layout/

style_ext.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 app_units::Au;
use layout_api::AxesOverflow;
use malloc_size_of_derive::MallocSizeOf;
use style::Zero;
use style::color::AbsoluteColor;
use style::computed_values::direction::T as Direction;
use style::computed_values::isolation::T as ComputedIsolation;
use style::computed_values::mix_blend_mode::T as ComputedMixBlendMode;
use style::computed_values::position::T as ComputedPosition;
use style::computed_values::transform_style::T as ComputedTransformStyle;
use style::computed_values::unicode_bidi::T as UnicodeBidi;
use style::logical_geometry::{Direction as AxisDirection, PhysicalSide, WritingMode};
use style::properties::ComputedValues;
use style::properties::longhands::backface_visibility::computed_value::T as BackfaceVisiblity;
use style::properties::longhands::box_sizing::computed_value::T as BoxSizing;
use style::properties::longhands::column_span::computed_value::T as ColumnSpan;
use style::properties::style_structs::Border;
use style::servo::selector_parser::PseudoElement;
use style::values::CSSFloat;
use style::values::computed::basic_shape::ClipPath;
use style::values::computed::image::Image as ComputedImageLayer;
use style::values::computed::{
    BorderSideWidth, BorderStyle, Color, Inset, ItemPlacement, LengthPercentage, Margin,
    SelfAlignment,
};
use style::values::generics::box_::Perspective;
use style::values::generics::position::{GenericAspectRatio, PreferredRatio};
use style::values::generics::transform::{GenericRotate, GenericScale, GenericTranslate};
use style::values::specified::align::AlignFlags;
use style::values::specified::{Overflow, WillChangeBits, box_ as stylo};
use unicode_bidi::Level;
use webrender_api as wr;
use webrender_api::units::LayoutTransform;

use crate::dom_traversal::Contents;
use crate::fragment_tree::FragmentFlags;
use crate::geom::{
    AuOrAuto, LengthPercentageOrAuto, LogicalSides, LogicalSides1D, LogicalVec2, PhysicalSides,
    PhysicalSize,
};
use crate::sizing::{Size, Sizes};
use crate::table::TableLayoutStyle;
use crate::{ContainingBlock, IndefiniteContainingBlock};

#[derive(Clone, Copy, Eq, PartialEq)]
pub(crate) enum Display {
    None,
    Contents,
    GeneratingBox(DisplayGeneratingBox),
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub(crate) enum DisplayGeneratingBox {
    OutsideInside {
        outside: DisplayOutside,
        inside: DisplayInside,
    },
    /// <https://drafts.csswg.org/css-display-3/#layout-specific-display>
    LayoutInternal(DisplayLayoutInternal),
}
impl DisplayGeneratingBox {
    pub(crate) fn display_inside(&self) -> DisplayInside {
        match *self {
            DisplayGeneratingBox::OutsideInside { inside, .. } => inside,
            DisplayGeneratingBox::LayoutInternal(layout_internal) => {
                layout_internal.display_inside()
            },
        }
    }

    pub(crate) fn used_value_for_contents(&self, contents: &Contents) -> Self {
        // From <https://www.w3.org/TR/css-display-3/#layout-specific-display>:
        // > When the display property of a replaced element computes to one of
        // > the layout-internal values, it is handled as having a used value of
        // > inline.
        if matches!(self, Self::LayoutInternal(_)) && contents.is_replaced() {
            Self::OutsideInside {
                outside: DisplayOutside::Inline,
                inside: DisplayInside::Flow {
                    is_list_item: false,
                },
            }
        } else if matches!(contents, Contents::Widget(_)) {
            // If it's a widget, make sure the display-inside is flow-root.
            // <https://html.spec.whatwg.org/multipage/#form-controls>
            // TODO: Do we want flow-root, or just an independent formatting context?
            if let DisplayGeneratingBox::OutsideInside { outside, .. } = self {
                DisplayGeneratingBox::OutsideInside {
                    outside: *outside,
                    inside: DisplayInside::FlowRoot {
                        is_list_item: false,
                    },
                }
            } else {
                *self
            }
        } else {
            *self
        }
    }
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub(crate) enum DisplayOutside {
    Block,
    Inline,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub(crate) enum DisplayInside {
    // “list-items are limited to the Flow Layout display types”
    // <https://drafts.csswg.org/css-display/#list-items>
    Flow { is_list_item: bool },
    FlowRoot { is_list_item: bool },
    Flex,
    Grid,
    Table,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
#[expect(clippy::enum_variant_names)]
/// <https://drafts.csswg.org/css-display-3/#layout-specific-display>
pub(crate) enum DisplayLayoutInternal {
    TableCaption,
    TableCell,
    TableColumn,
    TableColumnGroup,
    TableFooterGroup,
    TableHeaderGroup,
    TableRow,
    TableRowGroup,
}

impl DisplayLayoutInternal {
    /// <https://drafts.csswg.org/css-display-3/#layout-specific-displa>
    pub(crate) fn display_inside(&self) -> DisplayInside {
        // When we add ruby, the display_inside of ruby must be Flow.
        // TODO: this should be unreachable for everything but
        // table cell and caption, once we have box tree fixups.
        DisplayInside::FlowRoot {
            is_list_item: false,
        }
    }
}

/// Percentages resolved but not `auto` margins
#[derive(Clone, Debug)]
pub(crate) struct PaddingBorderMargin {
    pub padding: LogicalSides<Au>,
    pub border: LogicalSides<Au>,
    pub margin: LogicalSides<AuOrAuto>,

    /// Pre-computed sums in each axis
    pub padding_border_sums: LogicalVec2<Au>,
}

impl PaddingBorderMargin {
    pub(crate) fn zero() -> Self {
        Self {
            padding: LogicalSides::zero(),
            border: LogicalSides::zero(),
            margin: LogicalSides::zero(),
            padding_border_sums: LogicalVec2::zero(),
        }
    }

    pub(crate) fn sums_auto_is_zero(
        &self,
        ignore_block_margins: LogicalSides1D<bool>,
    ) -> LogicalVec2<Au> {
        let margin = self.margin.auto_is(Au::zero);
        let mut sums = self.padding_border_sums;
        sums.inline += margin.inline_sum();
        if !ignore_block_margins.start {
            sums.block += margin.block_start;
        }
        if !ignore_block_margins.end {
            sums.block += margin.block_end;
        }
        sums
    }
}

