tor-browser

The Tor Browser
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grid.rs (26570B)


      1 /* This Source Code Form is subject to the terms of the Mozilla Public
      2 * License, v. 2.0. If a copy of the MPL was not distributed with this
      3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
      4 
      5 //! Generic types for the handling of
      6 //! [grids](https://drafts.csswg.org/css-grid/).
      7 
      8 use crate::derives::*;
      9 use crate::parser::{Parse, ParserContext};
     10 use crate::values::specified;
     11 use crate::values::{CSSFloat, CustomIdent};
     12 use crate::{One, Zero};
     13 use cssparser::Parser;
     14 use std::fmt::{self, Write};
     15 use std::{cmp, usize};
     16 use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
     17 
     18 /// These are the limits that we choose to clamp grid line numbers to.
     19 /// http://drafts.csswg.org/css-grid/#overlarge-grids
     20 /// line_num is clamped to this range at parse time.
     21 pub const MIN_GRID_LINE: i32 = -10000;
     22 /// See above.
     23 pub const MAX_GRID_LINE: i32 = 10000;
     24 
     25 /// A `<grid-line>` type.
     26 ///
     27 /// <https://drafts.csswg.org/css-grid/#typedef-grid-row-start-grid-line>
     28 #[derive(
     29    Clone,
     30    Debug,
     31    Default,
     32    MallocSizeOf,
     33    PartialEq,
     34    SpecifiedValueInfo,
     35    ToComputedValue,
     36    ToResolvedValue,
     37    ToShmem,
     38    ToTyped,
     39 )]
     40 #[repr(C)]
     41 pub struct GenericGridLine<Integer> {
     42    /// A custom identifier for named lines, or the empty atom otherwise.
     43    ///
     44    /// <https://drafts.csswg.org/css-grid/#grid-placement-slot>
     45    pub ident: CustomIdent,
     46    /// Denotes the nth grid line from grid item's placement.
     47    ///
     48    /// This is clamped by MIN_GRID_LINE and MAX_GRID_LINE.
     49    ///
     50    /// NOTE(emilio): If we ever allow animating these we need to either do
     51    /// something more complicated for the clamping, or do this clamping at
     52    /// used-value time.
     53    pub line_num: Integer,
     54    /// Flag to check whether it's a `span` keyword.
     55    pub is_span: bool,
     56 }
     57 
     58 pub use self::GenericGridLine as GridLine;
     59 
     60 impl<Integer> GridLine<Integer>
     61 where
     62    Integer: PartialEq + Zero,
     63 {
     64    /// The `auto` value.
     65    pub fn auto() -> Self {
     66        Self {
     67            is_span: false,
     68            line_num: Zero::zero(),
     69            ident: CustomIdent(atom!("")),
     70        }
     71    }
     72 
     73    /// Check whether this `<grid-line>` represents an `auto` value.
     74    pub fn is_auto(&self) -> bool {
     75        self.ident.0 == atom!("") && self.line_num.is_zero() && !self.is_span
     76    }
     77 
     78    /// Check whether this `<grid-line>` represents a `<custom-ident>` value.
     79    pub fn is_ident_only(&self) -> bool {
     80        self.ident.0 != atom!("") && self.line_num.is_zero() && !self.is_span
     81    }
     82 
     83    /// Check if `self` makes `other` omittable according to the rules at:
     84    /// https://drafts.csswg.org/css-grid/#propdef-grid-column
     85    /// https://drafts.csswg.org/css-grid/#propdef-grid-area
     86    pub fn can_omit(&self, other: &Self) -> bool {
     87        if self.is_ident_only() {
     88            self == other
     89        } else {
     90            other.is_auto()
     91        }
     92    }
     93 }
     94 
     95 impl<Integer> ToCss for GridLine<Integer>
     96 where
     97    Integer: ToCss + PartialEq + Zero + One,
     98 {
     99    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
    100    where
    101        W: Write,
    102    {
    103        // 1. `auto`
    104        if self.is_auto() {
    105            return dest.write_str("auto");
    106        }
    107 
    108        // 2. `<custom-ident>`
    109        if self.is_ident_only() {
    110            return self.ident.to_css(dest);
    111        }
    112 
    113        // 3. `[ span && [ <integer [1,∞]> || <custom-ident> ] ]`
    114        let has_ident = self.ident.0 != atom!("");
    115        if self.is_span {
    116            dest.write_str("span")?;
    117            debug_assert!(!self.line_num.is_zero() || has_ident);
    118 
    119            // We omit `line_num` if
    120            // 1. we don't specify it, or
    121            // 2. it is the default value, i.e. 1.0, and the ident is specified.
