Convert a CGPoint from a UIView coordinate system to a CALayer coordinate system

Question

There are methods to transfer a CGPoint from one UIView to another and from one CALayer to another. I cannot find a way to change a CGPoint from a UIView's coordinate system to a CALayer's coordinate system.

Does a layer and it's host view have the same coordinate system? Do I need to transform points between them?

Thanks, Corey

[EDIT]

Thanks for the answer! It is hard to find information on the differences/similarities between CA on the iPhone and Mac. I am surprised I couldn't find this issue addressed directly in any Apple Documentation.

I was pursuing this answer to help with a bug I am troubleshooting, and this was so far my best guess, but I suppose I am barking up the wrong tree. If the coordinate systems are the same, then I have another issue...

The actual issue I am having can be found here on Stack Overflow: layer hit test only returning layer when bottom half of layer is touched

Answer 1

The documentation for hitTest says:

/* Returns the farthest descendant of the layer containing point 'p'.
 * Siblings are searched in top-to-bottom order. 'p' is in the
 * coordinate system of the receiver's superlayer. */

So you need to do (something like this):

CGPoint thePoint = [touch locationInView:self];
thePoint = [self.layer convertPoint:thePoint toLayer:self.layer.superlayer];
CALayer *theLayer = [self.layer hitTest:thePoint];

Answer 2

In terms of Apple documentation, I found an "iPhone OS Note" in the Layer Coordinate System section of the Core Animation Programming Guide (2008-11-13).

The default root layer of a UIView instance uses a flipped coordinate system that matches the default coordinate system of a UIView instance–the origin is in the top-left and values increase down and to the right. Layers created by instantiating CALayer directly use the standard Core Animation coordinate system.