layout: Move sizing logic from geom.rs to sizing.rs (#38568)

Moves `Size`, `SizeConstraint`, `Sizes` and `LazySizeData`.

Testing: Not needed, no change in behavior.

Signed-off-by: Oriol Brufau <obrufau@igalia.com>

components/layout/sizing.rs

@@ -4,17 +4,18 @@
 
 //! <https://drafts.csswg.org/css-sizing/>
 
-use std::cell::LazyCell;
+use std::cell::{LazyCell, OnceCell};
 use std::ops::{Add, AddAssign};
 
-use app_units::Au;
+use app_units::{Au, MAX_AU};
 use malloc_size_of_derive::MallocSizeOf;
 use style::Zero;
 use style::logical_geometry::Direction;
-use style::values::computed::LengthPercentage;
+use style::values::computed::{
+    LengthPercentage, MaxSize as StyleMaxSize, Percentage, Size as StyleSize,
+};
 
 use crate::context::LayoutContext;
-use crate::geom::{Size, SizeConstraint};
 use crate::style_ext::{AspectRatio, Clamp, ComputedValuesExt, ContentBoxSizesAndPBM, LayoutStyle};
 use crate::{ConstraintSpace, IndefiniteContainingBlock, LogicalVec2};
 
@@ -308,3 +309,517 @@ pub(crate) trait ComputeInlineContentSizes {
         result
     }
 }
+
+/// The possible values accepted by the sizing properties.
+/// <https://drafts.csswg.org/css-sizing/#sizing-properties>
+#[derive(Clone, Debug, PartialEq)]
+pub(crate) enum Size<T> {
+    /// Represents an `auto` value for the preferred and minimum size properties,
+    /// or `none` for the maximum size properties.
+    /// <https://drafts.csswg.org/css-sizing/#valdef-width-auto>
+    /// <https://drafts.csswg.org/css-sizing/#valdef-max-width-none>
+    Initial,
+    /// <https://drafts.csswg.org/css-sizing/#valdef-width-min-content>
+    MinContent,
+    /// <https://drafts.csswg.org/css-sizing/#valdef-width-max-content>
+    MaxContent,
+    /// <https://drafts.csswg.org/css-sizing-4/#valdef-width-fit-content>
+    FitContent,
+    /// <https://drafts.csswg.org/css-sizing-3/#funcdef-width-fit-content>
+    FitContentFunction(T),
+    /// <https://drafts.csswg.org/css-sizing-4/#valdef-width-stretch>
+    Stretch,
+    /// Represents a numeric `<length-percentage>`, but resolved as a `T`.
+    /// <https://drafts.csswg.org/css-sizing/#valdef-width-length-percentage-0>
+    Numeric(T),
+}
+
+impl<T: Copy> Copy for Size<T> {}
+
+impl<T> Default for Size<T> {
+    #[inline]
+    fn default() -> Self {
+        Self::Initial
+    }
+}
+
+impl<T> Size<T> {
+    #[inline]
+    pub(crate) fn is_initial(&self) -> bool {
+        matches!(self, Self::Initial)
+    }
+}
+
+impl<T: Clone> Size<T> {
+    #[inline]
+    pub(crate) fn to_numeric(&self) -> Option<T> {
+        match self {
+            Self::Numeric(numeric) => Some(numeric).cloned(),
+            _ => None,
+        }
+    }
+
+    #[inline]
+    pub(crate) fn map<U>(&self, f: impl FnOnce(T) -> U) -> Size<U> {
+        match self {
+            Size::Initial => Size::Initial,
+            Size::MinContent => Size::MinContent,
+            Size::MaxContent => Size::MaxContent,
+            Size::FitContent => Size::FitContent,
+            Size::FitContentFunction(size) => Size::FitContentFunction(f(size.clone())),
+            Size::Stretch => Size::Stretch,
+            Size::Numeric(numeric) => Size::Numeric(f(numeric.clone())),
+        }
+    }
+}
+
+impl From<StyleSize> for Size<LengthPercentage> {
+    fn from(size: StyleSize) -> Self {
+        match size {
+            StyleSize::LengthPercentage(lp) => Size::Numeric(lp.0),
+            StyleSize::Auto => Size::Initial,
+            StyleSize::MinContent => Size::MinContent,
+            StyleSize::MaxContent => Size::MaxContent,
+            StyleSize::FitContent => Size::FitContent,
+            StyleSize::FitContentFunction(lp) => Size::FitContentFunction(lp.0),
+            StyleSize::Stretch => Size::Stretch,
+            StyleSize::AnchorSizeFunction(_) | StyleSize::AnchorContainingCalcFunction(_) => {
+                unreachable!("anchor-size() should be disabled")
+            },
+        }
+    }
+}
+
+impl From<StyleMaxSize> for Size<LengthPercentage> {
+    fn from(max_size: StyleMaxSize) -> Self {
+        match max_size {
+            StyleMaxSize::LengthPercentage(lp) => Size::Numeric(lp.0),
+            StyleMaxSize::None => Size::Initial,
+            StyleMaxSize::MinContent => Size::MinContent,