    122            // https://drafts.csswg.org/css-grid/#grid-placement-span-int
    123            if !self.line_num.is_zero() && !(self.line_num.is_one() && has_ident) {
    124                dest.write_char(' ')?;
    125                self.line_num.to_css(dest)?;
    126            }
    127 
    128            if has_ident {
    129                dest.write_char(' ')?;
    130                self.ident.to_css(dest)?;
    131            }
    132            return Ok(());
    133        }
    134 
    135        // 4. `[ <integer [-∞,-1]> | <integer [1,∞]> ] && <custom-ident>? ]`
    136        debug_assert!(!self.line_num.is_zero());
    137        self.line_num.to_css(dest)?;
    138        if has_ident {
    139            dest.write_char(' ')?;
    140            self.ident.to_css(dest)?;
    141        }
    142        Ok(())
    143    }
    144 }
    145 
    146 impl Parse for GridLine<specified::Integer> {
    147    fn parse<'i, 't>(
    148        context: &ParserContext,
    149        input: &mut Parser<'i, 't>,
    150    ) -> Result<Self, ParseError<'i>> {
    151        let mut grid_line = Self::auto();
    152        if input.try_parse(|i| i.expect_ident_matching("auto")).is_ok() {
    153            return Ok(grid_line);
    154        }
    155 
    156        // <custom-ident> | [ <integer> && <custom-ident>? ] | [ span && [ <integer> || <custom-ident> ] ]
    157        // This <grid-line> horror is simply,
    158        // [ span? && [ <custom-ident> || <integer> ] ]
    159        // And, for some magical reason, "span" should be the first or last value and not in-between.
    160        let mut val_before_span = false;
    161 
    162        for _ in 0..3 {
    163            // Maximum possible entities for <grid-line>
    164            let location = input.current_source_location();
    165            if input.try_parse(|i| i.expect_ident_matching("span")).is_ok() {
    166                if grid_line.is_span {
    167                    return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
    168                }
    169 
    170                if !grid_line.line_num.is_zero() || grid_line.ident.0 != atom!("") {
    171                    val_before_span = true;
    172                }
    173 
    174                grid_line.is_span = true;
    175            } else if let Ok(i) = input.try_parse(|i| specified::Integer::parse(context, i)) {
    176                // FIXME(emilio): Probably shouldn't reject if it's calc()...
    177                let value = i.value();
    178                if value == 0 || val_before_span || !grid_line.line_num.is_zero() {
    179                    return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
    180                }
    181 
    182                grid_line.line_num = specified::Integer::new(cmp::max(
    183                    MIN_GRID_LINE,
    184                    cmp::min(value, MAX_GRID_LINE),
    185                ));
    186            } else if let Ok(name) = input.try_parse(|i| CustomIdent::parse(i, &["auto"])) {
    187                if val_before_span || grid_line.ident.0 != atom!("") {
    188                    return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
    189                }
    190                // NOTE(emilio): `span` is consumed above, so we only need to
    191                // reject `auto`.
    192                grid_line.ident = name;
    193            } else {
    194                break;
    195            }
    196        }
    197 
    198        if grid_line.is_auto() {
    199            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
    200        }
    201 
    202        if grid_line.is_span {
    203            if !grid_line.line_num.is_zero() {
    204                if grid_line.line_num.value() <= 0 {
    205                    // disallow negative integers for grid spans
    206                    return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
    207                }
    208            } else if grid_line.ident.0 == atom!("") {
    209                // integer could be omitted
    210                return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
    211            }
    212        }
    213 
    214        Ok(grid_line)
    215    }
    216 }
    217 
    218 /// A track breadth for explicit grid track sizing. It's generic solely to
    219 /// avoid re-implementing it for the computed type.
