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Re: [Proposal] CSS gradients

From: John Oyler <johnoyler.css@gmail.com>
Date: Sun, 9 Dec 2007 04:26:58 -0500
To: fantasai <fantasai.lists@inkedblade.net>
Message-Id: <16434F34-045B-4455-83D2-D5ED1BF72D26@gmail.com>


On Dec 8, 2007, at 5:05 PM, fantasai wrote:

>
> Charles A. Landemaine wrote:
>> Hello,
>> Here's my proposal for the next specifications of CSS:
>> We could style elements using scalable gradients using fixed and
>> variable units. For instance ...
>> I have uploaded an example for you to see better:
>> http://www.imgplace.com/directory/dir3583/1197135240.png
>> I hope you like the idea.
>
> Hiya Charles,
>
> I think we'll probably leave the gradient definitions with SVG:
> you can use an SVG image to define the gradients (which gives you
> a lot more flexibility than we could ever reasonably define in
> CSS) and position it using the CSS3 Backgrounds and Borders
> properties:
> http://www.w3.org/TR/css3-background/
>

SVG isn't appropriate in some instances. My understanding is that SVG  
is for actual images, or at least elements of them (a curve or shape).  
We're just talking about background colors here, but more than one of  
them. Even with the data uri, they'd be messy just for a gradient, and  
with an external uri to an svg file we're talking another http get for  
something that's purely style. A single gradient() is no big deal, and  
uses less bandwidth to get the same information into the renderer,  
information that is style.

Unlike this proposal, I'd roll all the various parameters into the  
gradient() function though. Something like:

gradient(linear, #000, x1, y1, #777, x2, y2, #999, d1, #fff, d2 ...)

Where the first color is for the first XY pair, the second color is  
for the second XY pair (this gives direction), and every subsequent  
color/d# is a distance and color combo. Variations could be worked up  
for radial and other types of gradients. Maybe a limit on the  
colorstops would be needed, but I'd like to see at least 4 or 5 to be  
possible. I have no idea how difficult it would be to write a parser  
that puts no practical limit on the number colorstops, though.

Such gradients should be usable anywhere a color is usable, certainly  
for the color (foreground) and background-color properties, but also  
for borders and shadows. Of course, only non-gradient() colors should  
be usable within a gradient().

Linear and radial should be required to comply with the spec, but  
other types would be optional or as part of a later spec, I dunno.

In addition to other parts of CSS2 and 3 (border-radius, opacity, and  
shadows come to mind), such gradients would make background images  
unnecessary on a large number of websites. Slashdot comes to mind.


> More browsers are supporting SVG, so I expect we'll see SVG as
> background images become a practical solution for gradient
> backgrounds on the Web.
>

Possible, but hardly practical. Another get, to fetch each SVG image,  
or really really ugly css with the data uri. All for what should  
probably be properly style. And background images aren't the only  
place you might want to use a gradient, foreground colors are nearly  
as important. How could you make an h1 a horizontal gradient from left  
to right, red to blue? If you use SVG, it loses whatever semantic  
meaning the html element has, as I understand things.

> ~fantasai
>

John Oyler
john@discrevolt.com
Received on Sunday, 9 December 2007 16:32:22 GMT

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