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

[Dirk Schulze]

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.

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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