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.
This is the key change in this patch series; it changes the object we
use for style data (currently nsIStyleRule) identity. It allows
removing some hacks we have to deal with that for StyleRule, and avoids
having to write similar hacks for nsCSSKeyframeRule and nsCSSPageRule
(which are broken without this).
I confirmed locally that it is this patch that fixes both of the todo_is
mochitests, by building and testing with the patch queue through patch
11, and again through patch 12.
This probably should have been done before, but prior to this patch
series, dynamic changes of the declarations on these rules were broken
due to rule immutability violations; now that is no longer the case, but
to benefit from that, I believe we actually need to mark the
declarations as immutable once matched so that dynamic changes will
trigger construction of a new declaration (which thus has a new
nsIStyleRule identity).
(This is part of a longer term plan to rename nsIStyleRule to StyleData
and nsIStyleRuleProcessor to StyleDataSource. I'm not doing all of that
here, though.)
The only substantive change here, apart from a few variables changing in
size from uint16_t to uint8_t, is FontFaceSet's use of SheetType::Unknown
(0xFF) instead of 0 for FontFaceRecords for script-created FontFaces.
The bulk of this commit was generated with a script, executed at the top
level of a typical source code checkout. The only non-machine-generated
part was modifying MFBT's moz.build to reflect the new naming.
CLOSED TREE makes big refactorings like this a piece of cake.
# The main substitution.
find . -name '*.cpp' -o -name '*.cc' -o -name '*.h' -o -name '*.mm' -o -name '*.idl'| \
xargs perl -p -i -e '
s/nsRefPtr\.h/RefPtr\.h/g; # handle includes
s/nsRefPtr ?</RefPtr</g; # handle declarations and variables
'
# Handle a special friend declaration in gfx/layers/AtomicRefCountedWithFinalize.h.
perl -p -i -e 's/::nsRefPtr;/::RefPtr;/' gfx/layers/AtomicRefCountedWithFinalize.h
# Handle nsRefPtr.h itself, a couple places that define constructors
# from nsRefPtr, and code generators specially. We do this here, rather
# than indiscriminantly s/nsRefPtr/RefPtr/, because that would rename
# things like nsRefPtrHashtable.
perl -p -i -e 's/nsRefPtr/RefPtr/g' \
mfbt/nsRefPtr.h \
xpcom/glue/nsCOMPtr.h \
xpcom/base/OwningNonNull.h \
ipc/ipdl/ipdl/lower.py \
ipc/ipdl/ipdl/builtin.py \
dom/bindings/Codegen.py \
python/lldbutils/lldbutils/utils.py
# In our indiscriminate substitution above, we renamed
# nsRefPtrGetterAddRefs, the class behind getter_AddRefs. Fix that up.
find . -name '*.cpp' -o -name '*.h' -o -name '*.idl' | \
xargs perl -p -i -e 's/nsRefPtrGetterAddRefs/RefPtrGetterAddRefs/g'
if [ -d .git ]; then
git mv mfbt/nsRefPtr.h mfbt/RefPtr.h
else
hg mv mfbt/nsRefPtr.h mfbt/RefPtr.h
fi
This makes it clearer that, unlike how SizeOf*() functions usually work, this
doesn't measure any children hanging off the array.
And do likewise for nsTObserverArray.
