style: Implement parsing of container relative lengths

- For now, implementation always returns the fallback value, i.e. small viewport lengths.
- Enabled via existing pref `layout.css.container-queries.enabled`.

Differential Revision: https://phabricator.services.mozilla.com/D158054

components/style/values/computed/length.rs

@@ -58,6 +58,13 @@ impl specified::NoCalcLength {
                     .add_flags(ComputedValueFlags::USES_VIEWPORT_UNITS);
                 length.to_computed_value(context)
             },
+            specified::NoCalcLength::ContainerRelative(length) => {
+                // Fallback uses small viewport size.
+                context
+                    .builder
+                    .add_flags(ComputedValueFlags::USES_VIEWPORT_UNITS);
+                length.to_computed_value(context)
+            },
             specified::NoCalcLength::ServoCharacterWidth(length) => {
                 length.to_computed_value(context.style().get_font().clone_font_size().size())
             },

components/style/values/generics/calc.rs

@@ -44,6 +44,12 @@ pub enum SortKey {
     Percentage,
     Cap,
     Ch,
+    Cqb,
+    Cqh,
+    Cqi,
+    Cqmax,
+    Cqmin,
+    Cqw,
     Deg,
     Dvb,
     Dvh,

components/style/values/specified/calc.rs

@@ -9,8 +9,8 @@
 use crate::parser::ParserContext;
 use crate::values::generics::calc as generic;
 use crate::values::generics::calc::{MinMaxOp, SortKey};
-use crate::values::specified::length::ViewportPercentageLength;
 use crate::values::specified::length::{AbsoluteLength, FontRelativeLength, NoCalcLength};
+use crate::values::specified::length::{ContainerRelativeLength, ViewportPercentageLength};
 use crate::values::specified::{self, Angle, Time};
 use crate::values::{CSSFloat, CSSInteger};
 use cssparser::{AngleOrNumber, CowRcStr, NumberOrPercentage, Parser, Token};
@@ -258,6 +258,14 @@ impl generic::CalcNodeLeaf for Leaf {
                     ViewportPercentageLength::Lvi(..) => SortKey::Lvi,
                     ViewportPercentageLength::Dvi(..) => SortKey::Dvi,
                 },
+                NoCalcLength::ContainerRelative(ref cq) => match *cq {
+                    ContainerRelativeLength::Cqw(..) => SortKey::Cqw,
+                    ContainerRelativeLength::Cqh(..) => SortKey::Cqh,
+                    ContainerRelativeLength::Cqi(..) => SortKey::Cqi,
+                    ContainerRelativeLength::Cqb(..) => SortKey::Cqb,
+                    ContainerRelativeLength::Cqmin(..) => SortKey::Cqmin,
+                    ContainerRelativeLength::Cqmax(..) => SortKey::Cqmax,
+                },
                 NoCalcLength::ServoCharacterWidth(..) => unreachable!(),
             },
         }

