In the case where values in CSS rules changed directly by CSSOM, the old
value in the CSS rule block is immediately replaced by the new one. So if
the element, which is applied to the CSS rule, has running animations, the
new value is used during cascading process in animation-only restyle. Thus
in a subsequent normal restyle, we can't tell whether the value in the CSS
rule has changed or not. As a result, transitions may not be triggered
(bug 1393323) and CSS animations may not be cancelled if the updated
animation-name is 'none' (this bug).
For the latter case of CSS animations where animation-name has been updated to
'none', this patch introduces a workaround whereby we trigger an update of
running animations whenever the traversal is triggered by changes to CSS rules
and we have existing CSS animations.
The only reason why we had the `existing_style_for_style_damage` bit is to apply
some optimizations that we don't have anymore.
I still want to reintroduce a few of them, at least for the non-eager
pseudo-element case... But I think I won't need this at all.
This allows us to remove a fair amount of Gecko code too.
Make replace_rules_internal return true only if important rules changed.
<!-- Please describe your changes on the following line: -->
https://bugzilla.mozilla.org/show_bug.cgi?id=1367975
---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/17951)
<!-- Reviewable:end -->
When display style is changed from 'none' to other in animation-only restyle
we need to resolve descendant elements' style that were in the display:none
subtree.
Three possible ways to resolve the descendant elements' style;
1) Traversing unstyled elements in animation-only restyle
We can't simply traverse unstyled elements in the animation-only restyle
since when we decided to traverse the unstyled elements we don't know yet
the elements will be initially styled or are in display:none subtree. It
will result that the new elements are styled in animation-only restyle,
it's undesirable.
2) Creating a SequentialTask and resolve the descendants' style with
ServoStyleSet::StyleNewSubtree()
We can't resolve the descendants' styles with ServoStyleSet::StyleNewSubtree()
in SequentialTask since at the moment we are still in servo traversal (i.e.
sInServoTraversal is true). That means AutoSetInServoTraversal fails
in PrepareAndTraverseSubtree().
3) Creating a SequentialTask and set restyle subtree hint and defer descendants'
restyle in a subsequent normal traversal
Note that, when we process throttled animations flush, we don't process
normal traversal so the descendants will not be traversed until normal
restyle happens but it will not be a big problem since it's really rare
that user clicks display animation element just at the right moment when
display property changes from none to other. Also, if it will be really
a problem, we should process *only* transform animations on the compositor,
it's ideally right thing to do. Display property never runs on the
compositor.
This patch takes the third approach.
We skipped updating the rule nodes for visited rules during animation-only restyle.
However, this causes isseus that visited style overrides animation styles on visited element.
So, it turns out that we should update the visited rules even during animation-only restyle.
Gecko bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1381235
The alias is left there temporarilly and will be removed completely in a later commit where
also components/style/gecko/generated/structs_{debug|release}.rs are re-generated (they still
use the old alias).
Before this refactoring, getComputedStyle could have side effects, and left the
style data in the element, so we could never arrive there without data.
There are a few crashtests that caught this, but this was already broken if you
called animate() on an element deep in a display: none subtree.
MozReview-Commit-ID: 1AvOvhAyOP3
This is unfortunate, but for now it complicates things, I would like not needing
a ElementData to get the style of an Element in order to fix all the
getDefaultComputedStyle bugs.
MozReview-Commit-ID: LZvsdFEqrDE
When a transition update is needed during restyling, `get_after_change_style` is
called to re-cascade without transition rules, and this style is then used for
primary styling instead of the style just computed.
`get_after_change_style` used to ignore visited styles, so this meant that if a
transition update was needed, visited styles were effectively dropped.
To fix the crash here, we pass through the existing visited styles when
re-cascading as part of `get_after_change_style`.
MozReview-Commit-ID: 4HBQAdeJ38B
Before this change, the `ComputedStyle` struct that is part of permanent style
data per element holds 2 `StrongRuleNode`s (unvisited and visited) and 2
`Arc<ComputedValues>` (unvisited and visited).
Both rule nodes and the visited values don't actually need to be here. This
patch moves these 3 to new temporary storage in `CascadeInputs` on
`CurrentElementInfo` during the match and cascade process. Rule nodes are
pushed down inside the `ComputedValues` for later access after the cascade.
(Visited values were already available there.)
The permanent style data per element now has just the `Arc<ComputedValues>` for
itself and eager pseudo-elements (plus the `RestyleHint`).
MozReview-Commit-ID: 3wq52ERMpdi
Right now when calling getComputedStyle with an element from another document,
we return the style using the pres context of that document, not of the document
of the window getComputedStyle was called on, so this holds.
But it will stop holding if we ever change this, so assert it doesn't happen.
Bug: 1374062
Reviewed-By: Manishearth
MozReview-Commit-ID: 3g8yQWWdsen
Before this commit, we assumed that if the element had no parent element, it was
the root of the document, which is plain false, since we can arrive there from,
let's say, getComputedStyle on a detached node.
Bug: 1374062
Reviewed-By: heycam
MozReview-Commit-ID: 65DxdzXgd0J
