layout: Improve our handling of inline absolute containing blocks.
Several issues are addressed in this commit:
* Inline flows now bubble up their absolute descendants instead of
making the inline flow the containing block for them. (In the future,
we will need to make the inline flow *sometimes* be the containing
block for them, but for now it improves sites to unconditionally
bubble up.)
* Fragments now look at their inline fragment context to determine
whether they are positioned.
* Inline flows now push the stacking-relative position of the absolute
containing block down to their inline-block fragments.
* Inline absolute hypothetical fragments can be containing blocks.
* Fixes the logic in
`containing_block_range_for_flow_surrounding_fragment_at_index`. The
condition to determine whether fragments are positioned was inverted!
* `Descendants`/`AbsDescendants` has been refactored in order to become
more friendly to inline absolute containing blocks in the future.
Improves the inline position of the green drop-down arrow in the Google
SERPs. (The block position is still wrong.)
r? @mbrubeck
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Several issues are addressed in this commit:
* Inline flows now bubble up their absolute descendants instead of
making the inline flow the containing block for them. (In the future,
we will need to make the inline flow *sometimes* be the containing
block for them, but for now it improves sites to unconditionally
bubble up.)
* Fragments now look at their inline fragment context to determine
whether they are positioned.
* Inline flows now push the stacking-relative position of the absolute
containing block down to their inline-block fragments.
* Inline absolute hypothetical fragments can be containing blocks.
* Fixes the logic in
`containing_block_range_for_flow_surrounding_fragment_at_index`. The
condition to determine whether fragments are positioned was inverted!
* `Descendants`/`AbsDescendants` has been refactored in order to become
more friendly to inline absolute containing blocks in the future.
Improves the inline position of the green drop-down arrow in the Google
SERPs. (The block position is still wrong.)
The failing `float-applies-to-*` CSS 2.1 tests never really should have
been passing in the first place; they depend on floats inside
fixed-layout tables working properly, which they don't.
Closes#6078.
Closes#6709.
Closes#6858.
It's not possible to correctly determine during the css cascade whether the container height
is explicitly specified. Additionally, the spec https://drafts.csswg.org/css2/visudet.html#the-height-property
says this should affect the *used* height, rather than the computed height.
This significantly improves the layout in #6643.
absolutely-positioned elements.
This also implements a little bit of the infrastructure needed to
support for fragmentation via support for multiple positioned fragments
in one flow.
Improves Google.
This add some properties to the style system and a new flow type, but the larger issues of dealing with fragmentation in the flow tree is still an open question.
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Known issues:
* Collapsed borders do not correctly affect the border-box of the table
itself.
* The content widths of all cells in a column and the content height of
all cells in a row is the same in this patch, but not in Gecko and
WebKit.
* Corners are not painted well. The spec does not say what to do here.
* Column spans are not handled well. The spec does not say what to do
here either.
flows and static positions of hypothetical boxes.
Before this change, Servo used one code path that computed the position
of flows with `position: static` or `position: relative` and another
separate code path that computed the position of flows with `position:
absolute` or `position: fixed`. The latter code attempted to duplicate
the former code to determine the static position of hypothetical boxes,
but this was both fragile and incorrect in the case of hypothetical
boxes nested inside floats. In fact, it's impossible to determine the
static position of an absolute flow relative to its containing block at
inline-size assignment time, because that static position could depend
on a float that cannot be placed until block-size assignment!
This patch changes block layout to use the same code path for static
positioning of regular flows and static positioning of absolute flows
where applicable. This both simplifies the code and improves its
efficiency, since it allows the `hypothetical_position` field and
`static_block_offsets` data structure to be removed. Moreover, it
improves correctness in the above case (which the new reftest checks).
This allows the sidebar in Facebook Timeline to be positioned properly.
Cycles were being created in the flow tree since absolutely positioned
descendants had pointers to their containing blocks. This adds
WeakFlowRef (based on Weak<T>) and makes these backpointers weak
references. This also harmonizes our custom Arc<T>, FlowRef, to be
consistent with the upstream implementation.
Fixes#4915.
§ 12.3-12.5.
Only simple alphabetic and numeric counter styles are supported. (This
is most of them though.)
Although this PR adds a sequential pass to layout, I verified that on
pages that contain a reasonable number of ordered lists (Reddit
`/r/rust`), the time spent in generated content resolution is dwarfed by
the time spent in the parallelizable parts of layout. So I don't expect
this to negatively affect our parallelism expect perhaps in pathological
cases.
...and vice-versa. This is not a complete fix for all mixed-direction layout
cases, but it fixes enough problems to make some simple test cases pass, like
tha attached reftest.
There are FIXME comments for many of the remaining issues. In particular,
this does not yet handle RTL layout of fixed/absolute elements.
