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style: Minor LengthPercentage improvements.

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* Use debug_unreachable for really unreachable code (having a release
   unreachable!() there gives us little to no benefit, as a borked union can
   already confuse us into reading an arbitrary pointer as a CalcPercentage).

 * Avoid a clone of the calc variant when clamping. We only need to mutate the
   clamping mode. This was the only clamp_to_non_negative function that didn't
   consume the value.

Differential Revision: https://phabricator.services.mozilla.com/D63584
This commit is contained in:
Emilio Cobos Álvarez 2020-02-23 22:27:13 +00:00
parent 582ccf4778
commit 37c382a74b
1 changed files with 27 additions and 12 deletions
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39
components/style/values/computed/length_percentage.rs
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@ -170,6 +170,13 @@ enum Unpacked<'a> {
Percentage(Percentage),
}
/// An unpacked `<length-percentage>` that mutably borrows the `calc()` variant.
enum UnpackedMut<'a> {
Calc(&'a mut CalcLengthPercentage),
Length(Length),
Percentage(Percentage),
}
/// An unpacked `<length-percentage>` that owns the `calc()` variant, for
/// serialization purposes.
#[derive(Deserialize, PartialEq, Serialize)]
@ -294,7 +301,18 @@ impl LengthPercentage {
LengthPercentageUnion::TAG_CALC => Tag::Calc,
LengthPercentageUnion::TAG_LENGTH => Tag::Length,
LengthPercentageUnion::TAG_PERCENTAGE => Tag::Percentage,
_ => unreachable!("Bogus tag?"),
_ => unsafe { debug_unreachable!("Bogus tag?") },
}
}
#[inline]
fn unpack_mut<'a>(&'a mut self) -> UnpackedMut<'a> {
unsafe {
match self.tag() {
Tag::Calc => UnpackedMut::Calc(&mut *self.calc_ptr()),
Tag::Length => UnpackedMut::Length(self.0.length.length),
Tag::Percentage => UnpackedMut::Percentage(self.0.percentage.percentage),
}
}
}
@ -425,11 +443,14 @@ impl LengthPercentage {
/// Returns the clamped non-negative values.
#[inline]
pub fn clamp_to_non_negative(&self) -> Self {
match self.unpack() {
Unpacked::Length(l) => Self::new_length(l.clamp_to_non_negative()),
Unpacked::Percentage(p) => Self::new_percent(p.clamp_to_non_negative()),
Unpacked::Calc(c) => c.clamp_to_non_negative(),
pub fn clamp_to_non_negative(mut self) -> Self {
match self.unpack_mut() {
UnpackedMut::Length(l) => Self::new_length(l.clamp_to_non_negative()),
UnpackedMut::Percentage(p) => Self::new_percent(p.clamp_to_non_negative()),
UnpackedMut::Calc(ref mut c) => {
c.clamping_mode = AllowedNumericType::NonNegative;
self
}
}
}
}
@ -665,12 +686,6 @@ impl CalcLengthPercentage {
}).unwrap();
Length::new(self.clamping_mode.clamp(px))
}
fn clamp_to_non_negative(&self) -> LengthPercentage {
let mut new = self.clone();
new.clamping_mode = AllowedNumericType::NonNegative;
LengthPercentage::new_calc_unchecked(Box::new(new))
}
}
// NOTE(emilio): We don't compare `clamping_mode` since we want to preserve the