On Fri, Sep 2, 2016 at 3:54 PM, Ben Noordhuis <i...@bnoordhuis.nl> wrote:
> On Fri, Sep 2, 2016 at 5:42 AM, Zach Bjornson <zbbjorn...@gmail.com>
> wrote:
> > Hello,
> >
> > I'm trying to fix some code that creates a wrapped C++ object ("Canvas",
> > emulating HTMLCanvasElement) with property accessors on the prototype.
> > Specifically, these assertions should work to reflect browsers'
> > HTMLCanvasElement API:
> >
> > var c = new Canvas(...);
> > assert(!c.hasOwnProperty("width"));
> > assert("width" in c);
> > assert(HTMLCanvasElement.prototype.hasOwnProperty("width"));
> >
> > Currently there's an assertion failure (from nan) because the
> > InternalFieldCount for the PrototypeTemplate is 0. Setting it to 1 fixes
> > this problem, but without touching the rest of the code, both the
> > FunctionTemplate and the PrototypeTemplate now have an
> InternalFieldCount of
> > 1. Is that the correct situation? I can't find any examples of setting
> > accessors on prototypes to work from.
> >
> > The class in question is this:
> > https://github.com/Automattic/node-canvas/blob/master/src/Canvas.cc#L30
> > (sorry it uses nan's macros and not raw v8 APIs)
> > and the patch setting the PrototypeTemplate's InternalFieldCount is
> > https://github.com/Automattic/node-canvas/issues/803#
> issuecomment-244275154
> >
> > Thanks,
> > Zach
>
> Nan maintainer here. What you describe sounds correct; setting the
> internal field count on a template reserves that many slots in
> instances of that template.
>
>
Thanks. To be totally clear -- setting the IFC on *both* the
PrototypeTemplate and FunctionTemplate is reasonable?
-Zach
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