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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#include "SMILAnimationController.h"
#include <algorithm>
#include "mozilla/AutoRestore.h"
#include "mozilla/PresShell.h"
#include "mozilla/PresShellInlines.h"
#include "mozilla/RestyleManager.h"
#include "mozilla/SMILTimedElement.h"
#include "mozilla/dom/DocumentInlines.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/SVGAnimationElement.h"
#include "nsContentUtils.h"
#include "nsCSSProps.h"
#include "nsRefreshDriver.h"
#include "mozilla/dom/Document.h"
#include "SMILCompositor.h"
#include "SMILCSSProperty.h"
using namespace mozilla::dom;
namespace mozilla {
// SMILAnimationController implementation
// ctors, dtors, factory methods
SMILAnimationController::SMILAnimationController(Document* aDoc)
: mDocument(aDoc) {
MOZ_ASSERT(aDoc, "need a non-null document");
if (nsRefreshDriver* refreshDriver = GetRefreshDriver()) {
mStartTime = refreshDriver->MostRecentRefresh();
} else {
mStartTime = mozilla::TimeStamp::Now();
mCurrentSampleTime = mStartTime;
SMILAnimationController::~SMILAnimationController() {
"Animation controller shouldn't be tracking any animation"
" elements when it dies");
"Leaving stale entry in refresh driver's observer list");
void SMILAnimationController::Disconnect() {
MOZ_ASSERT(mDocument, "disconnecting when we weren't connected...?");
MOZ_ASSERT(mRefCnt.get() == 1,
"Expecting to disconnect when doc is sole remaining owner");
"Expecting to be paused for pagehide before disconnect");
mDocument = nullptr; // (raw pointer)
// SMILTimeContainer methods:
void SMILAnimationController::Pause(uint32_t aType) {
void SMILAnimationController::Resume(uint32_t aType) {
bool wasPaused = !!mPauseState;
// Update mCurrentSampleTime so that calls to GetParentTime--used for
// calculating parent offsets--are accurate
mCurrentSampleTime = mozilla::TimeStamp::Now();
if (wasPaused && !mPauseState) {
SMILTime SMILAnimationController::GetParentTime() const {
return (SMILTime)(mCurrentSampleTime - mStartTime).ToMilliseconds();
// nsARefreshObserver methods:
// nsRefreshDriver Callback function
void SMILAnimationController::WillRefresh(mozilla::TimeStamp aTime) {
// Although we never expect aTime to go backwards, when we initialise the
// animation controller, if we can't get hold of a refresh driver we
// initialise mCurrentSampleTime to Now(). It may be possible that after
// doing so we get sampled by a refresh driver whose most recent refresh time
// predates when we were initialised, so to be safe we make sure to take the
// most recent time here.
aTime = std::max(mCurrentSampleTime, aTime);
// Sleep detection: If the time between samples is a whole lot greater than we
// were expecting then we assume the computer went to sleep or someone's
// messing with the clock. In that case, fiddle our parent offset and use our
// average time between samples to calculate the new sample time. This
// prevents us from hanging while trying to catch up on all the missed time.
// Smoothing of coefficient for the average function. 0.2 should let us track
// the sample rate reasonably tightly without being overly affected by
// occasional delays.
static const double SAMPLE_DUR_WEIGHTING = 0.2;
// If the elapsed time exceeds our expectation by this number of times we'll
// initiate special behaviour to basically ignore the intervening time.
static const double SAMPLE_DEV_THRESHOLD = 200.0;
SMILTime elapsedTime =
(SMILTime)(aTime - mCurrentSampleTime).ToMilliseconds();
if (mAvgTimeBetweenSamples == 0) {
// First sample.
mAvgTimeBetweenSamples = elapsedTime;
} else {
if (elapsedTime > SAMPLE_DEV_THRESHOLD * mAvgTimeBetweenSamples) {
// Unexpectedly long delay between samples.
