Re: [webkit-dev] Determine whether all resources have been successfully loaded

[Darin Adler]

On Aug 4, 2007, at 4:36 AM, Plessl Christian wrote:

What is the simplest way to check this? Will downloading the  
nightly webkit build and setting the DYLD_FRAMEWORK_PATH to / 
Applications/WebKit.app/Contents/Resources/ work?


Yes, that should work.

-- Darin

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Re: [webkit-dev] Determine whether all resources have been successfully loaded

[Plessl Christian]

Hi Darin

Thanks a lot for your insightful reply.

You are perfectly right, in general there is no specific point in  
time when a web page can be considered as fully loaded, since new  
loads can be triggered by JavaScript etc. For my specific application  
that converts HTML pages to PDF I will have to find a good heuristic  
to determine the point where I will start the PDF generation.


1) didFinishLoadingFromDataSource is also called for the _missing_  
resource. I would have expected that didFailLoadingWithError is  
called


I don't think this is a bug.
When confronted with a bad URL, I presume the web server passes  
back an error page. From the point of view of the WebKit API,  
loading that error page is a successful load


Good point, I did not think about missing resources like that. Your  
suggestion to evaluate the NSHTTPURLResponse seems like a good  
solution to the problem.


2) didFinishLoadForFrame myFrame is called, before all resources  
of frame f2 have been loaded


This might be a bug.

I believe the design is that each frame is independent and parent  
frames don't necessarily wait for subframes. But I could be wrong.  
It might be a bug.


I will file a bug report after I have checked that the same error is  
still present in the latest version of WebKit.


What is the simplest way to check this? Will downloading the nightly  
webkit build and setting the DYLD_FRAMEWORK_PATH to /Applications/ 
WebKit.app/Contents/Resources/ work?


3) didFinishLoadForFrame is called although the load was not  
successfull although. This contradicts Apple's documentation that  
says: "This method is invoked when a location request for frame  
has successfully; that is, when all the resources are done  
loading." (Although the first part of this sentence is unclear and  
incomplete)


That documentation seems pretty unclear, and quite possibly wrong.  
You can report bugs in the Apple documentation at bugreport.apple.com>.


I will report a bug with Apple.

Thanks a lot for your help,
 Christian

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Christian Plessl [EMAIL PROTECTED] http://plesslweb.ch

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Re: [webkit-dev] Determine whether all resources have been successfully loaded

[Maciej Stachowiak]

On Aug 3, 2007, at 12:54 PM, Darin Adler wrote:


On Aug 3, 2007, at 1:50 AM, Plessl Christian wrote:

2) didFinishLoadForFrame myFrame is called, before all resources of  
frame f2 have been loaded


This might be a bug.

I believe the design is that each frame is independent and parent  
frames don't necessarily wait for subframes. But I could be wrong.  
It might be a bug.


I think this is a bug (I believe design intent is to wait for subframe  
resources), and it looks like didFinishLoadForFrame for frame f2  
itself did not wait for f2's resources.


Regards,
Maciej

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Re: [webkit-dev] Determine whether all resources have been successfully loaded

[Darin Adler]

On Aug 3, 2007, at 1:50 AM, Plessl Christian wrote:

1) didFinishLoadingFromDataSource is also called for the _missing_  
resource. I would have expected that didFailLoadingWithError is called


I don't think this is a bug.

When confronted with a bad URL, I presume the web server passes back  
an error page. From the point of view of the WebKit API, loading that  
error page is a successful load; many clients want to handle error  
pages just as they would normal content. You can detect that it's an  
error from your point of view by looking at the NSURLResponse object.  
If it's a NSHTTPURLResponse then you can get at statusCode.


2) didFinishLoadForFrame myFrame is called, before all resources of  
frame f2 have been loaded


This might be a bug.

I believe the design is that each frame is independent and parent  
frames don't necessarily wait for subframes. But I could be wrong. It  
might be a bug.


3) didFinishLoadForFrame is called although the load was not  
successfull although. This contradicts Apple's documentation that  
says: "This method is invoked when a location request for frame has  
successfully; that is, when all the resources are done  
loading." (Although the first part of this sentence is unclear and  
incomplete)


That documentation seems pretty unclear, and quite possibly wrong. You  
can report bugs in the Apple documentation at .


What is the recommended way to find out, whether all resources have  
been loaded successfully?


Besides didFinishLoadForFrame, WebKit doesn't offer another built-in  
way to detect that all resources have been loaded.


"When have all the resources been loaded successfully?" is not a  
specific-enough question. At any point a timer can fire and JavaScript  
can add, say, a new  element to a page, creating a new unloaded  
resource. So there's always a potential for additional loading in the  
future. In the general case, there's no single "this page is entirely  
done" point in time. And there is also considerable ambiguity about  
what constitutes failure.


