Re: Strange performance behaviour related to <span>

"Sebastian Geerken" <[email protected]> 6 Jun 2016 22:13:15 +0200
Newsgroups	gmane.comp.web.dillo.devel
Message-ID	<[email protected]>
On Mo, Jun 06, 2016, Jorge Arellano Cid wrote:
> On Sun, Jun 05, 2016 at 11:34:13PM +0200, Sebastian Geerken wrote:
> > Hi!
> > 
> > I've stripped down one testcase to a sequence of simple HTML snippets.
> > Try
> > 
> > (for i in $(seq 1 20); do echo '<div style="float:left"><div></div><div style="display:table"><span></div></div>'; done) > tmp.html; dillo tmp.html
> > 
> > and the development version of dillo hangs for a while. You may vary
> > the number (second argument of seq).
> > 
> > If you look at the file tmp.html, you'll notice that it is incorrect
> > HTML. Interrestinly, leaving the <span> away still results in
> > incorrect and deeply nested HTML, but dillo is much faster:
> > 
> > (for i in $(seq 1 20); do echo '<div style="float:left"><div></div><div style="display:table"></div></div>'; done) > tmp.html; dillo tmp.html
> > 
> > Dillo 3.0.5 is fast in both cases.
> > 
> > Does anyone have an idea what effect the <span> has?
> > 
> > I've already run gprof, but the result does not look very meaningful
> > at a first glance.
> 
>   OK, after some experiments I see what happens.
> 
>   If you close the SPAN element, it's fast again.
> 
>   The problem lies in how the parser handles bad HTML, and how
> the rendering deals with it afterwards.
> 
>   In this case the span is left open, and so we end with an anomalous
> tree where an inline container has 20 levels of block containers
> inside inline containers.

I thought something like this.
 
>   You can surely imagine the mess textblock and OOFM get trapped-in
> when trying to make sense of it all! :)

Still, Dw should handle this. Look at this example:

(for i in $(seq 1 20); do echo '<div style="float:left"><div></div><div style="display:table"></div>'; done) > tmp.html; src/dillo tmp.html

Here, only some <div>s at the end are open (and it is simple to make
the snippet correct HTML), but it still takes much time. This looks
still like a Dw problem, especially since it is much faster if you
leave the float definition away.

>   Good news, I already have a working patch.
> 
>   It needs some testing because it constitutes a big change in how
> we deal with bad-formed HTML, but so far it makes more sense than what
> we have now.
> 
>   If you need the patch quick just drop me a note.

Take your time.

Sebastian

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