[Dynapi-Dev] [ dynapi-Bugs-787137 ] Memory leak in DynElement.deleteChild()

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Bugs item #787137, was opened at 2003-08-11 23:36
Message generated for change (Comment added) made by warp9pnt9
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Category: DynAPI 3 API
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Andrew Gillett (agillett)
Assigned to: Nobody/Anonymous (nobody)
Summary: Memory leak in DynElement.deleteChild()

Initial Comment:
The DynElement.deleteChild() function is implemented 
thus:

p.deleteChild = function(c) {
	c.removeFromParent();
   	c._delete();
};

Although the _delete() function is documented in 
quickref.dynelement.html, it is not implemented 
_anywhere_ in the DynAPI source code, except for 
being set to dynapi.functions.Null in event.js.

If you have a page that repeatedly adds and removes 
DynElements, it will leak memory.  If you replace the call
to _delete() with a call to _destroy(), the memory leak 
goes away:

p.deleteChild = function(c) {
	c.removeFromParent();
   	c._destroy();
};


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Comment By: L W (warp9pnt9)
Date: 2003-08-14 08:30

Message:
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My view on the matter.

I think the naming convention would be clearer if the
function that removes children from parents was called
removeChild / removeFromParent, but not destroying the
layer.  I think this is how it works now.  I think the
function that removes the child from the parent AND destroys
the layer should be called deleteChild / deleteFromParent or
maybe destroyChild / destroyFromParent.  I think it's
confusing to add a new name "dispose" when it doesn't
intuitively correspond to an underlying "dispose" function.
 It's a little vague.

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Comment By: Raymond Irving (xwisdom)
Date: 2003-08-13 22:37

Message:
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I see what's happening. IMO deleteChild() and removeChild 
means the same thing, correct? 

When a child layer is removed from the parent it's actually 
deleted from the parent, correct?  The layer is not completly 
destroyed as a reference to it still exists within DynObject.all 
collection. 

Calling _destroy() during a deleteChild() function will not only 
delete the child from its parent but it will also dispose of the 
child object.

I think we should change deleteChild/AllChildren/etc to 
disposeChild/AllChildren/etc wihich will clearly define what is 
been done to the object. The dispose functions will complete 
remove and destroy the object.

Are we all in agreement with changing delete to dispose? Or 
should we add the _destroy() function to deleteChild and 
keep the delete functions?  

(Note: If we keep the delete functions we'll have to 
document that it will completely destroy and remove the layer 
from the system.)



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Comment By: Andrew Gillett (agillett)
Date: 2003-08-13 20:31

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> Are you using the lastest snapshot?
Yes, I check out the code directly from CVS.
> What browsers are experiencing this memory leak?
IE6 & Mozilla1.4, but that is not really relevant.

On 29/07/2003 12:26 AM (my time), in response to my post 
about a bug in deleteAllChildren(), you wrote:
>To fix the memory and layer problem use the following:
>
>p.deleteAllChildren = function() {
>	var c,l = this.children.length;
>	for(var i=0;i<l;i++) {
>		c=this.children[i];
>		if(c) {
>			c._destroy();
>			c._created = c.isChild = false;
>		};
>		delete this.children[i];
>	}
>	this.children.length = 0;
>};
>
This fix worked perfectly. The _destroy() method is called on 
each child of the layer.

However this is not what was put into CVS.  In the current 
version of event.js, deleteAllChildren() calls deleteFromParent
() which calls deleteChild() which calls _delete() instead of 
_destroy().

It is the call to _delete() that I have a problem with.  There 
is simply no such function.  In line 184 of event.js there is:

... = p._delete = p._destroy = dynapi.functions.Null;

but nowhere else in the entire source tree is _delete() 
defined.


Try the attached example.  On my Windows XP system, IE 
grows by about 6MB each time the "Memory Leak" button is 
pressed.  But if I replace the call to _delete() with a call to 
_destroy() in the deleteChild function, then IE doesn't leak at 
all.


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Comment By: Raymond Irving (xwisdom)
Date: 2003-08-13 09:53

Message:
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Are you using the lastest snapshot?

What browsers are experiencing this memory leak?

You can get the lastest snapshot here:
http://dynapi.sourceforge.net/snapshot/?N=D


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