/// Resolved `aspect-ratio` property with respect to a specific element. Depends
/// on that element's `box-sizing` (and padding and border, if that `box-sizing`
/// is `border-box`).
#[derive(Clone, Copy, Debug)]
pub(crate) struct AspectRatio {
    /// If the element that this aspect ratio belongs to uses box-sizing:
    /// border-box, and the aspect-ratio property does not contain "auto", then
    /// the aspect ratio is in respect to the border box. This will then contain
    /// the summed sizes of the padding and border. Otherwise, it's 0.
    box_sizing_adjustment: LogicalVec2<Au>,
    /// The ratio itself (inline over block).
    i_over_b: CSSFloat,
}

impl AspectRatio {
    /// Given one side length, compute the other one.
    pub(crate) fn compute_dependent_size(
        &self,
        ratio_dependent_axis: AxisDirection,
        ratio_determining_size: Au,
    ) -> Au {
        match ratio_dependent_axis {
            // Calculate the inline size from the block size
            AxisDirection::Inline => {
                (ratio_determining_size + self.box_sizing_adjustment.block).scale_by(self.i_over_b) -
                    self.box_sizing_adjustment.inline
            },
            // Calculate the block size from the inline size
            AxisDirection::Block => {
                (ratio_determining_size + self.box_sizing_adjustment.inline)
                    .scale_by(1.0 / self.i_over_b) -
                    self.box_sizing_adjustment.block
            },
        }
    }

    pub(crate) fn from_logical_content_ratio(i_over_b: CSSFloat) -> Self {
        Self {
            box_sizing_adjustment: LogicalVec2::zero(),
            i_over_b,
        }
    }
}

#[derive(Clone)]
pub(crate) struct ContentBoxSizesAndPBM {
    pub content_box_sizes: LogicalVec2<Sizes>,
    pub pbm: PaddingBorderMargin,
    pub depends_on_block_constraints: bool,
    pub preferred_size_computes_to_auto: LogicalVec2<bool>,
}

#[derive(Clone, Debug, MallocSizeOf, PartialEq)]
pub(crate) struct BorderStyleColor {
    pub style: BorderStyle,
    pub color: AbsoluteColor,
}

impl BorderStyleColor {
    pub(crate) fn new(style: BorderStyle, color: AbsoluteColor) -> Self {
        Self { style, color }
    }

    pub(crate) fn from_border(
        border: &Border,
        current_color: &AbsoluteColor,
    ) -> PhysicalSides<Self> {
        let resolve = |color: &Color| color.resolve_to_absolute(current_color);
        PhysicalSides::<Self>::new(
            Self::new(border.border_top_style, resolve(&border.border_top_color)),
            Self::new(
                border.border_right_style,
                resolve(&border.border_right_color),
            ),
            Self::new(
                border.border_bottom_style,
                resolve(&border.border_bottom_color),
            ),
            Self::new(border.border_left_style, resolve(&border.border_left_color)),
        )
    }

    pub(crate) fn hidden() -> Self {
        Self::new(BorderStyle::Hidden, AbsoluteColor::TRANSPARENT_BLACK)
    }
}

impl Default for BorderStyleColor {
    fn default() -> Self {
        Self::new(BorderStyle::None, AbsoluteColor::TRANSPARENT_BLACK)
    }
}

/// <https://drafts.csswg.org/cssom-view/#overflow-directions>
/// > A scrolling box of a viewport or element has two overflow directions,
/// > which are the block-end and inline-end directions for that viewport or element.
pub(crate) struct OverflowDirection {
    /// Whether block-end or inline-end direction is [PhysicalSide::Right].
    pub rightward: bool,
    /// Whether block-end or inline-end direction is [PhysicalSide::Bottom].
    pub downward: bool,
}

pub(crate) trait ComputedValuesExt {
    fn physical_box_offsets(&self) -> PhysicalSides<LengthPercentageOrAuto<'_>>;
    fn box_offsets(&self, writing_mode: WritingMode) -> LogicalSides<LengthPercentageOrAuto<'_>>;
    fn box_size(
        &self,
        containing_block_writing_mode: WritingMode,
    ) -> LogicalVec2<Size<LengthPercentage>>;
    fn min_box_size(
        &self,
        containing_block_writing_mode: WritingMode,
    ) -> LogicalVec2<Size<LengthPercentage>>;
    fn max_box_size(
        &self,
        containing_block_writing_mode: WritingMode,
    ) -> LogicalVec2<Size<LengthPercentage>>;
    fn content_box_size_for_box_size(
        &self,
        box_size: LogicalVec2<Size<Au>>,
        pbm: &PaddingBorderMargin,
    ) -> LogicalVec2<Size<Au>>;
    fn content_min_box_size_for_min_size(
        &self,
        box_size: LogicalVec2<Size<Au>>,
        pbm: &PaddingBorderMargin,
    ) -> LogicalVec2<Size<Au>>;
    fn content_max_box_size_for_max_size(
        &self,
        box_size: LogicalVec2<Size<Au>>,
        pbm: &PaddingBorderMargin,
    ) -> LogicalVec2<Size<Au>>;
    fn border_style_color(
        &self,
        containing_block_writing_mode: WritingMode,
    ) -> LogicalSides<BorderStyleColor>;
    fn physical_margin(&self) -> PhysicalSides<LengthPercentageOrAuto<'_>>;
    fn margin(
        &self,
        containing_block_writing_mode: WritingMode,
    ) -> LogicalSides<LengthPercentageOrAuto<'_>>;
    fn is_transformable(&self, fragment_flags: FragmentFlags) -> bool;
    fn has_transform_or_perspective_style(&self) -> bool;
    fn has_effective_transform_or_perspective(&self, fragment_flags: FragmentFlags) -> bool;
    fn z_index_applies(&self, fragment_flags: FragmentFlags) -> bool;
    fn effective_z_index(&self, fragment_flags: FragmentFlags) -> i32;
    fn effective_overflow(&self, fragment_flags: FragmentFlags) -> AxesOverflow;
    fn establishes_block_formatting_context(&self, fragment_flags: FragmentFlags) -> bool;
    fn establishes_stacking_context(&self, fragment_flags: FragmentFlags) -> bool;
    fn establishes_scroll_container(&self, fragment_flags: FragmentFlags) -> bool;
    fn establishes_containing_block_for_absolute_descendants(
        &self,
        fragment_flags: FragmentFlags,
    ) -> bool;
    fn establishes_containing_block_for_all_descendants(
        &self,
        fragment_flags: FragmentFlags,
    ) -> bool;
    fn preferred_aspect_ratio(
        &self,
        natural_aspect_ratio: Option<CSSFloat>,
        padding_border_sums: &LogicalVec2<Au>,
    ) -> Option<AspectRatio>;
    fn background_is_transparent(&self) -> bool;
    fn get_webrender_primitive_flags(&self) -> wr::PrimitiveFlags;
    fn bidi_control_chars(&self) -> (&'static str, &'static str);
    fn resolve_align_self(
        &self,
        resolved_auto_value: ItemPlacement,
        resolved_normal_value: AlignFlags,
    ) -> SelfAlignment;
    fn depends_on_block_constraints_due_to_relative_positioning(
        &self,
        writing_mode: WritingMode,
    ) -> bool;
    fn is_inline_box(&self, fragment_flags: FragmentFlags) -> bool;
    fn overflow_direction(&self) -> OverflowDirection;
    fn to_bidi_level(&self) -> Level;
}