    220 ///
    221 /// <https://drafts.csswg.org/css-grid/#typedef-track-breadth>
    222 #[derive(
    223    Animate,
    224    Clone,
    225    Debug,
    226    MallocSizeOf,
    227    PartialEq,
    228    SpecifiedValueInfo,
    229    ToAnimatedValue,
    230    ToComputedValue,
    231    ToCss,
    232    ToResolvedValue,
    233    ToShmem,
    234 )]
    235 #[repr(C, u8)]
    236 pub enum GenericTrackBreadth<L> {
    237    /// The generic type is almost always a non-negative `<length-percentage>`
    238    Breadth(L),
    239    /// A flex fraction specified in `fr` units.
    240    #[css(dimension)]
    241    Fr(CSSFloat),
    242    /// `auto`
    243    Auto,
    244    /// `min-content`
    245    MinContent,
    246    /// `max-content`
    247    MaxContent,
    248 }
    249 
    250 pub use self::GenericTrackBreadth as TrackBreadth;
    251 
    252 impl<L> TrackBreadth<L> {
    253    /// Check whether this is a `<fixed-breadth>` (i.e., it only has `<length-percentage>`)
    254    ///
    255    /// <https://drafts.csswg.org/css-grid/#typedef-fixed-breadth>
    256    #[inline]
    257    pub fn is_fixed(&self) -> bool {
    258        matches!(*self, TrackBreadth::Breadth(..))
    259    }
    260 }
    261 
    262 /// A `<track-size>` type for explicit grid track sizing. Like `<track-breadth>`, this is
    263 /// generic only to avoid code bloat. It only takes `<length-percentage>`
    264 ///
    265 /// <https://drafts.csswg.org/css-grid/#typedef-track-size>
    266 #[derive(
    267    Clone,
    268    Debug,
    269    MallocSizeOf,
    270    PartialEq,
    271    SpecifiedValueInfo,
    272    ToAnimatedValue,
    273    ToComputedValue,
    274    ToResolvedValue,
    275    ToShmem,
    276 )]
    277 #[repr(C, u8)]
    278 pub enum GenericTrackSize<L> {
    279    /// A flexible `<track-breadth>`
    280    Breadth(GenericTrackBreadth<L>),
    281    /// A `minmax` function for a range over an inflexible `<track-breadth>`
    282    /// and a flexible `<track-breadth>`
    283    ///
    284    /// <https://drafts.csswg.org/css-grid/#valdef-grid-template-columns-minmax>
    285    #[css(function)]
    286    Minmax(GenericTrackBreadth<L>, GenericTrackBreadth<L>),
    287    /// A `fit-content` function.
    288    ///
    289    /// This stores a TrackBreadth<L> for convenience, but it can only be a
    290    /// LengthPercentage.
    291    ///
    292    /// <https://drafts.csswg.org/css-grid/#valdef-grid-template-columns-fit-content>
    293    #[css(function)]
    294    FitContent(GenericTrackBreadth<L>),
    295 }
    296 
    297 pub use self::GenericTrackSize as TrackSize;
    298 
    299 impl<L> TrackSize<L> {
    300    /// The initial value.
    301    const INITIAL_VALUE: Self = TrackSize::Breadth(TrackBreadth::Auto);
    302 
    303    /// Returns the initial value.
    304    pub const fn initial_value() -> Self {
    305        Self::INITIAL_VALUE
    306    }
    307 
    308    /// Returns true if `self` is the initial value.
    309    pub fn is_initial(&self) -> bool {
    310        matches!(*self, TrackSize::Breadth(TrackBreadth::Auto)) // FIXME: can't use Self::INITIAL_VALUE here yet: https://github.com/rust-lang/rust/issues/66585
    311    }
    312 
    313    /// Check whether this is a `<fixed-size>`
    314    ///
    315    /// <https://drafts.csswg.org/css-grid/#typedef-fixed-size>
    316    pub fn is_fixed(&self) -> bool {
    317        match *self {
    318            TrackSize::Breadth(ref breadth) => breadth.is_fixed(),
    319            // For minmax function, it could be either
    320            // minmax(<fixed-breadth>, <track-breadth>) or minmax(<inflexible-breadth>, <fixed-breadth>),
    321            // and since both variants are a subset of minmax(<inflexible-breadth>, <track-breadth>), we only
    322            // need to make sure that they're fixed. So, we don't have to modify the parsing function.
