1. Add a new preference, layout.css.step-position-jump.enabled, for
step(_, jump-*) timing functions.
2. We still keep JumpEnd and End tags, even though there is no difference
between them. Therefore, we could disable the preference if needed.
3. Update the calculation of StepTiming to match the algorithm in the spec.
4. For servo, we implement the correct step function algorithm except
for the handling of before_flag. This could be fixed later.
Depends on D9313
Differential Revision: https://phabricator.services.mozilla.com/D9314
First, we generate StyleComputedTimingFunction by cbindgen from Rust, and use
it in nsTimingFunction, so we could copy it directly without handling
the different memory layout. However, we have to rewrite the
nsTimingFunction and mozilla::ComputedTimingFunction for this.
Second, the rust-bindgen seems cannot generate the correct generic members
from complex C++ templates, especially for the nested template struct,
(https://github.com/rust-lang-nursery/rust-bindgen/issues/1429)
So we have to hide StyleTimingFunction to avoid the compilation errors.
Differential Revision: https://phabricator.services.mozilla.com/D9313
We make sure the step number is always positive, so using
computed::Integer is safe and can derive ToComputedValue.
Depends on D9311
Differential Revision: https://phabricator.services.mozilla.com/D9845
TimingFunction is defined in a separate spec (i.e. css-easing), instead
of transform, so we move it into a different file.
Depends on D9310
Differential Revision: https://phabricator.services.mozilla.com/D9311
