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Update PropertyDeclarationBlock::to_css so that the iteration of

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possible shorthands matches the linked spec.

Previously substep 5 attempted to serialize the complete shorthand
declaration and substep 6 skipped to the next shorthand only if the
current shorthand was not serialized, but this did not catch empty
serializations. The spec on the other hand specifically says that the
*value* should be evaluated first and if the value is empty substep 6
should skip to the next shorthand - which is what happens now.

To do this required some refactoring which mostly simplifies the code.
Specifically:
 - append_declaration_value was refactored so that importance is not
   required as a arg (by moving it to the end of append_serialization)
   and is_overflow_with_name was removed as an arg also (initially I
   refactored it elsewhere, but it turns out it's no longer required at
   all - more below). With these changes, append_declaration_value can
   be used within the algorithm for to_css to obtain just the value for
   substep 5.
 - Substeps 7 and 8 of the algorithm become explicit (they were implicit
   before) by passing the value, shorthand and importance to
   append_serialization.
 - serialize_shorthand_to_buffer is no longer required (as the algorithm
   serializes the value first instead, as per the spec.

A surprising result of this was that I could also remove a lot of code
handling the special case of the overflow properties serialization. This
is because the overflow's LonghandToCss implementation of
to_css_declared already does the right thing according to the spec - it
writes the single value if both overflow-x and -y are equal, and
writes nothing otherwise - so that the algorithm now skips that shorthand
instead rendering the longhands.
This commit is contained in:
Michael Nelson 2017-02-22 20:58:33 +11:00
parent 854d720b21
commit a0998d30d4
4 changed files with 36 additions and 141 deletions
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16
components/style/properties/shorthand/serialize.mako.rs
View file

@ -2,7 +2,7 @@
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
use properties::{AppendableValue, DeclaredValue, PropertyDeclaration, ShorthandId};
use properties::DeclaredValue;
use style_traits::ToCss;
use values::specified::{BorderStyle, CSSColor};
use std::fmt;
@ -91,17 +91,3 @@ fn serialize_directional_border<W, I,>(dest: &mut W,
_ => Ok(())
}
}
#[allow(missing_docs)]
pub fn is_overflow_shorthand<'a, I>(appendable_value: &AppendableValue<'a, I>) -> bool
where I: Iterator<Item=&'a PropertyDeclaration>
{
if let AppendableValue::DeclarationsForShorthand(shorthand, _) = *appendable_value {
if let ShorthandId::Overflow = shorthand {
return true;
}
}
false
}