[webkit-dev] DOM tree surgery and DOM tree destruction
darin at apple.com
Wed Jun 25 10:15:04 PDT 2008
On Jun 25, 2008, at 10:06 AM, Pitaga wrote:
> For example, suppose that a browser based on WebKit has loaded a Web
> page and parsed it, producing a DOM tree T. As an exercise, I want
> to perform surgery on T and then destroy both T and the constituents
> that the surgery removed from T, without leaking. For purposes of
> this exercise, the browser session itself is of no interest.
You don't explicitly destroy anything. DOM objects will be destroyed
when the last owner goes away; that's what reference counting is used
So "How do I destroy the tree?" is the wrong question. If there's a
test case where something's not getting destroyed, you could ask "Why
isn't it being destroyed?" but there's no need to write code to
explicitly destroy anything.
> What's the best practice here with respect to raw pointers,
> PassRefPtr's, and RefPtr's?
That question is too vague and broad for me to answer. Maybe you could
ask a more specific question?
> How do I destroy the subtree dominated by W after I remove it?
I had a lot of trouble following the letters in your example, so I'm
not sure about "W" or even what "dominated" means.
Generally if you remove a child with removeChild, then that child and
all its descendants will be destroyed when the last reference to it
goes away. Typically you are holding a RefPtr to the child you are
removing; in that case the most likely time it will be destroyed is
when that RefPtr goes out of scope. Or you might only have a raw
pointer. In that case, it's likely the child will destroyed within the
> How do I destroy T when I'm all finished?
You say that "WebKit has loaded a web page and parsed it [to produce
T]". Given that, T is a document and it's owned by the Frame that
loaded it. As long as its the current document in that Frame it will
be kept alive. When the Frame either goes away or loads a new
document, then it will be destroyed, unless someone else is holding a
reference to it. When the last reference to it goes away, it will be
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