[iOS] Hover gesture reports wrong pointerType

[AndreasHogstrom]

Description

The hover gesture reports the wrong type of pointer.

The eventExtraData method of the hover handler uses UITouchTypePencil instead of the RNGH internal RNGestureHandlerStylus, which causes the enum mapping to become MOUSE instead.

https://github.com/software-mansion/react-native-gesture-handler/blob/v2.30.0/packages/react-native-gesture-handler/apple/Handlers/RNHoverHandler.m#L160

The same method also causes the pointer type to be reported as the same, whether using a stylus or a mouse. There doesn't seem to be a clear way of separating the types on iOS, but checking if zOffset property of UIHoverGestureRecognizer is > 0 might suffice?

https://developer.apple.com/documentation/uikit/uihovergesturerecognizer/4098402-zoffset?language=objc

Steps to reproduce

1. Open Snack reproducer on an iOS device capable of stylus hover.
2. Hover salmon coloured square with Stylus (e.g. Apple Pencil Pro).
3. Tap the same area with the same Stylus.
4. Notice Tap Pointer Type label indicates STYLUS, while Hover Pointer Type indicates MOUSE.

A link to a Gist, an Expo Snack or a link to a repository based on this template that reproduces the bug.

https://snack.expo.dev/@andreashogstromnavigraph/rngh-hover-pointertype

Gesture Handler version

2.29.0

React Native version

0.83.0

Platforms

iOS

JavaScript runtime

Hermes

Workflow

React Native (without Expo)

Architecture

New Architecture (Fabric)

Build type

None

Device

Real device

Device model

iPad Pro 13-inch (M4)

Acknowledgements

Yes

[m-bert]

Hi @AndreasHogstrom! Thanks for reporting this issue. Also thanks for your investigation - it makes total sense that it returns wrong pointer type given those values.

Could you check if #3989 fixes this issue?

[AndreasHogstrom]

Hi @AndreasHogstrom! Thanks for reporting this issue. Also thanks for your investigation - it makes total sense that it returns wrong pointer type given those values.

Could you check if #3989 fixes this issue?

Thank you for looking into this.

Yes, that's a good change which fixes the initial issue.

But the secondary issue, which seems to be more complicated, is still present.

The same method also causes the pointer type to be reported as the same, whether using a stylus or a mouse. There doesn't seem to be a clear way of separating the types on iOS, but checking if zOffset property of UIHoverGestureRecognizer is > 0 might suffice?

There doesn't seem to be any correct way to identify the type of pointer device that is actually used to trigger the hover. It could be a pencil/stylus or a mouse/trackpad for example.

You can limit certain types when initialising the gesture;

Example from Apple docs;

hoverGesture.allowedTouchTypes = [ UITouch.TouchType.pencil.rawValue as NSNumber ]

https://developer.apple.com/documentation/UIKit/adopting-hover-support-for-apple-pencil

I'm running a patch locally that modified the hover handler to assume mouse by default, and stylus if a zOffset of over 0 is reported; (Note that the parameter type needs to be changed to UIHoverGestureRecognized instead of UIGestureRecognizer as well).

- (RNGestureHandlerEventExtraData *)eventExtraData:(UIHoverGestureRecognizer *)recognizer
{
  RNGestureHandlerPointerType pointerType = RNGestureHandlerMouse;
#if CHECK_TARGET(16_1)
  if (@available(iOS 16.1, *)) {
    if (recognizer.zOffset > 0) {
      pointerType = RNGestureHandlerStylus;
    }
  }
#endif

But I'm not sure if that's a good idea for the general public.

Also I'm by no stretch an iOS developer and there might be more obvious ways to do this that I'm not seeing :)

And by the way, you can test hover in the iPad simulator by enabled I/O -> Input -> Send Pointer to Device in the top menus. Although it will act as a "mouse" only, no way to simulate an actual pencil at the moment.

[m-bert]

But I'm not sure if that's a good idea for the general public.

If using mouse results in zOffset == 0.0, then it sounds ok. I don't think we have better option for now. Would you like to open PR with your patch?

And by the way, you can test hover in the iPad simulator by enabled I/O -> Input -> Send Pointer to Device in the top menus. Although it will act as a "mouse" only, no way to simulate an actual pencil at the moment.

Thank you!