UIView parent window's frame and bound dimensions while rotating iPad

I a have a following line of code invoked after a touch gesture has completed:

CGRect parentBounds = self.view.bounds;
CGRect parentFrame = self.view.frame;

when iPad is placed in a vertical way both parentFrame and parentBounds have similar dimensions of w:768 h:1004 (or something close to that), but when I rotate parentBounds is 1024x748 while parentFrame is 768x1024. Is this behavior normal? I thought I understood the concepts beetwen frames and bounds (and how they relate to each other)... but now I am really confused.

Could anyone explain what is happening w开发者_如何学Cith frame and bounds of a window (superview) when rotation occurs?

The window does not change orientation; the root view does. It does this by applying a view transform (self.view.transform). You're not supposed to call frame if transform is not CGAffineTransformIdentity.

This is not a complete answer, but might help if you don't get something better: When the device is rotated, the top-level window's frame does not change. Instead, a transform gets applied that rotates everything 90 degrees (or 180 degrees), and then the subviews will get resized to fit in the new coordinate system.

From Apple's PhotoScroller sample code:

We have to use our paging scroll view's bounds, not frame, to calculate the page placement. When the device is in landscape orientation, the frame will still be in portrait because the pagingScrollView is the root view controller's view, so its frame is in window coordinate space, which is never rotated. Its bounds, however, will be in landscape because it has a rotation transform applied.

In short, the view's frame is not affected by device rotations, but its bounds is.