- From: Ian Hickson <ian@hixie.ch>
- Date: Fri, 27 Sep 2013 22:35:35 +0000 (UTC)
- To: "whatwg@whatwg.org" <whatwg@whatwg.org>
On Mon, 9 Sep 2013, Rik Cabanier wrote:
> On Mon, Sep 9, 2013 at 9:33 AM, Ian Hickson <ian@hixie.ch> wrote:
> > On Thu, 5 Sep 2013, Rik Cabanier wrote:
> > >
> > > we've looked over the algorithm in the Canvas spec that describes
> > > how strokes are computed. [1] We think that this section is making
> > > some incorrect assumptions. For instance, the dashes are calculated
> > > over the total lenght of all subpaths, but each subpath should be
> > > treated separately.
> >
> > That's intentional, otherwise if you stroke an already-dashed line,
> > you get weird results.
>
> As Stephan said, when would this happen? Are you thinking of a case
> where you did the dashing yourself and then dash/stroke it again? If so,
> that is expected to give different results.
Expected by whom?
The idea here is that this line:
------------------------------
...would result in this dash (assuming equally spaced on-off):
--- --- --- --- ---
...while this line, dashed with the same stroke:
--- --- --- --- ---
...would result in this different line, rather than result in no change:
--- --- ---
...and this line, dashed with the same stroke:
-- -- -- -- -- -- -- --
...would result in something more like:
-- - -- - -- -
...rather than, again, resulting in no change.
> > > It's also a bit strange that the spec is trying to describe how to
> > > stroke.
> >
> > It's trying to describe sufficient detail to get interoperable
> > behaviour.
> >
> > > For instance, it goes in minute detail on how dashes are applied but
> > > the hardest part of stroking ("inflating the paths in path
> > > perpendicular to the direction") is not described at all.
> >
> > Is there any ambiguity in the part that's not described?
>
> Yes. What is "inflating"?
The dictionary definition is what I intended. To grow, increase in size,
get bigger in all directions. Inflate.
If you have any better suggestion for how to word this, I'm all for it.
> A stroked bezier curve is no longer a bezier and has to be calculated.
Yes. The idea of defining it in terms of the earlier path is that there's
no need to be explicit about the maths here.
--
Ian Hickson U+1047E )\._.,--....,'``. fL
http://ln.hixie.ch/ U+263A /, _.. \ _\ ;`._ ,.
Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'
Received on Friday, 27 September 2013 22:35:59 UTC