"Detected really long delay between samples, continuing from "
"previous sample");
mParentOffset += elapsedTime - mAvgTimeBetweenSamples;
// Update the moving average. Due to truncation here the average will
// normally be a little less than it should be but that's probably ok.
mAvgTimeBetweenSamples =
mAvgTimeBetweenSamples * (1.0 - SAMPLE_DUR_WEIGHTING));
mCurrentSampleTime = aTime;
// Animation element registration methods:
void SMILAnimationController::RegisterAnimationElement(
SVGAnimationElement* aAnimationElement) {
const bool wasEmpty = mAnimationElementTable.IsEmpty();
if (wasEmpty) {
void SMILAnimationController::UnregisterAnimationElement(
SVGAnimationElement* aAnimationElement) {
if (mAnimationElementTable.IsEmpty()) {
// Page show/hide
void SMILAnimationController::OnPageShow() {
void SMILAnimationController::OnPageHide() {
// Cycle-collection support
void SMILAnimationController::Traverse(
nsCycleCollectionTraversalCallback* aCallback) {
// Traverse last compositor table
if (mLastCompositorTable) {
for (SMILCompositor& compositor : *mLastCompositorTable) {
void SMILAnimationController::Unlink() { mLastCompositorTable = nullptr; }
// Refresh driver lifecycle related methods
void SMILAnimationController::NotifyRefreshDriverCreated(
nsRefreshDriver* aRefreshDriver) {
void SMILAnimationController::NotifyRefreshDriverDestroying(
nsRefreshDriver* aRefreshDriver) {
// Timer-related implementation helpers
bool SMILAnimationController::ShouldSample() const {
return !mPauseState && !mAnimationElementTable.IsEmpty() &&
void SMILAnimationController::UpdateSampling() {
const bool shouldSample = ShouldSample();
const bool isSampling = mRegisteredWithRefreshDriver;
if (shouldSample == isSampling) {
nsRefreshDriver* driver = GetRefreshDriver();
if (!driver) {
if (shouldSample) {
// We're effectively resuming from a pause so update our current sample time
// or else it will confuse our "average time between samples" calculations.
mCurrentSampleTime = mozilla::TimeStamp::Now();
driver->AddRefreshObserver(this, FlushType::Style, "SMIL animations");
mRegisteredWithRefreshDriver = true;
Sample(); // Run the first sample manually.
} else {
void SMILAnimationController::StopSampling(nsRefreshDriver* aRefreshDriver) {
if (aRefreshDriver && mRegisteredWithRefreshDriver) {
// NOTE: The document might already have been detached from its PresContext
// (and RefreshDriver), which would make GetRefreshDriver() return null.
MOZ_ASSERT(!GetRefreshDriver() || aRefreshDriver == GetRefreshDriver(),
"Stopping sampling with wrong refresh driver");
aRefreshDriver->RemoveRefreshObserver(this, FlushType::Style);
mRegisteredWithRefreshDriver = false;
// Sample-related methods and callbacks
void SMILAnimationController::DoSample() {
DoSample(true); // Skip unchanged time containers
void SMILAnimationController::DoSample(bool aSkipUnchangedContainers) {
if (!mDocument) {
NS_ERROR("Shouldn't be sampling after document has disconnected");
if (mRunningSample) {
NS_ERROR("Shouldn't be recursively sampling");
mResampleNeeded = false;
// Set running sample flag -- do this before flushing styles so that when we
// flush styles we don't end up requesting extra samples
AutoRestore<bool> autoRestoreRunningSample(mRunningSample);
mRunningSample = true;
// STEP 1: Bring model up to date
// (i) Rewind elements where necessary
// (ii) Run milestone samples
// STEP 2: Sample the child time containers
// When we sample the child time containers they will simply record the sample
// time in document time.
TimeContainerHashtable activeContainers(mChildContainerTable.Count());
for (SMILTimeContainer* container : mChildContainerTable.Keys()) {
if (!container) {
if (!container->IsPausedByType(SMILTimeContainer::PAUSE_BEGIN) &&
(container->NeedsSample() || !aSkipUnchangedContainers)) {
// STEP 3: (i) Sample the timed elements AND
// (ii) Create a table of compositors
// (i) Here we sample the timed elements (fetched from the
// SVGAnimationElements) which determine from the active time if the
// element is active and what its simple time etc. is. This information is
// then passed to its time client (SMILAnimationFunction).
