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[fxtf-drafts] [filter-effects] drop-shadow() null value for interpolation is incorrect

From: Amelia Bellamy-Royds via GitHub <sysbot+gh@w3.org>
Date: Tue, 27 Jun 2017 03:09:58 +0000
To: public-fxtf-archive@w3.org
Message-ID: <issues.opened-238725849-1498532997-sysbot+gh@w3.org>
AmeliaBR has just created a new issue for https://github.com/w3c/fxtf-drafts:

== [filter-effects] drop-shadow() null value for interpolation is incorrect ==
Regarding the `drop-shadow()` filter shorthand, the [spec](https://drafts.fxtf.org/filters/#funcdef-filter-drop-shadow) currently says:

> The initial value for interpolation is all length values set to 0 and the used color is taken from the color property.

However, a zero-offset, zero-blur shadow in `currentColor` is *not* the same as no shadow at all.
If there are semi-transparent regions in the element, you will see a colored shadow through them.  Chrome, Safari, and Firefox all interpolate the filter starting from a _transparent_ shadow when transitioning from `filter: none`.   (MS Edge doesn't yet support `drop-shadow()` as a shorthand filter function.)

The spec should be changed to match the browsers.

Demo/test case: https://codepen.io/AmeliaBR/pen/xrPOxj

- 1st sample has a `currentColor` zero-offset, zero-blur shadow
- 2nd sample has no filter (note that it looks different!)
- 3rd sample starts with no filter, but on hover transitions to a colored, blurred, offset shadow

(Aside: Thanks Dirk for banishing the word "lacuna" from the spec!)

Please view or discuss this issue at https://github.com/w3c/fxtf-drafts/issues/204 using your GitHub account
Received on Tuesday, 27 June 2017 03:10:05 UTC

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