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RE: [NavigationTiming] few comments

From: Nic Jansma <Nic.Jansma@microsoft.com>
Date: Tue, 22 Mar 2011 23:45:36 +0000
To: "Olli@pettay.fi" <Olli@pettay.fi>, Jonas Sicking <jonas@sicking.cc>
CC: Tony Gentilcore <tonyg@google.com>, "public-web-perf@w3.org" <public-web-perf@w3.org>, Jatinder Mann <jmann@microsoft.com>, Zhiheng Wang <zhihengw@google.com>
Message-ID: <F677C405AAD11B45963EEAE5202813BD19CB7040@TK5EX14MBXW651.wingroup.windeploy.ntdev.microsoft.com>
IE does not have a bfcache.

For NavigationTiming, we have focused on exposing the timing information about the initial navigation to the page.  For example, we do not clear or overwrite the performance.timing attributes for document.open()s or fragment navigation within the page.  This is described in our processing model:

We currently have a test that document.open() does not clear the timing data:

The .navigation.type and .timing.* attributes are synchronized here -- you wouldn't update navigation.type while keeping the old .timing.* attributes.

- Nic
-----Original Message-----
From: Olli Pettay [mailto:Olli.Pettay@helsinki.fi] 
Sent: Tuesday, March 22, 2011 3:48 PM
To: Jonas Sicking
Cc: Tony Gentilcore; public-web-perf@w3.org; Jatinder Mann; Nic Jansma; Zhiheng Wang
Subject: Re: [NavigationTiming] few comments

On 03/23/2011 12:32 AM, Jonas Sicking wrote:
> On Tue, Mar 22, 2011 at 3:05 PM, Tony Gentilcore<tonyg@google.com>  wrote:
>>> How do current implementations handle cached DOM + back-forward?
>> WebKit has a bfcache called PageCache, but it is disabled in Chrome.
>> Since it is moot there, I haven't payed attention to the details here.
>> Nic or Jatinder can probably comment on what IE does here. If they 
>> don't use it either, mozilla is probably the first implementation 
>> with a bfcache and you might suggest reasonable behavior to Zhiheng.
> We should definitely simply leave the values untouched when going 
> back/forward to a DOM-cached page.
Why? Then .navigation.type may actually lie what was the previous navigation. And writing tests for BACK_FORWARD becomes really hard, since you don't know what value browser returns in .navigation.type.
Some browsers may return NAVIGATION (because they have bfcache), some may return BACK_FORWARD.
Also, that kind of behavior would actually prevent one kind of performance timing - BACK_FORWARD + cached DOM.

> Generally speaking the page should
> act as if you never left it. The only difference is that we send it 
> events telling it it's going into and out from the cache, as to give 
> it a chance to halt things like animations and status updates.
> / Jonas
Received on Tuesday, 22 March 2011 23:46:10 UTC

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