// (ii) During the same loop we also build up a table that contains one
// compositor for each animated attribute and which maps animated elements to
// the corresponding compositor for their target attribute.
// Note that this compositor table needs to be allocated on the heap so we can
// store it until the next sample. This lets us find out which elements were
// animated in sample 'n-1' but not in sample 'n' (and hence need to have
// their animation effects removed in sample 'n').
// Parts (i) and (ii) are not functionally related but we combine them here to
// save iterating over the animation elements twice.
// Create the compositor table
UniquePtr<SMILCompositorTable> currentCompositorTable(
new SMILCompositorTable(0));
nsTArray<RefPtr<SVGAnimationElement>> animElems(
for (SVGAnimationElement* animElem : mAnimationElementTable.Keys()) {
SampleTimedElement(animElem, &activeContainers);
AddAnimationToCompositorTable(animElem, currentCompositorTable.get());
// STEP 4: Compare previous sample's compositors against this sample's.
// (Transfer cached base values across, & remove animation effects from
// no-longer-animated targets.)
if (mLastCompositorTable) {
// * Transfer over cached base values, from last sample's compositors
for (SMILCompositor& compositor : *currentCompositorTable) {
SMILCompositor* lastCompositor =
if (lastCompositor) {
if (!lastCompositor->HasSameNumberOfAnimationFunctionsAs(compositor)) {
// If we have multiple animations on the same element, they share a
// compositor. If an active animation ends, it will no longer be in
// the compositor table. We need to force compositing to ensure we
// render the element with any remaining frozen animations even though
// they would not normally trigger compositing.
// * For each compositor in current sample's hash table, remove entry from
// prev sample's hash table -- we don't need to clear animation
// effects of those compositors, since they're still being animated.
for (const auto& key : currentCompositorTable->Keys()) {
// * For each entry that remains in prev sample's hash table (i.e. for
// every target that's no longer animated), clear animation effects.
for (SMILCompositor& compositor : *mLastCompositorTable) {
// return early if there are no active animations to avoid a style flush
if (currentCompositorTable->IsEmpty()) {
mLastCompositorTable = nullptr;
// STEP 5: Compose currently-animated attributes.
// XXXdholbert: This step traverses our animation targets in an effectively
// random order. For animation from/to 'inherit' values to work correctly
// when the inherited value is *also* being animated, we really should be
// traversing our animated nodes in an ancestors-first order (bug 501183)
bool mightHavePendingStyleUpdates = false;
for (auto& compositor : *currentCompositorTable) {
// Update last compositor table
mLastCompositorTable = std::move(currentCompositorTable);
mMightHavePendingStyleUpdates = mightHavePendingStyleUpdates;
NS_ASSERTION(!mResampleNeeded, "Resample dirty flag set during sample!");
void SMILAnimationController::RewindElements() {
const bool rewindNeeded = std::any_of(
mChildContainerTable.Keys().cbegin(), mChildContainerTable.Keys().cend(),
[](SMILTimeContainer* container) { return container->NeedsRewind(); });
if (!rewindNeeded) return;
for (SVGAnimationElement* animElem : mAnimationElementTable.Keys()) {
SMILTimeContainer* timeContainer = animElem->GetTimeContainer();
if (timeContainer && timeContainer->NeedsRewind()) {
for (SMILTimeContainer* container : mChildContainerTable.Keys()) {
void SMILAnimationController::DoMilestoneSamples() {
// We need to sample the timing model but because SMIL operates independently
// of the frame-rate, we can get one sample at t=0s and the next at t=10min.
// In between those two sample times a whole string of significant events
// might be expected to take place: events firing, new interdependencies
// between animations resolved and dissolved, etc.
// Furthermore, at any given time, we want to sample all the intervals that
// end at that time BEFORE any that begin. This behaviour is implied by SMIL's
// endpoint-exclusive timing model.
