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Re: [css3-background] border-radius color transitions using gradients recommended but undefined

From: fantasai <fantasai.lists@inkedblade.net>
Date: Tue, 26 Jan 2010 15:04:21 -0800
Message-ID: <4B5F74F5.5090107@inkedblade.net>
To: Brian Manthos <brianman@microsoft.com>
CC: Brad Kemper <brad.kemper@gmail.com>, Arron Eicholz <Arron.Eicholz@microsoft.com>, Sylvain Galineau <sylvaing@microsoft.com>, "www-style@w3.org" <www-style@w3.org>, Andrew Fedoniouk <news@terrainformatica.com>, Zachary Weinberg <zweinberg@mozilla.com>
On 01/26/2010 01:49 PM, Brian Manthos wrote:
> I'm curious about the working group take on Zachary's comments...
> "As an immediate practical problem, conic gradients are not a widely
> available drawing primitive.  They're not in Postscript or PDF *at all*
> as far as I know, which means they're not in Cairo, and I didn't find
> them in a cursory look at the Windows and MacOS drawing APIs either."
> "How are you drawing the conic gradients?  I've not been able to find
> them as an accelerated primitive on any common OS."
> Question 1:
> Does the presence or absence of {PostScript, PDF, Cairo, Windows, MacOS,
> Linux, etc.} primitives weigh into the decision-making on this topic?
> Question 2:
> Does the presence or absence of hardware-accelerated primitives weigh
> into the decision-making on this topic?
> If the answer to questions 1 and/or 2 is "yes, that's important" then
> evaluating the platform capabilities of that set should be considered
> first before going much deeper IMO.

I think these are both good questions and that we should answer them
before speccing anything.

> If the answer to questions 1&  2 are a simple "no", then it seems the
> simplest specification route is:
> (a) define the shape the gradient should fill
> (b) define the function used to calculate the color as a function of x and y

Defining the gradient function seems overkill to me. Whether the
gradient's velocity function is linear or S-curve or parabolic
is, as Tab and Brad have asserted, not important to interoperability
in the useful sense. Defining the shape of the region and the color
stops is about as far as I think we ought to go here. The latter is
not thoroughly defined yet, and I'm happy to clarify the spec on that
matter. But I don't think working out the appropriate gradient velocity
curves and the requiring them is the right thing to do here at this time.

I know that Microsoft wants everything defined down to the sheen on
the door nails, but sometimes it is appropriate to intentionally leave
slack in a W3C specification, and I believe the details of corner joins
for CSS3 Backgrounds and Borders is one of those places. Again, I'm
happy to add an informative appendix with examples and explanations of
good corner joins, and to let that appendix evolve over the CR period
as we gain experience, but I'm hesitant to make the normative prose any
more stringent than it already is.

Received on Tuesday, 26 January 2010 23:04:58 UTC

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