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style: Refactor grid types to preserve repeat() at computed value time and use cbindgen.

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I'm _really_ sorry for the size of the patch. I tried to do this in two steps
but it was a lot of work and pretty ugly.

This patch makes us use cbindgen for grid-template-{rows,columns}, in order to:

 * Make us preserve repeat() at computed-value time. This is per spec since
   interpolation needs to know about repeat(). Except for subgrid, which did the
   repeat expansion at parse-time and was a bit more annoying (plus it doesn't
   really animate yet so we don't need it to comply with the spec).

 * Tweaks the WPT tests for interpolation to adopt the resolution at:
   https://github.com/w3c/csswg-drafts/issues/3503.

Trade-off here, as this patch stands, is that this change makes us use less
long-living memory, since we expand repeat() during layout, but at the cost of a
bit of CPU time during layout (conditional on the property applying though,
which wasn't the case before). It should be very easy to store a cached version
of the template, should this be too hot (I expect it isn't), or to change the
representation in other ways to optimize grid layout code if it's worth it.

Another trade-off: I've used SmallPointerArray to handle line-name merging,
pointing to the individual arrays in the style data, rather than actually
heap-allocating the merged lists. This would also be pretty easy to change
should we measure and see that it's not worth it.

This patch also opens the gate to potentially improving memory usage in some
other ways, by reference-counting line-name lists for example, though I don't
have data that suggests it is worth it.

In general, this patch makes much easier to tweak the internal representation of
the grid style data structures. Overall, I think it's a win, the amount of magic
going on in that mako code was a bit huge; it took a bit to wrap my head around
it.

This patch comments out the style struct size assertions. They will be
uncommented in a follow-up patch which contains some improvements for this type,
which are worth getting reviewed separately.

Also, this patch doesn't remove as much code as I would've hoped for because of
I tried not to change most of the dom/grid code for inspector, but I think a
fair bit of the nsGridContainerFrame.cpp code that collects information for it
can be simplified / de-copy-pasted to some extent. But that was a pre-existing
problem and this patch is already quite massive.

Differential Revision: https://phabricator.services.mozilla.com/D36598
This commit is contained in:
Emilio Cobos Álvarez 2019-06-28 13:27:19 +02:00
parent 0e8b1853a7
commit 3e39998068
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GPG key ID: E1152D0994E4BF8A
8 changed files with 142 additions and 505 deletions
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163
components/style/values/specified/grid.rs
View file