// So we have the animations (specifically the timed elements) register the
// next significant moment (called a milestone) in their lifetime and then we
// step through the model at each of these moments and sample those animations
// registered for those times. This way events can fire in the correct order,
// dependencies can be resolved etc.
SMILTime sampleTime = std::numeric_limits<SMILTime>::min();
while (true) {
// We want to find any milestones AT OR BEFORE the current sample time so we
// initialise the next milestone to the moment after (1ms after, to be
// precise) the current sample time and see if there are any milestones
// before that. Any other milestones will be dealt with in a subsequent
// sample.
SMILMilestone nextMilestone(GetCurrentTimeAsSMILTime() + 1, true);
for (SMILTimeContainer* container : mChildContainerTable.Keys()) {
if (container->IsPausedByType(SMILTimeContainer::PAUSE_BEGIN)) {
SMILMilestone thisMilestone;
bool didGetMilestone =
if (didGetMilestone && thisMilestone < nextMilestone) {
nextMilestone = thisMilestone;
if (nextMilestone.mTime > GetCurrentTimeAsSMILTime()) {
nsTArray<RefPtr<dom::SVGAnimationElement>> elements;
for (SMILTimeContainer* container : mChildContainerTable.Keys()) {
if (container->IsPausedByType(SMILTimeContainer::PAUSE_BEGIN)) {
container->PopMilestoneElementsAtMilestone(nextMilestone, elements);
// During the course of a sampling we don't want to actually go backwards.
// Due to negative offsets, early ends and the like, a timed element might
// register a milestone that is actually in the past. That's fine, but it's
// still only going to get *sampled* with whatever time we're up to and no
// earlier.
// Because we're only performing this clamping at the last moment, the
// animations will still all get sampled in the correct order and
// dependencies will be appropriately resolved.
sampleTime = std::max(nextMilestone.mTime, sampleTime);
for (RefPtr<dom::SVGAnimationElement>& elem : elements) {
MOZ_ASSERT(elem, "nullptr animation element in list");
SMILTimeContainer* container = elem->GetTimeContainer();
if (!container)
// The container may be nullptr if the element has been detached from
// its parent since registering a milestone.
SMILTimeValue containerTimeValue =
if (!containerTimeValue.IsDefinite()) continue;
// Clamp the converted container time to non-negative values.
SMILTime containerTime =
std::max<SMILTime>(0, containerTimeValue.GetMillis());
if (nextMilestone.mIsEnd) {
} else {
void SMILAnimationController::SampleTimedElement(
SVGAnimationElement* aElement, TimeContainerHashtable* aActiveContainers) {
SMILTimeContainer* timeContainer = aElement->GetTimeContainer();
if (!timeContainer) return;
// We'd like to call timeContainer->NeedsSample() here and skip all timed
// elements that belong to paused time containers that don't need a sample,
// but that doesn't work because we've already called Sample() on all the time
// containers so the paused ones don't need a sample any more and they'll
// return false.
// Instead we build up a hashmap of active time containers during the previous
// step (SampleTimeContainer) and then test here if the container for this
// timed element is in the list.
if (!aActiveContainers->GetEntry(timeContainer)) return;
SMILTime containerTime = timeContainer->GetCurrentTimeAsSMILTime();
"Doing a regular sample but the time container is still seeking");
void SMILAnimationController::AddAnimationToCompositorTable(
SVGAnimationElement* aElement, SMILCompositorTable* aCompositorTable) {
// Add a compositor to the hash table if there's not already one there
SMILTargetIdentifier key;
if (!GetTargetIdentifierForAnimation(aElement, key))
// Something's wrong/missing about animation's target; skip this animation
SMILAnimationFunction& func = aElement->AnimationFunction();
// Only add active animation functions. If there are no active animations
// targeting an attribute, no compositor will be created and any previously
// applied animations will be cleared.
if (func.IsActiveOrFrozen()) {
// Look up the compositor for our target, & add our animation function
// to its list of animation functions.
