270567 - no parent chain for anonymous content causes anonymous <option> to fail

Status: RESOLVED WONTFIX

(Core Graveyard :: XTF, defect)

Description

[Brian Ryner (not reading)]

I tried creating an XTF element which has as its anonymous child an HTML
<option> element, and inserting this element inside an HTML select.  This fails
to work because nsHTMLOptionElement tries to walk up the content tree to find
its select.  When it gets to the root of the anonymous content, it can't go any
further and fails.

This is a rather complicated problem because there are non-trivial implications
to hooking up the parent pointer on the root anonymous content.  Events can
start bubbling out, so you either have to stop them or perform some kind of
event retargeting like XBL does.

Another option would be to add a different method on nsIContent that's like
GetParent() but will reach across the anonymous content boundary.  It could be
used in cases like this where an element needs to find a parent element that
it's expected to be contained in.  This doesn't help the event situation, we'd
have to deal with that separately.

I'm undecided on which approach I like better; hyatt notes that in sXBL, the
parent element linkage was removed.  It's definitely lower-risk to make all
interaction with the anonymous content tree explicit.  If we do decide we want
the parent linkage to work like XBL, I'd like to seriously look at sharing this
mechanism with XBL so we're not duplicating it... basically enabling the binding
manager to handle both XBL and XTF bindings.

What do you guys think?

Comment 1

[Brian Ryner (not reading)]

adding a few more people

Comment 2

[Hixie (not reading bugmail)]

In sXBL we also have a separate interface for going up the parent chains (and 
for doing so in various different ways):

   http://www.w3.org/TR/sXBL/#the-nodexbl

A similar mechanism might be relevant here, with HTML form elements all being 
changed so that they crawl up appropriately.

However, you have to be careful. You don't want the anonymous <html:select> 
inside an <xforms:select> appearing in an <html:form> ancestor. There needs to 
be a way for the <xforms:select> to say "this is the root of your subtree" to 
the <html:select> and <html:option>s, etc.

Comment 3

[Boris Zbarsky [:bzbarsky]]

> When it gets to the root of the anonymous content, it can't go any further and
> fails.

Hmm... Why is this?  The parent pointer for anonymous content should be set, no?
 It was last I checked.  See
http://lxr.mozilla.org/seamonkey/source/layout/html/style/src/nsCSSFrameConstructor.cpp#5429

> Events can start bubbling out, so you either have to stop them or perform some
> kind of event retargeting like XBL does.

We already perform event retargeting for native anonymous content.  See 
http://lxr.mozilla.org/seamonkey/source/content/base/src/nsGenericElement.cpp#1867
 Otherwise form controls would screw up events quite badly.. (well, more than
they do now).

Comment 4

[Boris Zbarsky [:bzbarsky]]

Note that hixie's point about anonymous form controls in non-anonymous forms is
well-taken.  We'd have to watch out for that...  I bet we get it wrong right now.

Comment 5

[Alex Vincent [:WeirdAl]]

XTF has been removed from the tree.  [xtfisdead] for filtering purposes.