ian at hixie.ch
Thu Feb 4 03:45:13 PST 2010
On Fri, 29 Jan 2010, Olli Pettay wrote:
> On 1/29/10 3:32 AM, Ian Hickson wrote:
> > I've tried to spec this. There is a high risk of compatibility issues,
> > so I would very much welcome feedback from implementors who try to
> > implement this.
> > The main goal of the change here is to make it possible to implement
> > this (if not completely sanely, but it's the Web, there's only so much
> > I can do) in a situation with each browsing context having its own
> > process, as seen to some extent in IE and Chrome, and as is being
> > examined by other browser vendors also.
> So why sync history isn't possible in IE or Chrome?
Anything's _possible_, it's just that it's a lot more complicated. As
Jonas said earlier in the thread, making history traversal asynchronous is
likely to make things easier for Mozilla too. Sorry for overstating the
case above, I have a tendency to exaggerate!
> How should UA handle this case? User presses back (which hopefully does
> pretty much the same as history.back()) but web page has some loop like
> script which sets location.hash all the time.
I would recommend that implementations prioritise tasks queued by user
interaction, so that the script does not preempt the user's action.
However, since that is a user interface issue, the spec does not specify
it in any detail. (The spec doesn't require that you expose a back button
> > If we can't do this asynchronously, it's going to really suck for
> > multiprocess UAs,
> Depends for example on whether UA wants to put different domains in same
> tab to different processes. And even if it does do, synchronous
> back()/forward() should be possible. Maybe just not as easy. So I'm not
> sure that "suck for multiprocess UAs" is a really good argument here.
Certainly it isn't well-expressed, but it does seem important to make sure
that the technology we are specifying can be sanely implemented in a
multi-process architecture, since two UAs are already shipping with that
technology, and at least one other (Mozilla) is working on a similar
effort. I don't think anyone would deny that there are advantages to such
> Uh, changing hashchange again to async. We must stop changing that all
> the time. Though in this case I like the change. I never really
> understood the sync hashchange, or the reasoning why it was changed to
> be sync.
Yeah, my apologies for the back-and-forth on this particular issue. I try
to minimise churn in general, but in this case I failed.
> So history.back(); history.back(); would queue 2 tasks?
> And first one document is loaded (maybe from bfcache), and it could
> synchronously do something like dispatch pageshow or whatever which
> could do things like alert() and then second document was loaded at somepoint.
> Kind of strange way to handle history.back().
For cross-document loads, back() has always been asynchronous, so I don't
think that particular case is a change.
I agree that it is not completely intuitive.
Ian Hickson U+1047E )\._.,--....,'``. fL
http://ln.hixie.ch/ U+263A /, _.. \ _\ ;`._ ,.
Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'
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