impl ComputedValuesExt for ComputedValues {
    fn physical_box_offsets(&self) -> PhysicalSides<LengthPercentageOrAuto<'_>> {
        fn convert(inset: &Inset) -> LengthPercentageOrAuto<'_> {
            match inset {
                Inset::LengthPercentage(v) => LengthPercentageOrAuto::LengthPercentage(v),
                Inset::Auto => LengthPercentageOrAuto::Auto,
                Inset::AnchorFunction(_) => unreachable!("anchor() should be disabled"),
                Inset::AnchorSizeFunction(_) => unreachable!("anchor-size() should be disabled"),
                Inset::AnchorContainingCalcFunction(_) => {
                    unreachable!("anchor() and anchor-size() should be disabled")
                },
            }
        }
        let position = self.get_position();
        PhysicalSides::new(
            convert(&position.top),
            convert(&position.right),
            convert(&position.bottom),
            convert(&position.left),
        )
    }

    fn box_offsets(&self, writing_mode: WritingMode) -> LogicalSides<LengthPercentageOrAuto<'_>> {
        LogicalSides::from_physical(&self.physical_box_offsets(), writing_mode)
    }

    fn box_size(
        &self,
        containing_block_writing_mode: WritingMode,
    ) -> LogicalVec2<Size<LengthPercentage>> {
        let position = self.get_position();
        LogicalVec2::from_physical_size(
            &PhysicalSize::new(
                position.clone_width().into(),
                position.clone_height().into(),
            ),
            containing_block_writing_mode,
        )
    }

    fn min_box_size(
        &self,
        containing_block_writing_mode: WritingMode,
    ) -> LogicalVec2<Size<LengthPercentage>> {
        let position = self.get_position();
        LogicalVec2::from_physical_size(
            &PhysicalSize::new(
                position.clone_min_width().into(),
                position.clone_min_height().into(),
            ),
            containing_block_writing_mode,
        )
    }

    fn max_box_size(
        &self,
        containing_block_writing_mode: WritingMode,
    ) -> LogicalVec2<Size<LengthPercentage>> {
        let position = self.get_position();
        LogicalVec2::from_physical_size(
            &PhysicalSize::new(
                position.clone_max_width().into(),
                position.clone_max_height().into(),
            ),
            containing_block_writing_mode,
        )
    }

    fn content_box_size_for_box_size(
        &self,
        box_size: LogicalVec2<Size<Au>>,
        pbm: &PaddingBorderMargin,
    ) -> LogicalVec2<Size<Au>> {
        match self.get_position().box_sizing {
            BoxSizing::ContentBox => box_size,
            // These may be negative, but will later be clamped by `min-width`/`min-height`
            // which is clamped to zero.
            BoxSizing::BorderBox => box_size.map_inline_and_block_sizes(
                |value| value - pbm.padding_border_sums.inline,
                |value| value - pbm.padding_border_sums.block,
            ),
        }
    }

    fn content_min_box_size_for_min_size(
        &self,
        min_box_size: LogicalVec2<Size<Au>>,
        pbm: &PaddingBorderMargin,
    ) -> LogicalVec2<Size<Au>> {
        match self.get_position().box_sizing {
            BoxSizing::ContentBox => min_box_size,
            // Clamp to zero to make sure the used size components are non-negative
            BoxSizing::BorderBox => min_box_size.map_inline_and_block_sizes(
                |value| Au::zero().max(value - pbm.padding_border_sums.inline),
                |value| Au::zero().max(value - pbm.padding_border_sums.block),
            ),
        }
    }

    fn content_max_box_size_for_max_size(
        &self,
        max_box_size: LogicalVec2<Size<Au>>,
        pbm: &PaddingBorderMargin,
    ) -> LogicalVec2<Size<Au>> {
        match self.get_position().box_sizing {
            BoxSizing::ContentBox => max_box_size,
            // This may be negative, but will later be clamped by `min-width`
            // which itself is clamped to zero.
            BoxSizing::BorderBox => max_box_size.map_inline_and_block_sizes(
                |value| value - pbm.padding_border_sums.inline,
                |value| value - pbm.padding_border_sums.block,
            ),
        }
    }

    fn border_style_color(
        &self,
        containing_block_writing_mode: WritingMode,
    ) -> LogicalSides<BorderStyleColor> {
        let current_color = self.get_inherited_text().clone_color();
        LogicalSides::from_physical(
            &BorderStyleColor::from_border(self.get_border(), &current_color),
            containing_block_writing_mode,
        )
    }

    fn physical_margin(&self) -> PhysicalSides<LengthPercentageOrAuto<'_>> {
        fn convert(inset: &Margin) -> LengthPercentageOrAuto<'_> {
            match inset {
                Margin::LengthPercentage(v) => LengthPercentageOrAuto::LengthPercentage(v),
                Margin::Auto => LengthPercentageOrAuto::Auto,
                Margin::AnchorSizeFunction(_) | Margin::AnchorContainingCalcFunction(_) => {
                    unreachable!("anchor-size() should be disabled")
                },
            }
        }
        let margin = self.get_margin();
        PhysicalSides::new(
            convert(&margin.margin_top),
            convert(&margin.margin_right),
            convert(&margin.margin_bottom),
            convert(&margin.margin_left),
        )
    }

    fn margin(
        &self,
        containing_block_writing_mode: WritingMode,
    ) -> LogicalSides<LengthPercentageOrAuto<'_>> {
        LogicalSides::from_physical(&self.physical_margin(), containing_block_writing_mode)
    }

    fn is_inline_box(&self, fragment_flags: FragmentFlags) -> bool {
        self.get_box().display.is_inline_flow() &&
            !fragment_flags.intersects(FragmentFlags::IS_REPLACED | FragmentFlags::IS_WIDGET)
    }