+            StyleMaxSize::MaxContent => Size::MaxContent,
+            StyleMaxSize::FitContent => Size::FitContent,
+            StyleMaxSize::FitContentFunction(lp) => Size::FitContentFunction(lp.0),
+            StyleMaxSize::Stretch => Size::Stretch,
+            StyleMaxSize::AnchorSizeFunction(_) | StyleMaxSize::AnchorContainingCalcFunction(_) => {
+                unreachable!("anchor-size() should be disabled")
+            },
+        }
+    }
+}
+
+impl Size<LengthPercentage> {
+    #[inline]
+    pub(crate) fn to_percentage(&self) -> Option<Percentage> {
+        self.to_numeric()
+            .and_then(|length_percentage| length_percentage.to_percentage())
+    }
+
+    /// Resolves percentages in a preferred size, against the provided basis.
+    /// If the basis is missing, percentages are considered cyclic.
+    /// <https://www.w3.org/TR/css-sizing-3/#preferred-size-properties>
+    /// <https://www.w3.org/TR/css-sizing-3/#cyclic-percentage-size>
+    #[inline]
+    pub(crate) fn resolve_percentages_for_preferred(&self, basis: Option<Au>) -> Size<Au> {
+        match self {
+            Size::Numeric(numeric) => numeric
+                .maybe_to_used_value(basis)
+                .map_or(Size::Initial, Size::Numeric),
+            Size::FitContentFunction(numeric) => {
+                // Under discussion in https://github.com/w3c/csswg-drafts/issues/11805
+                numeric
+                    .maybe_to_used_value(basis)
+                    .map_or(Size::FitContent, Size::FitContentFunction)
+            },
+            _ => self.map(|_| unreachable!("This shouldn't be called for keywords")),
+        }
+    }
+
+    /// Resolves percentages in a maximum size, against the provided basis.
+    /// If the basis is missing, percentages are considered cyclic.
+    /// <https://www.w3.org/TR/css-sizing-3/#preferred-size-properties>
+    /// <https://www.w3.org/TR/css-sizing-3/#cyclic-percentage-size>
+    #[inline]
+    pub(crate) fn resolve_percentages_for_max(&self, basis: Option<Au>) -> Size<Au> {
+        match self {
+            Size::Numeric(numeric) => numeric
+                .maybe_to_used_value(basis)
+                .map_or(Size::Initial, Size::Numeric),
+            Size::FitContentFunction(numeric) => {
+                // Under discussion in https://github.com/w3c/csswg-drafts/issues/11805
+                numeric
+                    .maybe_to_used_value(basis)
+                    .map_or(Size::MaxContent, Size::FitContentFunction)
+            },
+            _ => self.map(|_| unreachable!("This shouldn't be called for keywords")),
+        }
+    }
+}
+
+impl LogicalVec2<Size<LengthPercentage>> {
+    pub(crate) fn percentages_relative_to_basis(
+        &self,
+        basis: &LogicalVec2<Au>,
+    ) -> LogicalVec2<Size<Au>> {
+        LogicalVec2 {
+            inline: self.inline.map(|value| value.to_used_value(basis.inline)),
+            block: self.block.map(|value| value.to_used_value(basis.block)),
+        }
+    }
+}
+
+impl Size<Au> {
+    /// Resolves a preferred size into a numerical value.
+    /// <https://www.w3.org/TR/css-sizing-3/#preferred-size-properties>
+    #[inline]
+    pub(crate) fn resolve_for_preferred<F: FnOnce() -> ContentSizes>(
+        &self,
+        automatic_size: Size<Au>,
+        stretch_size: Option<Au>,
+        content_size: &LazyCell<ContentSizes, F>,
+    ) -> Au {
+        match self {
+            Self::Initial => {
+                assert!(!automatic_size.is_initial());
+                automatic_size.resolve_for_preferred(automatic_size, stretch_size, content_size)
+            },
+            Self::MinContent => content_size.min_content,
+            Self::MaxContent => content_size.max_content,
+            Self::FitContentFunction(size) => content_size.shrink_to_fit(*size),
+            Self::FitContent => {
+                content_size.shrink_to_fit(stretch_size.unwrap_or_else(|| content_size.max_content))
+            },
+            Self::Stretch => stretch_size.unwrap_or_else(|| content_size.max_content),
+            Self::Numeric(numeric) => *numeric,
+        }
+    }
+
+    /// Resolves a minimum size into a numerical value.
+    /// <https://www.w3.org/TR/css-sizing-3/#min-size-properties>
+    #[inline]
