[svgwg] Issue: Change definition of percentages to match implementations marked as SVG 2

AmeliaBR has just labeled an issue for https://github.com/w3c/svgwg as
 "SVG 2":

== Change definition of percentages to match implementations ==
The [Units section](https://svgwg.org/svg2-draft/coords.html#Units) 
says:

> For any x-coordinate value or width value expressed as a percentage 
of the SVG viewport, the value to use is the specified percentage of 
the actual-width in user units for the nearest containing SVG 
viewport, where actual-width is the ***width dimension of the SVG 
viewport element*** within the user coordinate system for the SVG 
viewport element. [emphasis added]

(and similar for y/height)

No SVG implementation I know about uses the ***width dimension of the 
SVG viewport element*** as the basis for a horizontal percentage 
length.  They use the viewBox width, regardless of whether or not the 
viewBox takes up the full width of the element.  (Or even if it takes 
up more, in a `slice` aspect-ratio mode).

([Simple demo](http://jsbin.com/nubikepuka/1/edit?html,output), if you
 think better visually.)

The text hasn't been changed since 1.1 (or since 1.0), so this isn't a
 recent careless edit, as I first thought when I read it.  

I don't know whether maybe I'm reading the prose wrong and maybe 
"actual width" was intended to mean "the viewBox width, after scaling 
to fill the element," and everyone involved understood it so the exact
 wording didn't matter at the time. The example that follows the prose
 isn't useful for distinguishing original intent, as it uses a viewBox
 that fills the full width and height.  

But regardless of whether implementations do or don't match the 
intended meaning of the original spec writers, all implementations are
 consistent and the spec should clearly define the standard behavior.

Also, maybe change the example so that it clearly distinguishes 
between element dimensions and viewBox dimensions.

See https://github.com/w3c/svgwg/issues/209

Received on Saturday, 16 July 2016 01:19:01 UTC