[webkit-dev] Notifying PageClient when page transition has begun

[Thiago Lacerda]

On Thu, Jul 25, 2013 at 2:34 PM, Brady Eidson <beidson at apple.com> wrote:

>
> On Jul 25, 2013, at 10:10 AM, Thiago Lacerda <thiago.lacerda at openbossa.org>
> wrote:
>
> Hi Brady
>
>
> On Thu, Jul 25, 2013 at 1:48 PM, Brady Eidson <beidson at apple.com> wrote:
>
>>
>> On Jul 25, 2013, at 9:08 AM, Thiago Lacerda <thiago.lacerda at openbossa.org>
>> wrote:
>>
>> Hi,
>>
>> We in the Nix port team (which is going upstream), are facing an issue
>> that we need our WebView to know when the page transition has begun.
>>
>> There was callback, in PageClient, that was making a similar job, called
>> didCommitLoadForMainFrame, but it was removed recently.
>>
>>
>> If by “PageClient” you mean the WKPageLoaderClient in WKPage.h, then
>> didCommitLoadForFrame is there.
>>
>> I don’t even recall there ever being a didCommitLoadForMainFrame, but
>> didCommitLoadForFrame combined with a quick call to WKPageGetMainFrame will
>> do the exact same thing.
>>
>
> By PageClient I mean the one in Source/WebKit2/UIProcess/PageClient.h
> (which WebView inherits from)
>
>
> I see.  I misunderstood and thought you were talking about the API layer.
>
> PageClient is largely a platform abstraction and not all platforms inherit
> a WebView from it.  And since it’s a platform abstraction, I can’t tell you
> how your platform should behave with it.
>
> But that’s probably neither here-nor-there…
>
>  WebPage does have a callback that tells this (didStartPageTransition),
>> but this is not forwarded to UIProcess, which is kind of weird, since its
>> opposite (didCompletePageTransition) is fired to PageClient when a page has
>> completed its transition.
>>
>>
>> didStartPageTransition is about starting a provisional load, and
>> didCompletePageTransition is *not* about committing a provisional load.
>>  Additionally, neither of these are actually sent to any API clients;  They
>> are internal to WebPage.
>>
>> If you think didCommitLoadForFrame() for the main frame was what you
>> wanted, then both of these are irrelevant anyways.
>>
>
> didCompletePageTransition is forwarded to the C API client.
>
> In WebPage it calls WebPageProxy::pageTransitionViewportReady ->
> WebView(inheriting PageClient)::pageTransitionViewportReady ->
> WebViewClient::didCompletePageTransition
>
>
>
> This is not true in general for the WK2 project.  Cross platform WK2 API
> is in terms of the WK* objects and their clients.  What you’re describing
> here is something very platform specific to your platform’s WebView
> implementation.
>

Please take a look at WKViewClient code, you will see that there is a
didCompletePageTransition callback

>
> Anyways, in your original message, you mentioned that you wanted to know
> didCommitLoadForFrame for the main frame, and you intended to pipe
> didStartPageTransition through to the UIProcess to approximate that.
>
> didStartPageTransition is more about tiled backing stores being set up
> properly and not about loading transitions.  It’s not remotely the same
> thing as didCommitLoadForFrame was called for the main frame.
>

Hum... maybe I have misunderstood the concepts here, by looking at the name
(didPageStartTransition) I though it was totally related with page
transitions. Despite of that, I think we have an inconsistent API here,
which tells when the transition is over but not when it has started. That
is the main reason I think it would be good to put that callback in
WKViewClient as well.

>
> Thanks,
> ~Brady
>

Cheers

-- 
Thiago de Barros Lacerda
OpenBossa - INdT
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