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[Filter Effects] 'filter' property, SVG and filter functions

From: Dirk Schulze <dschulze@adobe.com>
Date: Fri, 20 Apr 2012 14:53:22 -0700
To: "public-fx@w3.org" <public-fx@w3.org>
Message-ID: <E613C0A3-F22E-4CDC-BC12-39C19A3B2605@adobe.com>
Hi,

Just some comments to the current filter specification.

* The current version of the specification says:

5. The ‘filter’ property

The description of the ‘filter’ property is as follows:

‘filter’
Value:  	none | <filter-function> [ <filter-function> ]*
Initial:  	none
Applies to:  	All elements In SVG 1.1 it applies only to "container elements (except ‘mask’) and graphics elements"
Inherited:  	no
Percentages:  	N/A
Media:  	visual
Animatable:  	yes

The value <funciri> is missing that references an SVG 'filter' element (That is currently defined that way by SVG[1]). At the moment is listed as a <filter-function>. Does it mean that it is possible to combine shorthands and filter elements? 

filter: blur(20px) url(#filter-element);

Don't we want to have backward compatibility and therefore list it separately, even if you want to combine them?

* The type of the values seem not to be defined for the values of the filter functions yet (<length>, <percentage>, <number>).

* To the elements the filter can get applied to:
The SVG specification says:

container element [2]:
An element which can have graphics elements and other container elements as child elements. Specifically: ‘a’, ‘defs’, ‘glyph’, ‘g’, ‘marker’, ‘mask’, ‘missing-glyph’, ‘pattern’, ‘svg’, ‘switch’ and ‘symbol’.

graphics element [3]:
One of the element types that can cause graphics to be drawn onto the target canvas. Specifically: ‘circle’, ‘ellipse’, ‘image’, ‘line’, ‘path’, ‘polygon’, ‘polyline’, ‘rect’, ‘text’ and ‘use’.

That means that filter would be supported for <a>, <defs>, <glyph>, <missing-glyph>, <pattern> and even <use> elements that reference a <mask> or any other elements I listed before. I don't think that we want to support filters on all these elements. Note: This might also be an issue with SVG 1.1 Filters specification[4].

* 'enable-background' property [5]
I have not checked why there is such a big paragraph to explain the difference in SVG. But this section does not mention that we have the attribute 'enable-background'. IMO it should mention that it gets to a presentation attribute (or it gets mentioned in SVG 2).

* 'lightning-color'[6] was copy pasted from SVG 1.1 Filters. The issue that I see is the usage of <icccolor>. This is not defined in CSS Values and Units IIRC. Therefore there should be a link to the definition [7] (Or a section 'module intercation' mentions that separately like other specs do it).

Greetings,
Dirk

[1] http://www.w3.org/TR/SVG/filters.html#FilterProperty
[2] http://www.w3.org/TR/SVG/intro.html#TermContainerElement
[3] http://www.w3.org/TR/SVG/intro.html#TermGraphicsElement
[4] http://www.w3.org/TR/SVG/filters.html#Introduction
[5] https://dvcs.w3.org/hg/FXTF/raw-file/tip/filters/index.html#AccessBackgroundImageSVG
[6] https://dvcs.w3.org/hg/FXTF/raw-file/tip/filters/index.html#LightingColorProperty
[7] http://www.w3.org/TR/SVG/types.html#DataTypeICCColor
Received on Friday, 20 April 2012 21:53:51 GMT

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