components/style/values/specified/length.rs

@@ -642,6 +642,102 @@ impl Add<AbsoluteLength> for AbsoluteLength {
     }
 }
 
+/// A container query length.
+///
+/// <https://drafts.csswg.org/css-contain-3/#container-lengths>
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToCss, ToShmem)]
+pub enum ContainerRelativeLength {
+    /// 1% of query container's width
+    #[css(dimension)]
+    Cqw(CSSFloat),
+    /// 1% of query container's height
+    #[css(dimension)]
+    Cqh(CSSFloat),
+    /// 1% of query container's inline size
+    #[css(dimension)]
+    Cqi(CSSFloat),
+    /// 1% of query container's block size
+    #[css(dimension)]
+    Cqb(CSSFloat),
+    /// The smaller value of `cqi` or `cqb`
+    #[css(dimension)]
+    Cqmin(CSSFloat),
+    /// The larger value of `cqi` or `cqb`
+    #[css(dimension)]
+    Cqmax(CSSFloat),
+}
+
+impl ContainerRelativeLength {
+    fn unitless_value(&self) -> CSSFloat {
+        match *self {
+            ContainerRelativeLength::Cqw(v) |
+            ContainerRelativeLength::Cqh(v) |
+            ContainerRelativeLength::Cqi(v) |
+            ContainerRelativeLength::Cqb(v) |
+            ContainerRelativeLength::Cqmin(v) |
+            ContainerRelativeLength::Cqmax(v) => v,
+        }
+    }
+
+    fn is_zero(&self) -> bool {
+        self.unitless_value() == 0.
+    }
+
+    fn is_negative(&self) -> bool {
+        self.unitless_value() < 0.
+    }
+
+    fn try_sum(&self, other: &Self) -> Result<Self, ()> {
+        use self::ContainerRelativeLength::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return Err(());
+        }
+
+        Ok(match (self, other) {
+            (&Cqw(one), &Cqw(other)) => Cqw(one + other),
+            (&Cqh(one), &Cqh(other)) => Cqh(one + other),
+            (&Cqi(one), &Cqi(other)) => Cqi(one + other),
+            (&Cqb(one), &Cqb(other)) => Cqb(one + other),
+            (&Cqmin(one), &Cqmin(other)) => Cqmin(one + other),
+            (&Cqmax(one), &Cqmax(other)) => Cqmax(one + other),
+
+            // See https://github.com/rust-lang/rust/issues/68867, then
+            // https://github.com/rust-lang/rust/pull/95161. rustc isn't
+            // able to figure it own on its own so we help.
+            _ => unsafe {
+                match *self {
+                    Cqw(..) | Cqh(..) | Cqi(..) | Cqb(..) | Cqmin(..) | Cqmax(..) => {},
+                }
+                debug_unreachable!("Forgot to handle unit in try_sum()")
+            },
+        })
+    }
+
+    /// Computes the given container-relative length.
+    pub fn to_computed_value(&self, context: &Context) -> CSSPixelLength {
+        // TODO(dshin): For now, use the small viewport size.
+        let small_viewport_size = match *self {
+            ContainerRelativeLength::Cqw(v) => ViewportPercentageLength::Svw(v),
+            ContainerRelativeLength::Cqh(v) => ViewportPercentageLength::Svh(v),
+            ContainerRelativeLength::Cqi(v) => ViewportPercentageLength::Svi(v),
+            ContainerRelativeLength::Cqb(v) => ViewportPercentageLength::Svb(v),
+            ContainerRelativeLength::Cqmin(v) => ViewportPercentageLength::Svmin(v),
+            ContainerRelativeLength::Cqmax(v) => ViewportPercentageLength::Svmax(v),
+        };
+        small_viewport_size.to_computed_value(context)
+    }
+}
+
+#[cfg(feature = "gecko")]
+fn are_container_queries_enabled() -> bool {
+    static_prefs::pref!("layout.css.container-queries.enabled")
+}
+#[cfg(feature = "servo")]
+fn are_container_queries_enabled() -> bool {
+    false
+}
+
 /// A `<length>` without taking `calc` expressions into account
 ///
 /// <https://drafts.csswg.org/css-values/#lengths>
@@ -662,6 +758,10 @@ pub enum NoCalcLength {
     /// <https://drafts.csswg.org/css-values/#viewport-relative-lengths>
     ViewportPercentage(ViewportPercentageLength),
 
