Re: [css3-background] Curved borders intersecting backgrounds of inner boxes

On Apr 17, 2010, at 6:34 PM, fantasai wrote:

> On 04/12/2010 11:41 AM, Brad Kemper wrote:
>> 
>>> I think 'background-clip' should just affect backgrounds, not other
>>> things like 'overflow'. 'border-radius' affects other properties
>>> because it changes the shape of the border and padding (and content)
>>> edges, but only affects them in that it changes that shape.
>> 
>> Good point. So then how do you determine the "appropriate" curve for 
>> border-radius overflow clipping? The CR says it is based on 
>> 'background-clip', but you are saying that should not affect overflow.
> 
> The CR says that *backgrounds* determine the appropriate curve to
> clip to via 'background-clip'. It does not say which curve other
> clip effects use: that is determined by the property doing the
> clipping. In the case of 'overflow', the definition of 'overflow'
> says which edge to clip to. The 'border-radius' property just
> alters the shape of that edge, it does not change which edge.
> 
> ~fantasai

Ah, so "the curve" in the second sentence ("Other effects that clip...also must clip to **the curve**.") does not necessarily refer to the same "appropriate curve" in the first sentence, if I understand you correctly. It's whatever edge is appropriate for that clipping effect. 

That's reasonable. Maybe someday we will have a "overflow-edge: border-box" property/value, but since the padding edge is the most useful one for overflow anyway, I'm in no hurry to change this. Perhaps an editorial change could clarify the meaning though, as I read "the curve" to mean the same curve that was deemed "appropriate" in the preceding sentence. Perhaps you would consider something like this:

Backgrounds, but not the border-image, are clipped to the appropriate curve (as determined by ‘background-clip’). Other effects that clip to the border or padding edge (such as ‘overflow’ other than ‘visible’) also must clip to the curve _of that edge (the padding edge in the case of 'overflow)_.