+    pub(crate) fn resolve_for_min<F: FnOnce() -> ContentSizes>(
+        &self,
+        get_automatic_minimum_size: impl FnOnce() -> Au,
+        stretch_size: Option<Au>,
+        content_size: &LazyCell<ContentSizes, F>,
+        is_table: bool,
+    ) -> Au {
+        let result = match self {
+            Self::Initial => get_automatic_minimum_size(),
+            Self::MinContent => content_size.min_content,
+            Self::MaxContent => content_size.max_content,
+            Self::FitContentFunction(size) => content_size.shrink_to_fit(*size),
+            Self::FitContent => content_size.shrink_to_fit(stretch_size.unwrap_or_default()),
+            Self::Stretch => stretch_size.unwrap_or_default(),
+            Self::Numeric(numeric) => *numeric,
+        };
+        if is_table {
+            // In addition to the specified minimum, the inline size of a table is forced to be
+            // at least as big as its min-content size.
+            //
+            // Note that if there are collapsed columns, only the inline size of the table grid will
+            // shrink, while the size of the table wrapper (being computed here) won't be affected.
+            // However, collapsed rows should typically affect the block size of the table wrapper,
+            // so it might be wrong to use this function for that case.
+            // This is being discussed in https://github.com/w3c/csswg-drafts/issues/11408
+            result.max(content_size.min_content)
+        } else {
+            result
+        }
+    }
+
+    /// Resolves a maximum size into a numerical value.
+    /// <https://www.w3.org/TR/css-sizing-3/#max-size-properties>
+    #[inline]
+    pub(crate) fn resolve_for_max<F: FnOnce() -> ContentSizes>(
+        &self,
+        stretch_size: Option<Au>,
+        content_size: &LazyCell<ContentSizes, F>,
+    ) -> Option<Au> {
+        Some(match self {
+            Self::Initial => return None,
+            Self::MinContent => content_size.min_content,
+            Self::MaxContent => content_size.max_content,
+            Self::FitContentFunction(size) => content_size.shrink_to_fit(*size),
+            Self::FitContent => content_size.shrink_to_fit(stretch_size.unwrap_or(MAX_AU)),
+            Self::Stretch => return stretch_size,
+            Self::Numeric(numeric) => *numeric,
+        })
+    }
+
+    /// Tries to resolve an extrinsic size into a numerical value.
+    /// Extrinsic sizes are those based on the context of an element, without regard for its contents.
+    /// <https://drafts.csswg.org/css-sizing-3/#extrinsic>
+    ///
+    /// Returns `None` if either:
+    /// - The size is intrinsic.
+    /// - The size is the initial one.
+    ///   TODO: should we allow it to behave as `stretch` instead of assuming it's intrinsic?
+    /// - The provided `stretch_size` is `None` but we need its value.
+    #[inline]
+    pub(crate) fn maybe_resolve_extrinsic(&self, stretch_size: Option<Au>) -> Option<Au> {
+        match self {
+            Self::Initial |
+            Self::MinContent |
+            Self::MaxContent |
+            Self::FitContent |
+            Self::FitContentFunction(_) => None,
+            Self::Stretch => stretch_size,
+            Self::Numeric(numeric) => Some(*numeric),
+        }
+    }
+}
+
+/// Represents the sizing constraint that the preferred, min and max sizing properties
+/// impose on one axis.
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq)]
+pub(crate) enum SizeConstraint {
+    /// Represents a definite preferred size, clamped by minimum and maximum sizes (if any).
+    Definite(Au),
+    /// Represents an indefinite preferred size that allows a range of values between
+    /// the first argument (minimum size) and the second one (maximum size).
+    MinMax(Au, Option<Au>),
+}
+
+impl Default for SizeConstraint {
+    #[inline]
+    fn default() -> Self {
+        Self::MinMax(Au::default(), None)
+    }
+}
+
+impl SizeConstraint {
+    #[inline]
+    pub(crate) fn new(preferred_size: Option<Au>, min_size: Au, max_size: Option<Au>) -> Self {
+        preferred_size.map_or_else(
+            || Self::MinMax(min_size, max_size),
+            |size| Self::Definite(size.clamp_between_extremums(min_size, max_size)),
