Re: [css3-background] vastly different takes on "blur"

On Jun 21, 2010, at 11:02 AM, "Tab Atkins Jr." <>  

> On Sat, Jun 19, 2010 at 9:45 AM, Brad Kemper <>  
> wrote:
>> On Jun 18, 2010, at 5:16 PM, Simon Fraser wrote:
>> On Jun 14, 2010, at 6:00 PM, Robert O'Callahan wrote:
>> On Tue, Jun 15, 2010 at 12:17 PM, Tab Atkins Jr. < 
>> >
>> wrote:
>>> I have no opinion on the name, but the most intuitive thing for me  
>>> is
>>> for the specified length to be the amount that the blur extends  
>>> out of
>>> the native shadow box.
>> When an author just wants to extend the shadow, that is what  
>> _spread_ is
>> for, so it makes sense for spread to be specified that way.
> Spread is orthogonal to blur.  Its operation has no bearing on the
> operation of blur, except that it's probably good to make them work
> similarly.

My point was that the value should relate most closely to what purpose  
of the setting is for. For 'spread', the whole purpose is to extend  
outward. For 'blur', the main purpose is not that; it is to create a  
region of blurriiness, and the extending out is just a reasonable side  

One of the reasons for 'spread' is that if you use 'blur' as a means  
to extend the shadow, you get unwanted side effects, such as the  
shadow seeming lighter because you are often only seeing the outer  
half of the blur. And the corners get rounder and the shape gets less  

So, there is a distinction to be made between the main effect of  
'spread' and that of 'blur', and that should be taken into  
consideration. The visual effect of the former is only to extend the  
shadow out, while the visual effect of the latter goes in two  

>> But when an
>> author provides a measure for blur, it is because he wants a  
>> certain amount
>> of blurriness.  It does not make sense to me that the number he  
>> picks should
>> only measure the part of the blur that extends outside the original  
>> box, and
>> not the whole blur.
> It's fine that you think that makes the most sense.  I think the
> opposite.  ^_^  To me, the fact that the blur extends inward is
> sensical but irrelevant here.

The size of the blur when you provide a distance measurement for blur  
can not be irrelevant. It is the primary reason and use case for  
having blur on a shadow!

> I care about how large the shadow
> becomes post-blur, and so to me having the length indicate the
> distance the blur extends outward from the shadow is most sensical.

If you care about how far it extends, you can still figure that out  
easily (divide by two), if you are worried about it overlapping  
something, for instance. But for simplicity it should still be a total  
blur amount specified when specifying blur.

> Having the blur length match the spread length thematically is an
> added bonus - both lengths act similarly and thus are easier to use.

Far from it. It just adds confusion to what is being measured, when it  
can be pretty obvious, based on the extent of the visual effect. 

Received on Monday, 21 June 2010 21:06:04 UTC