    323            TrackSize::Minmax(ref breadth_1, ref breadth_2) => {
    324                if breadth_1.is_fixed() {
    325                    return true; // the second value is always a <track-breadth>
    326                }
    327 
    328                match *breadth_1 {
    329                    TrackBreadth::Fr(_) => false, // should be <inflexible-breadth> at this point
    330                    _ => breadth_2.is_fixed(),
    331                }
    332            },
    333            TrackSize::FitContent(_) => false,
    334        }
    335    }
    336 }
    337 
    338 impl<L> Default for TrackSize<L> {
    339    fn default() -> Self {
    340        Self::initial_value()
    341    }
    342 }
    343 
    344 impl<L: ToCss> ToCss for TrackSize<L> {
    345    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
    346    where
    347        W: Write,
    348    {
    349        match *self {
    350            TrackSize::Breadth(ref breadth) => breadth.to_css(dest),
    351            TrackSize::Minmax(ref min, ref max) => {
    352                // According to gecko minmax(auto, <flex>) is equivalent to <flex>,
    353                // and both are serialized as <flex>.
    354                if let TrackBreadth::Auto = *min {
    355                    if let TrackBreadth::Fr(_) = *max {
    356                        return max.to_css(dest);
    357                    }
    358                }
    359 
    360                dest.write_str("minmax(")?;
    361                min.to_css(dest)?;
    362                dest.write_str(", ")?;
    363                max.to_css(dest)?;
    364                dest.write_char(')')
    365            },
    366            TrackSize::FitContent(ref lp) => {
    367                dest.write_str("fit-content(")?;
    368                lp.to_css(dest)?;
    369                dest.write_char(')')
    370            },
    371        }
    372    }
    373 }
    374 
    375 /// A `<track-size>+`.
    376 /// We use the empty slice as `auto`, and always parse `auto` as an empty slice.
    377 /// This means it's impossible to have a slice containing only one auto item.
    378 #[derive(
    379    Clone,
    380    Debug,
    381    Default,
    382    MallocSizeOf,
    383    PartialEq,
    384    SpecifiedValueInfo,
    385    ToComputedValue,
    386    ToCss,
    387    ToResolvedValue,
    388    ToShmem,
    389    ToTyped,
    390 )]
    391 #[repr(transparent)]
    392 pub struct GenericImplicitGridTracks<T>(
    393    #[css(if_empty = "auto", iterable)] pub crate::OwnedSlice<T>,
    394 );
    395 
    396 pub use self::GenericImplicitGridTracks as ImplicitGridTracks;
    397 
    398 impl<T: fmt::Debug + Default + PartialEq> ImplicitGridTracks<T> {
    399    /// Returns true if current value is same as its initial value (i.e. auto).
    400    pub fn is_initial(&self) -> bool {
    401        debug_assert_ne!(
    402            *self,
    403            ImplicitGridTracks(crate::OwnedSlice::from(vec![Default::default()]))
    404        );
    405        self.0.is_empty()
    406    }
    407 }
    408 
    409 /// Helper function for serializing identifiers with a prefix and suffix, used
    410 /// for serializing <line-names> (in grid).
    411 pub fn concat_serialize_idents<W>(
    412    prefix: &str,
    413    suffix: &str,
    414    slice: &[CustomIdent],
    415    sep: &str,
    416    dest: &mut CssWriter<W>,
    417 ) -> fmt::Result
    418 where
    419    W: Write,
    420 {
    421    if let Some((ref first, rest)) = slice.split_first() {
    422        dest.write_str(prefix)?;
    423        first.to_css(dest)?;
    424        for thing in rest {
    425            dest.write_str(sep)?;
    426            thing.to_css(dest)?;
    427        }
    428 
    429        dest.write_str(suffix)?;
    430    }
    431 
    432    Ok(())
    433 }
    434 
    435 /// The initial argument of the `repeat` function.
