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Re: [css3-images] remaining gradient issues

From: Alan Gresley <alan@css-class.com>
Date: Wed, 27 Jul 2011 17:55:25 +1000
Message-ID: <4E2FC46D.2090303@css-class.com>
To: Brad Kemper <brad.kemper@gmail.com>
CC: Brian Manthos <brianman@microsoft.com>, www-style list <www-style@w3.org>
On 27/07/2011 9:36 AM, Brad Kemper wrote:
> On Jul 26, 2011, at 4:06 PM, Brian Manthos wrote:
>> Brad:
>>> Well I, for one, found term "gradient vector" an unfamiliar and
>>> mathy way of talking about direction. Anyone can understand what
>>> a line is though, and that it can be described by endpoints and
>>> direction.
>> Incorrect.
>> (1) A line does not have a direction.  You might argue it has two
>> directions, but it definitely does not have exactly 1 direction.
>> (2) A line does not have endpoints; instead it extends infinitely.
>> A line can be indicated by expressing two points that it passes
>> through.  A line *segment* has endpoints. (3) "mathy" --  More
>> specifically it's geometry.  Without geometry, it's a bit difficult
>> to talk about gradients at all.
> I've talk about gradients with other authors, without ever using the
> term "vector" or "segment" and I've never encountered any resulting
> confusion (I doubt that throwing the word "vector" into the
> conversation would have clarified it to those I conversed with).
> "Starting point", "ending point", and "angle" are understandable, and
> direction can be understood as a result of using those words.

A gradient can be used to make things look rounded but that is not 
because something has a direction but rather there is a change that 
follows a path through color space and the points you have are color 
points and the distance between these color points can be smaller or 
larger than the width of an element. Having starting points and ending 
points is to help an author know what the syntax of a gradient will do 
when rendering a gradient. If this was wrong, then a gradient would not 
be considered as something that a no intrinsic dimension on one axis.

>> Much of CSS uses both "general math" and specifically geometry.
>> Are you suggesting we stop using one or both of them going forward
>> for CSS?
> Of course not. I'm suggesting that authors do not necessarily think
> and speak in the same way as spec writers, and I contest that
> "gradient vector" is an intrinsically better notion for authors than
> "keyword means starting point" if it is clear enough that keywords DO
> means starting point. They are just two different ways to describe
> direction.

Path not direction. From S to E is a linear path [1].

|    /|
|  /  |
|/    |

|     |
S - - E
|     |

If the element are rotated, so are these paths. If you believe this is a 
direction, then you have not considered elements that have be rotated or 
are undergoing rotation.

[1] http://en.wikipedia.org/wiki/Path_(topology)

Alan Gresley
Received on Wednesday, 27 July 2011 07:55:54 UTC

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