+        )
+    }
+
+    #[inline]
+    pub(crate) fn is_definite(self) -> bool {
+        matches!(self, Self::Definite(_))
+    }
+
+    #[inline]
+    pub(crate) fn to_definite(self) -> Option<Au> {
+        match self {
+            Self::Definite(size) => Some(size),
+            _ => None,
+        }
+    }
+}
+
+impl From<Option<Au>> for SizeConstraint {
+    fn from(size: Option<Au>) -> Self {
+        size.map(SizeConstraint::Definite).unwrap_or_default()
+    }
+}
+
+#[derive(Clone, Debug, Default)]
+pub(crate) struct Sizes {
+    /// <https://drafts.csswg.org/css-sizing-3/#preferred-size-properties>
+    pub preferred: Size<Au>,
+    /// <https://drafts.csswg.org/css-sizing-3/#min-size-properties>
+    pub min: Size<Au>,
+    /// <https://drafts.csswg.org/css-sizing-3/#max-size-properties>
+    pub max: Size<Au>,
+}
+
+impl Sizes {
+    #[inline]
+    pub(crate) fn new(preferred: Size<Au>, min: Size<Au>, max: Size<Au>) -> Self {
+        Self {
+            preferred,
+            min,
+            max,
+        }
+    }
+
+    /// Resolves the three sizes into a single numerical value.
+    #[inline]
+    pub(crate) fn resolve(
+        &self,
+        axis: Direction,
+        automatic_size: Size<Au>,
+        get_automatic_minimum_size: impl FnOnce() -> Au,
+        stretch_size: Option<Au>,
+        get_content_size: impl FnOnce() -> ContentSizes,
+        is_table: bool,
+    ) -> Au {
+        if is_table && axis == Direction::Block {
+            // The intrinsic block size of a table already takes sizing properties into account,
+            // but it can be a smaller amount if there are collapsed rows.
+            // Therefore, disregard sizing properties and just defer to the intrinsic size.
+            // This is being discussed in https://github.com/w3c/csswg-drafts/issues/11408
+            return get_content_size().max_content;
+        }
+        let (preferred, min, max) = self.resolve_each(
+            automatic_size,
+            get_automatic_minimum_size,
+            stretch_size,
+            get_content_size,
+            is_table,
+        );
+        preferred.clamp_between_extremums(min, max)
+    }
+
+    /// Resolves each of the three sizes into a numerical value, separately.
+    /// - The 1st returned value is the resolved preferred size.
+    /// - The 2nd returned value is the resolved minimum size.
+    /// - The 3rd returned value is the resolved maximum size. `None` means no maximum.
+    #[inline]
+    pub(crate) fn resolve_each(
+        &self,
+        automatic_size: Size<Au>,
+        get_automatic_minimum_size: impl FnOnce() -> Au,
+        stretch_size: Option<Au>,
+        get_content_size: impl FnOnce() -> ContentSizes,
+        is_table: bool,
+    ) -> (Au, Au, Option<Au>) {
+        // The provided `get_content_size` is a FnOnce but we may need its result multiple times.
+        // A LazyCell will only invoke it once if needed, and then reuse the result.
+        let content_size = LazyCell::new(get_content_size);
+        (
+            self.preferred
+                .resolve_for_preferred(automatic_size, stretch_size, &content_size),
+            self.min.resolve_for_min(
+                get_automatic_minimum_size,
+                stretch_size,
+                &content_size,
+                is_table,
+            ),
+            self.max.resolve_for_max(stretch_size, &content_size),
+        )
+    }
+
+    /// Tries to extrinsically resolve the three sizes into a single [`SizeConstraint`].
+    /// Values that are intrinsic or need `stretch_size` when it's `None` are handled as such:
+    /// - On the preferred size, they make the returned value be an indefinite [`SizeConstraint::MinMax`].
+    /// - On the min size, they are treated as `auto`, enforcing the automatic minimum size.
+    /// - On the max size, they are treated as `none`, enforcing no maximum.
+    #[inline]
+    pub(crate) fn resolve_extrinsic(
+        &self,
+        automatic_size: Size<Au>,
+        automatic_minimum_size: Au,
+        stretch_size: Option<Au>,
+    ) -> SizeConstraint {
+        let (preferred, min, max) =
+            self.resolve_each_extrinsic(automatic_size, automatic_minimum_size, stretch_size);
+        SizeConstraint::new(preferred, min, max)
