On 09/07/2009, at 11:06 AM, Peter Ammon wrote:
- (BOOL)menu:(NSMenu *)menu updateItem:(NSMenuItem *)item atIndex:
(NSInteger)index shouldCancel:(BOOL)shouldCancel
is actually invoked on some sort of background thread/queue, so
implementing these methods (the above + numberOfItemsInMenu:) in
your menu delegate would allow you to update each item with the
attributed title fairly simply and it wouldn't drag your main
thread's performance down.
--Graham
What this method does is check at regular intervals for events that
would cancel tracking. If one is detected, it passes YES for
shouldCancel. So if your design is "if the user clicks on the menu,
sit and spin until it's built," then you could use this API to
detect cancellation, to stop spinning.
However, "sit and spin" isn't a very good user experience, and
Leopard allows you to append items to a menu in the menu bar while
it is open. So for menus that may take a while to build, consider
appending the items as they come in (like the Airport status item),
or showing a "Building..." item until you're ready to add the
complete set of items.
OK... this clarification has confused me a little though.
Can this delegate method be used as suggested or not? In other words,
if I use it to change each item's plain title to a more complex
attributed title, will that cause a performance problem? What I expect
to see is that I pop open the menu and see plain titles, gradually
being replaced one by one with the attributed titles but menu tracking
proceeds normally. But if my code inside this method takes significant
time, will that make tracking sluggish? Also, if menu tracking ends,
are the remainder of the items passed to this method or does it stop
there?
If so, I. Savant's original plan would probably be better so that the
titles can be processed in the background even if the menu isn't shown
(though in that case it could be wasted work if the user *never* opens
the menu).
--Graham
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