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Re: [css3-images] linear-gradient keywords and angles are opposite

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Thu, 9 Jun 2011 16:23:13 -0700
Message-ID: <BANLkTin2SM_roRL2JuTHuR=HeVqL+x85-yuXrGfFg=7cdEyK4Q@mail.gmail.com>
To: Brian Manthos <brianman@microsoft.com>
Cc: "www-style@w3.org" <www-style@w3.org>
On Tue, Jun 7, 2011 at 11:34 AM, Brian Manthos <brianman@microsoft.com> wrote:
> Paraphrasing [1]:
> When specified via angle, the angle can be understood as both the direction ("toward the <angle>") and the ending point ("ends at <angle>").
> Paraphrasing [2] and [3]:
> When specified via keyword, the keyword can be understood as both opposite direction ("away from the <keyword(s)>") and the starting point ("starts at  <keyword>").
> Is it intentional that these two ways of specifying gradient-line are opposite?

I've just committed a change to switch the way keywords are interpreted.

I'm sticking with top/right/bottom/left for now, but explicitly saying
that they indicate where the ending-point of the gradient should be.

In the same commit, I also fixed the spec bug where interpolating from
"left" (270deg) to "top" (0deg) would give a 270deg CCW rotation,
instead of the expected 90deg CW rotation.  Now, if both gradients
have their direction specified with keywords, and the absolute
difference of the angles they map to is greater than 180deg, the
smaller angle is increased by 360deg.  So, the above example would now
interpolate from 270deg to 360deg.  If you interpolated from "top
right" (roughly 45deg) to "top left" (roughly 315deg), it will
similarly now interpolate from 405deg to 315deg instead.

(In the course of this, I also moved the "used value conversion" rules
from the gradient section to the interpolation section, as that's
where it matters.  I may need to move it again and create explicit
guides for the computed/used values, separate from the serialization

Received on Thursday, 9 June 2011 23:24:01 UTC

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