+    /// A container query length.
+    ///
+    /// <https://drafts.csswg.org/css-contain-3/#container-lengths>
+    ContainerRelative(ContainerRelativeLength),
     /// HTML5 "character width", as defined in HTML5 § 14.5.4.
     ///
     /// This cannot be specified by the user directly and is only generated by
@@ -679,6 +779,7 @@ impl Mul<CSSFloat> for NoCalcLength {
             NoCalcLength::Absolute(v) => NoCalcLength::Absolute(v * scalar),
             NoCalcLength::FontRelative(v) => NoCalcLength::FontRelative(v * scalar),
             NoCalcLength::ViewportPercentage(v) => NoCalcLength::ViewportPercentage(v * scalar),
+            NoCalcLength::ContainerRelative(v) => NoCalcLength::ContainerRelative(v * scalar),
             NoCalcLength::ServoCharacterWidth(_) => panic!("Can't multiply ServoCharacterWidth!"),
         }
     }
@@ -691,6 +792,7 @@ impl NoCalcLength {
             NoCalcLength::Absolute(v) => v.unitless_value(),
             NoCalcLength::FontRelative(v) => v.unitless_value(),
             NoCalcLength::ViewportPercentage(v) => v.unitless_value(),
+            NoCalcLength::ContainerRelative(v) => v.unitless_value(),
             NoCalcLength::ServoCharacterWidth(c) => c.0 as f32,
         }
     }
@@ -701,6 +803,7 @@ impl NoCalcLength {
             NoCalcLength::Absolute(v) => v.is_negative(),
             NoCalcLength::FontRelative(v) => v.is_negative(),
             NoCalcLength::ViewportPercentage(v) => v.is_negative(),
+            NoCalcLength::ContainerRelative(v) => v.is_negative(),
             NoCalcLength::ServoCharacterWidth(c) => c.0 < 0,
         }
     }
@@ -711,8 +814,11 @@ impl NoCalcLength {
     /// because the font they're relative to should be zoomed already.
     pub fn should_zoom_text(&self) -> bool {
         match *self {
-            Self::Absolute(..) | Self::ViewportPercentage(..) => true,
+            Self::Absolute(..) |
-            Self::ServoCharacterWidth(..) | Self::FontRelative(..) => false,
+            Self::ViewportPercentage(..) |
+            Self::ContainerRelative(..) => true,
+            Self::ServoCharacterWidth(..) |
+            Self::FontRelative(..) => false,
         }
     }
 
@@ -810,6 +916,26 @@ impl NoCalcLength {
             "dvi" if !context.in_page_rule() => {
                 NoCalcLength::ViewportPercentage(ViewportPercentageLength::Dvi(value))
             },
+            // Container query lengths. Inherit the limitation from viewport units since
+            // we may fall back to them.
+            "cqw" if !context.in_page_rule() && are_container_queries_enabled() => {
+                NoCalcLength::ContainerRelative(ContainerRelativeLength::Cqw(value))
+            },
+            "cqh" if !context.in_page_rule() && are_container_queries_enabled() => {
+                NoCalcLength::ContainerRelative(ContainerRelativeLength::Cqh(value))
+            },
+            "cqi" if !context.in_page_rule() && are_container_queries_enabled() => {
+                NoCalcLength::ContainerRelative(ContainerRelativeLength::Cqi(value))
+            },
+            "cqb" if !context.in_page_rule() && are_container_queries_enabled() => {
+                NoCalcLength::ContainerRelative(ContainerRelativeLength::Cqb(value))
+            },
+            "cqmin" if !context.in_page_rule() && are_container_queries_enabled() => {
+                NoCalcLength::ContainerRelative(ContainerRelativeLength::Cqmin(value))
+            },
+            "cqmax" if !context.in_page_rule() && are_container_queries_enabled() => {
+                NoCalcLength::ContainerRelative(ContainerRelativeLength::Cqmax(value))
+            },
             _ => return Err(()),
         })
     }
@@ -828,6 +954,9 @@ impl NoCalcLength {
             (&ViewportPercentage(ref one), &ViewportPercentage(ref other)) => {
                 ViewportPercentage(one.try_sum(other)?)
             },
+            (&ContainerRelative(ref one), &ContainerRelative(ref other)) => {
+                ContainerRelative(one.try_sum(other)?)
+            },
             (&ServoCharacterWidth(ref one), &ServoCharacterWidth(ref other)) => {
                 ServoCharacterWidth(CharacterWidth(one.0 + other.0))
             },
@@ -838,6 +967,7 @@ impl NoCalcLength {
                     Absolute(..) |
                     FontRelative(..) |
                     ViewportPercentage(..) |
+                    ContainerRelative(..) |
                     ServoCharacterWidth(..) => {},
                 }
                 debug_unreachable!("Forgot to handle unit in try_sum()")
@@ -877,6 +1007,7 @@ impl PartialOrd for NoCalcLength {
             (&ViewportPercentage(ref one), &ViewportPercentage(ref other)) => {
                 one.partial_cmp(other)
             },
+            (&ContainerRelative(ref one), &ContainerRelative(ref other)) => one.partial_cmp(other),
             (&ServoCharacterWidth(ref one), &ServoCharacterWidth(ref other)) => {
                 one.0.partial_cmp(&other.0)
             },
@@ -887,6 +1018,7 @@ impl PartialOrd for NoCalcLength {
                     Absolute(..) |
                     FontRelative(..) |
                     ViewportPercentage(..) |
+                    ContainerRelative(..) |
                     ServoCharacterWidth(..) => {},
                 }
                 debug_unreachable!("Forgot an arm in partial_cmp?")
@@ -905,6 +1037,7 @@ impl Zero for NoCalcLength {
             NoCalcLength::Absolute(v) => v.is_zero(),
             NoCalcLength::FontRelative(v) => v.is_zero(),
             NoCalcLength::ViewportPercentage(v) => v.is_zero(),
+            NoCalcLength::ContainerRelative(v) => v.is_zero(),
             NoCalcLength::ServoCharacterWidth(v) => v.0 == 0,
         }
     }
@@ -986,6 +1119,51 @@ impl Mul<CSSFloat> for FontRelativeLength {
     }
 }
 
