This is so that when we have code like:
elem.animate({ opacity: 0 }, 1000)
the resulting Animation object is kept alive by |elem| based on the following
ownership chain:
elem --(strong)--> KeyframeEffectReadOnly --(strong)--> Animation
Now, there is an ownership cycle introduced here because KeyframeEffectReadOnly
objects also store owning references to their target elements. This is broken
when the Animation finishes (if it does not fill forwards) or is cancelled
since either event will trigger a call to
KeyframeEffectReadOnly::UpdateTargetRegistration.
If the Animation fills forwards, the resource will not be released until
it is cancelled. For Animations corresponding to CSS Animations / CSS
Transitions this happens when the Element is unbound or when the corresponding
style property is updated causing the animation to be replaced or removed.
For the general case of script-generated animations, however, this cycle won't
be broken until the Element is unbound and all external references to the
Animation or KeyframeEffectReadOnly are dropped.
It's unfortunate that we can't more aggressively prune these objects but it's
what the spec currently says. I've posted to the mailing list[1] about this but
have yet to find a good solution.
[1] https://lists.w3.org/Archives/Public/public-fx/2015OctDec/0029.html
Now that Declaration implements nsIStyleRule, we don't need the memory
overhead of storing a StyleRule object for style attributes.
We also need to change this prior to patch 5, because the changes in
patch 5 that will allow rules to change (but declarations not) would
otherwise break due to style attribute object merging done by
nsAttrValue::ParseStyleAttribute.
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
The bulk of this commit was generated by running:
run-clang-tidy.py \
-checks='-*,llvm-namespace-comment' \
-header-filter=^/.../mozilla-central/.* \
-fix
