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Re: Gradient syntax proposal -- Problems

From: James Elmore <James.Elmore@cox.net>
Date: Thu, 27 Aug 2009 17:10:27 -0700
Message-Id: <B42A3FA5-659F-479A-BE8F-53779888082C@cox.net>
Cc: CSS <www-style@w3.org>
To: "Tab Atkins Jr." <jackalmage@gmail.com>

On Aug 27, 2009, at 4:57 PM, James Elmore wrote:

>> Edits have been made to the master proposal, located at
>> http://www.xanthir.com/:4bhipd.  I also added a line with the syntax
>> to the first example.
>> I'm not happy with how I phrased the comma thing, or with the fact
>> that I had to say it at all.  I think it's confusing.  I suspect that
>> it would be better to handle that in the grammar, but I'm not sure of
>> how to write it.  Ideas?
>> ~TJ
> Thanks for the updated proposal. I am working my way through it and  
> hope to find few problems -- many have already been pointed out in  
> the discussion. However, in the following paragraph, I believe the  
> corners are misstated.
> <<If the <bg-position> is omitted in the first argument, the  
> starting-point is in one of the box's corners, based on the  
> <angle>. If the angle is between [0deg,90deg], the starting point  
> is the bottom-left corner. If the angle is between [90deg,180deg],  
> the starting point is the bottom-right corner. If the angle is  
> between [180deg,270deg], the starting point is the top-left corner.  
> If the angle is between [270deg,360deg], the starting point is the  
> top-right corner. The ending-point is determined in the manner  
> described by the previous paragraph.>>
> Odeg to 90deg is the lower left corner. [correct]
> 90 to 180 is the lower right corner. [correct]
> 180 to 270 should be the upper right corner. [states top-right]
> and 270deg to 360deg then has to be the top left corner.

Oops -- sorry. 90deg is always straight up. My mental model slipped a  
cog. The preceding problem is still a problem. What follows simply  
needs to be considered a lapse.

Is there still a problem if the 90deg line is on the left edge of the  
box or on the right? I don't think so, but after my lapse, someone  
else needs to verify this.


> Also -- what about overlaps? Can we safely ignore 0/360, 90, 180,  
> and 270 degrees simply because they align with one side of the box?  
> Would the gradient not still be visible, but be drawn in opposite  
> directions, depending on which direction the gradient line is drawn?
> For example, suppose the user specifies 90 degrees. The gradient  
> line would be parallel to the bottom of the box. If there are no  
> offsets from the bg-position, it will be on top (underneath?) the  
> bottom of the box. However, if the UA selects 90 degrees to start  
> at the bottom left corner, the gradient line would be oriented left- 
> to-right. Or, if the UA selects 90 degrees as the bottom right  
> corner, the gradient line would be oriented right-to-left. The  
> specification needs to make clear which behavior is correct, or  
> allow some way for users / designers to specify the direction of  
> the gradient line. Clearly, the users can reverse the order of  
> their color-stops, PROVIDED they know in advance which direction  
> the UA will pick. Otherwise, the gradient might be reversed and the  
> users will not be able to know the correct direction.

Received on Friday, 28 August 2009 00:11:11 UTC

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