[Greasemonkey] Can anybody explain to me the strange namespace rule?

[Linan Wang]

Thank you guys very much.

Summary:
1, GM introduces userscript into a temporay namespace, which is above the
current page context.
2, The temporary namespace is destoried when there is no more references
used.
3, use alink.addEventListener to remain a reference to the temporary
namespace.

On 6/6/06, esquifit <esquifit at googlemail.com> wrote:
>
> Userscripts execute in a temporary context that ceases to exist when the
> page is loaded.  Any function defined in the script is then no longer
> available from the page unless a reference to this function is passed to
> it.
>
> When you do
>
> unsafeWindow.self_defined_function= function() {...}
>
> you are passing a reference to 'self_defined_function' to the page context
> (unsafeWindow); the second function, 'another_function' would normally not
> be available from the loaded page, but you are encapsulating a reference
> to
> it in 'self_defined_function', so that mozilla does not destroy
> another_function until no references to it are left.
>
> Regardless of that, I think there are better ways to accomplish what your
> are trying to do, namely, by using the preferred way to attach behaviour
> to
> a DOM element: through the addEventListener method.  This has the
> advantage
> that the page cannot override your function because the context in which
> self_defined_function was declared is not available to page content.
>
> var alink=document.createElement('A');
> alink.innerHTML='A link';
> alink.href="javascript:return false;";
> self_defined_function=function(){
>     alert('foo');
> };
>
> alink.addEventListener ('click',self_defined_function,false);
>
> document.body.appendChild(alink);
>
> Note: true, the 'alink.href="javascript:return false;"' is really ugly; it
> is there to avoid reloading the page after clicking on the link; href="#"
> would also do, but it repositions the page at the top.
>
> With this approach you are passing a reference to self_defined_function to
> the page context.
>
> 2006/6/5, Linan Wang < tali.wang+maillist at gmail.com >:
> >
> > I noticed that in greasemonkey scripts, to add a link in a page call a
> > self
> > defined function, have to 'hook' the function into the unsafeWindow. For
> > example:
> >
> > var alink=document.createElement('a');
> > a.innerHTML='A link';
> > a.href='javascript:self_defined_function()';
> >
> > unsafeWindow.self_defined_function=function (){
> >      another_function();
> > };
> >
> > function another_function(){}
> >
> > It is understandable, but in the 'self_defined_function', if i want to
> > call
> > another function defined in userscript, that function should NOT be
> hooked
> >
> > into unsafe. Why? Can anybody explain to me?
> >
> > Many thanks!
> >
> > Best regards
> >
> > Linan Wang
> > _______________________________________________
> > Greasemonkey mailing list
> > Greasemonkey at mozdev.org
> > http://mozdev.org/mailman/listinfo/greasemonkey
> >
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>



-- 
Best regards

Linan Wang