[whatwg] Dashed strokes on <canvas>

Ian Hickson ian at hixie.ch
Wed May 16 19:34:35 PDT 2007

On Wed, 16 May 2007, David Flanagan wrote:
> > 
> > ...which would have to be defined, including error handling logic, 
> > including how to handle corners, including how to do dot distribution 
> > to have nice symmetry, etc, etc, etc. It's actually quite complex.
> I believe that most of these issues can and should be left to the 
> implementation.  If the implementation is allowed to choose whether or 
> not to draw shadows, then I think it is fine to allow the implementation 
> to choose the minor details of dash rendering.

Whether to support something is different from how to support it. How to 
render shadows is defined. How to render dashes should also be defined.

> > Anything that isn't specified to the virtual pixel is an error in the 
> > spec. (The canvas section is especially prone to these given my lack 
> > of a graphics background.) In theory, the canvas section is supposed 
> > to specify everything down to the level just before anti-aliasing.
> I just want to point out here that optional support for shadows 
> contradicts this.

No, the shadows are defined, it's just that whether to render them or not 
is left open. So there are exactly two allowed renderings.

> And I think I'm ready to drop this now.  I've posted an entry on my 
> (low-readership) blog about the (surprising, I think) fact that there is 
> no plan to add support for dashed lines.  Maybe that will generate a few 
> more requests for the feature.  Or maybe you're right and no one except 
> me really cares about this :-)

It's not that there's no plan. It's just that the plan is more along the 
lines of "we'll wait and maybe add it later" rather than "we'll add it 
now", since there are workarounds and seemingly little demand.

Please let us know if you get any input on your blog post.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

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