[SVG] Implement 'discard' element

Source/core/svg/animation/SMILTimeContainer.cpp

Index: Source/core/svg/animation/SMILTimeContainer.cpp
diff --git a/Source/core/svg/animation/SMILTimeContainer.cpp b/Source/core/svg/animation/SMILTimeContainer.cpp
old mode 100644
new mode 100755
index 71dc1c2cc84ef4ed1e6eb91e9c34c5ad0968518f..8dfbbe0c720ca0a4e4cf9781d7e6c24b5954ee47
--- a/Source/core/svg/animation/SMILTimeContainer.cpp
+++ b/Source/core/svg/animation/SMILTimeContainer.cpp
@@ -325,6 +325,16 @@ void SMILTimeContainer::updateAnimations(SMILTime elapsed, bool seekToTime)
     m_preventScheduledAnimationsChanges = false;
 #endif
 
+    for (unsigned n = 0; n < animationsToApply.size(); n++) {

[rwlbuis, 2013/12/16 21:31:34]

Better use prefix ++ variant, it is not slower but may be quicker than postfix
++.
Also it looks like you can reuse animationsToApplySize here.

[pavane, 2013/12/16 22:03:50]

Sure, i missed it. I am not changing the size of the vector here after deleting
the discard element. So, i can use animationsToApplySize as well

[pdr., 2013/12/18 22:40:33]

I don't think this is safe.

Can't the remove() call in this for loop change the vector itself? For example,
if the remove target was a later element in this vector.

[pavane, 2013/12/19 07:17:03]

This is the exact problem i am facing currently with one use case i have with
me. This code is producing dangling pointers. I am planning to check whether the
target element exists in the vector and if it exists, i want to set it to NULL
before removing the target element. But this looks to be inefficient as it needs
to search the vector every time. Any other better way to do this? Should i
change this to a vector of references and check for object to be inDocument() on
every iteration?

+        if (animationsToApply[n]->isDiscardable()) {

[rwlbuis, 2013/12/16 21:31:34]

Do you need a flag for isDiscardable? I am not an expert with the anim system,
but isn't isDiscardable always true for the case at the time when the <discard>
can be applied, i.e. when begin time has been reached?

[pavane, 2013/12/16 22:03:50]

you are right. only animations which are already started are added into
animationsToApply and we need to remove discard and it's target as soon as the
discard element is started. So, isDiscardable is not needed. We just need a way
to check whether it is a discard element.

+            SVGSMILElement* animDiscard = animationsToApply[n];
+            SVGElement* targetElement = animDiscard->targetElement();
+            animDiscard->remove(IGNORE_EXCEPTION);
+            if (targetElement)
+                targetElement->remove(IGNORE_EXCEPTION);
+        }
+    }
+
     startTimer(earliestFireTime, animationFrameDelay);
 }