Review property value definitions to ensure unitless lengths are correctly included

[AmeliaBR]

See discussion in #529, where it was discovered that stroke-width syntax definition in SVG 2 erroneously left out unitless length. There may be other errors.

[ewilligers]

Lists of properties that accept a numeric value, in quirks mode and standard mode: https://docs.google.com/spreadsheets/d/1HRzb_-S28xq7GqYKhHbMP2YQlqWLvOWSS_twLXy-I40/edit?usp=sharing

[ewilligers]

Raised w3c/csswg-drafts#3057
Blink and Safari also support numeric values for cx cy r rx ry x y.

[css-meeting-bot]

The SVG Working Group just discussed Review property value definitions to ensure unitless lengths are correctly included, and agreed to the following:

• RESOLUTION: Ask the CSS WG for feedback on number length values for currently SVG specific CSS propertoes

The full IRC log of that discussion

<krit> topic: Review property value definitions to ensure unitless lengths are correctly included
<krit> GitHub: https://github.com//issues/534
<krit> ericwilligers: The google docs demonstrates which properties in implementations currently support length and number values as length: https://docs.google.com/spreadsheets/d/1HRzb_-S28xq7GqYKhHbMP2YQlqWLvOWSS_twLXy-I40/edit#gid=1297517027
<krit> ericwilligers: we need to look at the properties which we are going to change in the implementations and which in the specification like stroke-dash-array
<krit> AmeliaBR: those were defined in SVG 1. though it was redefined by CSS and we need to propose changes to the CSS WG.
<krit> AmeliaBR: for the geometry properties, thet are SVG specific and already ship in multiple properties I am happy to add the plain numbers for them
<krit> krit: there would be some inconsistencies for instance with width and height which do not support numbers.
<krit> krit: also, the layout properties currently are SVG specific but might not be in the future.
<krit> ericwilligers: we could say that those are in the quirks mode for SVG.
<krit> krit: IIRC there is no official quirks mode yet
<AmeliaBR> Usage data: https://developer.microsoft.com/en-us/microsoft-edge/platform/usage/css/cx/
<krit> krit: I'd suggest that we look if the cx, cy and so on properties could change to length only values
<krit> krit: seems like 20% are number versions
<krit> krit: I guess we have to decide case by case then
<krit> ericwilligers: but the numbers are all very very slow
<krit> krit: that is true
<krit> krit: starting with the layout properties first... anyone we want to reach out to or investigate?
<krit> AmeliaBR: we could bring this up as part of CSS discussions.
<krit> AmeliaBR: especially with being consistent with width and height and already shipping presentation attributes.
<krit> krit: we already have differences between attribute and property value definition so that by itself is not argument for number values on properties.
<krit> AmeliaBR: yes
<krit> krit: could we send the document to the CSS WG and ask for their feedback?
<krit> ericwilligers: I prepared it already and can present to the CSS WG
<krit> AmeliaBR: for the stroke-* properties this is just a correction but the other properties are more of a debate.
<krit> RESOLUTION: Ask the CSS WG for feedback on number length values for currently SVG specific CSS propertoes
<krit> s/propertoes/properties/

[svgeesus]

CSS WG discussed this and resolved

• RESOLVED: Only accept unitless values on SVG 1.1 supported properties with the exception of baseline-shift

[svgeesus]

So, is the stroke-width definition in SVG2 the normative one, or the one in CSS fill and stroke?

@ericwilligers looks like we need a bit on SVGWG discussion of your document before making edits to SVG2?

[ewilligers]

stroke-dashoffset and stroke-width accept unitless lengths in SVG 1.1, and in all browsers.
The SVG 1.1 definition for length says

A length is a distance measurement, given as a number along with a unit which may be optional.

We kept the SVG 1.1 grammar <length> for these properties, but this is incorrect as we changed the definition of <length>. We need to change stroke-dashoffset and stroke-width to accept <number>

is the stroke-width definition in SVG2 the normative one, or the one in CSS fill and stroke?

The SVG 2 definition is normative. CSS Fill and Stroke is not a normative reference for SVG 2.

[dirkschulze]

I think I covered the changes. @ericwilligers please review otherwise I'll close the issue within the next days.