Allow pointer events to be used if supported

[adroitwhiz]

Description

This PR adds support for using pointer events instead of mouse/touch events if supported in the browser.

Previously, paper.js was testing for pointer event support by checking navigator.pointerEnabled, but that was removed from the pointer events spec back in 2013 and no longer implemented in modern browsers. Now it tests for the existence of window.PointerEvent.

Related issues

• Relates to Support w3c pointer events api #1354
• Resolves Pen tablets don't register mouse events on Firefox 59 + Windows 10 #1463

Checklist

• New tests added or existing tests modified to cover all changes
  • This kind of thing is next to impossible to test automatically...
• Code conforms with the JSHint rules (npm run jshint passes)

[lehni]

One small change, then good to go. Thanks!

[adroitwhiz]

One other thing: Pointer events seem to break UI code that expects mouse events. Should pointer events have to be explicitly enabled, or should there be a version bump of some sort, to indicate that this may change applications' behavior?

[lehni]

@adroitwhiz could you explain how they break things? I don't quite understand the problem

[adroitwhiz]

If there's external code that expects you to click on a canvas (e.g. an eyedropper tool, or dropdown that is supposed to close when you click on another element), for some reason it won't receive those "click" events if pointer events are enabled. I ran into this when testing out this change on a real-world codebase.

[adroitwhiz]

Looks like the "pointer events break mouse events" behavior was talked about a bit here.

[danrha]

Would this potentially fix #1959?

[eeropic]

@danrha yes I think so. I'm doing this same change locally for easier differentiation between stylus, touch and mouse inputs

[CallMeTuesday]

What is the status with this PR @lehni? We've run into an issue that requires pointer support, a drawing app for use with iPad and Wacom tablets that are listening for pointer events (eyedropper, drawing, etc). Any chance we can get this pushed?

[zalo]

I've found that the window.PointerEvent check doesn't work in modern Chrome on Windows, but "onpointerdown" in window appears to work well.

I've needed this to get the pointerId to enable setPointerCapture.