    436 ///
    437 /// <https://drafts.csswg.org/css-grid/#typedef-track-repeat>
    438 #[derive(
    439    Clone,
    440    Copy,
    441    Debug,
    442    MallocSizeOf,
    443    PartialEq,
    444    SpecifiedValueInfo,
    445    ToAnimatedValue,
    446    ToComputedValue,
    447    ToCss,
    448    ToResolvedValue,
    449    ToShmem,
    450 )]
    451 #[repr(C, u8)]
    452 pub enum RepeatCount<Integer> {
    453    /// A positive integer. This is allowed only for `<track-repeat>` and `<fixed-repeat>`
    454    Number(Integer),
    455    /// An `<auto-fill>` keyword allowed only for `<auto-repeat>`
    456    AutoFill,
    457    /// An `<auto-fit>` keyword allowed only for `<auto-repeat>`
    458    AutoFit,
    459 }
    460 
    461 impl Parse for RepeatCount<specified::Integer> {
    462    fn parse<'i, 't>(
    463        context: &ParserContext,
    464        input: &mut Parser<'i, 't>,
    465    ) -> Result<Self, ParseError<'i>> {
    466        if let Ok(mut i) = input.try_parse(|i| specified::Integer::parse_positive(context, i)) {
    467            if i.value() > MAX_GRID_LINE {
    468                i = specified::Integer::new(MAX_GRID_LINE);
    469            }
    470            return Ok(RepeatCount::Number(i));
    471        }
    472        try_match_ident_ignore_ascii_case! { input,
    473            "auto-fill" => Ok(RepeatCount::AutoFill),
    474            "auto-fit" => Ok(RepeatCount::AutoFit),
    475        }
    476    }
    477 }
    478 
    479 /// The structure containing `<line-names>` and `<track-size>` values.
    480 #[derive(
    481    Clone,
    482    Debug,
    483    MallocSizeOf,
    484    PartialEq,
    485    SpecifiedValueInfo,
    486    ToAnimatedValue,
    487    ToComputedValue,
    488    ToResolvedValue,
    489    ToShmem,
    490 )]
    491 #[css(function = "repeat")]
    492 #[repr(C)]
    493 pub struct GenericTrackRepeat<L, I> {
    494    /// The number of times for the value to be repeated (could also be `auto-fit` or `auto-fill`)
    495    pub count: RepeatCount<I>,
    496    /// `<line-names>` accompanying `<track_size>` values.
    497    ///
    498    /// If there's no `<line-names>`, then it's represented by an empty vector.
    499    /// For N `<track-size>` values, there will be N+1 `<line-names>`, and so this vector's
    500    /// length is always one value more than that of the `<track-size>`.
    501    pub line_names: crate::OwnedSlice<crate::OwnedSlice<CustomIdent>>,
    502    /// `<track-size>` values.
    503    pub track_sizes: crate::OwnedSlice<GenericTrackSize<L>>,
    504 }
    505 
    506 pub use self::GenericTrackRepeat as TrackRepeat;
    507 
    508 impl<L: ToCss, I: ToCss> ToCss for TrackRepeat<L, I> {
    509    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
    510    where
    511        W: Write,
    512    {
    513        dest.write_str("repeat(")?;
    514        self.count.to_css(dest)?;
    515        dest.write_str(", ")?;
    516 
    517        let mut line_names_iter = self.line_names.iter();
    518        for (i, (ref size, ref names)) in self
    519            .track_sizes
    520            .iter()
    521            .zip(&mut line_names_iter)
    522            .enumerate()
    523        {
    524            if i > 0 {
    525                dest.write_char(' ')?;
    526            }
    527 
    528            concat_serialize_idents("[", "] ", names, " ", dest)?;
    529            size.to_css(dest)?;
    530        }
    531 
    532        if let Some(line_names_last) = line_names_iter.next() {
    533            concat_serialize_idents(" [", "]", line_names_last, " ", dest)?;
    534        }
    535 
    536        dest.write_char(')')?;
    537 
    538        Ok(())
    539    }
    540 }
    541 
    542 /// Track list values. Can be <track-size> or <track-repeat>
    543 #[derive(
    544    Animate,
    545    Clone,
    546    Debug,
    547    MallocSizeOf,
    548    PartialEq,
    549    SpecifiedValueInfo,
    550    ToAnimatedValue,
    551    ToComputedValue,
    552    ToCss,
    553    ToResolvedValue,
    554    ToShmem,
    555 )]
    556 #[repr(C, u8)]
    557 pub enum GenericTrackListValue<LengthPercentage, Integer> {
    558    /// A <track-size> value.
