This patch (currently WIP) alters the way we determine whether jank is user-visible or not.
Instead of measuring the total time spent doing JS, we now use an
indicator provided by the vsync driver: how long it takes to deliver
the signal from the vsync timer to the main thread. This lets us find
out more accurately if there is user-visible jank. In the future, this
will also let us add an observer to find out whether the process
itself is janky, regardless of JS.
nsPresContext contains a mLastStyleUpdateForAllAnimations flag which is simply
used to prevent unnecessarily posting restyles when throttled animations are
already up to date. Since part 13 we now accurately record whether we have
posted a restyle for each throttled animation and only post a restyle if we
have not done so already. As a result, this flag is no longer needed since
calling PostRestyleForThrottledAnimations is effectively a noop when throttled
animations are up-to-date.
To refine its alerts, Performance Stats API needs to be able to know whether a long-running operation is actually causing user-visible jank in the current process. This patch introduces a trivial API that lets clients ask the refresh driver whether any kind of animation is ongoing.
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 patch also reworks the dispatch of events in nsRefreshDriver. Previously
the refresh driver would dispatch the transition events for all subdocuments
then the animation events. This arrangement is complicated and not obviously
necessary. This patch simplifies this arrangement by dispatching transition
events and animation events for each document before proceeding to
subdocuments.
This patch causes transition events to be dispatched as a separate step after
sampling the transitions. Eventually this will allow us to sample transitions
from their timeline (independently of where they came from and in potentially
any order) by separating the concepts of sampling and event dispatch.
This patch prepares the way for script-generated events by making
event dispatch a separate process that happens after sampling animations.
This will allow us to sample animations from their associated timeline
(removing the need for a further manager to tracker script-generated
animations).
Furthermore, once we sample animations from timelines the order in which they
are sampled is likely to be more or less random so by making event dispatch at
separate step, we have an opportunity to sort the events and dispatch in
a consistent and sensible order. It also ensures that event callbacks will
not be run until all animations (including transitions) have been updated
ensuring they see a consistent view of timing properties.
This patch only affects event handling for CSS animations. Transitions will
be dealt with in a subsequent patch.
When the refresh driver ticks it clears the RAF callbacks (content asks for another RAF if it desires) but it wasn't checking if it should exit high precision mode at this point.
The previous code seemed like it was using the wrong model that a RAF is persistent until it is revoked. But that is not the case.