    /// Returns true if this is a transformable element.
    fn is_transformable(&self, fragment_flags: FragmentFlags) -> bool {
        // "A transformable element is an element in one of these categories:
        //   * all elements whose layout is governed by the CSS box model except for
        //     non-replaced inline boxes, table-column boxes, and table-column-group
        //     boxes,
        //   * all SVG paint server elements, the clipPath element  and SVG renderable
        //     elements with the exception of any descendant element of text content
        //     elements."
        // <https://drafts.csswg.org/css-transforms/#transformable-element>
        // TODO: check for all cases listed in the above spec.
        !self.is_inline_box(fragment_flags)
    }

    /// Returns true if this style has a transform or perspective property set.
    fn has_transform_or_perspective_style(&self) -> bool {
        !self.get_box().transform.0.is_empty() ||
            self.get_box().scale != GenericScale::None ||
            self.get_box().rotate != GenericRotate::None ||
            self.get_box().translate != GenericTranslate::None ||
            self.get_box().perspective != Perspective::None
    }

    /// Returns true if this style has a transform or perspective property set, and
    /// it applies to this element.
    #[inline]
    fn has_effective_transform_or_perspective(&self, fragment_flags: FragmentFlags) -> bool {
        self.is_transformable(fragment_flags) && self.has_transform_or_perspective_style()
    }

    /// Whether the `z-index` property applies to this fragment.
    fn z_index_applies(&self, fragment_flags: FragmentFlags) -> bool {
        // As per CSS 2 § 9.9.1, `z-index` applies to positioned elements.
        // <http://www.w3.org/TR/CSS2/visuren.html#z-index>
        if self.get_box().position != ComputedPosition::Static {
            return true;
        }
        // More modern specs also apply it to flex and grid items.
        // - From <https://www.w3.org/TR/css-flexbox-1/#painting>:
        //   > Flex items paint exactly the same as inline blocks [CSS2], except that order-modified
        //   > document order is used in place of raw document order, and z-index values other than auto
        //   > create a stacking context even if position is static (behaving exactly as if position
        //   > were relative).
        // - From <https://drafts.csswg.org/css-flexbox/#painting>:
        //   > The painting order of grid items is exactly the same as inline blocks [CSS2], except that
        //   > order-modified document order is used in place of raw document order, and z-index values
        //   > other than auto create a stacking context even if position is static (behaving exactly
        //   > as if position were relative).
        fragment_flags.contains(FragmentFlags::IS_FLEX_OR_GRID_ITEM)
    }

    /// Get the effective z-index of this fragment. Z-indices only apply to positioned elements
    /// per CSS 2 9.9.1 (<http://www.w3.org/TR/CSS2/visuren.html#z-index>), so this value may differ
    /// from the value specified in the style.
    fn effective_z_index(&self, fragment_flags: FragmentFlags) -> i32 {
        if self.z_index_applies(fragment_flags) {
            self.get_position().z_index.integer_or(0)
        } else {
            0
        }
    }

    /// Get the effective overflow of this box. The property only applies to block containers,
    /// flex containers, and grid containers. And some box types only accept a few values.
    /// <https://www.w3.org/TR/css-overflow-3/#overflow-control>
    fn effective_overflow(&self, fragment_flags: FragmentFlags) -> AxesOverflow {
        // https://www.w3.org/TR/css-overflow-3/#overflow-propagation
        // The element from which the value is propagated must then have a used overflow value of visible.
        if fragment_flags.contains(FragmentFlags::PROPAGATED_OVERFLOW_TO_VIEWPORT) {
            return AxesOverflow::default();
        }

        let mut overflow = AxesOverflow::from(self);

        // From <https://www.w3.org/TR/css-overflow-4/#overflow-control>:
        // "On replaced elements, the used values of all computed values other than visible is clip."
        if fragment_flags.contains(FragmentFlags::IS_REPLACED) {
            if overflow.x != Overflow::Visible {
                overflow.x = Overflow::Clip;
            }
            if overflow.y != Overflow::Visible {
                overflow.y = Overflow::Clip;
            }
            return overflow;
        }

        let ignores_overflow = match self.get_box().display.inside() {
            // <https://drafts.csswg.org/css-overflow-3/#overflow-control>
            // `overflow` doesn't apply to inline boxes.
            stylo::DisplayInside::Flow => self.is_inline_box(fragment_flags),

            // According to <https://drafts.csswg.org/css-tables/#global-style-overrides>,
            // - overflow applies to table-wrapper boxes and not to table grid boxes.
            //   That's what Blink and WebKit do, however Firefox matches a CSSWG resolution that says
            //   the opposite: <https://lists.w3.org/Archives/Public/www-style/2012Aug/0298.html>
            //   Due to the way that we implement table-wrapper boxes, it's easier to align with Firefox.
            // - Tables ignore overflow values different than visible, clip and hidden.
            //   This affects both axes, to ensure they have the same scrollability.
            stylo::DisplayInside::Table => {
                !matches!(self.pseudo(), Some(PseudoElement::ServoTableGrid)) ||
                    matches!(overflow.x, Overflow::Auto | Overflow::Scroll) ||
                    matches!(overflow.y, Overflow::Auto | Overflow::Scroll)
            },

            // <https://drafts.csswg.org/css-tables/#global-style-overrides>
            // Table-track and table-track-group boxes ignore overflow.
            stylo::DisplayInside::TableColumn |
            stylo::DisplayInside::TableColumnGroup |
            stylo::DisplayInside::TableRow |
            stylo::DisplayInside::TableRowGroup |
            stylo::DisplayInside::TableHeaderGroup |
            stylo::DisplayInside::TableFooterGroup => true,

            _ => false,
        };
        if ignores_overflow {
            return AxesOverflow::default();
        }

        overflow
    }

    /// Return true if this style is a normal block and establishes
    /// a new block formatting context.
    ///
    /// NOTE: This should be kept in sync with the checks in `impl
    /// TElement::compute_layout_damage` for `ServoLayoutElement` in
    /// `components/script/layout_dom/element.rs`.
    fn establishes_block_formatting_context(&self, fragment_flags: FragmentFlags) -> bool {
        if self.establishes_scroll_container(fragment_flags) {
            return true;
        }

        if self.get_column().is_multicol() {
            return true;
        }

        if self.get_column().column_span == ColumnSpan::All {
            return true;
        }

        // Per <https://drafts.csswg.org/css-align/#distribution-block>:
        // Block containers with an `align-content` value that is not `normal` should
        // form an independent block formatting context. This should really only happen
        // for block containers, but we do not support subgrid containers yet which is the
        // only other case.
        if self.get_position().align_content.primary() != AlignFlags::NORMAL {
            return true;
        }