+    }
+
+    /// Tries to extrinsically resolve each of the three sizes into a numerical value, separately.
+    /// This can't resolve values that are intrinsic or need `stretch_size` but it's `None`.
+    /// - The 1st returned value is the resolved preferred size. If it can't be resolved then
+    ///   the returned value is `None`. Note that this is different than treating it as `auto`.
+    ///   TODO: This needs to be discussed in <https://github.com/w3c/csswg-drafts/issues/11387>.
+    /// - The 2nd returned value is the resolved minimum size. If it can't be resolved then we
+    ///   treat it as the initial `auto`, returning the automatic minimum size.
+    /// - The 3rd returned value is the resolved maximum size. If it can't be resolved then we
+    ///   treat it as the initial `none`, returning `None`.
+    #[inline]
+    pub(crate) fn resolve_each_extrinsic(
+        &self,
+        automatic_size: Size<Au>,
+        automatic_minimum_size: Au,
+        stretch_size: Option<Au>,
+    ) -> (Option<Au>, Au, Option<Au>) {
+        (
+            if self.preferred.is_initial() {
+                automatic_size.maybe_resolve_extrinsic(stretch_size)
+            } else {
+                self.preferred.maybe_resolve_extrinsic(stretch_size)
+            },
+            self.min
+                .maybe_resolve_extrinsic(stretch_size)
+                .unwrap_or(automatic_minimum_size),
+            self.max.maybe_resolve_extrinsic(stretch_size),
+        )
+    }
+}
+
+struct LazySizeData<'a> {
+    sizes: &'a Sizes,
+    axis: Direction,
+    automatic_size: Size<Au>,
+    get_automatic_minimum_size: fn() -> Au,
+    stretch_size: Option<Au>,
+    is_table: bool,
+}
+
+/// Represents a size that can't be fully resolved until the intrinsic size
+/// is known. This is useful in the block axis, since the intrinsic size
+/// depends on layout, but the other inputs are known beforehand.
+pub(crate) struct LazySize<'a> {
+    result: OnceCell<Au>,
+    data: Option<LazySizeData<'a>>,
+}
+
+impl<'a> LazySize<'a> {
+    pub(crate) fn new(
+        sizes: &'a Sizes,
+        axis: Direction,
+        automatic_size: Size<Au>,
+        get_automatic_minimum_size: fn() -> Au,
+        stretch_size: Option<Au>,
+        is_table: bool,
+    ) -> Self {
+        Self {
+            result: OnceCell::new(),
+            data: Some(LazySizeData {
+                sizes,
+                axis,
+                automatic_size,
+                get_automatic_minimum_size,
+                stretch_size,
+                is_table,
+            }),
+        }
+    }
+
+    /// Creates a [`LazySize`] that will resolve to the intrinsic size.
+    /// Should be equivalent to [`LazySize::new()`] with default parameters,
+    /// but avoiding the trouble of getting a reference to a [`Sizes::default()`]
+    /// which lives long enough.
+    ///
+    /// TODO: It's not clear what this should do if/when [`LazySize::resolve()`]
+    /// is changed to accept a [`ContentSizes`] as the intrinsic size.
+    pub(crate) fn intrinsic() -> Self {
+        Self {
+            result: OnceCell::new(),
+            data: None,
+        }
+    }
+
+    /// Resolves the [`LazySize`] into [`Au`], caching the result.
+    /// The argument is a callback that computes the intrinsic size lazily.
+    ///
+    /// TODO: The intrinsic size should probably be a [`ContentSizes`] instead of [`Au`].
+    pub(crate) fn resolve(&self, get_content_size: impl FnOnce() -> Au) -> Au {
+        *self.result.get_or_init(|| {
+            let Some(ref data) = self.data else {
+                return get_content_size();
+            };
+            data.sizes.resolve(
+                data.axis,
+                data.automatic_size,
+                data.get_automatic_minimum_size,
+                data.stretch_size,
+                || get_content_size().into(),
+                data.is_table,
+            )
+        })
+    }
+}
+
+impl From<Au> for LazySize<'_> {
+    /// Creates a [`LazySize`] that will resolve to the given [`Au`],
+    /// ignoring the intrinsic size.
+    fn from(value: Au) -> Self {
+        let result = OnceCell::new();
+        result.set(value).unwrap();
+        LazySize { result, data: None }
+    }
+}