W3C home > Mailing lists > Public > www-style@w3.org > November 2009

Re: radial-gradient() proposal

From: Dean Jackson <dino@apple.com>
Date: Fri, 06 Nov 2009 13:41:47 +1100
Message-id: <C68EEED1-CC05-4503-AC07-CB73CAC7A296@apple.com>
To: Brad Kemper <brad.kemper@gmail.com>
Cc: Simon Fraser <smfr@me.com>, "Tab Atkins Jr." <jackalmage@gmail.com>, www-style list <www-style@w3.org>

On 06/11/2009, at 12:48, Brad Kemper <brad.kemper@gmail.com> wrote:

> On Nov 5, 2009, at 2:55 PM, Dean Jackson <dino@apple.com> wrote:
>>> Is Tranforms the only other module using angles right now?
>> SVG - http://www.w3.org/TR/SVG/coords.html
>> It doesn't use the CSS module, but CSS transforms was designed to  
>> be compatible.
> Ah. I see. So it seems that if a person is familiar with the  
> backwards way that SVG specifies linear angles (if that's what it  
> does, or is it just for rotating, etc.?), then that person might  
> reasonably expect CSS to behave in a similar way, even though it  
> goes against everything else he would expect from a lifetime of  
> seeing diagrams of angles and tools for measuring angles in the  
> opposite direction.

I realize it is backwards to you, but there is 20+ years of CG  
research and use that has managed to survive with a Y-down coordinate  

In the early days of SVG there were heated arguments about this. I was  
pushing for Y-up but in the end it made sense to go for compatibility.  
I don't think anyone suffered too much.

> Or is it just rotate() and skew() in SVG? Because frankly, if so,  
> then I don't have any problem at all with linear directions  
> following the protactor convention, and transforms following the SVG  
> convention. If someone wants to match a gradient to a rotated  
> object, they can easily add a minus sign.

But you can't?

Surely compatibility and interoperability are more important in  
standards? You have specs that have been deployed for many years,  
based on technologies that are even older.

> Brendan has indicate that there are bloggers out there commenting on  
> the current transform implementations as being buggy or wrong for  
> going clockwise with it's degrees. Just wait until we are all asked  
> to flip our protractors over and read the numbers backwards in order  
> to specify direction! It is completely unintuitive to the average  
> person, for whom 90 degrees is up.

Bloggers complain. We can't even agree here so it seems understandable  
that a blogger without context might not realize why a particular  
decision was made. However in this case it is a fairly small use case  
(compared to axis aligned gradients or using two points), it is  
immediately obvious to the author what the problem is and easy to fix.


> We could go with compass directions, I suppose, but it would be  
> harder to be precise. NE is 45deg (for ordinary people, I mean) and  
> NNE is 67.5deg, but I wouldn't know how to specify something in  
> between that way.

Received on Friday, 6 November 2009 02:42:31 UTC

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