firefox/servo/components/style/properties/computed_value_flags.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/. */

//! Misc information about a given computed style.

/// Misc information about a given computed style.
///
/// All flags are currently inherited for text, pseudo elements, and
/// anonymous boxes, see StyleBuilder::for_inheritance and its callsites.
/// If we ever want to add some flags that shouldn't inherit for them,
/// we might want to add a function to handle this.
#[repr(C)]
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
pub struct ComputedValueFlags(u32);

bitflags! {
    impl ComputedValueFlags: u32 {
        /// Whether the style or any of the ancestors has a text-decoration-line
        /// property that should get propagated to descendants.
        ///
        /// text-decoration-line is a reset property, but gets propagated in the
        /// frame/box tree.
        const HAS_TEXT_DECORATION_LINES = 1 << 0;

        /// Whether line break inside should be suppressed.
        ///
        /// If this flag is set, the line should not be broken inside,
        /// which means inlines act as if nowrap is set, <br> element is
        /// suppressed, and blocks are inlinized.
        ///
        /// This bit is propagated to all children of line participants.
        /// It is currently used by ruby to make its content unbreakable.
        const SHOULD_SUPPRESS_LINEBREAK = 1 << 1;

        /// A flag used to mark text that that has text-combine-upright.
        ///
        /// This is used from Gecko's layout engine.
        const IS_TEXT_COMBINED = 1 << 2;

        /// A flag used to mark styles under a relevant link that is also
        /// visited.
        const IS_RELEVANT_LINK_VISITED = 1 << 3;

        /// A flag used to mark styles which are a ::first-line or under one.
        const IS_IN_FIRST_LINE_SUBTREE = 1 << 4;

        /// A flag used to mark styles which have contain:style or under one.
        const SELF_OR_ANCESTOR_HAS_CONTAIN_STYLE = 1 << 5;

        /// Whether this style's `display` property depends on our parent style.
        ///
        /// This is important because it may affect our optimizations to avoid
        /// computing the style of pseudo-elements, given whether the
        /// pseudo-element is generated depends on the `display` value.
        const DISPLAY_DEPENDS_ON_INHERITED_STYLE = 1 << 6;

        /// Whether this style's `content` depends on our parent style.
        ///
        /// Important because of the same reason.
        const CONTENT_DEPENDS_ON_INHERITED_STYLE = 1 << 7;

        /// Whether the child explicitly inherits any reset property.
        const INHERITS_RESET_STYLE = 1 << 8;

        /// Whether any value on our style is font-metric-dependent on our
        /// primary font.
        const DEPENDS_ON_SELF_FONT_METRICS = 1 << 9;

        /// Whether any value on our style is font-metric-dependent on the
        /// primary font of our parent.
        const DEPENDS_ON_INHERITED_FONT_METRICS = 1 << 10;

        /// Whether the style or any of the ancestors has a multicol style.
        ///
        /// Only used in Servo.
        const CAN_BE_FRAGMENTED = 1 << 11;

        /// Whether this style is the style of the document element.
        const IS_ROOT_ELEMENT_STYLE = 1 << 12;

        /// Whether this element is inside an `opacity: 0` subtree.
        const IS_IN_OPACITY_ZERO_SUBTREE = 1 << 13;

        /// Whether there are author-specified rules for border-* properties
        /// (except border-image-*), background-color, or background-image.
        ///
        /// TODO(emilio): Maybe do include border-image, see:
        ///
        /// https://github.com/w3c/csswg-drafts/issues/4777#issuecomment-604424845
        const HAS_AUTHOR_SPECIFIED_BORDER_BACKGROUND = 1 << 14;

        /// Whether we have author-specified font-size or margin, for <h1> purposes.
        const HAS_AUTHOR_SPECIFIED_MARGIN_AND_FONT_SIZE = 1 << 15;

        /// Whether there are author-specified rules for `font-family`.
        const HAS_AUTHOR_SPECIFIED_FONT_FAMILY = 1 << 16;

        /// Whether there are author-specified rules for `font-synthesis-weight`.
        const HAS_AUTHOR_SPECIFIED_FONT_SYNTHESIS_WEIGHT = 1 << 17;

        /// Whether there are author-specified rules for `font-synthesis-style`.
        const HAS_AUTHOR_SPECIFIED_FONT_SYNTHESIS_STYLE = 1 << 18;

        // (There's also font-synthesis-small-caps and font-synthesis-position,
        // but we don't currently need to keep track of those.)

