[webkit-dev] About fixing "old" layout bugs

[Xianzhu Wang]

Thanks Dan for reply.

2010/6/2 Dan Bernstein <mitz at apple.com>

> Hi Xianzhu,
>
> On Jun 1, 2010, at 9:37 PM, Xianzhu Wang wrote:
>
> Hi,
>
> I'm new to webkit development, and I'd like to hear opinions about the
> problems I met.
>
> Now I'm trying to fix some "old" layout bugs, for example:
>   * white space preceding <br> (
> https://bugs.webkit.org/show_bug.cgi?id=37261)
>   * relative font-size (https://bugs.webkit.org/show_bug.cgi?id=18413)
>   * line breaking around some punctuations (
> https://bugs.webkit.org/show_bug.cgi?id=37698)
>
> Some people have warned me about the difficulty of fixing these bugs, and
> now I have realized it. Fixing the bugs themselves is not very difficult,
> for example, only 2 functional lines change can fix the first bug. However,
> the change will break more than 4000 existing layout tests mostly because
> trailing spaces preceding <br>s in current expectations of the tests (for
> example, "PASS " vs "PASS"). I tried to rebaseline all effected layout tests
> (for now on mac only), and the patch is about 6MB (Sorry I overlooked the
> "Bigfile" option when I submitted the patch, so I split it into 4 parts).
>
> My questions are:
>
> 1. The bugs violate the standards and cause some site compatibility issues.
> However, because the bugs are old, some web developers might treat them as
> features and depend on them, so fixing them might break some existing pages.
> Is there any existing policy about this problem?
>
>
> Not sure. I think WebKit should not make a policy decision to diverge from
> the standard (quirks mode withstanding) unless WebKit developers are
> actively advocating a change to the relevant standard.
>
> Are these bugs worth fixing?
>
>
>   * white space preceding <br> (
> https://bugs.webkit.org/show_bug.cgi?id=37261)
>
> Unless I’m missing something, there is no known downside to fixing this
> bug. Seems worthwhile.
>
>   * relative font-size (https://bugs.webkit.org/show_bug.cgi?id=18413)
>
> Is this really a standards compliance issue or just compatibility with
> Firefox? If there is a standards issue, is there a subset of the change
> that’s sufficient for standards compliance? Unless WebKit is in violation of
> a standard here, I personally don’t consider this important, but I know that
> other contributors have agreed to this change in principle, and it’s just
> that the patch has been abandoned by the original author.
>

Yes, this is a standard compliance issue (
http://www.w3.org/TR/CSS2/fonts.html#font-size-props). I have asked the
original author and he'd like me to continue his work.


>
>   * line breaking around some punctuations (
> https://bugs.webkit.org/show_bug.cgi?id=37698)
>
> Seems worthwhile if it aligns WebKit with Firefox and IE. If moves away
> from IE compatibility, I wouldn’t do it. The main issue here is efficiency.
>
>
I've uploaded another patch (for preview) that should have the same
efficiency as the current algorithm and keep IE compatibility. I'll upload
the whole patch soon.

Personally, I think it’s good that you’re looking into such long-standing
> standards/compatibility issues!
>
> Regards,
> —Dan
>
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