On Jan 24, 2012, at 5:52 PM, David Duncan wrote:
>> Can anyone explain what's going on?
>
>
> The frame is an entirely synthesized property, based on the bounds, position,
> anchorPoint and transform of a given layer. When you set the latter
> parameters, the frame updates automatically but when you set the frame Core
> Animation has to derive the new bounds & position values by applying the
> anchorPoint and inverse transform. Thus when you set the frame of a layer
> while it is under a transform, the inverse transform is first applied to get
> a new size, then that size updates the bounds size.
Short of guessing the order of operations and doing the matrix math myself, I
have only intuition to tell me that the size ending up at {1000, 0} is… odd.
I'm hesitant to say wrong, but in my head I don't see who the inverse x the
frame = {1000, 0}.
> Moral of the story is that when a layer is transformed (or may be) you should
> only manipulate its position and bounds. Stay far far away from the frame
> property, as its just a bag of hurt.
So let me just throw this out there. Is there some reason it couldn't be
changed so that
layer.frame = (0, 0, 100, 100);
layer.transform = xfm;
...
layer.frame = (0, 0, 200, 200);
is equivalent to:
layer.frame = (0, 0, 100, 100);
layer.transform = xfm;
…
layer.transform = identity;
layer.frame = (0, 0, 200, 200);
layer.transform = xfm;
The latter behaves nice and predictably, and if everyone is avoiding the "bag
full of hurt" does it actually break anything? *wishful thinking*
--
Seth Willits
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