Open Radar

 
Summary:

The `locationInView:` method in its documentation specifies that passing in `nil` as the view parameter results the returned point being in the window's coordinate system. 

> A UIView object on which the gesture took place. Specify nil to indicate the window.

and

> If nil is specified for view, the method returns the gesture location in the window’s base coordinate system.

This is true for some gesture recognizers (e.g., `UIPanGestureRecognizer`), but not for others (e.g., `UILongPressGestureRecognizer`). For `UILongPressGestureRecognizer` the returned point when passing in `nil` will be in the screen's coordinate system. 

Steps to Reproduce:

Open the attached project. Follow the on screen instructions. Inspect the code when the assertion triggers for the long press gesture recognizer. 

Expected Results:

locationInView:nil would always return the location in the window’s coordinate system

Actual Results:

locationInView:nil returns the location in the screen’s coordinate system for UILongPressGestureRecognizer

Regression:

Tested on iOS 10.2 and 9.3. The behavior is the same. 

Notes:

The documentation mentions that the behavior of this method may differ between `UIGestureRecognizer` subclasses. 

> For objects of the UISwipeGestureRecognizer and UITapGestureRecognizer classes, the location returned by this method has a significance special to the gesture. This significance is documented in the reference for those classes.

However in contrast to `UISwipeGestureRecognizer.h`, `UILongPressGestureRecognizer.h` doesn't say anything about how that method behaves. I would like to request that either this behavior is unified (my preferred resolution), or that the documentation is updated accordingly.