[whatwg] new constructor method for Path2D

[Rik Cabanier]

On Sun, Mar 9, 2014 at 10:52 PM, Dirk Schulze <dschulze at adobe.com> wrote:

>
>
> > On Mar 10, 2014, at 3:44 AM, "Rik Cabanier" <cabanier at gmail.com> wrote:
> >
> >> On Wed, Mar 5, 2014 at 1:46 PM, Rik Cabanier <cabanier at gmail.com>
> wrote:
> >>
> >> While implementing the Path2D object in mozilla, we ran into a
> performance
> >> issue.
> >>
> >> The mozilla implementation uses different "backends" for the canvas 2D
> >> context.
> >> Even within the same document, different canvas objects can be on top of
> >> different graphics libraries. For best performance, the Path2D object
> >> should use the same graphics interface as the canvas context you're
> >> applying it to. If this is not the case, the path segments have to be
> >> walked and converted which is a costly operation.
> >>
> >> To work around this, we could add a couple of constructor methods to the
> >> 2D context:
> >>
> >> Path2D createPath();
> >>
> >> Creates a new empty Path object.
> >>
> >> Path2D createPath(path);
> >>
> >> Creates a new Path object that is a copy of the argument.
> >>
> >> Path2D createPath(d);
> >>
> >> Creates a new path with the path described by the argument, interpreted
> as
> >> SVG path data. [SVG]
> >>
> >> This way, we can guarantee that they use the same underlying technology
> >> and performance won't be impacted.
> >> You could still pass these objects to other canvas contexts but
> >> performance might be impacted.
> >
> > I was thinking about this a bit more and an alternate solution would be
> to
> > pass an optional 2D context to the Path2D constructors.
> > A UA could ignore that context, or it could see it as a hint that the
> path
> > is going to be used with that context.
> >
> > Thoughts?
>
> Slightly better. Still not sure.
>

What are you not sure about?

The current Path2D interface might be unacceptably slow under certain
circumstances and there's currently no way for authors to work around this.
There has to be a hint. If not, I don't see a way that firefox will ship
this.