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

David Hyatt hyatt at apple.com
Fri Jun 4 12:27:41 PDT 2010

For this particular bug (the <br> one), even ref tests would be inadequate, since the reference renderings would have to change too.


On Jun 4, 2010, at 2:17 PM, Dirk Pranke wrote:

> One admittedly painful way to do this would be to dump two render
> trees, an old format and a new format, and then build tooling to roll
> between the versions. Most of the pain would probably be in modifying
> the dump code to accept version flags and know whether to output old
> or new as necessary.
> Of course, you can't really do this for pixel tests, so you're still
> kind of stuck.
> ref tests might be a  better answer in both situations.
> -- Dirk
> On Fri, Jun 4, 2010 at 10:36 AM, David Hyatt <hyatt at apple.com> wrote:
>> In fact the (really lousy) model I've employed in the past when this
>> situation has arisen is that I hack the render tree dump to continue to dump
>> the old rendering.  The render tree dumping code is full of hacks as a
>> result and is basically lying about many things at this point.
>> It would be really nice to take the time to remove all of these hacks and
>> just update every test, but we need a good solution for how to update many
>> tests without breaking the tree.
>> dave
>> On Jun 3, 2010, at 6:16 PM, Ojan Vafai wrote:
>> When there are only a couple tests that need new expectations, you can get
>> away with committing your patch with the expectations for the platforms you
>> have access to and then immediately grabbing the new expectations off the
>> buildbots.
>> There is currently no good way to address the cases where your patch causes
>> many tests to need new results. There are ideas to make it better, but I
>> don't think anyone is actively working on them. Specifically, the EWS bots
>> could run the layout tests and give you access to the results.
>> For now, with patches where you need to change many results and they're
>> different on different platforms, you need to either get access to that
>> platform, or get the help of someone who has access to it.
>> Ojan
>> On Wed, Jun 2, 2010 at 7:32 PM, Xianzhu Wang <phnixwxz at gmail.com> wrote:
>>> Hi,
>>> I'm still wondering what the best practice is to deal with many updated
>>> layout tests in a patch. It seems I must run the layout tests on all
>>> effected platforms by myself to ensure a green build after committing the
>>> patch, right? This is really difficult to me. Is there a easier way?
>>> Thanks,
>>> Xianzhu
>>> 2010/6/2 Xianzhu Wang <phnixwxz at gmail.com>
>>>> 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? Are these
>>>> bugs worth fixing?
>>>> 2. What's the best practice to deal with a patche containing many updated
>>>> layout test expectations? Is there a good way to rebaseline the effected
>>>> tests on all platforms?
>>>> Thanks,
>>>> Xianzhu
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