mpizenberg / elm-pep Goto Github PK

On touch devices, a "tap" on the touch surface will generate an emulated mouse click few millisecond later. This behavior is to reduce the potential non usability of websites that do not take into account touch interactions.

In our case, this is an issue since it doubles the number of pointer events generated. An example of this problem is testable with this JS fiddle : https://jsfiddle.net/6aw0z9hL/1/
Try a "tap" with either a touch device (smartphone/tablet) or firefox in responsive mode with touch activated.

I read that event.preventDefault() should prevent this emulated mouse event from happening but it is not the case in the example above.

There is a touchcancel but no mousecancel so should we add this?

This was initially reported to the demo project: mpizenberg-archived/demo-elm-image-annotation#1. I've since narrowed the issue down a bit.

Serving the code at https://ellie-app.com/993kLCWvga1/0 locally and testing with iOS, it turns out that touch.identifier is a "random" large integer, so the primary detection based on identifer == 0 does not work.

It seems that to do this correctly, it would be necessary to keep some state. (E.g. for a sequence finger-1-down finger-2-down finger-1-up finger-2-up.)