[whatwg] Proposal: Add CanvasRenderingContext2D.fillRule with "nonzero" (default) and "evenodd" options

Boris Zbarsky bzbarsky at MIT.EDU
Wed Jan 9 17:19:51 PST 2013

On 1/9/13 6:56 PM, James Ascroft-Leigh wrote:
> How can the presence of the winding rule parameter of the fill() and clip()
> operations be detected by client code?

This is a case where .length including optional arguments would have 
been useful.  :(

That said, you can detect this via hacks like this, I expect:

   var ruleArgSupported = false;
   try {
     ctx.fill({ defaultValue: function() { ruleArgSupported = true; 
return false; } });
   } catch (e) {
     // Really shouldn't happen, but who knows


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