        // TODO: We need to handle CSS Contain here.
        false
    }

    /// Whether or not the `overflow` value of this style establishes a scroll container.
    fn establishes_scroll_container(&self, fragment_flags: FragmentFlags) -> bool {
        // Checking one axis suffices, because the computed value ensures that
        // either both axes are scrollable, or none is scrollable.
        self.effective_overflow(fragment_flags).x.is_scrollable()
    }

    /// Returns true if this fragment establishes a new stacking context and false otherwise.
    fn establishes_stacking_context(&self, fragment_flags: FragmentFlags) -> bool {
        // From <https://www.w3.org/TR/css-will-change/#valdef-will-change-custom-ident>:
        // > If any non-initial value of a property would create a stacking context on the element,
        // > specifying that property in will-change must create a stacking context on the element.
        let will_change_bits = self.clone_will_change().bits;
        if will_change_bits
            .intersects(WillChangeBits::STACKING_CONTEXT_UNCONDITIONAL | WillChangeBits::OPACITY)
        {
            return true;
        }

        // From <https://www.w3.org/TR/CSS2/visuren.html#z-index>, values different than `auto`
        // make the box establish a stacking context.
        if self.z_index_applies(fragment_flags) &&
            (!self.get_position().z_index.is_auto() ||
                will_change_bits.intersects(WillChangeBits::Z_INDEX))
        {
            return true;
        }

        // Fixed position and sticky position always create stacking contexts.
        // Note `will-change: position` is handled above by `STACKING_CONTEXT_UNCONDITIONAL`.
        if matches!(
            self.get_box().position,
            ComputedPosition::Fixed | ComputedPosition::Sticky
        ) {
            return true;
        }

        // From <https://www.w3.org/TR/css-transforms-1/#transform-rendering>
        // > For elements whose layout is governed by the CSS box model, any value other than
        // > `none` for the `transform` property results in the creation of a stacking context.
        //
        // From <https://www.w3.org/TR/css-transforms-2/#individual-transforms>
        // > all other values […] create a stacking context and containing block for all
        // > descendants, per usual for transforms.
        //
        // From <https://www.w3.org/TR/css-transforms-2/#perspective-property>
        // > any value other than none establishes a stacking context.
        //
        // From <https://www.w3.org/TR/css-transforms-2/#transform-style-property>
        // > A computed value of `preserve-3d` for `transform-style` on a transformable element
        // > establishes both a stacking context and a containing block for all descendants.
        if self.is_transformable(fragment_flags) &&
            (self.has_transform_or_perspective_style() ||
                self.get_box().transform_style == ComputedTransformStyle::Preserve3d ||
                will_change_bits
                    .intersects(WillChangeBits::TRANSFORM | WillChangeBits::PERSPECTIVE))
        {
            return true;
        }

        // From <https://www.w3.org/TR/css-color-3/#transparency>
        // > implementations must create a new stacking context for any element with opacity less than 1.
        // Note `will-change: opacity` is handled above by `WillChangeBits::OPACITY`.
        let effects = self.get_effects();
        if effects.opacity != 1.0 {
            return true;
        }

        // From <https://www.w3.org/TR/filter-effects-1/#FilterProperty>
        // > A computed value of other than `none` results in the creation of a stacking context
        // Note `will-change: filter` is handled above by `STACKING_CONTEXT_UNCONDITIONAL`.
        if !effects.filter.0.is_empty() {
            return true;
        }

        // From <https://www.w3.org/TR/compositing-1/#mix-blend-mode>
        // > Applying a blendmode other than `normal` to the element must establish a new stacking context
        // Note `will-change: mix-blend-mode` is handled above by `STACKING_CONTEXT_UNCONDITIONAL`.
        if effects.mix_blend_mode != ComputedMixBlendMode::Normal {
            return true;
        }

        // From <https://www.w3.org/TR/css-masking-1/#the-clip-path>
        // > A computed value of other than `none` results in the creation of a stacking context.
        // Note `will-change: clip-path` is handled above by `STACKING_CONTEXT_UNCONDITIONAL`.
        if self.get_svg().clip_path != ClipPath::None {
            return true;
        }

        // From <https://www.w3.org/TR/compositing-1/#isolation>
        // > For CSS, setting `isolation` to `isolate` will turn the element into a stacking context.
        // Note `will-change: isolation` is handled above by `STACKING_CONTEXT_UNCONDITIONAL`.
        if self.get_box().isolation == ComputedIsolation::Isolate {
            return true;
        }

        // From https://www.w3.org/TR/CSS22/visuren.html#z-index:
        // > The root element forms the root stacking context.
        if fragment_flags.contains(FragmentFlags::IS_ROOT_ELEMENT) {
            return true;
        }

        // TODO: We need to handle CSS Contain here.
        false
    }

    /// Returns true if this style establishes a containing block for absolute
    /// descendants (`position: absolute`). If this style happens to establish a
    /// containing block for “all descendants” (ie including `position: fixed`
    /// descendants) this method will return true, but a true return value does
    /// not imply that the style establishes a containing block for all descendants.
    /// Use `establishes_containing_block_for_all_descendants()` instead.
    fn establishes_containing_block_for_absolute_descendants(
        &self,
        fragment_flags: FragmentFlags,
    ) -> bool {
        if self.establishes_containing_block_for_all_descendants(fragment_flags) {
            return true;
        }

        // From <https://www.w3.org/TR/css-will-change/#valdef-will-change-custom-ident>:
        // > If any non-initial value of a property would cause the element to
        // > generate a containing block for absolutely positioned elements, specifying that property in
        // > will-change must cause the element to generate a containing block for absolutely positioned elements.
        if self
            .clone_will_change()
            .bits
            .intersects(WillChangeBits::POSITION)
        {
            return true;
        }

        self.clone_position() != ComputedPosition::Static
    }

    /// Returns true if this style establishes a containing block for
    /// all descendants, including fixed descendants (`position: fixed`).
    /// Note that this also implies that it establishes a containing block
    /// for absolute descendants (`position: absolute`).
    fn establishes_containing_block_for_all_descendants(
        &self,
        fragment_flags: FragmentFlags,
    ) -> bool {
        // From <https://www.w3.org/TR/css-will-change/#valdef-will-change-custom-ident>:
        // > If any non-initial value of a property would cause the element to generate a
        // > containing block for fixed positioned elements, specifying that property in will-change
        // > must cause the element to generate a containing block for fixed positioned elements.
        let will_change_bits = self.clone_will_change().bits;