    559    TrackSize(#[animation(field_bound)] GenericTrackSize<LengthPercentage>),
    560    /// A <track-repeat> value.
    561    TrackRepeat(#[animation(field_bound)] GenericTrackRepeat<LengthPercentage, Integer>),
    562 }
    563 
    564 pub use self::GenericTrackListValue as TrackListValue;
    565 
    566 impl<L, I> TrackListValue<L, I> {
    567    // FIXME: can't use TrackSize::initial_value() here b/c rustc error "is not yet stable as a const fn"
    568    const INITIAL_VALUE: Self = TrackListValue::TrackSize(TrackSize::Breadth(TrackBreadth::Auto));
    569 
    570    fn is_repeat(&self) -> bool {
    571        matches!(*self, TrackListValue::TrackRepeat(..))
    572    }
    573 
    574    /// Returns true if `self` is the initial value.
    575    pub fn is_initial(&self) -> bool {
    576        matches!(
    577            *self,
    578            TrackListValue::TrackSize(TrackSize::Breadth(TrackBreadth::Auto))
    579        ) // FIXME: can't use Self::INITIAL_VALUE here yet: https://github.com/rust-lang/rust/issues/66585
    580    }
    581 }
    582 
    583 impl<L, I> Default for TrackListValue<L, I> {
    584    #[inline]
    585    fn default() -> Self {
    586        Self::INITIAL_VALUE
    587    }
    588 }
    589 
    590 /// A grid `<track-list>` type.
    591 ///
    592 /// <https://drafts.csswg.org/css-grid/#typedef-track-list>
    593 #[derive(
    594    Clone,
    595    Debug,
    596    MallocSizeOf,
    597    PartialEq,
    598    SpecifiedValueInfo,
    599    ToAnimatedValue,
    600    ToComputedValue,
    601    ToResolvedValue,
    602    ToShmem,
    603 )]
    604 #[repr(C)]
    605 pub struct GenericTrackList<LengthPercentage, Integer> {
    606    /// The index in `values` where our `<auto-repeat>` value is, if in bounds.
    607    #[css(skip)]
    608    pub auto_repeat_index: usize,
    609    /// A vector of `<track-size> | <track-repeat>` values.
    610    pub values: crate::OwnedSlice<GenericTrackListValue<LengthPercentage, Integer>>,
    611    /// `<line-names>` accompanying `<track-size> | <track-repeat>` values.
    612    ///
    613    /// If there's no `<line-names>`, then it's represented by an empty vector.
    614    /// For N values, there will be N+1 `<line-names>`, and so this vector's
    615    /// length is always one value more than that of the `<track-size>`.
    616    pub line_names: crate::OwnedSlice<crate::OwnedSlice<CustomIdent>>,
    617 }
    618 
    619 pub use self::GenericTrackList as TrackList;
    620 
    621 impl<L, I> TrackList<L, I> {
    622    /// Whether this track list is an explicit track list (that is, doesn't have
    623    /// any repeat values).
    624    pub fn is_explicit(&self) -> bool {
    625        !self.values.iter().any(|v| v.is_repeat())
    626    }
    627 
    628    /// Whether this track list has an `<auto-repeat>` value.
    629    pub fn has_auto_repeat(&self) -> bool {
    630        self.auto_repeat_index < self.values.len()
    631    }
    632 }
    633 
    634 impl<L: ToCss, I: ToCss> ToCss for TrackList<L, I> {
    635    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
    636    where
    637        W: Write,
    638    {
    639        let mut values_iter = self.values.iter().peekable();
    640        let mut line_names_iter = self.line_names.iter().peekable();
    641 
    642        for idx in 0.. {
    643            let names = line_names_iter.next().unwrap(); // This should exist!
