[webkit-dev] Adding CSS3 background-position offsets.

[Alexis Menard]

On Mon, Dec 3, 2012 at 10:42 AM, Dirk Schulze <dschulze at adobe.com> wrote:
>
> On Dec 3, 2012, at 5:31 AM, Alexis Menard <alexis at webkit.org> wrote:
>
>> On Mon, Dec 3, 2012 at 10:19 AM, Dirk Schulze <dschulze at adobe.com> wrote:
>>>
>>> On Dec 3, 2012, at 4:51 AM, Alexis Menard <alexis at webkit.org> wrote:
>>>
>>>> Hi everyone,
>>>>
>>>> I wanted to let you know that I have added the new CSS3
>>>> background-position offsets support to WebKit.
>>>>
>>>> This support is behind the ENABLE_CSS3_BACKGROUND feature define and
>>>> it's disabled by default on all ports. I took the conservative
>>>> approach despite it's a cool feature.
>>>>
>>>> Long story short, it allows you to specify three or four values to
>>>> background-position. It's a nice addition as you can now position the
>>>> images using length or values in relation to any of the four corners
>>>> of elements, not just the top left corner.
>>>>
>>>> Opera, IE10 and Firefox implements this feature already (though the
>>>> latter returns weird results using getComputedStyle).
>>>>
>>>> It is tracked by https://bugs.webkit.org/show_bug.cgi?id=37514 and the
>>>> two patches landed (parsing and rendering) are
>>>> http://trac.webkit.org/changeset/135632 and
>>>> http://trac.webkit.org/changeset/136378.
>>>>
>>>> I believe the <position> type (3-4 values) could be/or is used in
>>>> other cases so we can reuse the parsing code for four/three values if
>>>> needed. I will investigate this afterwards and make appropriate
>>>> patches.
>>>
>>> I really hope that we don't use it any where else again (with the exception of -webkit-mask-position which should have same behavior as background-position). This is the use case for the calc() function. Sadly the calc() function came to late for CSS3 Backgrounds.
>>
>> -webkit-mask-position should behave the same way as
>> background-position? Even if I add feature to the latter? Why so?
>
> Because -webkit-mask and background share the same properties and syntax. Why should it be different on -webkit-mask-position? (Btw. CSS Masking already adapted the background-position syntax for mask-position[1])

Ok sure. Then I will make -webkit-mask-position to behave the same per
http://dvcs.w3.org/hg/FXTF/raw-file/tip/masking/index.html#the-mask-position
. I did know they share the code but I didn't know how far. Thanks for
pointing it out.

>
>>
>> it seems like transform-origin supports something similar. I need to look at it.
>>
>> http://www.w3.org/TR/css3-transforms/#transform-origin-property
>
> It definitely does not :)

Sorry about that I read super quickly and based my thought of one of
the test of css3test.com which expect "right 10px bottom 20px" and
https://bugs.webkit.org/show_bug.cgi?id=37514#c8 . I'm not sure what
is valid or not. Maybe Simon could tell us.

>
> Greetings,
> Dirk
>
> [1] http://dvcs.w3.org/hg/FXTF/raw-file/tip/masking/index.html#the-mask-position
>
>>
>>>
>>> That said, great work regarding the interoperability with other browsers.
>>>
>>> Greetings,
>>> Dirk
>>>
>>>
>>>>
>>>> I plan to enable it by default on Qt and EFL ports this week. If
>>>> somebody wants me to enable it on their ports please tell me, I'll be
>>>> happy to do it.
>>>>
>>>> Looking forward to your comments.
>>>>
>>>> Spec : http://www.w3.org/TR/css3-background/#the-background-position
>>>>
>>>> --
>>>> Software Engineer @
>>>> Intel Open Source Technology Center
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>>>> webkit-dev mailing list
>>>> webkit-dev at lists.webkit.org
>>>> http://lists.webkit.org/mailman/listinfo/webkit-dev
>>>
>>
>>
>>
>> --
>> Software Engineer @
>> Intel Open Source Technology Center
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>



-- 
Software Engineer @
Intel Open Source Technology Center