When we go to switch CSS Animations over to using
KeyframeEffectReadOnly::SetFrames we will need a way to represent any filled-in
from/to values as nsCSSValue objects. These objects are built from the current
computed style. We currently use StyleAnimationValue::ExtractComputedValue for
this which returns a StyleAnimationValue. In order to convert this to an
nsCSSValue we can use StyleAnimationValue::UncomputeValue. However, in some
cases, the nsCSSValue objects returned by that method are dependent on the
passed-in StyleAnimationValue object.
This patch adds an overload to UncomputeValue that takes an rvalue
StyleAnimationValue reference and produces an nsCSSValue that is independent
of the StyleAnimationValue through a combination of copying data and
transferring ownership of data.
This patch also adjusts the return value for the case of filter and shadow
lists when the list is empty so that we return a none value in this case.
These are the only list types which are allowed to have a null list value.
Not only does this produce the correct result when these values are serialized
(the initial value for 'filter', 'text-shadow', and 'box-shadow' is 'none') it
also means that UncomputeValue should never return an nsCSSValue whose unit is
null which is important because when we later pass that value to BuildStyleRule
it will treat a null nsCSSValue as an error case (specifically, "longhand failed
to parse").
MozReview-Commit-ID: 4RoCn39ntiJ
In the next patch in this series, we would like to update the error handling of
the call to StyleAnimationValue::Interpolate in
KeyframeEffectReadOnly::ComposeStyle. Using AnimValuesStyleRule::AddEmptyValue
there, however, makes handling the error case difficult because we need a means
of clearing the allocated StyleAnimationValue.
However, simply using AnimationValuesStyleRule::AddValue means we will end up
doing needless allocations for StyleAnimationValue objects (the copy
constructor for which can result in performing potentially expensive heap
allocations, such as when lists are deep-copied).
Instead, we add a Move constructor to StyleAnimationValue and add an overload
of AnimValuesStyleRule::AddValue that takes an rvalue reference. This
provides a more consistent interface to AnimValuesStyleRule and avoids the
unnecessary allocations from copying StyleAnimationValue objects.
MozReview-Commit-ID: CaP1uPAgNnm
StyleAnimationValue::ComputeValue(s) will automatically look up the style
context of the supplied element. This is mostly fine, but when we start using
this method in scenarios where we are building the initial style context
(as happens later in this patch series) it can easily land us in a situation
where we iterate indefinitely.
It would be better, instead, to just explicitly pass in the style context we
want to use, as we already do for StyleAnimationValue::ExtractComputedValue.
MozReview-Commit-ID: ZoVBlBRRBI
Matrix4x4 remains a typedef for Matrix4x4Typed<UnknownUnits, UnknownUnits>.
No client code needed changing, except for forward-declarations of Matrix4x4
as a class (since it's now a typedef).