    644            concat_serialize_idents("[", "]", names, " ", dest)?;
    645 
    646            match values_iter.next() {
    647                Some(value) => {
    648                    if !names.is_empty() {
    649                        dest.write_char(' ')?;
    650                    }
    651 
    652                    value.to_css(dest)?;
    653                },
    654                None => break,
    655            }
    656 
    657            if values_iter.peek().is_some()
    658                || line_names_iter.peek().map_or(false, |v| !v.is_empty())
    659                || (idx + 1 == self.auto_repeat_index)
    660            {
    661                dest.write_char(' ')?;
    662            }
    663        }
    664 
    665        Ok(())
    666    }
    667 }
    668 
    669 /// The `<name-repeat>` for subgrids.
    670 ///
    671 /// <name-repeat> = repeat( [ <integer [1,∞]> | auto-fill ], <line-names>+)
    672 ///
    673 /// https://drafts.csswg.org/css-grid/#typedef-name-repeat
    674 #[derive(
    675    Clone,
    676    Debug,
    677    MallocSizeOf,
    678    PartialEq,
    679    SpecifiedValueInfo,
    680    ToAnimatedValue,
    681    ToComputedValue,
    682    ToResolvedValue,
    683    ToShmem,
    684 )]
    685 #[repr(C)]
    686 pub struct GenericNameRepeat<I> {
    687    /// The number of times for the value to be repeated (could also be `auto-fill`).
    688    /// Note: `RepeatCount` accepts `auto-fit`, so we should reject it after parsing it.
    689    pub count: RepeatCount<I>,
    690    /// This represents `<line-names>+`. The length of the outer vector is at least one.
    691    pub line_names: crate::OwnedSlice<crate::OwnedSlice<CustomIdent>>,
    692 }
    693 
    694 pub use self::GenericNameRepeat as NameRepeat;
    695 
    696 impl<I: ToCss> ToCss for NameRepeat<I> {
    697    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
    698    where
    699        W: Write,
    700    {
    701        dest.write_str("repeat(")?;
    702        self.count.to_css(dest)?;
    703        dest.write_char(',')?;
    704 
    705        for ref names in self.line_names.iter() {
    706            if names.is_empty() {
    707                // Note: concat_serialize_idents() skip the empty list so we have to handle it
    708                // manually for NameRepeat.
    709                dest.write_str(" []")?;
    710            } else {
    711                concat_serialize_idents(" [", "]", names, " ", dest)?;
    712            }
    713        }
    714 
    715        dest.write_char(')')
    716    }
    717 }
    718 
    719 impl<I> NameRepeat<I> {
    720    /// Returns true if it is auto-fill.
    721    #[inline]
    722    pub fn is_auto_fill(&self) -> bool {
    723        matches!(self.count, RepeatCount::AutoFill)
    724    }
    725 }
    726 
    727 /// A single value for `<line-names>` or `<name-repeat>`.
    728 #[derive(
    729    Clone,
    730    Debug,
    731    MallocSizeOf,
    732    PartialEq,
    733    SpecifiedValueInfo,
    734    ToAnimatedValue,
    735    ToComputedValue,
    736    ToResolvedValue,
    737    ToShmem,
    738 )]
    739 #[repr(C, u8)]
    740 pub enum GenericLineNameListValue<I> {
    741    /// `<line-names>`.
    742    LineNames(crate::OwnedSlice<CustomIdent>),
    743    /// `<name-repeat>`.
    744    Repeat(GenericNameRepeat<I>),
    745 }
    746 
    747 pub use self::GenericLineNameListValue as LineNameListValue;
    748 
    749 impl<I: ToCss> ToCss for LineNameListValue<I> {
    750    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
    751    where
    752        W: Write,
    753    {
    754        match *self {
    755            Self::Repeat(ref r) => r.to_css(dest),
    756            Self::LineNames(ref names) => {
    757                dest.write_char('[')?;
    758 
    759                if let Some((ref first, rest)) = names.split_first() {
    760                    first.to_css(dest)?;
    761                    for name in rest {
    762                        dest.write_char(' ')?;
    763                        name.to_css(dest)?;
    764                    }
    765                }
    766 
    767                dest.write_char(']')
    768            },
    769        }
    770    }
    771 }
    772 
    773 /// The `<line-name-list>` for subgrids.