The concept of "completely done loading" that's used for Safari's  
status bar is the progress computation that's done by WebView. It  
sends out a WebViewProgressFinishedNotification when "the load has  
finished"; I think this is the same timing as didFinishLoadForFrame in  
the frame load delegate.


-- Darin

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[webkit-dev] Determine whether all resources have been successfully loaded

[Plessl Christian]

Hi Webkit developers

I have posted this question a couple of weeks ago on the webkit-sdk  
mailinglist, but did not get any answer. I assume that subscribers of  
this list are more familiar with the implementation of webkit and  
might know the answer.


I'm working on a command-line applications that uses WebKit for  
creating PDF documents from webpages (http://wkpdf.plesslweb.ch).


While I found WebKit intuitive to use, I'm stuck with a seemingly  
simple problem: how can I check, whether all resources referenced by  
a webpage have been loaded successfully?


To get information about the loading of frames and resources, I'm  
implementing the following delegate methods.


 WebResourceLoadDelegate methods:

 - webView:identifierForInitialRequest:fromDataSource:
 - webView:resource:didFinishLoadingFromDataSource:
 - webView:resource:didFailLoadingWithError:fromDataSource:

 WebFramLoadDelegate methods:

 - webView:didStartProvisionalLoadForFrame:(WebFrame *)frame;
 - webView:didFinishLoadForFrame:
 - webView:didCommitLoadForFrame:
 - webView:didFailLoadWithError:forFrame:
 - webView:didFailProvisionalLoadWithError:forFrame:

The problem is, that didFinishLoadingFromDataSource is called, _even_  
if not all resources could be loaded successfully.


I have created a minimal test case to show you what I mean.

The main function creates a WebView, adds delegates, and load the URL  
request like this:


  WebView * webView = [[WebView alloc] initWithFrame:NSMakeRect 
(0,0,800,600)

   frameName:@"myFrame"
   groupName:@"myGroup"];
  [webView setFrameLoadDelegate: controller];
  [webView setResourceLoadDelegate: controller];
  NSURLRequest * request = ... @"test_missing_frame.html"
[[webView mainFrame] loadRequest:request];


The HTML file test_missing_frame.html is a frameset referencing two  
frames (frame1.html,frame2.html), where frame2 references a missing  
resource. The code for these HTML files is shown below.


I have instrumented all delegate methods to generate a trace listing  
the call sequence and the most important arguments to the delegate  
calls. identifierForInitialRequest returns an identifier that  
contains a unique number and the name of the resource:


didStartProvisionalLoadForFrame myFrame
identifierForInitialRequest -> (id:0 (http://xxx/ 
test_missing_frame.html))

didCommitLoadForFrame myFrame
didStartProvisionalLoadForFrame f1
identifierForInitialRequest -> (id:1 (http://xxx/frame1.html))
didStartProvisionalLoadForFrame f2
identifierForInitialRequest -> (id:2 (http://xxx/frame2.html))
didFinishLoadingFromDataSource id: id:0 (http://xxx/ 
test_missing_frame.html)

didCommitLoadForFrame f1
didFinishLoadForFrame f1
didFinishLoadingFromDataSource id: id:1 (http://xxx/frame1.html)
didCommitLoadForFrame f2
identifierForInitialRequest -> (id:3 (http://xxx/missing.jpg))
didFinishLoadingFromDataSource id: id:2 (http://xxx/frame2.html)
->  didFinishLoadForFrame f2
->  didFinishLoadForFrame myFrame
->  didFinishLoadingFromDataSource id: id:3 (http://xxx/missing.jpg)


This call sequence shows 3 surprises (or bugs):

 1) didFinishLoadingFromDataSource is also called for the _missing_  
resource. I would have expected that didFailLoadingWithError is called


 2) didFinishLoadForFrame myFrame is called, before all resources of  
frame f2 have been loaded


 3) didFinishLoadForFrame is called although the load was not  
successfull although. This contradicts Apple's documentation that  
says: "This method is invoked when a location request for frame has  
successfully; that is, when all the resources are done  
loading." (Although the first part of this sentence is unclear and  
incomplete)


What is the recommended way to find out, whether all resources have  
been loaded successfully?


Did I misunderstand something or is this a bug in WebKit? Should I  
file a bugreport with WebKit?


I would appreciate any help.

Cheers,
 Christian



-- test_missing_frame.html ---
http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd";>
http://www.w3.org/1999/xhtml"; xml:lang="en" lang="en">

missing resources test



  




-- frame1.html ---
http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd";>
http://www.w3.org/1999/xhtml"; xml:lang="en" lang="en">



  This is frame1
  No resource is missing for this frame!




-- frame2.html ---
http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd";>
http://www.w3.org/1999/xhtml"; xml:lang="en" lang="en">



  This is frame2
  There is 1 resource missing for this frame.src="missing.jpg"/>





--
Christian Plessl [EMAIL PROTECTED] http://plesslweb.ch



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