[whatwg] <object> behavior

[Ian Hickson]

On Thu, 6 Aug 2009, Andrew Oakley wrote:
>
> The rules in the HTML5 spec for which plugin to load for an <object> do 
> not seem to be followed by any browser, and in some cases are different 
> to behavior that is common to Opera, Webkit and Gecko (I haven't tested 
> with IE due to its lack of nsplugin support).
> 
> Most notably HTML5 says that the Content-Type header is used in 
> preference to the type attribute, whereas the browsers seem to honour 
> the attribute in preference to the header.  (If the spec is changed to 
> match the browsers behaviour then the conditions on when to load a new 
> plugin also need to be changed.)  HTML5 also seems to prefer the type 
> attribute on <script>s rather than the Content-Type header.
> 
> Detaching and reattaching a <object> from the document seems to make the 
> browsers destroy the object and then recreate it.  Presumably this means 
> that the DOM objects also change depending on whether or not an <object> 
> is attached to the document (haven't confirmed that this is the case).
> 
> Changing the attributes on an <object> that is attached to the document 
> doesn't seem to "work" - Webkit does nothing, Opera seems to stop 
> scripting (presumably some kind of error), Firefox reloads the plugin in 
> some cases (even if its not the right one anymore).
> 
> Removing an <object> from the document (browsers destroy plugin object), 
> changing the attributes and reattaching it to the document (browser 
> creates plugin object) seems to work fairly reliably across browsers.
> 
> In effect it seems that browsers use the attributes that were on the 
> <object> when it was attached to the document, and do not respond to 
> changes in the attributes.
> 
> The test cases I used are available at 
> http://ado.is-a-geek.net/~andrew/pluginstest.tar.bz2 (sorry they are 
> somewhat linux based due to the platform specific plugins).
> 
> In summary I have a few questions related to <object>s:
> - Should the type attribute take precedence over the Content-Type header?

No, I believe what the spec says here is the preferred behaviour. Unless 
this is incompatible with legacy content, we should try to move towards 
this behaviour.


> - Should <object>s exist all the time whether they are attached to the
> document or not?

Assuming you mean the plugins, as opposed to the elements themselves, then 
the way the spec is written, the plugin instantiates regardless of whether 
it is in the document or not.


> - Should changing the attributes change the plugin, or should we just 
> use the attributes when the object was attached to the document?

I'm pretty sure that for compatibility with legacy content, only the type, 
data, and classid attributes would cause the plugin to be restarted if 
changed.


On Thu, 6 Aug 2009, Boris Zbarsky wrote:
>
> The exact Gecko behavior is the following.
> 
> 1)  If the header type is application/octet-stream and the type
>     attribute was set to something that parsed as a MIME type, use the
>     type attribute's type.
> 2)  If the type attribute was set to something that parsed as a MIME
>     type, and if that type would be handled by a plug-in (that is, we
>     have a plug-in to handle it, and have no other method for handling
>     it), then use the type attribute's type instead of the header type.
> 3)  In all other cases the header type is used.

Step 2 above isn't what the spec says. The rest is, more or less.

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
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