        // From <https://drafts.csswg.org/css-transforms-1/#transform-rendering>:
        // > any value other than `none` for the `transform` property also causes the element
        // > to establish a containing block for all descendants.
        //
        // From <https://www.w3.org/TR/css-transforms-2/#individual-transforms>
        // > all other values […] create a stacking context and containing block for all
        // > descendants, per usual for transforms.
        //
        // From <https://drafts.csswg.org/css-transforms-2/#perspective-property>:
        // > The use of this property with any value other than `none` […] establishes a
        // > containing block for all descendants, just like the `transform` property does.
        //
        // From <https://drafts.csswg.org/css-transforms-2/#transform-style-property>:
        // > A computed value of `preserve-3d` for `transform-style` on a transformable element
        // > establishes both a stacking context and a containing block for all descendants.
        if self.is_transformable(fragment_flags) &&
            (self.has_transform_or_perspective_style() ||
                self.get_box().transform_style == ComputedTransformStyle::Preserve3d ||
                will_change_bits
                    .intersects(WillChangeBits::TRANSFORM | WillChangeBits::PERSPECTIVE))
        {
            return true;
        }

        // From <https://www.w3.org/TR/filter-effects-1/#propdef-filter>:
        // > A value other than none for the filter property results in the creation of a containing
        // > block for absolute and fixed positioned descendants unless the element it applies to is
        // > a document root element in the current browsing context.
        if !fragment_flags.contains(FragmentFlags::IS_ROOT_ELEMENT) &&
            (!self.get_effects().filter.0.is_empty() ||
                will_change_bits.intersects(WillChangeBits::FIXPOS_CB_NON_SVG))
        {
            return true;
        }

        // TODO: We need to handle CSS Contain here.
        false
    }

    /// Resolve the preferred aspect ratio according to the given natural aspect
    /// ratio and the `aspect-ratio` property.
    /// See <https://drafts.csswg.org/css-sizing-4/#aspect-ratio>.
    fn preferred_aspect_ratio(
        &self,
        natural_aspect_ratio: Option<CSSFloat>,
        padding_border_sums: &LogicalVec2<Au>,
    ) -> Option<AspectRatio> {
        let GenericAspectRatio {
            auto,
            ratio: mut preferred_ratio,
        } = self.clone_aspect_ratio();

        // For all cases where a ratio is specified:
        // "If the <ratio> is degenerate, the property instead behaves as auto."
        if matches!(preferred_ratio, PreferredRatio::Ratio(ratio) if ratio.is_degenerate()) {
            preferred_ratio = PreferredRatio::None;
        }

        let to_logical_ratio = |physical_ratio| {
            if self.writing_mode.is_horizontal() {
                physical_ratio
            } else {
                1.0 / physical_ratio
            }
        };

        match (auto, preferred_ratio) {
            // The value `auto`. Either the ratio was not specified, or was
            // degenerate and set to PreferredRatio::None above.
            //
            // "Replaced elements with a natural aspect ratio use that aspect
            // ratio; otherwise the box has no preferred aspect ratio. Size
            // calculations involving the aspect ratio work with the content box
            // dimensions always."
            (_, PreferredRatio::None) => natural_aspect_ratio
                .map(to_logical_ratio)
                .map(AspectRatio::from_logical_content_ratio),
            // "If both auto and a <ratio> are specified together, the preferred
            // aspect ratio is the specified ratio of width / height unless it
            // is a replaced element with a natural aspect ratio, in which case
            // that aspect ratio is used instead. In all cases, size
            // calculations involving the aspect ratio work with the content box
            // dimensions always."
            (true, PreferredRatio::Ratio(preferred_ratio)) => Some({
                let physical_ratio = natural_aspect_ratio
                    .unwrap_or_else(|| (preferred_ratio.0).0 / (preferred_ratio.1).0);
                AspectRatio::from_logical_content_ratio(to_logical_ratio(physical_ratio))
            }),

            // "The box’s preferred aspect ratio is the specified ratio of width
            // / height. Size calculations involving the aspect ratio work with
            // the dimensions of the box specified by box-sizing."
            (false, PreferredRatio::Ratio(preferred_ratio)) => {
                // If the `box-sizing` is `border-box`, use the padding and
                // border when calculating the aspect ratio.
                let box_sizing_adjustment = match self.clone_box_sizing() {
                    BoxSizing::ContentBox => LogicalVec2::zero(),
                    BoxSizing::BorderBox => *padding_border_sums,
                };
                Some(AspectRatio {
                    i_over_b: to_logical_ratio((preferred_ratio.0).0 / (preferred_ratio.1).0),
                    box_sizing_adjustment,
                })
            },
        }
    }

    /// Whether or not this style specifies a non-transparent background.
    fn background_is_transparent(&self) -> bool {
        let background = self.get_background();
        let color = self.resolve_color(&background.background_color);
        color.alpha == 0.0 &&
            background
                .background_image
                .0
                .iter()
                .all(|layer| matches!(layer, ComputedImageLayer::None))
    }

    /// Generate appropriate WebRender `PrimitiveFlags` that should be used
    /// for display items generated by the `Fragment` which owns this style.
    fn get_webrender_primitive_flags(&self) -> wr::PrimitiveFlags {
        match self.get_box().backface_visibility {
            BackfaceVisiblity::Visible => wr::PrimitiveFlags::default(),
            BackfaceVisiblity::Hidden => wr::PrimitiveFlags::empty(),
        }
    }

    /// If the 'unicode-bidi' property has a value other than 'normal', return the bidi control codes
    /// to inject before and after the text content of the element.
    /// See the table in <http://dev.w3.org/csswg/css-writing-modes/#unicode-bidi>.
    fn bidi_control_chars(&self) -> (&'static str, &'static str) {
        match (
            self.get_text().unicode_bidi,
            self.get_inherited_box().direction,
        ) {
            (UnicodeBidi::Normal, _) => ("", ""),
            (UnicodeBidi::Embed, Direction::Ltr) => ("\u{202a}", "\u{202c}"),
            (UnicodeBidi::Embed, Direction::Rtl) => ("\u{202b}", "\u{202c}"),
            (UnicodeBidi::Isolate, Direction::Ltr) => ("\u{2066}", "\u{2069}"),
            (UnicodeBidi::Isolate, Direction::Rtl) => ("\u{2067}", "\u{2069}"),
            (UnicodeBidi::BidiOverride, Direction::Ltr) => ("\u{202d}", "\u{202c}"),
            (UnicodeBidi::BidiOverride, Direction::Rtl) => ("\u{202e}", "\u{202c}"),
            (UnicodeBidi::IsolateOverride, Direction::Ltr) => {
                ("\u{2068}\u{202d}", "\u{202c}\u{2069}")
            },
            (UnicodeBidi::IsolateOverride, Direction::Rtl) => {
                ("\u{2068}\u{202e}", "\u{202c}\u{2069}")
            },
            (UnicodeBidi::Plaintext, _) => ("\u{2068}", "\u{2069}"),
        }
    }

