Re: Tracking rects, tracking areas and events
Re: Tracking rects, tracking areas and events
- Subject: Re: Tracking rects, tracking areas and events
- From: Quincey Morris <email@hidden>
- Date: Mon, 20 Apr 2009 15:07:49 -0700
On Apr 19, 2009, at 15:20, Erik Österlund wrote:
1. What is the difference between tracking areas and tracking rects?
Tracking rects are available pre-Leopard. NSTrackingArea was
introduced in Leopard to fix significant problems that made tracking
rects pretty much useless for anything but the simplest cases.
2. If I register a tracking rect, will the mouseMoved: message keep
on spamming, or will only mouseEntered: and mouseExited: be sent?
Tracking rects have no effect on the production of mouseMoved messages.
If I understood this correctly, all three are activated with the
setAcceptsMouseMovedEvents: message.
No, setAcceptsMouseMovedEvents is something else again.
If you're not using NSTrackingArea, or if the mouse isn't inside a
NSTrackingArea, you'll get "old-style" mouseMoved events if
setAcceptsMouseMovedEvents: YES has been called for the window. Pre-
Leopard, this was the only way to get mouseMoved events.
If the mouse is inside a NSTrackingArea, you'll get "new-style"
mouseMoved events instead. To prevent confusion, you'd almost
certainly never call setAcceptsMouseMovedEvents: YES if you're using
NSTrackingArea.
3. What happens if two rects intersect?
If you're asking about tracking rects, there were supposed to be rules
about which one won, but I don't recall you could ever rely on it
working properly in all cases.
Which one will be called?
If you asking about NSTrackingArea, all of the relevant areas respond.
You're responsible for choosing which ones should really do something.
Is it possible to create tree-like priorities like views and subviews?
Not with NSTrackingArea. Keep in mind that mouseEntered/mouseExited/
mouseMoved are sent to the tracking area's owner, regardless of the
view/subview structure. (OTOH cursorUpdate is sent to the topmost view
under the mouse pointer, regardless of the tracking area's owner.)
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