no primary events on iOS

[robx]

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.)

[robx]

I'm not that sure of my diagnostic anymore, compare PR #5. It seems that the missing movement{X,Y} is the more immediate bug.

[mpizenberg]

Ok thanks, I will continue conversation in PR #5.