[webkit-dev] Can node->renderer()->node() == node ever be false?

[Dimitri Glazkov]

Any takers? :) https://bugs.webkit.org/show_bug.cgi?id=45821

:DG<

On Tue, Sep 14, 2010 at 9:16 PM, Dimitri Glazkov <dglazkov at chromium.org> wrote:
> Ok, after following down a few rabbit holes, I can with some degree of
> certainty say that node->renderer()->node() == 0 can only at the end
> of RenderWidget::destroy(), but that is clearly not the case we're
> fishing for.
>
> Even if we modify the loop to start at the parent, we're jumping into
> the render tree to find a node to fire an event on, which is unhealthy
> for various layering reasons.
>
> In summary, to quote the great protagonists from a TV show:
> "Exterminate! Exterminate!"
>
> :DG<
>
> On Tue, Sep 14, 2010 at 7:19 PM, Dimitri Glazkov <dglazkov at chromium.org> wrote:
>> Sounds good, I will look into this. FWIW, when I remove this loop, I
>> see no regressions in layout tests, including the tests added with the
>> same commit as the loop.
>>
>> :DG<
>>
>> On Tue, Sep 14, 2010 at 5:55 PM, Maciej Stachowiak <mjs at apple.com> wrote:
>>>
>>> On Sep 14, 2010, at 5:41 PM, Dimitri Glazkov wrote:
>>>
>>>> Sorry, I meant node->renderer()->node() != 0. My bad. This loop will
>>>> always exit in in the first iteration.
>>>
>>> It definitely is possible for renderers to have a null result from node(). I do not know for sure that it's impossible for node->renderer()->node() to be null under any circumstances. Anonymous renderers and inline continuations are among the ways a null node pointers. It might be that in all such circumstances, the renderer won't be returned by any node's renderer() method. It would be worth some analysis.
>>>
>>>  - Maciej
>>>
>>>>
>>>> :DG<
>>>>
>>>> On Tue, Sep 14, 2010 at 4:45 PM, Adam Roben <aroben at apple.com> wrote:
>>>>> On Sep 14, 2010, at 6:46 PM, Dimitri Glazkov wrote:
>>>>>
>>>>>> I've been looking at this line here and it doesn't seem to make sense
>>>>>> to me: http://trac.webkit.org/browser/trunk/WebCore/page/EventHandler.cpp#L2153
>>>>>>
>>>>>> It looks like the loop in question will always exit early, because it
>>>>>> short-circuits to node->renderer()->node() == node, which seems like
>>>>>> it always will be true. At least, that's what the layout tests say
>>>>>> when I remove it.
>>>>>
>>>>> I don't see anything in that loop that is equivalent to node->renderer()->node() == node. All I see are null-checks. Note that line 2154 declares a new variable with the name "node".
>>>>>
>>>>> I don't know anything else about this code or what you're asking, though.
>>>>>
>>>>> -Adam
>>>>>
>>>>>
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>>>
>>
>