[whatwg] proposal: Add support for masking to canvas
bzbarsky at MIT.EDU
Tue Jan 29 22:05:29 PST 2013
On 1/30/13 12:55 AM, Rik Cabanier wrote:
> void maskImage(optional MaskOptions options);
> Why is it optional?
Because http://dev.w3.org/2006/webapi/WebIDL/#idl-operations says (if
you scroll down a ways):
If the type of an argument is a dictionary type or a union type that
has a dictionary type as one of its flattened member types, and this
argument is either the final argument or is followed by an optional
argument, then the argument MUST be specified as optional. Such
arguments are always considered to have a default value of an empty
dictionary, unless otherwise specified.
> It's not optional for 'addHitRegion' in the spec either...
Well, then whenever someone tries to actually parse that IDL with a
WebIDL parser/validator they'll come filing bugs. ;)
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