10.8, and implement `vertical-align: middle` per CSS 2.1 § 10.8.1.
`InlineMetrics` has been split into `InlineMetrics` for fragments and
`LineMetrics` for lines. Both structures' fields have been renamed in
order to more clearly delineate the difference between *space* and
*content*. Vertical positioning of fragments has been reworked to take
margins and borders into account only for replaced content.
This patch fixes the `vertical_align_super_a.html` reftest. Servo now
matches the rendering that Gecko and WebKit produce.
Additionally, this includes a test for the popular inline-block
centering technique described here:
https://s.codepen.io/shshaw/fullpage/gEiDt?#Inline-Block
We don't need this for Gecko, and it's hard to implement in that case because
there's nowhere obvious to put it (we don't plan to create TSDs for non-dirty
nodes, and non-dirty nodes can have dirty children which require the
children_to_process atomic). There are various solutions here, but punting is
the easiest.
We'll need to rethink this if/when we need to do a bottom-up traversal for
Gecko.
It's not possible to implement a Ref::map equivalent method on AtomicRefCell
while having AtomicRefCell implemented on top of RwArc. We could potentially
reimplement AtomicRefCell to be more like RefCell and add a Ref::map equivalent
method, but I (and pcwalton) think we should try just cloning a few extra
Arcs at these callsites instead.
MozReview-Commit-ID: 6H8vAWguO3z
Because this is a bottom-up traversal it can generates flows and throw them away. To prevent that, this cascades an internal `-servo-under-display-none` property and then checks that during flow construction. Fixes#1536.
Empty fragments may need to be layed out to draw borders, padding/background,
and insertion points. (Fragments that consist of discardable whitespace and
control characters, on the other hand, can still be discarded.)
This ends up preserving some useless empty fragments. It's possible we could
avoid this by storing some sort of flag on "important" empty fragments, so we
can discard the rest.
Factor out a new `meld_with_prev_inline_fragment` method that mirrors the
existing `meld_with_next_inline_fragment`.
This also fixes a bug in `meld_with_next` that was already fixed in the
`meld_with_prev` by @notriddle in #10419. The bug is that it was traversing
the inline context nodes in the wrong order. It should start at the outermost
enclosing node, since the fragments might be at different nesting levels under
some common ancestor.
Reduce size of layout::fragment::Fragment struct
This reduces the size of the SpecificFragmentInfo enum from 48 to 24.
r? @pcwalton
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