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Re: [css3-background] color transition line

From: Brad Kemper <brad.kemper@gmail.com>
Date: Tue, 1 Nov 2011 06:54:26 -0700
Message-Id: <207AB21F-8D6D-43D0-BA36-669A0FA260A5@gmail.com>
Cc: fantasai <fantasai.lists@inkedblade.net>, "www-style@w3.org" <www-style@w3.org>
To: Brian Manthos <brianman@microsoft.com>
>>> http://www.w3.org/TR/css3-background/#corner-transitions
>>> # The center of color and style transitions between adjoining borders
>>> # is at the point on the curve that is at an angle that is
>> proportional
>>> # to the ratio of the border widths. 

>> No, you're missing the last sentence in the spec. It's not drawn at a
>> 45deg
>> angle. The 45deg ray is used to find the intersection point on the
>> inner
>> and outer curves, and the line segment drawn between them is the
>> transition
>> line.


On Nov 1, 2011, at 1:43 AM, Brian Manthos <brianman@microsoft.com> wrote:

> Ok, I think we're interpreting the 3rd sentence differently.
> 
>> # The line demarcating this
>> # transition is drawn between the point at that angle on the outer arc
>> # and the point at that angle on the inner arc.
> 
> I read "that angle" as referring to the 45deg / 30deg in the preceding sentence, and the phrasing in the 3rd sentence as meaning "draw a line segment connecting where that line meets the inner arc/point and the outer arc".
> 
> I think you're reading it as "use the angle an indicator of the location along the partial ellipse of the outer curve, do the same with the inner curve, and connect the dots".

I believe that was the intention. 

I thought this meant that for a 45deg ray, "the point on the curve" would be where 45deg was perpendicular to the tangent. Is that not right? It has been a long time since I have been in a geometry class, and describing a point on a curve as an angle has just never come up in any of my conversations since then. 

The third rendering doesn't look to me like it is where a 45deg angle would bisect the outer curve at a place where a tangent to the curve would be perpendicular to that angle. 

> Perhaps my interpretation is the less common interpretation.
> 
> That said, upon further inspection referring to the "inner arc" at all is folly since sometimes it's a point not an arc and thus it's just confusing at best.

I disagree with that statement. The inner arc is infinitely small in this case, and there is clearly only one point to intersect with, so there is no confusion as to where to intersect that point. 

> Perhaps we should just strike the 3rd sentence entirely.  Is that the proposal?
> 
> 
> -Brian
Received on Tuesday, 1 November 2011 13:55:13 GMT

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