    774 ///
    775 /// <line-name-list> = [ <line-names> | <name-repeat> ]+
    776 /// <name-repeat> = repeat( [ <integer [1,∞]> | auto-fill ], <line-names>+)
    777 ///
    778 /// https://drafts.csswg.org/css-grid/#typedef-line-name-list
    779 #[derive(
    780    Clone,
    781    Debug,
    782    Default,
    783    MallocSizeOf,
    784    PartialEq,
    785    SpecifiedValueInfo,
    786    ToAnimatedValue,
    787    ToComputedValue,
    788    ToResolvedValue,
    789    ToShmem,
    790 )]
    791 #[repr(C)]
    792 pub struct GenericLineNameList<I> {
    793    /// The pre-computed length of line_names, without the length of repeat(auto-fill, ...).
    794    // We precomputed this at parsing time, so we can avoid an extra loop when expanding
    795    // repeat(auto-fill).
    796    pub expanded_line_names_length: usize,
    797    /// The line name list.
    798    pub line_names: crate::OwnedSlice<GenericLineNameListValue<I>>,
    799 }
    800 
    801 pub use self::GenericLineNameList as LineNameList;
    802 
    803 impl<I: ToCss> ToCss for LineNameList<I> {
    804    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
    805    where
    806        W: Write,
    807    {
    808        dest.write_str("subgrid")?;
    809 
    810        for value in self.line_names.iter() {
    811            dest.write_char(' ')?;
    812            value.to_css(dest)?;
    813        }
    814 
    815        Ok(())
    816    }
    817 }
    818 
    819 /// Variants for `<grid-template-rows> | <grid-template-columns>`
    820 #[derive(
    821    Animate,
    822    Clone,
    823    Debug,
    824    MallocSizeOf,
    825    PartialEq,
    826    SpecifiedValueInfo,
    827    ToAnimatedValue,
    828    ToComputedValue,
    829    ToCss,
    830    ToResolvedValue,
    831    ToShmem,
    832    ToTyped,
    833 )]
    834 #[value_info(other_values = "subgrid")]
    835 #[repr(C, u8)]
    836 pub enum GenericGridTemplateComponent<L, I> {
    837    /// `none` value.
    838    None,
    839    /// The grid `<track-list>`
    840    TrackList(
    841        #[animation(field_bound)]
    842        #[compute(field_bound)]
    843        #[resolve(field_bound)]
    844        #[shmem(field_bound)]
    845        Box<GenericTrackList<L, I>>,
    846    ),
    847    /// A `subgrid <line-name-list>?`
    848    /// TODO: Support animations for this after subgrid is addressed in [grid-2] spec.
    849    #[animation(error)]
    850    Subgrid(Box<GenericLineNameList<I>>),
    851    /// `masonry` value.
    852    /// https://github.com/w3c/csswg-drafts/issues/4650
    853    Masonry,
    854 }
    855 
    856 pub use self::GenericGridTemplateComponent as GridTemplateComponent;
    857 
    858 impl<L, I> GridTemplateComponent<L, I> {
    859    /// The initial value.
    860    const INITIAL_VALUE: Self = Self::None;
    861 
    862    /// Returns length of the <track-list>s <track-size>
    863    pub fn track_list_len(&self) -> usize {
    864        match *self {
    865            GridTemplateComponent::TrackList(ref tracklist) => tracklist.values.len(),
    866            _ => 0,
    867        }
    868    }
    869 
    870    /// Returns true if `self` is the initial value.
    871    pub fn is_initial(&self) -> bool {
    872        matches!(*self, Self::None) // FIXME: can't use Self::INITIAL_VALUE here yet: https://github.com/rust-lang/rust/issues/66585
    873    }
    874 }
    875 
    876 impl<L, I> Default for GridTemplateComponent<L, I> {
    877    #[inline]
    878    fn default() -> Self {
    879        Self::INITIAL_VALUE
    880    }
    881 }