[SVG] Implement 'discard' element

Source/core/svg/animation/SMILTimeContainer.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 307 matching lines @@
     }
 
     // Apply results to target elements.
     for (unsigned i = 0; i < animationsToApplySize; ++i)
         animationsToApply[i]->applyResultsToTarget();
 
 #ifndef NDEBUG
     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);
 }
 
 }