) &&
+            self.style.get_list().clone_list_style_type().is_bullet() &&
+            self.style.get_counters().clone_content() == Content::Normal;
+        if !is_legacy_marker {
+            return;
+        }
+        let flags = self.style.flags.get();
+        if !flags.contains(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_FONT_FAMILY) {
+            self.style
+                .mutate_font()
+                .set_font_family(FontFamily::moz_bullet().clone());
+
+            // FIXME(mats): We can remove this if support for font-synthesis is added to @font-face rules.
+            // Then we can add it to the @font-face rule in html.css instead.
+            // https://github.com/w3c/csswg-drafts/issues/6081
+            if !flags.contains(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_FONT_SYNTHESIS_WEIGHT) {
+                self.style
+                    .mutate_font()
+                    .set_font_synthesis_weight(FontSynthesis::None);
+            }
+            if !flags.contains(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_FONT_SYNTHESIS_STYLE) {
+                self.style
+                    .mutate_font()
+                    .set_font_synthesis_style(FontSynthesis::None);
+            }
+        }
+        if !flags.contains(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_LETTER_SPACING) {
+            self.style
+                .mutate_inherited_text()
+                .set_letter_spacing(LetterSpacing::normal());
+        }
+        if !flags.contains(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_WORD_SPACING) {
+            self.style
+                .mutate_inherited_text()
+                .set_word_spacing(WordSpacing::normal());
+        }
+    }
+
+    /// Adjusts the style to account for various fixups that don't fit naturally
+    /// into the cascade.
+    ///
+    /// When comparing to Gecko, this is similar to the work done by
+    /// `ComputedStyle::ApplyStyleFixups`, plus some parts of
+    /// `nsStyleSet::GetContext`.
+    pub fn adjust<E>(&mut self, layout_parent_style: &ComputedValues, element: Option<E>)
+    where
+        E: TElement,
+    {
+        if cfg!(debug_assertions) {
+            if element.map_or(false, |e| e.is_pseudo_element()) {
+                // It'd be nice to assert `self.style.pseudo == Some(&pseudo)`,
+                // but we do resolve ::-moz-list pseudos on ::before / ::after
+                // content, sigh.
+                debug_assert!(self.style.pseudo.is_some(), "Someone really messed up");
+            }
+        }
+        // FIXME(emilio): The apply_declarations callsite in Servo's
+        // animation, and the font stuff for Gecko
+        // (Stylist::compute_for_declarations) should pass an element to
+        // cascade(), then we can make this assertion hold everywhere.
+        // debug_assert!(
+        //     element.is_some() || self.style.pseudo.is_some(),
+        //     "Should always have an element around for non-pseudo styles"
+        // );
+
+        self.adjust_for_visited(element);
+        #[cfg(feature = "gecko")]
+        {
+            self.adjust_for_prohibited_display_contents(element);
+            self.adjust_for_fieldset_content(layout_parent_style);
+            // NOTE: It's important that this happens before
+            // adjust_for_overflow.
+            self.adjust_for_text_control_editing_root();
+        }
+        self.adjust_for_top_layer();
+        self.blockify_if_necessary(layout_parent_style, element);
+        self.adjust_for_webkit_line_clamp();
+        self.adjust_for_position();
+        self.adjust_for_overflow();
+        self.adjust_for_contain();
+        #[cfg(feature = "gecko")]
+        {
+            self.adjust_for_table_text_align();
+            self.adjust_for_justify_items();
+        }
+        #[cfg(feature = "servo")]
+        {
+            self.adjust_for_alignment(layout_parent_style);
+        }
+        self.adjust_for_border_width();
+        self.adjust_for_column_rule_width();
+        self.adjust_for_outline_width();
+        self.adjust_for_writing_mode(layout_parent_style);
+        #[cfg(feature = "gecko")]
+        {
+            self.adjust_for_ruby(layout_parent_style, element);
+        }
+        #[cfg(feature = "servo")]
+        {
+            self.adjust_for_text_decorations_in_effect();
+        }
+        #[cfg(feature = "gecko")]
+        {
+            self.adjust_for_appearance(element);
+            self.adjust_for_marker_pseudo();
+        }
+        self.set_bits();
+    }
+}