    fn resolve_align_self(
        &self,
        resolved_auto_value: ItemPlacement,
        resolved_normal_value: AlignFlags,
    ) -> SelfAlignment {
        SelfAlignment(match self.clone_align_self().0 {
            AlignFlags::AUTO => resolved_auto_value.0,
            AlignFlags::NORMAL => resolved_normal_value,
            value => value,
        })
    }

    fn depends_on_block_constraints_due_to_relative_positioning(
        &self,
        writing_mode: WritingMode,
    ) -> bool {
        if !matches!(
            self.get_box().position,
            ComputedPosition::Relative | ComputedPosition::Sticky
        ) {
            return false;
        }
        let box_offsets = self.box_offsets(writing_mode);
        let has_percentage = |offset: LengthPercentageOrAuto<'_>| {
            offset
                .non_auto()
                .is_some_and(LengthPercentage::has_percentage)
        };
        has_percentage(box_offsets.block_start) || has_percentage(box_offsets.block_end)
    }

    // <https://drafts.csswg.org/cssom-view/#overflow-directions>
    fn overflow_direction(&self) -> OverflowDirection {
        let inline_end_direction = self.writing_mode.inline_end_physical_side();
        let block_end_direction = self.writing_mode.block_end_physical_side();

        let rightward = inline_end_direction == PhysicalSide::Right ||
            block_end_direction == PhysicalSide::Right;
        let downward = inline_end_direction == PhysicalSide::Bottom ||
            block_end_direction == PhysicalSide::Bottom;

        // TODO(stevennovaryo): We should consider the flex-container's CSS (e.g. flow-direction: column-reverse).
        OverflowDirection {
            rightward,
            downward,
        }
    }

    /// The default bidirectional embedding level for the writing mode of this style.
    ///
    /// Returns bidi level 0 if the mode is LTR, or 1 otherwise.
    fn to_bidi_level(&self) -> Level {
        if self.writing_mode.is_bidi_ltr() {
            Level::ltr()
        } else {
            Level::rtl()
        }
    }
}

pub(crate) enum LayoutStyle<'a> {
    Default(&'a ComputedValues),
    Table(TableLayoutStyle<'a>),
}

impl LayoutStyle<'_> {
    #[inline]
    pub(crate) fn style(&self) -> &ComputedValues {
        match self {
            Self::Default(style) => style,
            Self::Table(table) => table.style(),
        }
    }

    #[inline]
    pub(crate) fn is_table(&self) -> bool {
        matches!(self, Self::Table(_))
    }

    pub(crate) fn content_box_sizes_and_padding_border_margin(
        &self,
        containing_block: &IndefiniteContainingBlock,
    ) -> ContentBoxSizesAndPBM {
        // <https://drafts.csswg.org/css-sizing-3/#cyclic-percentage-contribution>
        // If max size properties or preferred size properties are set to a value containing
        // indefinite percentages, we treat the entire value as the initial value of the property.
        // However, for min size properties, as well as for margins and paddings,
        // we instead resolve indefinite percentages against zero.
        let containing_block_size_or_zero =
            containing_block.size.map(|value| value.unwrap_or_default());
        let writing_mode = containing_block.style.writing_mode;
        let pbm = self.padding_border_margin_with_writing_mode_and_containing_block_inline_size(
            writing_mode,
            containing_block_size_or_zero.inline,
        );
        let style = self.style();
        let box_size = style.box_size(writing_mode);
        let min_size = style.min_box_size(writing_mode);
        let max_size = style.max_box_size(writing_mode);
        let preferred_size_computes_to_auto = box_size.map(|size| size.is_initial());

        let depends_on_block_constraints = |size: &Size<LengthPercentage>| {
            match size {
                // fit-content is like clamp(min-content, stretch, max-content), but currently
                // min-content and max-content have the same behavior in the block axis,
                // so there is no dependency on block constraints.
                // TODO: for flex and grid layout, min-content and max-content should be different.
                // TODO: We are assuming that Size::Initial doesn't stretch. However, it may actually
                // stretch flex and grid items depending on the CSS Align properties, in that case
                // the caller needs to take care of it.
                Size::Stretch => true,
                Size::Numeric(length_percentage) => length_percentage.has_percentage(),
                _ => false,
            }
        };
        let depends_on_block_constraints = depends_on_block_constraints(&box_size.block) ||
            depends_on_block_constraints(&min_size.block) ||
            depends_on_block_constraints(&max_size.block) ||
            style.depends_on_block_constraints_due_to_relative_positioning(writing_mode);

        let box_size = box_size.map_with(&containing_block.size, |size, basis| {
            size.resolve_percentages_for_preferred(*basis)
        });
        let content_box_size = style.content_box_size_for_box_size(box_size, &pbm);
        let min_size = min_size.percentages_relative_to_basis(&containing_block_size_or_zero);
        let content_min_box_size = style.content_min_box_size_for_min_size(min_size, &pbm);
        let max_size = max_size.map_with(&containing_block.size, |size, basis| {
            size.resolve_percentages_for_max(*basis)
        });
        let content_max_box_size = style.content_max_box_size_for_max_size(max_size, &pbm);
        ContentBoxSizesAndPBM {
            content_box_sizes: LogicalVec2 {
                block: Sizes::new(
                    content_box_size.block,
                    content_min_box_size.block,
                    content_max_box_size.block,
                ),
                inline: Sizes::new(
                    content_box_size.inline,
                    content_min_box_size.inline,
                    content_max_box_size.inline,
                ),
            },
            pbm,
            depends_on_block_constraints,
            preferred_size_computes_to_auto,
        }
    }

    pub(crate) fn padding_border_margin(
        &self,
        containing_block: &ContainingBlock,
    ) -> PaddingBorderMargin {
        self.padding_border_margin_with_writing_mode_and_containing_block_inline_size(
            containing_block.style.writing_mode,
            containing_block.size.inline,
        )
    }

