Implement pointersStream

[appsforartists]

On every pointer{down,move,up}, dispatch an array of all the current pointers.

[appsforartists]

A naïve version of this would be

observableFrom(
  [
    'pointerenter',
    'pointerdown',
    'pointermove',
    'pointerup',
    'pointercancel',
    'pointerout',
    'pointerleave',
    'gotpointercapture',
    'lostpointercapture',
  ].map(
    type => observableFromEvent(target, type)
  )
)::mergeAll()::groupBy(
  event => event.pointerId
);

but that's not super helpful. We don't care about most of the non-core pointer events, but would want to handle down, move, and up independently.

[appsforartists]

For the streams I need to implement, I don't think I need to even bother grouping by pointerId. If we can batch them into frames, we can map each frame into {position,rotation,scale} in the appropriate streams.

[appsforartists]

Prototyping this in this pen

[appsforartists]

Should takeUntil(event.buttons & 1 == 0) to ensure that we only pay attention to events that include the primary button being depressed. That means is a particular pointer has the primary button down, then releases it without releasing all the buttons, then depresses it again, pointerStream will ignore it. Since this seems edge-casey, that should be fine for a first version.

We can always write a custom observable after the basics of direct manipulation are implemented and tested to handle this edge case.

[appsforartists]

Working pen

[appsforartists]

💻 I'm working on a diff at http://codereview.cc/D1692

[jverkoey]

Deprecated by latest spec.