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RE: [css3-images] Summary of recent gradient issues

From: Brian Manthos <brianman@microsoft.com>
Date: Fri, 17 Jun 2011 18:00:32 +0000
To: Simon Fraser <smfr@me.com>
CC: Brad Kemper <brad.kemper@gmail.com>, divya manian <divya.manian@gmail.com>, Tab Atkins Jr. <jackalmage@gmail.com>, "www-style list" <www-style@w3.org>
Message-ID: <9710FCC2E88860489239BE0308AC5D1703A18C@TK5EX14MBXC264.redmond.corp.microsoft.com>
I never said it's hard to understand.  I said it's opposite from the way angles work, which is unnecessary and counter-intuitive.  Sure, it's explained away in the text but -- frankly -- you don't need the text crutch if you don't do it backwards.

Let's try it another way...
(a) linear-gradient(from 180deg, to 0deg, red, blue);
(b) linear-gradient(from bottom, to top, red, blue);

(a') linear-gradient(180deg, 0deg, red, blue);
(b') linear-gradient(bottom, top, red, blue);

(a'') linear-gradient(0deg, red, blue);
(b'') linear-gradient(bottom, red, blue);

Why would you omit the first parameter in a'' but omit the second parameter in b''?  Arbitrary inconsistency.

> -----Original Message-----
> From: Simon Fraser [mailto:smfr@me.com]
> Sent: Friday, June 17, 2011 10:54 AM
> To: Brian Manthos
> Cc: Brad Kemper; divya manian; Tab Atkins Jr.; www-style list
> Subject: Re: [css3-images] Summary of recent gradient issues
> On Jun 17, 2011, at 10:34 AM, Brian Manthos wrote:
> > I'm not clear who's saying which in the original mail, perhaps we
> need a W3C spec for e-mail applications.
> >
> > I'll try to address the assertions generally.
> >
> >
> >> I also think CSS authors are familiar by now of the top, right,
> bottom, left keywords. This intuitively suggests the beginning
> position.
> >
> > You're welcome to that position.  I disagree.  For linear gradients,
> the three key elements are color stops and {start, stop} locations.
> The current syntax (WD, ED 1.08, and ED 1.07) choose to omit either the
> start or stop location.  In the absence of that, an "almost as
> expressive" alternative is to treat the two key elements as color stops
> and direction.  As an expression of direction, the keyword syntax prior
> to 1.08 is opposite that of the angle syntax in expressing direction --
> fixed in ED 1.08 version.
> >
> >> Using the 'to' keyword would beg the question, why there is no
> equivalent 'to' keywords elsewhere in CSS (also should there be a
> 'from'?).
> > Perhaps this is an oversight, perhaps it's because gradients
> represent some new concept.
> >
> > Perhaps it's because the "to" keyword is imbedded in abbreviations
> such as "LTR" and "RTL".
> > http://dev.w3.org/csswg/css3-writing-modes/#direction
> >
> > If you prefer the "precedent must be correct" approach to design,
> then perhaps we should use the following:
> > LTR RTL TTB BTT etc.
> >
> >> I think it introduces additional complexity that could be avoided.
> > Apparently it can't be avoided, because there are enough people that
> prefer "to right" over "rightwards" or "right" (as end point).
> >
> >> In my view, this:
> >> linear-gradient(top left indianred, 50% midnightblue, right
> mistyrose);
> >> would be something that would be understandable, given we make
> similar
> >> assumptions of default keyword values for background-position
> >> http://dev.w3.org/csswg/css3-background/#the-background-position
> >
> > Once again, the position argument returns.  Unless you are expressing
> two positions, you haven't expressed a direction.  So the argument that
> you can omit one and be clear is incorrect.
> Not at all. The spec is very clear about this:
> "The second way is to simply provide a side or corner of the box that
> the gradient should start at; the gradient will then automatically
> angle itself to extend from the specified side or corner to the
> opposite side or corner in a straight line."
> I dont see why this is hard to understand. If you use the keywords,
> you're specifying the starting point of a vector that passes through
> the center. If you use the angle form, you're specifying a vector
> through the center with the given angle. In both cases, the end points
> of the gradient are specified in the same way (explained by the figure
> in Example VII).
> >
> >> linear-gradient(top left indianred, 50% midnightblue, right
> mistyrose);
> > This seems cumbersome because you now have two places to spec start
> and stop locations and there's now a blending with stop location and
> end point.
> >
> > This is a bit more acceptable in my book:
> >  linear-gradient(top left, indianred, 50% midnightblue, mistyrose,
> right);
> >
> > But it's not quite there, because it's introducing a new case that
> the spec currently doesn't deal with "top left to right".  Avoiding
> that for now you get...
> >  linear-gradient(top left, indianred, 50% midnightblue, mistyrose,
> bottom right);
> >  or
> >  linear-gradient(top, indianred, 50% midnightblue, bottom);
> > and prior discussion on this thread had (to my recollection) pushed
> back on the "specifying both start and end point" as cumbersome.
> "top left to right" is not dealt with in the spec because it's
> redundant. Such a gradient is horizontal, so there is no need to
> specify "top"; it's equivalent to "left to right".
> Simon
Received on Friday, 17 June 2011 18:01:03 GMT

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