RE: Initial comments on SVG Strokes, 2015-04-09

Dear Cameron and WG members,

1. Firstly, I should say I have a biased viewpoint, driven by meteorological uses cases that evolved on paper with pencils and erasers over the last 50 or so years and are now implemented in many interactive drawing applications.

2. My main concern is the "2.2 Specifying stroke alignment". 'Inside' and 'outside' are persistent, well understood properties for closed paths, and result in consistent and expected behaviour. As indicated in the draft, this is problematic for open paths.

In particular, of the seven examples in 2.2, 'inside' and 'outside' give 'flipping' behaviour, and possibly other side-effects, in the context of an interactive drawing application when the curvature of the path is changed. Only the last, seventh, example ('left') would give expected consistent behaviour. This assumes that the path has a 'start' and a consistent direction of drawing.

The 'left' and 'right' attributes would be consistent with 'inside' and 'outside' for closed paths, but would map differently depending on which way the path is closed (I think it is determined mathematically by the "winding number").

Much as it is amusing to achieve fancy affects with side effects in graphics systems, I would prefer consistency of mental models and expectations.  

3. I have no strong views on dashed lines.  

4. Is it worth having Section 5 also stating changes since SVG10, 1.1 or 1.2?

HTH, Chris

Chris Little
Co-Chair, OGC Meteorology & Oceanography Domain Working Group

IT Fellow - Operational Infrastructures
Met Office  FitzRoy Road  Exeter  Devon  EX1 3PB  United Kingdom
Tel: +44(0)1392 886278  Fax: +44(0)1392 885681  Mobile: +44(0)7753 880514
E-mail: chris.little@metoffice.gov.uk  http://www.metoffice.gov.uk


I am normally at work Tuesday, Wednesday and Thursday each week

Received on Thursday, 16 April 2015 11:48:01 UTC