It will be interesting to see what the behavior of this issue is in swf9.
On Jan 9, 2008 5:37 PM, P T Withington <[EMAIL PROTECTED]> wrote:
> yes please.
>
> Simple test case is to compare the behaviour of the attribute and
> method declarations.
>
> It's a swf-only bug.
>
> On 2008-01-09, at 17:34 EST, André Bargull wrote:
>
> > Should we create a JIRA-entry for this bug, so either to create a
> > fix (somehow), or to document it at least.
> >
> > - André
> >
> > On 1/9/2008 11:07 PM, P T Withington wrote:
> >> I take back my explanation regarding `this`.
> >>
> >> What it really is is a bug in the Flash implementation of "function
> >> scope". When you define a function, it is supposed to capture the
> >> scope that it was defined in (and use that scope to look up free
> >> references in). The Flash player makes a optimization of never
> >> capturing the scope of a function defined in the global scope.
> >> This would be fine, because you call all your functions in the
> >> global scope, so it will be there when you call.
> >>
> >> BUT, Henry is right (as usual).
> >>
> >> There are a bunch of places in the player where as functions are
> >> being called by player internals (surely C or C++), and the player
> >> "forgets" to call the function in the global scope. The most
> >> common place we run into this is in the idle loop. But apparently
> >> the Array#sort method is another case. We used to have to write
> >> all our code that would be used in the idle loop to explicitly
> >> reference everything from `_root` (which must somehow be specially
> >> looked up, not just looked up in the scope chain).
> >>
> >> A while back, we worked around this issue by making sure that every
> >> method we define is defined in such a way as to trick the runtime
> >> into capturing the global scope on the function. It seems like
> >> that technique is not working 100%.
> >>
> >> And it seems that when a free reference is made from a function and
> >> the scope chain is empty, the function just immediately exits,
> >> which is why you see no output.
> >>
> >> The (apparent) reason that tracing or closing over the function
> >> works is that both are invoking the scope-less function inside a
> >> function that _does_ have a scope, so it all works out.
> >>
> >> So, really, this is a bug in our compiler's work-around for the
> >> scope issue. If you rewrite the canvas method as:
> >>
> >> <attribute name="laszloMethod" value='function (n1, n2)
> >> { Debug.write("%s: %d - %d (%s)", arguments.callee, n1, n2, Debug);
> >> return 0}' />
> >>
> >> (which should be equivalent), everything works...
> >>
> >> On 2008-01-09, at 16:13 EST, André Bargull wrote:
> >>
> >>> Another riddle for Tucker:
> >>>
> >>> I can call:
> >>> _root.Debug.write("%s: %d - %d", arguments.callee, n1, n2);
> >>>
> >>> But I cannot call:
> >>> _root.Debug.write("%s: %d - %d (%s)", arguments.callee, n1, n2,
> >>> Debug);//or i.e. global, canvas etc. breaks, too
> >>>
> >>> So, in which context does get Array#sort(..) called?
> >>>
> >>>> It _is_ getting called. For some reason, your Debug.write is
> >>>> failing to send any output:
> >>>>
> >>>> lzx> Debug.trace(canvas, 'laszloMethod')
> >>>> lzx> [1,2,3].sort(canvas.laszloMethod)
> >>>> TRACE: [394491.00] laszloMethod.apply(?undefined?, [1, 2])
> >>>> laszloMethod( 1 , 2 )
> >>>> TRACE: [394501.00] laszloMethod -> 0
> >>>> TRACE: [394505.00] laszloMethod.apply(?undefined?, [1, 3])
> >>>> laszloMethod( 1 , 3 )
> >>>> TRACE: [394512.00] laszloMethod -> 0
> >>>> TRACE: [394516.00] laszloMethod.apply(?undefined?, [1, 2])
> >>>> laszloMethod( 1 , 2 )
> >>>> TRACE: [394523.00] laszloMethod -> 0
> >>>> TRACE: [394527.00] laszloMethod.apply(?undefined?, [2, 3])
> >>>> laszloMethod( 2 , 3 )
> >>>> TRACE: [394536.00] laszloMethod -> 0
> >>>> ?Array(3)#15| [1, 2, 3]?
> >>>> lzx>
> >>>>
> >>>> Oh, hah-hah. I see why. Because laslzoMethod is a method, it
> >>>> expects a 'this' argument, and our compiler inserts an implicit
> >>>> `with (this)` around your method body, but you are calling it as
> >>>> a function, and `this` is undefined in that case (see the trace
> >>>> output above). So your code is turning into `with (undefined)`
> >>>> and I bet that causes the global reference to Debug to fail.
> >>>> Amusingly, tracing the method makes the debug output work. I
> >>>> can't really explain that.
> >>>>
> >>>> If you were to make a closure to call your method, it should work:
> >>>>
> >>>> lzx> Debug.untrace(canvas, 'laszloMethod')
> >>>> lzx> [1,2,3].sort(function (a, b) { return canvas.laszloMethod(a,
> >>>> b) })
> >>>> laszloMethod( 1 , 2 )
> >>>> laszloMethod( 1 , 3 )
> >>>> laszloMethod( 1 , 2 )
> >>>> laszloMethod( 2 , 3 )
> >>>> ?Array(3)#57| [1, 2, 3]?
> >>>> lzx>
> >>>>
> >>>> On 2008-01-09, at 14:28 EST, Pablo Kang wrote:
> >>>>
> >>>>
> >>>>> Btw, I know that I can call a laszloMethod from a Javascript
> >>>>> function like:
> >>>>>
> >>>>> <method name="javascriptFunction" args="n1,n2">
> >>>>> return canvas.laszloMethod(n1,n2);
> >>>>> </method>
> >>>>>
> >>>>> What I want to know is why it is I can't pass in the the
> >>>>> laszloMethod directly.
> >>>>>
> >>>>> Thanks,
> >>>>> pablo
> >>>>>
> >>>>> On Wed, 9 Jan 2008, Pablo Kang wrote:
> >>>>>
> >>>>>
> >>>>>> Anyone know why passing in a function defined with an LZX
> >>>>>> method tag into Array.sort doesn't work? Here's a test case:
> >>>>>>
> >>>>>> <canvas debug="true">
> >>>>>>
> >>>>>> <method name="laszloMethod" args="n1,n2">
> >>>>>> Debug.write('laszloMethod(', n1, ',', n2, ')');
> >>>>>> return 0;
> >>>>>> </method>
> >>>>>>
> >>>>>> <script>
> >>>>>> function javascriptFunction(n1,n2) {
> >>>>>> Debug.write('javascriptFunction(', n1, ',', n2 ,')');
> >>>>>> return 0;
> >>>>>> }
> >>>>>> </script>
> >>>>>>
> >>>>>> <handler name="oninit">
> >>>>>> var arr = [ 1,2,3 ];
> >>>>>>
> >>>>>> Debug.write('-- Javascript Function --');
> >>>>>> arr.sort( javascriptFunction );
> >>>>>>
> >>>>>> Debug.write('-- Laszlo Method --------');
> >>>>>> arr.sort( canvas.laszloMethod );
> >>>>>> </handler>
> >>>>>>
> >>>>>> </canvas>
> >>>>>>
> >>>>>> pablo
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>
> >>>>
> >>>
> >>
> >>
> >
>
>
>
--
Henry Minsky
Software Architect
[EMAIL PROTECTED]