@ -6,10 +6,9 @@
//! [grids](https://drafts.csswg.org/css-grid/)
use crate::parser::{Parse, ParserContext};
use crate::values::computed::{self, Context, ToComputedValue};
use crate::values::generics::grid::{GridTemplateComponent, RepeatCount, TrackBreadth};
use crate::values::generics::grid::{LineNameList, TrackRepeat, TrackSize};
use crate::values::generics::grid::{TrackList, TrackListType, TrackListValue};
use crate::values::generics::grid::{TrackList, TrackListValue};
use crate::values::specified::{Integer, LengthPercentage};
use crate::values::{CSSFloat, CustomIdent};
use cssparser::{ParseError as CssParseError, Parser, Token};
@ -101,7 +100,7 @@ impl Parse for TrackSize<LengthPercentage> {
/// <https://drafts.csswg.org/css-grid/#typedef-line-names>
pub fn parse_line_names<'i, 't>(
input: &mut Parser<'i, 't>,
) -> Result<Box<[CustomIdent]>, ParseError<'i>> {
) -> Result<crate::OwnedSlice<CustomIdent>, ParseError<'i>> {
input.expect_square_bracket_block()?;
input.parse_nested_block(|input| {
let mut values = vec![];
@ -112,7 +111,7 @@ pub fn parse_line_names<'i, 't>(
values.push(ident);
}
Ok(values.into_boxed_slice())
Ok(values.into())
})
}
@ -155,9 +154,8 @@ impl TrackRepeat<LengthPercentage, Integer> {
let mut current_names;
loop {
current_names = input
.try(parse_line_names)
.unwrap_or(vec![].into_boxed_slice());
current_names =
input.try(parse_line_names).unwrap_or_default();
if let Ok(track_size) = input.try(|i| TrackSize::parse(context, i)) {
if !track_size.is_fixed() {
if is_auto {
@ -183,7 +181,7 @@ impl TrackRepeat<LengthPercentage, Integer> {
names.push(
input
.try(parse_line_names)
.unwrap_or(vec![].into_boxed_slice()),
.unwrap_or_default()
);
break;
}
@ -201,9 +199,9 @@ impl TrackRepeat<LengthPercentage, Integer> {
}
let repeat = TrackRepeat {
count: count,
track_sizes: values,
line_names: names.into_boxed_slice(),
count,
track_sizes: values.into(),
line_names: names.into(),
};
Ok((repeat, repeat_type))
@ -221,47 +219,35 @@ impl Parse for TrackList<LengthPercentage, Integer> {
let mut names = vec![];
let mut values = vec![];
// assume it's the simplest case.
let mut list_type = TrackListType::Explicit;
// holds <auto-repeat> value. It can only be only one in a TrackList.
let mut auto_repeat = None;
// if there is any <auto-repeat> the list will be of type TrackListType::Auto(idx)
// where idx points to the position of the <auto-repeat> in the track list. If there
// is any repeat before <auto-repeat>, we need to take the number of repetitions into
// account to set the position of <auto-repeat> so it remains the same while computing
// values.
let mut auto_offset = 0;
// Whether we've parsed an `<auto-repeat>` value.
let mut auto_repeat_index = None;
// assume that everything is <fixed-size>. This flag is useful when we encounter <auto-repeat>
let mut atleast_one_not_fixed = false;
let mut at_least_one_not_fixed = false;
loop {
current_names.extend_from_slice(
&mut input
.try(parse_line_names)
.unwrap_or(vec![].into_boxed_slice()),
.unwrap_or_default()
);
if let Ok(track_size) = input.try(|i| TrackSize::parse(context, i)) {
if !track_size.is_fixed() {
atleast_one_not_fixed = true;
if auto_repeat.is_some() {
at_least_one_not_fixed = true;
if auto_repeat_index.is_some() {
// <auto-track-list> only accepts <fixed-size> and <fixed-repeat>
return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
}
}
let vec = mem::replace(&mut current_names, vec![]);
names.push(vec.into_boxed_slice());
names.push(vec.into());
values.push(TrackListValue::TrackSize(track_size));
} else if let Ok((repeat, type_)) =
input.try(|i| TrackRepeat::parse_with_repeat_type(context, i))
{
if list_type == TrackListType::Explicit {
list_type = TrackListType::Normal; // <explicit-track-list> doesn't contain repeat()
}
match type_ {
RepeatType::Normal => {
atleast_one_not_fixed = true;
if auto_repeat.is_some() {
at_least_one_not_fixed = true;
if auto_repeat_index.is_some() {
// only <fixed-repeat>
return Err(
input.new_custom_error(StyleParseErrorKind::UnspecifiedError)
@ -269,132 +255,38 @@ impl Parse for TrackList<LengthPercentage, Integer> {
}
},
RepeatType::Auto => {
if auto_repeat.is_some() || atleast_one_not_fixed {
if auto_repeat_index.is_some() || at_least_one_not_fixed {
