The basic idea here is as follows:
* Rule nodes are reference-counted, but releasing them adds them to a linked
list rather than freeing them. This allows for the reuse that motivated the
original GC scheme.
* We get rid of the marking, and instead rely on the reference count.
* Sweeping no longer requires a complicated traversal. We just pop items
off the free list until it's empty. When a child is destroyed, its parent
may go onto the free list.
* We remove special handling for the root node, and use a regular reference-counted
edge from the style set.
* The free list automatically asserts that it's empty (meaning all nodes have been
freed) in its destructor, which runs when the style set is destroyed.
* We get rid of the list of style context roots on the style set. We still need
a count though, because of the HasCachedStyleData check.
These new enum values are added with same behavior as their modern flexbox
equivalents -- they're hooked up to NS_NewFlexContainerFrame, and they're
listed alongside the modern flexbox enums in 'switch' & 'if' statements.
There's one exception, which I call out with a comment at the end of the patch:
we don't treat -webkit-box the same as flexbox in IsFlexOrGridDisplayType(),
because that method is used to determine whether we should blockify
inline-level children of a flex/grid container, and we don't want to blockify
any children of a -webkit-box. (Instead, we want to wrap them in an anonymous
flex item. That happens in the next patch.)
MozReview-Commit-ID: 9BB4Ib2KpvE
In order to convert CSSPseudoElementType into its underlying type easier,
we define CSSPseudoElementTypeBase. However, keep using uint8_t directly for
forward declarations.
The flag SkipParentDisplayBasedStyleFixup is for flex/grid fixup, and it is set
for all pseudo elements other than before/after. This is not desirable for ruby
case.
Moving the code out also means elements will inherit the suppress flag directly
from "display: contents" parent (instead of the container), which is fine since
the parent should have had its flag set properly as well.
This is needed to avoid hitting the assertion:
Assertion failure: !!(structsFound & (1 << uint64_t(eStyleStruct_Visibility))) == !!PeekStyleVisibility() (PeekStyleData results must not change in the middle of difference calculation.), at ./nsStyleStructList.h:62
once exact PeekStyleData is backed out in the later patches.
Without this patch, we can compute a new nsStyleVisibility struct inside
of nsStylePosition::CalcDifference. This patch ensures we use
PeekStyleVisibility() instead of StyleVisibility().
This assertion catches the condition that led to the bug.
I confirmed that without patch 10 on this bug, the assert fires on the
reftest added in patch 4, but does not fire on slight modifications of
that testcase that don't show the bug.
This means we obey the invariant that if we've requested an inherited
struct on a context, that struct will be cached on the style context. I
believe bug 527977 intended to do make us obey this invariant, but it
missed the case where nsRuleNode::GetStyle* found cached data already on
the rule node, and the case where nsRuleNode::WalkRuleTree found a
usable struct higher in the rule tree.
Without this change, patch 10 will not function correctly for inherited
structs when we encounter this case, and will cause assertions in
dom/base/test/test_bug560780.html due to triggering style change hints
on text nodes that inherited a color struct from a parent on whose rule
node the struct was stored. (It may also have caused some of the other
test failures.)
This should be a clear performance improvement, since the path that's
being slowed down by the added work in this patch will, with the patch,
now only execute once because of that work.
