Closures and delegates are isomorphic, except that in the current
(swf8 and previous) player, closures don't close over `this`, which
is why we need delegates. In swf9, this is fixed. We could make
delegates be closures, that we 'fix up'. Last time I measured
though, closures were space-inefficient compared to delegates.
Perhaps this has been fixed in more modern players. (I'm guessing
that in old players, closures may have hung on to their entire
environment, rather than just the particular value-cells they closed
over.) [There is also, in the current compiler, still vestiges of
the kludge to make functions execute in the correct context, which
can break some closures. We'd need to root this out if we made
delegates be closures.]
As to callback vs. event, the whole rest of LZX is event-based, so I
wonder why you would introduce callbacks? (Have I mentioned how much
I hate Perl lately?)
On 1 Dec 2005, at 01:21, Henry Minsky wrote:
So, I have been oscillating back and forth over what kind of
callback API to
support for the right-click menu API.
The problem is as follows:
The user wants to specify what should happen when a menu item is
clicked on.
Do they pass in a function (closure) that gets called? Does the
menu item
object
get a "onselect" event sent to it? Does the user pass in a
LzDelegate to get
called back?
I could not decide which mechanism to support, and after going back
and
forth a few times , I decided to
support all three. So in my current API implementation, when
setting the
callback, the menu and menuitem classes accept either a function,
or an
LzDelegate for the callback, and they also send a "onselect" event to
themselves.
This seems like the right thing to do and also the wrong thing to
do, I'm
not sure which.
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