Before switching CSS animations over to using KeyframeEffectReadOnly::SetFrames
we update the getFrames() API to return the set frame objects (when available)
so that we can test that we are setting the correct frames.
MozReview-Commit-ID: 4SpBRM7Ykyv
Specifically, for the 'composite' member on keyframes, we now indicate "use the
composite value specified on the effect" using a missing/undefined 'composite'
member as opposed to a null value.
MozReview-Commit-ID: ZH45GvCTlP
Later in this patch series when we convert tests from web-platform tests to
mochitest-chrome tests, some of the test cases that use zero-length segments
(overlapping keyframes at certain offsets) would trigger failed assertions
in KeyframeEffectReadOnly::ComposeStyle. This is because this method was
originally written with CSS animations in mind where segments cannot be
zero-length. Furthermore, when these same tests cases are run as
web-platform-tests, the failed assertions are not visible.
This patch adjusts the handling of segments to allow zero-length segments and
adds a test to check that the handling matches that defined in Web Animations
which is summarized in the following informative note,
"this procedure permits overlapping keyframes. The behavior is that at the
point of overlap the output value jumps to the value of the last defined
keyframe at that offset. For overlapping frames at 0 or 1, the output value
for iteration progress values less than 0 or greater than or equal to 1 is the
value of the first keyframe or the last keyframe in keyframes
respectively."[1]
[1] https://w3c.github.io/web-animations/#the-effect-value-of-a-keyframe-animation-effect
MozReview-Commit-ID: JdyYbGZtbot
Before we go fixing endTime, we should add tests that activeDuration (which
endTime builds on) is being calculated correctly. (Spoiler: it wasn't, hence
parts 2 and 3 in this patch series.)
This patch just simplifies the keyframe-effect tests so that we don't have to
repeat default values. This makes the tests shorter, easier to scan, and
easier to understand what is being tested.
In some cases we still repeat the default values in order to indicate that
we're testing that we get a particular default value.