        /// Whether there are author-specified rules for `letter-spacing`.
        const HAS_AUTHOR_SPECIFIED_LETTER_SPACING = 1 << 19;

        /// Whether there are author-specified rules for `word-spacing`.
        const HAS_AUTHOR_SPECIFIED_WORD_SPACING = 1 << 20;

        /// Whether the style depends on viewport units.
        const USES_VIEWPORT_UNITS = 1 << 21;

        /// Whether the style depends on viewport units on container queries.
        ///
        /// This needs to be a separate flag from `USES_VIEWPORT_UNITS` because
        /// it causes us to re-match the style (rather than re-cascascading it,
        /// which is enough for other uses of viewport units).
        const USES_VIEWPORT_UNITS_ON_CONTAINER_QUERIES = 1 << 22;

        /// A flag used to mark styles which have `container-type` of `size` or
        /// `inline-size`, or under one.
        const SELF_OR_ANCESTOR_HAS_SIZE_CONTAINER_TYPE = 1 << 23;
        /// Whether the style uses container query units, in which case the style depends on the
        /// container's size and we can't reuse it across cousins (without double-checking the
        /// container at least).
        const USES_CONTAINER_UNITS = 1 << 24;

        /// Whether there are author-specific rules for text `color`.
        const HAS_AUTHOR_SPECIFIED_TEXT_COLOR = 1 << 25;

        /// Whether this style considered a scope style rule.
        const CONSIDERED_NONTRIVIAL_SCOPED_STYLE = 1 << 26;
    }
}

impl Default for ComputedValueFlags {
    #[inline]
    fn default() -> Self {
        Self::empty()
    }
}

impl ComputedValueFlags {
    /// Flags that are unconditionally propagated to descendants.
    #[inline]
    fn inherited_flags() -> Self {
        Self::IS_RELEVANT_LINK_VISITED |
            Self::CAN_BE_FRAGMENTED |
            Self::IS_IN_FIRST_LINE_SUBTREE |
            Self::HAS_TEXT_DECORATION_LINES |
            Self::IS_IN_OPACITY_ZERO_SUBTREE |
            Self::SELF_OR_ANCESTOR_HAS_CONTAIN_STYLE |
            Self::SELF_OR_ANCESTOR_HAS_SIZE_CONTAINER_TYPE
    }

    /// Flags that may be propagated to descendants.
    #[inline]
    fn maybe_inherited_flags() -> Self {
        Self::inherited_flags() | Self::SHOULD_SUPPRESS_LINEBREAK
    }

    /// Flags that are an input to the cascade.
    #[inline]
    fn cascade_input_flags() -> Self {
        Self::USES_VIEWPORT_UNITS_ON_CONTAINER_QUERIES |
        Self::CONSIDERED_NONTRIVIAL_SCOPED_STYLE
    }

    /// Returns the flags that are always propagated to descendants.
    ///
    /// See StyleAdjuster::set_bits and StyleBuilder.
    #[inline]
    pub fn inherited(self) -> Self {
        self & Self::inherited_flags()
    }

    /// Flags that are conditionally propagated to descendants, just to handle
    /// properly style invalidation.
    #[inline]
    pub fn maybe_inherited(self) -> Self {
        self & Self::maybe_inherited_flags()
    }

    /// Flags that are an input to the cascade.
    #[inline]
    pub fn for_cascade_inputs(self) -> Self {
        self & Self::cascade_input_flags()
    }
}