Re: Do tracking rectangles move along with their views?
Re: Do tracking rectangles move along with their views?
- Subject: Re: Do tracking rectangles move along with their views?
- From: Henry McGilton <email@hidden>
- Date: Sat, 23 Apr 2005 14:53:04 -0700
On Apr 22, 2005, at 6:24 PM, Ken Tozier wrote:
I'm getting some squirrely tracking rectangle behavior in a custom
view in which the location of subviews can change depending on the
containing view width and height.
Is it necessary to void all old tracking rectangles and create new
ones every time a subview changes location? If you have hundreds of
subviews (which my class could easily have) having to void everything
every time the window changes by even a pixel seems awfully wasteful.
Well, the computer is doing the work . . .
Basically, although the tracking rects are set outside of the views,
it's actually the views' *window* that manages the tracking
behaviour.
So if views move around or change size for any reason, you have
to reset the tracking rects.
Also having trouble figuring out what to supply to NSView's
"addTrackingRect:toView:owner:userData:assumeInside:"; method.
If my understanding is correct (based on some code I developed
through error and trial), the tracking rect for a given view is
defined in terms of that view's coordinate system. The
tracking rect mechanism then does whatever magic such that the
window manages the rects from then on.
What type of rect are you supposed to feed this method? The subview
frame translated to window coordinates? Containing view coordinates?
I've tried both and when I manually draw the view rect using
NSFrameRect() the resultant rectangles either never appear, are in the
lower left corner of the window or appear below and to the left of
where the subview appears in the containing view. The documentation
isn't very clear on whether it expects the absolute position within
the window coordinates or what it's looking for.
I had a view sub-class called Memo, and Memo contained three parts,
Head, Body, and Base. The head contained images that would light
up on mouseEnter. In Memo's initWithFrame method, I call super's
initWithFrame, then set up the Head, Body, and Base instances, call
their respective initWithFrame methods, and then add then as Memo's
subviews.
Memo has methods to catch any resize or movement of itself to a
different position in the window's content view. This seems to be
a similar case to what you describe as your situation, above.
In each case, the call [self setHeadTrackingRects]; is issued.
So, in my Memo class I have this code:
- (void)setHeadTrackingRects
{
[head removeTrackingRect: closerTrackingTag];
closerTrackingTag = [head addTrackingRect: NSMakeRect(1, 0, 11, 11)
owner: head userData: nil assumeInside: NO];
[head removeTrackingRect: colorpopTrackingTag];
colorpopTrackingTag = [head addTrackingRect: NSMakeRect(14, 0, 11,
11) owner: head userData: nil assumeInside: NO];
}
So, Memo, the superview of head, tells head to add tracking rects
for its light-up controls. The two NSMakeRect calls in the above code
define the position of the light-up controls on a Head view in that
view's coordinate system.
The owner of the tracking rect is designated as a Head instance, since
it is that class which implements mouseEntered and mouseExited events
to light up its controls.
I don't need user data in this case. And, one can assume that the
cursor is not inside the tracking rect at the time that the rect is
set up.
I read the NSView documentation, looked at some example code and read
tech note which says you can't define tracking rectangles til after
they are added to a view, but am still having problems with it.
I believe that is correct. At an early stage in the development
of the Head class, I made a plausible but wrong assumption that
a quite reasonable place to install the tracking rects for a
Head instance would be in the Head's initWithFrame method.
But that did not work, and I had to revert to setting the tracking
rects outside.
Possibly, had I pursued the issue further, I could maybe have
a - (void)setHeadTrackingRect in the Head class, and invoke that
method from the superview after a Head instance had been added
as a subview.
Hope This Helps,
........ Henry
===============================+============================
Henry McGilton, Boulevardier | Trilithon Software
Objective-C/Java Composer | Seroia Research
-------------------------------+----------------------------
mailto:email@hidden | http://www.trilithon.com
|
===============================+============================
===============================+============================
Henry McGilton, Boulevardier | Trilithon Software
Objective-C/Java Composer | Seroia Research
-------------------------------+----------------------------
mailto:email@hidden | http://www.trilithon.com
|
===============================+============================
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