Bug 1315874 - Don't allocate separate heap memory for nsSMILCompositor::mCachedBaseValue; r?dholbert
nsSMILCompositor::mCachedBaseValue is an nsAutoPtr<nsSMILValue> that we allocate
on the heap. It looks like we did that back in
bug 533291 presumably because it
makes transferring these cached values between nsSMILCompositor objects cheaper.
One drawback of this, however, is that mCachedBaseValue has two null states:
the mCachedBaseValue pointer can be null, and the pointed-to nsSMILValue can be
a null value (i.e. IsNull() returns true).
Now that we have move ctors and operators defined for nsSMILValue we can
transfer these objects between compositors cheaply without requiring the object
to be allocated as separate heap object. This patch makes mCachedBaseValue just
a regular nsSMILValue class member (i.e. drops the nsAutoPtr).
There's a subtle difference in behavior with regards to the first sample.
Previously we would compare the (initially) null mCachedBaseValue pointer with
the passed-in nsSMILValue and set mForceCompositing to true. With this patch,
however, we will only set mForceCompositing to true if the passed-in
mCachedBaseValue is not null.
I believe this is correct, however, since if we don't call GetBaseValue in
ComposeAttribute we should not be setting mForceCompositing to true (something
else should ensure that gets set to true), and if we do call GetBaseValue the
result should not be a null nsSMILValue (except in some OOM cases where we don't
really care if we miss a sample). This patch adds an assertion to check that
GetBaseValue does, in fact, return a non-null value. (I checked the code and
this appears to be the case. Even in error cases we typically return an empty
nsSMILValue of a non-null type. For example, the early return in
nsSMILCSSProperty::GetBaseValue() does this.)
MozReview-Commit-ID: BRJFa4xMdxz
--- a/dom/smil/nsSMILCompositor.cpp
+++ b/dom/smil/nsSMILCompositor.cpp
@@ -77,16 +77,18 @@ nsSMILCompositor::ComposeAttribute(bool&
// THIRD: Step backwards through animation functions to find out
// which ones we actually care about.
uint32_t firstFuncToCompose = GetFirstFuncToAffectSandwich();
// FOURTH: Get & cache base value
nsSMILValue sandwichResultValue;
if (!mAnimationFunctions[firstFuncToCompose]->WillReplace()) {
sandwichResultValue = smilAttr->GetBaseValue();
+ MOZ_ASSERT(!sandwichResultValue.IsNull(),
+ "Result of GetBaseValue should not be null");
}
UpdateCachedBaseValue(sandwichResultValue);
if (!mForceCompositing) {
return;
}
// FIFTH: Compose animation functions
@@ -193,19 +195,14 @@ nsSMILCompositor::GetFirstFuncToAffectSa
}
}
return i;
}
void
nsSMILCompositor::UpdateCachedBaseValue(const nsSMILValue& aBaseValue)
{
- if (!mCachedBaseValue) {
- // We don't have last sample's base value cached. Assume it's changed.
- mCachedBaseValue = new nsSMILValue(aBaseValue);
- NS_WARNING_ASSERTION(mCachedBaseValue, "failed to cache base value (OOM?)");
- mForceCompositing = true;
- } else if (*mCachedBaseValue != aBaseValue) {
+ if (mCachedBaseValue != aBaseValue) {
// Base value has changed since last sample.
- *mCachedBaseValue = aBaseValue;
+ mCachedBaseValue = aBaseValue;
mForceCompositing = true;
}
}
--- a/dom/smil/nsSMILCompositor.h
+++ b/dom/smil/nsSMILCompositor.h
@@ -4,17 +4,16 @@
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef NS_SMILCOMPOSITOR_H_
#define NS_SMILCOMPOSITOR_H_
#include "mozilla/Move.h"
#include "mozilla/UniquePtr.h"
-#include "nsAutoPtr.h"
#include "nsTHashtable.h"
#include "nsString.h"
#include "nsSMILAnimationFunction.h"
#include "nsSMILTargetIdentifier.h"
#include "nsSMILCompositorTable.h"
#include "PLDHashTable.h"
//----------------------------------------------------------------------
@@ -94,14 +93,14 @@ public:
// Member data for detecting when we need to force-recompose
// ---------------------------------------------------------
// Flag for tracking whether we need to compose. Initialized to false, but
// gets flipped to true if we detect that something has changed.
bool mForceCompositing;
// Cached base value, so we can detect & force-recompose when it changes
- // from one sample to the next. (nsSMILAnimationController copies this
+ // from one sample to the next. (nsSMILAnimationController moves this
// forward from the previous sample's compositor.)
- nsAutoPtr<nsSMILValue> mCachedBaseValue;
+ nsSMILValue mCachedBaseValue;
};
#endif // NS_SMILCOMPOSITOR_H_