SMILCompositor* result = aCompositorTable->PutEntry(key);
} else if (func.HasChanged()) {
// Look up the compositor for our target, and force it to skip the
// "nothing's changed so don't bother compositing" optimization for this
// sample. |func| is inactive, but it's probably *newly* inactive (since
// it's got HasChanged() == true), so we need to make sure to recompose
// its target.
SMILCompositor* result = aCompositorTable->PutEntry(key);
// We've now made sure that |func|'s inactivity will be reflected as of
// this sample. We need to clear its HasChanged() flag so that it won't
// trigger this same clause in future samples (until it changes again).
static inline bool IsTransformAttribute(int32_t aNamespaceID,
nsAtom* aAttributeName) {
return aNamespaceID == kNameSpaceID_None &&
(aAttributeName == nsGkAtoms::transform ||
aAttributeName == nsGkAtoms::patternTransform ||
aAttributeName == nsGkAtoms::gradientTransform);
// Helper function that, given a SVGAnimationElement, looks up its target
// element & target attribute and populates a SMILTargetIdentifier
// for this target.
bool SMILAnimationController::GetTargetIdentifierForAnimation(
SVGAnimationElement* aAnimElem, SMILTargetIdentifier& aResult) {
// Look up target (animated) element
Element* targetElem = aAnimElem->GetTargetElementContent();
if (!targetElem)
// Animation has no target elem -- skip it.
return false;
// Look up target (animated) attribute
// SMILANIM section 3.1, attributeName may
// have an XMLNS prefix to indicate the XML namespace.
RefPtr<nsAtom> attributeName;
int32_t attributeNamespaceID;
if (!aAnimElem->GetTargetAttributeName(&attributeNamespaceID,
// Animation has no target attr -- skip it.
return false;
// animateTransform can only animate transforms, conversely transforms
// can only be animated by animateTransform
if (IsTransformAttribute(attributeNamespaceID, attributeName) !=
return false;
// Construct the key
aResult.mElement = targetElem;
aResult.mAttributeName = attributeName;
aResult.mAttributeNamespaceID = attributeNamespaceID;
return true;
void SMILAnimationController::PreTraverse() { PreTraverseInSubtree(nullptr); }
void SMILAnimationController::PreTraverseInSubtree(Element* aRoot) {
if (!mMightHavePendingStyleUpdates) {
nsPresContext* context = mDocument->GetPresContext();
if (!context) {
for (SVGAnimationElement* animElement : mAnimationElementTable.Keys()) {
SMILTargetIdentifier key;
if (!GetTargetIdentifierForAnimation(animElement, key)) {
// Something's wrong/missing about animation's target; skip this animation
// Ignore restyles that aren't in the flattened tree subtree rooted at
// aRoot.
if (aRoot && !nsContentUtils::ContentIsFlattenedTreeDescendantOf(
key.mElement, aRoot)) {
key.mElement, PseudoStyleType::NotPseudo, RestyleHint::RESTYLE_SMIL);
// Only clear the mMightHavePendingStyleUpdates flag if we definitely posted
// all restyles.
if (!aRoot) {
mMightHavePendingStyleUpdates = false;
// Add/remove child time containers
nsresult SMILAnimationController::AddChild(SMILTimeContainer& aChild) {
const bool wasEmpty = mChildContainerTable.IsEmpty();
TimeContainerPtrKey* key = mChildContainerTable.PutEntry(&aChild);
if (wasEmpty) {
return NS_OK;
void SMILAnimationController::RemoveChild(SMILTimeContainer& aChild) {
if (mChildContainerTable.IsEmpty()) {
// Helper method
nsRefreshDriver* SMILAnimationController::GetRefreshDriver() {
if (!mDocument) {
NS_ERROR("Requesting refresh driver after document has disconnected!");
return nullptr;
nsPresContext* context = mDocument->GetPresContext();
return context ? context->RefreshDriver() : nullptr;
void SMILAnimationController::FlagDocumentNeedsFlush() {
if (PresShell* presShell = mDocument->GetPresShell()) {
} // namespace mozilla