[webkit-dev] CSS Masking in WebKit

[Dirk Schulze]

Hi Dave,

On Aug 31, 2012, at 11:57 AM, David Hyatt <hyatt at apple.com> wrote:

> This is great! I'd like to be the goto reviewer for any changes you make on the CSS Masking side, since I implemented the original code. I also want to be kept in the loop if any changes are made to the way any of the -webkit-mask-* properties are specified. There are some interesting differences (especially in default values) when compared with the corresponding background/border-image properties, and I want to make sure all of that is well understood.
I try to be careful and definitely keep you in the loop for -webkit-mask* related patches. Thank you for your interest!

> 
> Also, it's important to make sure if there are any deviations/changes, that the -webkit-prefixed versions of these properties don't change behavior. Backwards compatibility is extremely important here. You'll notice that the way I preserved backwards compatibility on border-image for example was to go ahead and implement the unprefixed versions. I don't really have a good suggestion for how to do that here... it's possible a new prefix will be necessary.  It all depends on if any changes are made that would break existing code.
There is indeed one change in the Spec, that differs to the behavior in WebKit. The CSS WG resolved to remove -webkit-mask-attachment from the specification (unless it is requested by developers to add it again). This itself doesn't affect the behavior on WebKit much - rendering wise. However, it influences the syntax of the the shorthand -webkit-mask, which doesn't take <attachment> as type anymore.

Greetings,
Dirk

> 
> dave
> (hyatt at apple.com)
> 
> On Aug 29, 2012, at 5:41 PM, Dirk Schulze wrote:
> 
>> Hi WebKit folks,
>> 
>> The CSS WG and SVG WG agreed to work on a CSS Masking specification [1]. Basically the spec aims to specify the behavior of -webkit-mask/-webkit-box-mask on WebKit browsers and SVG Mask/ SVG ClipPath on Firefox.
>> 
>> I would like to implement the specification in the next weeks and months. Since masking and clipping are basic operations that use the existing capabilities in all graphic libraries, and sine we are using it heavily internally in WebKit already, I do not plan to introduce a new compiler flag. 
>> 
>> However, some features will be covered by existing compiler flags like SVG Mask and SVG ClipPath, allowing to disable these parts.
>> 
>> I created a master bug that covers the work [2].
>> 
>> Greetings,
>> Dirk
>> 
>> [1] http://dvcs.w3.org/hg/FXTF/raw-file/tip/masking/index.html
>> [2] https://bugs.webkit.org/show_bug.cgi?id=95389
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