// We've either seen <auto-repeat> earlier, or there's at least one non-fixed value
return Err(
input.new_custom_error(StyleParseErrorKind::UnspecifiedError)
);
}
list_type = TrackListType::Auto(values.len() as u16 + auto_offset);
auto_repeat = Some(repeat);
let vec = mem::replace(&mut current_names, vec![]);
names.push(vec.into_boxed_slice());
continue;
auto_repeat_index = Some(values.len());
},
RepeatType::Fixed => (),
RepeatType::Fixed => {},
}
let vec = mem::replace(&mut current_names, vec![]);
names.push(vec.into_boxed_slice());
if let RepeatCount::Number(num) = repeat.count {
auto_offset += (num.value() - 1) as u16;
}
names.push(vec.into());
values.push(TrackListValue::TrackRepeat(repeat));
} else {
if values.is_empty() && auto_repeat.is_none() {
if values.is_empty() && auto_repeat_index.is_none() {
return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
}
names.push(current_names.into_boxed_slice());
names.push(current_names.into());
break;
}
}
Ok(TrackList {
list_type: list_type,
values: values,
line_names: names.into_boxed_slice(),
auto_repeat: auto_repeat,
auto_repeat_index: auto_repeat_index.unwrap_or(std::usize::MAX),
values: values.into(),
line_names: names.into(),
})
}
}
impl ToComputedValue for TrackList<LengthPercentage, Integer> {
type ComputedValue = TrackList<computed::LengthPercentage, computed::Integer>;
#[inline]
fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
// Merge the line names while computing values. The resulting values will
// all be bunch of `<track-size>` and one <auto-repeat>.
//
// For example,
// `[a b] 100px [c d] repeat(1, 30px [g]) [h]` will be merged as `[a b] 100px [c d] 30px [g h]`
// whereas, `[a b] repeat(2, [c] 50px [d]) [e f] repeat(auto-fill, [g] 12px) 10px [h]` will be merged as
// `[a b c] 50px [d c] 50px [d e f] repeat(auto-fill, [g] 12px) 10px [h]`, with the `<auto-repeat>` value
// set in the `auto_repeat` field, and the `idx` in TrackListType::Auto pointing to the values after
// `<auto-repeat>` (in this case, `10px [h]`).
let mut prev_names = vec![];
let mut line_names = Vec::with_capacity(self.line_names.len() + 1);
let mut values = Vec::with_capacity(self.values.len() + 1);
for (pos, names) in self.line_names.iter().enumerate() {
prev_names.extend_from_slice(&names);
if pos >= self.values.len() {
let vec = mem::replace(&mut prev_names, vec![]);
line_names.push(vec.into_boxed_slice());
continue;
}
match self.values[pos] {
TrackListValue::TrackSize(ref size) => {
let vec = mem::replace(&mut prev_names, vec![]);
line_names.push(vec.into_boxed_slice());
values.push(TrackListValue::TrackSize(size.to_computed_value(context)));
},
TrackListValue::TrackRepeat(ref repeat) => {
// If the repeat count is numeric, we expand and merge the values.
let mut repeat = repeat.expand();
let mut repeat_names_iter = repeat.line_names.iter();
for (size, repeat_names) in
repeat.track_sizes.drain(..).zip(&mut repeat_names_iter)
{
prev_names.extend_from_slice(&repeat_names);
let vec = mem::replace(&mut prev_names, vec![]);
line_names.push(vec.into_boxed_slice());
values.push(TrackListValue::TrackSize(size.to_computed_value(context)));
}
if let Some(names) = repeat_names_iter.next() {
prev_names.extend_from_slice(&names);
}
},
}
}
TrackList {
list_type: self.list_type.to_computed_value(context),
values: values,
line_names: line_names.into_boxed_slice(),
auto_repeat: self
.auto_repeat
.clone()
.map(|repeat| repeat.to_computed_value(context)),
}
}
#[inline]
fn from_computed_value(computed: &Self::ComputedValue) -> Self {
let mut values = Vec::with_capacity(computed.values.len() + 1);
for value in computed
.values
.iter()
.map(ToComputedValue::from_computed_value)
{
values.push(value);
}
TrackList {
list_type: computed.list_type,
values: values,
line_names: computed.line_names.clone(),
auto_repeat: computed
.auto_repeat
.clone()
.map(|ref repeat| TrackRepeat::from_computed_value(repeat)),
}
}
}
#[cfg(feature = "gecko")]
#[inline]
fn allow_grid_template_subgrids() -> bool {
@ -409,7 +301,6 @@ fn allow_grid_template_subgrids() -> bool {
}
impl Parse for GridTemplateComponent<LengthPercentage, Integer> {
// FIXME: Derive Parse (probably with None_)
fn parse<'i, 't>(
context: &ParserContext,
input: &mut Parser<'i, 't>,