    pub(crate) fn padding_border_margin_with_writing_mode_and_containing_block_inline_size(
        &self,
        writing_mode: WritingMode,
        containing_block_inline_size: Au,
    ) -> PaddingBorderMargin {
        let padding = self
            .padding(writing_mode)
            .percentages_relative_to(containing_block_inline_size);
        let style = self.style();
        let border = self.border_width(writing_mode);
        let margin = style
            .margin(writing_mode)
            .percentages_relative_to(containing_block_inline_size);
        PaddingBorderMargin {
            padding_border_sums: LogicalVec2 {
                inline: padding.inline_sum() + border.inline_sum(),
                block: padding.block_sum() + border.block_sum(),
            },
            padding,
            border,
            margin,
        }
    }

    pub(crate) fn padding(
        &self,
        containing_block_writing_mode: WritingMode,
    ) -> LogicalSides<LengthPercentage> {
        if matches!(self, Self::Table(table) if table.collapses_borders()) {
            // https://drafts.csswg.org/css-tables/#collapsed-style-overrides
            // > The padding of the table-root is ignored (as if it was set to 0px).
            return LogicalSides::zero();
        }
        let padding = self.style().get_padding().clone();
        LogicalSides::from_physical(
            &PhysicalSides::new(
                padding.padding_top.0,
                padding.padding_right.0,
                padding.padding_bottom.0,
                padding.padding_left.0,
            ),
            containing_block_writing_mode,
        )
    }

    pub(crate) fn border_width(
        &self,
        containing_block_writing_mode: WritingMode,
    ) -> LogicalSides<Au> {
        let border_width = match self {
            // For tables in collapsed-borders mode we halve the border widths, because
            // > in this model, the width of the table includes half the table border.
            // https://www.w3.org/TR/CSS22/tables.html#collapsing-borders
            Self::Table(table) if table.collapses_borders() => table
                .halved_collapsed_border_widths()
                .to_physical(self.style().writing_mode),
            _ => {
                let border = self.style().get_border();
                let resolve = |width: &BorderSideWidth, style: BorderStyle| {
                    if style.none_or_hidden() {
                        Au::zero()
                    } else {
                        width.0
                    }
                };
                PhysicalSides::new(
                    resolve(&border.border_top_width, border.border_top_style),
                    resolve(&border.border_right_width, border.border_right_style),
                    resolve(&border.border_bottom_width, border.border_bottom_style),
                    resolve(&border.border_left_width, border.border_left_style),
                )
            },
        };
        LogicalSides::from_physical(&border_width, containing_block_writing_mode)
    }
}

impl From<stylo::Display> for Display {
    fn from(packed: stylo::Display) -> Self {
        let outside = packed.outside();
        let inside = packed.inside();

        let outside = match outside {
            stylo::DisplayOutside::Block => DisplayOutside::Block,
            stylo::DisplayOutside::Inline => DisplayOutside::Inline,
            stylo::DisplayOutside::TableCaption => {
                return Display::GeneratingBox(DisplayGeneratingBox::LayoutInternal(
                    DisplayLayoutInternal::TableCaption,
                ));
            },
            stylo::DisplayOutside::InternalTable => {
                let internal = match inside {
                    stylo::DisplayInside::TableRowGroup => DisplayLayoutInternal::TableRowGroup,
                    stylo::DisplayInside::TableColumn => DisplayLayoutInternal::TableColumn,
                    stylo::DisplayInside::TableColumnGroup => {
                        DisplayLayoutInternal::TableColumnGroup
                    },
                    stylo::DisplayInside::TableHeaderGroup => {
                        DisplayLayoutInternal::TableHeaderGroup
                    },
                    stylo::DisplayInside::TableFooterGroup => {
                        DisplayLayoutInternal::TableFooterGroup
                    },
                    stylo::DisplayInside::TableRow => DisplayLayoutInternal::TableRow,
                    stylo::DisplayInside::TableCell => DisplayLayoutInternal::TableCell,
                    _ => unreachable!("Non-internal DisplayInside found"),
                };
                return Display::GeneratingBox(DisplayGeneratingBox::LayoutInternal(internal));
            },
            // This should not be a value of DisplayInside, but oh well
            // special-case display: contents because we still want it to work despite the early return
            stylo::DisplayOutside::None if inside == stylo::DisplayInside::Contents => {
                return Display::Contents;
            },
            stylo::DisplayOutside::None => return Display::None,
        };

        let inside = match packed.inside() {
            stylo::DisplayInside::Flow => DisplayInside::Flow {
                is_list_item: packed.is_list_item(),
            },
            stylo::DisplayInside::FlowRoot => DisplayInside::FlowRoot {
                is_list_item: packed.is_list_item(),
            },
            stylo::DisplayInside::Flex => DisplayInside::Flex,
            stylo::DisplayInside::Grid => DisplayInside::Grid,

            // These should not be values of DisplayInside, but oh well
            stylo::DisplayInside::None => return Display::None,
            stylo::DisplayInside::Contents => return Display::Contents,

            stylo::DisplayInside::Table => DisplayInside::Table,
            stylo::DisplayInside::TableRowGroup |
            stylo::DisplayInside::TableColumn |
            stylo::DisplayInside::TableColumnGroup |
            stylo::DisplayInside::TableHeaderGroup |
            stylo::DisplayInside::TableFooterGroup |
            stylo::DisplayInside::TableRow |
            stylo::DisplayInside::TableCell => unreachable!("Internal DisplayInside found"),
        };
        Display::GeneratingBox(DisplayGeneratingBox::OutsideInside { outside, inside })
    }
}

pub(crate) trait Clamp: Sized {
    fn clamp_below_max(self, max: Option<Self>) -> Self;
    fn clamp_between_extremums(self, min: Self, max: Option<Self>) -> Self;
}

impl Clamp for Au {
    fn clamp_below_max(self, max: Option<Self>) -> Self {
        match max {
            None => self,
            Some(max) => self.min(max),
        }
    }

    fn clamp_between_extremums(self, min: Self, max: Option<Self>) -> Self {
        self.clamp_below_max(max).max(min)
    }
}

pub(crate) trait TransformExt {
    fn change_basis(&self, x: f32, y: f32, z: f32) -> Self;
}

impl TransformExt for LayoutTransform {
    /// <https://drafts.csswg.org/css-transforms/#transformation-matrix-computation>
    fn change_basis(&self, x: f32, y: f32, z: f32) -> Self {
        let pre_translation = Self::translation(x, y, z);
        let post_translation = Self::translation(-x, -y, -z);
        post_translation.then(self).then(&pre_translation)
    }
}