Re: SimpleWebKit (was GNUstep Web browser (was Re: WebKit Bounty))

[Dr . H . Nikolaus Schaller]

Peter,

Am 07.03.2007 um 14:55 schrieb Peter Cooper:

> > Basically the approach is to parse HTML into a DOM tree (DOMHTML.h) -
> > exactly as KHTML/WebKit does. Then, rendering is done top down from
> > the WebHTMLView which has a single child, an NSTextView and the root
> > of the DOM tree. The NSTextView finally renders an attributedString
> > (well, an NSTextStorage), that is built from the DOM Tree. I.e.
> > building this attributedString does half of the work and the other
> > one is NSTextView.
>
> Ok. And the rendering activity may create additional subviews? I  
> can see
> this being useful for optimisations to make fast fluid-layout  
> redrawing
> with the CSS box model possible. It'd be nice not to have to re- 
> render the
> entire document everytime the view is resized ;-)

It is pretty fast on a Mac. Apparently needs just some milliseconds  
to do
all that work.

View resizing does not need to re-render anything. Rendering geometry  
is currently
done in the NSTextView. But I don't know if that changes by the CSS  
box model.

> > This allows the trick for NSAttributedString(Additions) to fetch the
> > attributedString out of the WebView to e.g. convert to RTF.
>
> Yup.
>
> > Now, adding CSS would be a similar approach. Either, the CSS
> > description must load from a separate file first, or it is included
> > in the DOM tree as <style> tags. So, the first step would be to parse
> > the CSS into an DOMCSS tree. As soon as this is available, the DOM to
> > attributedString conversion can use it to return a well formatted
> > string. Finished loading of an external CSS must trigger the
> > rendering to be repeated since layout and style may have changed.
> > This is a bahaviour that you can see sometimes with Safari on a slow
> > connection - firstly, you get a page with raw text and then the
> > background, tables, images and formats come in.
>
> Cool. Do you want me to do translation of the DOM level 2 IDL files  
> into
> objc headers using the same approach (compatible names) as WebKit?  
> Should
> be achievable before the weekend.

That would be nice!

You can base the DOMCSSxxx.h files and classes by including DOMCore.h
And, you need to create a WebCSSDocumentRepresentation class that  
handles getting the file in NSData fragments when the CSS is loaded  
from an external source.
It should try to parse it as good as possible since the file may be  
incomplete. You can take WebHTMLDocumentRepresentation as a sample.

The basic process for loading from external resources works as follows:
* a <link> element tells the HTML engine that it has to load an  
external CSS
* it creates a new WebDataSource for it
* that one opens an NSURLConnection
* as soon as it is clear that it is a CSS resource, a new  
WebCSSDocumentRepresentation is opened
* that one receives the new data from the NSURLConnection through -  
(void) receivedData:(NSData *) data withDataSource:(WebDataSource *)  
source;

What the HTML parser also needs to have is some -initWithString: to  
directly handle the style attribute and <style> tag with inline CSS.  
Well, it could also create a WebDataSource with a given NSData source  
and go the standard way as described above but a shortcut would be  
nice IMHO.

Finally, there must be a query method to find the style attributes  
for a given tuple of (tag, tagpath, id, class).

Hope this works as you have intended...

Nikolaus