Re: Feature request for SVG2 : stroke-position

On Mon, Sep 19, 2011 at 1:53 PM, Jeremie Patonnier <
jeremie.patonnier@gmail.com> wrote:

> Thanks for your answers :)
>
> 2011/9/19 Rik Cabanier <cabanier@gmail.com>
>
>> What I meant to say:
>> fill rule will only work if the path segment will participate if the shape
>> is filled.
>>
>
> Are there some cases where it's possible to have a shape that cannot be
> filled (note that to have the fill not visible does not mean that it's
> impossible to fill the shape, a straight line is a good example of that
> issue) ?
>

Correct.


>
>
>> Simple lines or path segments that are filled on both sides are still
>> undefined.
>>
>
> I guess you are talking about something like that :
> <path d="M0,0 L0,100 L100,100 L100,0 M0,50 L100,50" />
> In this case the M0,50 L100,50 segment is filled on both side, am I right
> ?
>

Yes. (You're missing a closepath but I understand what you're drawing)


>
>
>> On Mon, Sep 19, 2011 at 9:50 AM, Rik Cabanier <cabanier@gmail.com> wrote:
>>
>>> this sounds like a reasonable feature.
>>
>>
> Thanks, the intent is to provide an easy way for author to control the
> position of the stroke. It's especially true when you use SVG on a browser
> and try to have a pixel perfect shape.
>
> The following looks blury in a browser (and the viewbox is not obvious) :
>
> <svg width="12px" height="12px" viewbox="-1 -1 12 12">
>     <rect x="0" y="0" width="10" height="10" stroke="black"
> stroke-width="1px" fill="none" />
> </svg>
>
> Where this is sharp (but the rect size is not obvious) :
>
> <svg width="10px" height="10px" viewbox="0 0 10 10">
>     <rect x="0.5" y="0.5" width="9" height="9" stroke="black"
> stroke-width="1px" fill="none" />
> </svg>
>
> for authors it would a lot more easier to understand (and to manipulate) to
> have this :
>
> <svg width="10px" height="10px" viewbox="0 0 10 10">
>     <rect x="0" y="0" width="10" height="10" stroke="black"
> stroke-width="1px" stroke-position="inside" fill="none" />
> </svg>
>

I guess this depends how the browser is rendering the SVG. If there's a CSS
transform on the SVG block, your output might still be blurry.


>
>
>
>> The <value> attribute will introduce significant complexities since it
>>> might cause strokes to overlap each other
>>>
>>
> I'm not sure to understand what you mean here. Can a shape have multiple
> stroke ?
>

I think you answered your own question below. :-)


> However, just having "middle", "outisde" and "inside" would be awesome
> already.
>
>
>> and it will make the stroke no longer match the fill.
>>>
>>
> Yes... and is it a problem ? In an author point of view, it's something
> that could be wanted.
> For example, this is something ok and stroke-position="<value>" could be
> an easy way for author to achieve such an effect :
>
> [image: stroke-position-value-off.png]
>
>
Note that the shape of the stroke can become very different.
Also, you might want to use different mitering values.


> By writing that example, I think I realize what you mean by "it might cause
> strokes to overlap each other". What happen if we have that path :
>
> <path d="M0,0 L100,0 L60,50 L100,100 L0,100 L40,50 Z"
>     fill="none" stroke="red" stroke-width="10"
>     stroke-position="-20" />
>
> Does it look like this (the black line materialize the true path) :
>
> [image: stroke-position-inner-full.png]
>
> or like this :
>
> [image: stroke-position-inner-hide.png]
>
> Well, both result are acceptable and, once again, it's up to the author.
> So, to let him choose in here, it could be necessary to have another
> attribute : stroke-overlap with two values : "show" to have the first case
> and "hide" to have the second case. I vote to be "hide" the default value.
>
>
If you have Illustrator, you should experiment with "offset path". I think
its behavior is pretty close to what you have in mind.

Rik