+impl Mul<CSSFloat> for ContainerRelativeLength {
+    type Output = ContainerRelativeLength;
+
+    #[inline]
+    fn mul(self, scalar: CSSFloat) -> ContainerRelativeLength {
+        match self {
+            ContainerRelativeLength::Cqw(v) => ContainerRelativeLength::Cqw(v * scalar),
+            ContainerRelativeLength::Cqh(v) => ContainerRelativeLength::Cqh(v * scalar),
+            ContainerRelativeLength::Cqi(v) => ContainerRelativeLength::Cqi(v * scalar),
+            ContainerRelativeLength::Cqb(v) => ContainerRelativeLength::Cqb(v * scalar),
+            ContainerRelativeLength::Cqmin(v) => ContainerRelativeLength::Cqmin(v * scalar),
+            ContainerRelativeLength::Cqmax(v) => ContainerRelativeLength::Cqmax(v * scalar),
+        }
+    }
+}
+
+impl PartialOrd for ContainerRelativeLength {
+    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+        use self::ContainerRelativeLength::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return None;
+        }
+
+        match (self, other) {
+            (&Cqw(ref one), &Cqw(ref other)) => one.partial_cmp(other),
+            (&Cqh(ref one), &Cqh(ref other)) => one.partial_cmp(other),
+            (&Cqi(ref one), &Cqi(ref other)) => one.partial_cmp(other),
+            (&Cqb(ref one), &Cqb(ref other)) => one.partial_cmp(other),
+            (&Cqmin(ref one), &Cqmin(ref other)) => one.partial_cmp(other),
+            (&Cqmax(ref one), &Cqmax(ref other)) => one.partial_cmp(other),
+
+            // See https://github.com/rust-lang/rust/issues/68867, then
+            // https://github.com/rust-lang/rust/pull/95161. rustc isn't
+            // able to figure it own on its own so we help.
+            _ => unsafe {
+                match *self {
+                    Cqw(..) | Cqh(..) | Cqi(..) | Cqb(..) | Cqmin(..) | Cqmax(..) => {},
+                }
+                debug_unreachable!("Forgot to handle unit in try_sum()")
+            },
+        }
+    }
+}
+
 impl Mul<CSSFloat> for ViewportPercentageLength {
     type Output = ViewportPercentageLength;