Subj : Re: [SpiderMonkey] Confused about class property
To   : netscape.public.mozilla.jseng
From : Peter Paulus
Date : Tue Oct 04 2005 05:26 pm



Not just to start a monologue, I've disassembled the javascript:

var x = ColorSpace.lab;

into:

00000:   0  defvar "x"
main:
00003:   0  bindname "x"
00006:   0  name "ColorSpace"
00009:   0  getprop "lab"
00012:   0  setname "x"
00015:   0  pop

So I guess it must be the interpreter that turns ColorSpace into a 
Function object, rather than an 'ColorSpace' object.

Are there flags on my JSClass struct or otherwise to manipulate this 
behavior?

With kind regards,
Peter Paulus

Peter Paulus wrote:
> Hello all,
> 
> In my host class 'ColorSpace' I've added, a.o., a class property 'lab' 
> with flags: JSPROP_READONLY | JSPROP_PERMANENT | JSPROP_GETTER | 
> JSPROP_SHARED and a getter: getClassProperty().
> 
> This property mimics a value where in other languages one would use an 
> enumeration.
> 
> My testscript contains:
> var x = ColorSpace.lab;
> 
> When getClassProperty() is invoked the tinyid is correct. But the 
> JSobject* obj parameter supplied, contains a Function object, instead of 
> an object of class "ColorSpace".
> 
> The 'this' object retrieved from the stackframe is my global object.
> 
> I have been fiddling with the flags of JSClass and JSPropertySpec, but I 
> can't seem to find how to set them correctly. Most of the time 
> js_InvokeInternal() is invoked and crashes.
> 
> I do realize that there is a possibility to say in javascript:
> 
> if (ColorSpace.convert)
>   {
>   ...
>   }
> else
>   {
>   ...
>   }
> 
> In order to check if a method exists. Can I take any actions as to 
> resolve the ambiguity between getting a 'class' property and checking 
> for the existence of a method.
> 
> Thank you in advance.
> 
> With kind regards,
> Peter Paulus

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